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This study quantified the immediate impact of soil deformation caused by agricultural vehicle traffic on the anisotropy of the topsoil pore system and gas transport properties (air permeability, gas diffusivity). A field experiment was conducted with five repeated passes of a two-axle self-propelled agricultural vehicle (wheel load 8 Mg, tyre size: 1050/50 R32, tyre inflation pressure: 100 kPa) on an arable clay soil (crop at the time of the experiment: grass ley) in north-western Switzerland. Undisturbed cylindrical soil cores were collected in non-wheeled areas, at the edge of the wheel rut (i.e., at 0.5 m lateral distance from the centre of the wheel track), and at the centre line of the wheel track. The soil cores (0.1 m diameter, 0.06 m in height) were taken in two directions (vertical and horizontal) in the topsoil (0.1 m depth). Air-filled porosity (ε a), air permeability (k a) and relative gas diffusivity (D p / D 0) were measured at three matric potentials (corresponding to p F 1.5, 2.0, and 2.5, respectively). The vehicle-induced deformation resulted in significantly reduced ε a , k a , D p / D 0 in the topsoil. Air permeability was highly anisotropic in non-wheeled soil, with higher k a in vertical direction. Compaction mainly affected macropores and hence k a at the wet end (p F 1.5), decreased the vertical k a more than the horizontal k a , and consequently, k a became less anisotropic due to compaction. This effect was stronger under the edge of the wheel rut than in the centre of the wheel rut. The anisotropy of D p / D 0 was little affected by the vehicle-induced soil deformation. Our results show that soil deformation due to vehicle traffic not only decreases the gas transport capacity of soil but also changes the anisotropy of air permeability, with consequences on soil aeration and soil-atmosphere gas exchange. • Impacts of wheeling are different under the centre and under the edge of the wheel rut. • Wheeling decreased the gas transport properties and changed the anisotropy. • Air permeability was more affected than gas diffusivity. [ABSTRACT FROM AUTHOR]

Here, we investigated the effects of biogas digestate application on flow pathways and soil properties in a sandy soil aiming at unraveling phosphorus accumulation and depletion processes in fertilized soils. Dye tracer experiments were conducted to visualize and distinguish between various flow pathways, while X-ray tomography was utilized to characterize the soil structure. The dye tracer experiments revealed differences between the control and the digestate-treated group of soil profiles in the top-soils although no statistical verification was possible amid a single plot per treatment. The stained soil profiles in both treatments indicate extensive areas of homogeneous and heterogeneous matrix flow. However, the digestate-treated group showed a decrease in homogeneous matrix flow and a notable presence of preferential flow with low interaction. The application of biogas digestate impacted various soil properties, including organic carbon content, water drop penetration time, and pH levels. Accordingly, the topsoil experienced an increase in soil organic carbon, water repellency, and a decrease in pH levels. The fraction of macropores also increased in the topsoil of the digestate-treated group, accompanied by an increase in tortuosity. Double lactate-extractable phosphorus (DL-P) distribution varied across the different flow pathways, with higher concentrations detected in matrix flow and a depletion observed in preferential flow regions in both treatments. These findings confirm the close relationship between the type of flow pathway and phosphorus distribution in soils. Additionally, a significant correlation was observed between pH levels and DL-P in the digestate-treated group, indicating potential implications for phosphorus availability. Overall, the results of this study suggest that the long-term application of biogas digestate is likely to improve soil properties as related to soil organic matter content, particularly in the topsoil of sandy soils. The study highlights the significance of the prevailing flow and transport pattern on nutrient distribution, with potential implications for nutrient management in agricultural systems. While the study design presented prevents the unequivocal assignment of differences to treatment effects, our data likely illustrate the impacts of biogas digestate amendment on the investigated sandy soil. Further research should focus on assessing the long-term effects of digestate application in loamy and clayey soils. • The impact of digestate on topsoil organic matter and water repellency is notable. • The application of biogas digestate tends to reduce the extent of homogenous matrix flow. • Macroporosity, air-filled porosity, and tortuosity alter with digestate application. • The spatial distribution of soil phosphorus exhibits high variability and is influenced by the flow field. [ABSTRACT FROM AUTHOR]

Soil shrinkage during the drying process (water stress) is one of the main issues in expansive soils of paddy fields. It occurs due to decrease in soil water content, resulting in changes in soil volume and the geometry of pores, leading to the formation of cracks and higher water loss. The aim of this study was to assess the shrinkage characteristic curve and pore size of paddy soils to determine the shrinkage -swelling behavior in Guilan province, Iran. 120 soil samples were collected from the study area. Pore size was determined using soil moisture retention curve (SMRC). It was established by plotting the soil water content (θ) versus the corresponding matric suction (h), and the shrinkage curve by plotting the void ratio (e) against the moisture ratio (υ). The suction-pore relationships were also determined. Furthermore, the geometric factors indicating the change in vertical (subsidence) and horizontal (crack) volume of the soils were determined and varied from 1.23 to 2.53, indicating that the vertical change in soil volume is predominant. The zero, residual and proportional shrinkage phases accounted for less than 2 %, 8–38 %, and 61–91 % of the total soil volume change, respectively. The shrinkage capacity of the soils ranged from 0.52 to 1.37. Cation exchange capacity and clay content were identified as the most important factors affecting soil shrinkage properties. In general, the studied paddy soils have great potential for swelling- shrinkage and cracking during the drying process due to the large percentage of expandable clays and the medium to fine pores. The resultant cracks negatively affect crop yield by damaging plant roots and increasing water losses through the soil profiles. • Guilan paddy soils have a great potential for swelling- shrinkage and cracking during drying process. • Predicting indicators related to shrinkage curve can be an effective way to manage soil and water. • Wetting and drying intensity in paddy soil had a greater impact on soil shrinkage. • The cation exchange capacity and clay were the most important factors affecting the soil shrinkage properties. [ABSTRACT FROM AUTHOR]

Continuous rotary tillage has resulted in several issues, including a thin tillage layer with low soil organic carbon (SOC) and soil compaction, impeding crop root development and resulting in low crop yields, especially in clay soils. Although deep tillage can increase crop yields by loosening the soil structure and expanding the tillage layer it is rarely applied in soils with high clay contents (such as lime concretion black soil) because of its high energy consumption and low economic benefit. This study aimed at investigating the modified tillage practice with lower energy consumption (combining rotary and deep tillage to return crop straw into different depths among different years) in the higher crop yield on a clay soil. We conducted a 5-year (2017–2021) field experiment in a lime concretion black soil with high clay content. The experiment included four treatments: conventional tillage (CT) to return crop straw into the 15-cm layer without and with fertilizer addition, modified tillage (MT) to return crop straw into different depths (i.e., 35 cm in 2017, 20 cm in 2018, 10 cm in 2019, and 20 cm in 2020) with fertilizer addition, and MT combined with fertilizer and activator addition. We investigated the crop yields, soil physicochemical properties, and microbial communities at the topsoil (0–15 cm) and subsoil (15–30 cm) layers. Compared with CT, MT increased maize (Zea mays Linn.) and wheat (Triticum aestivum L.) yields by 9.8 % and 11.4 %, respectively, by enhancing the SOC content and improving the soil physical properties of the subsoil (i.e., aggregate stability, macroaggregate proportion, soil porosity, and the proportion of large and small pores). We suggest a scientific tillage practice for future attempts to increase SOC sequestration and promote crop productivity in agricultural soils, especially those with a high clay content. • Combining rotary and deep tillage increased crop yield in lime concretion black soil. • Combining rotary and deep tillage increased soil organic carbon content of subsoil. • Combining rotary and deep tillage improved soil physical structure of subsoil. [ABSTRACT FROM AUTHOR]

Soil health or soil degradation criteria are until now not well documented for a greater number of soil profiles under conventional and conservation tillage management in the literature. In order to evaluate the compaction status of more than 700 arable sites analyzed within the last 40 years, the Compaction Verification Tool (CVT) was applied according to Zink et al. (2011). Besides the ratio of air capacity (AC, at a matric potential of −6 kPa) and saturated hydraulic conductivity (Ks), the ratio of AC and air conductivity (Ka, at a matric potential of −6 kPa) was considered for evaluating the compaction status with respect to potentially harmful soil alterations. The compaction status was classified into the CVT classes I–IV, where a harmful subsoil compaction was assumed, if both values of AC and Ks or AC and Ka simultaneously exceeded (are smaller than) their defined critical value indicating limited conditions for plant growth (CVT class IV). We analyzed the compaction status of soil profiles with respect to clay content, soil type, structural stage (aggregate forms) and time span of sampling (1980–1999, 2000–2020) under conventional and conservation tillage for top- and subsoil horizons. While also some of the annually plowed topsoils under conventional tillage showed critical values of AC, Ks and Ka, the occurrence of harmful soil compaction is most dominant in the subsoil horizons (> 30 cm depth) because of a higher proportion of class IV which increased with the clay content (from < 12 % to > 12 % clay), irrespective of the applied ratio used for verification (AC/Ks or AC/Ka). Especially the highly productive Luvisols showed a high percentage of harmful compaction in the subsoil (30–41 % in CVT class IV). Soil profiles under conservation tillage management are less affected by harmful compaction. The more aggregated subsoils showed smaller proportions of class IV, which was further influenced by the clay content. • The soil threat by harmful soil compaction (CVT IV) can be explained on the ratio of AC:Ks and AC:Ka. • Luvisols show severe subsoil compaction, documented by a higher number of Class IV subsoil sites. • Soils with clay contents > 12 % are often more intensely deformed than sandier sites. • The ratios between AC and Ks and AC and Ka show similar results. • Soils under conservation tillage are less degraded than under conventional tillage. [ABSTRACT FROM AUTHOR]

Micro-near-infrared (Micro-NIR) spectroscopy has emerged as a promising technique for accurate and cost-effective estimation of soil attributes compared to traditional wet chemistry methods and conventional NIR spectroscopy. Despite its potential, the full extent of its capabilities and applications under different soil conditions remained unexplored. This study has evaluated the potential of a low-cost micro-NIR sensor for predicting soil organic carbon (SOC) and clay contents in agricultural soils under dry and fresh conditions. Two sets of soil samples i.e., A (92 samples, Netherlands) and B (92 samples, Belgium, France, and Germany) were collected and analysed for SOC and clay contents using standard laboratory methods. A micro-NIR of 2000 ∼ 2450 nm spectral range with 18–28 nm resolution (NIRONE D2.5, Spectral Engine, Germany) was used to scan both fresh and air-dried soil samples. Partial least squares regression (PLSR) models were developed for each dataset separately with and without feature selection using competitive adaptive reweighted sampling (CARS), successive projections algorithm (SPA), and slime mould algorithm (SMA). Micro-NIR sensor performed differently for the two datasets, predicting SOC and clay contents accurately for the dataset A while failing for the dataset B. The best accuracy achieved for SOC in the dataset A-fresh (coefficient of determination in prediction (R P 2) = 0.76 and root mean square errors in prediction (RMSE P) = 0.27 %) was improved with the dry samples (R P 2 = 0.81 and RMSE P = 0.27 %). The prediction of clay content was rather poor (R P 2 = 0.48 and RMSE P = 5 %). Feature selection by SMA and CARS methods improved SOC prediction for the dataset A of fresh (R p 2 = 0.79 and RMSE P = 0.25 %) and dry soils (R p 2 = 0.84 and RMSE P = 0.25 %), respectively. Using CARS improved the results of clay prediction for the dataset A of dry soil (R p 2 = 0.56; RMSE P = 4.62 %). Poor performance for the dataset B could be attributed to the non-normal data distribution (SOC skewness = 4.30 and clay skewness = 3.05) and the larger soil variability encountered including soil types. Therefore, this study indicates that a micro-NIR sensor is a potential innovation and can predict SOC accurately and clay with rather moderate accuracy for a normally distributed dataset. • Micro-NIR sensor can accurately predict soil organic carbon. • Micro-NIR sensor can predict soil clay content to a certain degree of accuracy. • Feature analysis can enhance the accuracy of micro-NIR for SOC and clay content predictions. • Sample's attributes distribution has influence on the prediction using micro-NIR. [ABSTRACT FROM AUTHOR]

Soil structure is a dynamic property which controls a wide range of soil functions and is closely linked with soil carbon content. The carbon contents of agricultural soils are subject to several ongoing trends, including declining carbon stocks and attempts to increase the soil carbon reserves. In this study, we aimed to quantify how organic soil amendments, which have been shown to reduce long-term nutrient loads from agricultural fields, can impact soil structure. The structural impacts of a large one-time addition (8 tons carbon per hectare, three different soil amendments) of pulp and paper mill side stream sludges to a boreal clay soil were explored quantitatively in aggregate (X-ray microtomography, sample size 1–2 mm), core (water retention measurements, sample size 195 cm3) and column (macropores ≥80 µm, sample size ∼ 20 dm3) scales. Our results showed no micrometer-scale structural changes within soil aggregates despite the large number (25 aggregate per treatment) of imaged samples. However, the organic soil amendments had a statistically significant impact on the macroporosity. The macroporosity was on average 20–27 % higher compared to the control samples and visible even five years after the application of the amendments. Such change in soil structure improves soil aeration and fast infiltration of water during wet periods and extreme rain events and may thereby also reduce erosion risk by decreasing surface runoff. The increased microporosity was visible only in the column scale. No statistically significant differences were observed in the fraction of large pores in core scale water retention measurements. Probing the soil structural changes in macropore regime by X-ray tomography or developing sub-micron scale analysis methods are recommended approaches to improve our understanding of clay soil's structural changes induced by organic soil amendments. • The effect of a large single dose of organic matter on soil structure was studied. • Soil structure was investigated from aggregate to column scale. • 100 aggregates imaged with X-ray tomography. • Differences in intra-aggregate porosity were not found. • Only macropores (≥80 µm) were affected by the organic soil amendments. [ABSTRACT FROM AUTHOR]

The application of spent coffee grounds (SCGs) to soil has been widely encouraged because of the agronomic benefits of SCGs. However, the negative impacts of this practice are not fully understood. This study aims to present the effect of nanosized SCGs (n SCGs) on the dispersibility/transportability of soil clay. An n SCG sample with an average hydrodynamic size of ∼260 nm was extracted from SCG waste, and its effects on the dispersibility of clay were tracked over a pH range of ∼3 to ∼9 and an ionic strength range of 0.001–0.1 N by using dynamic light scattering techniques and a test tube-based method. n SCGs were found to carry negative charges (zeta potential, ζ, varying from −2 to −30 mV), and the presence of n SCGs in clay suspensions resulted in decreases in the surface charge (towards more negative charge) of the clay suspensions, particularly at pH < 6. By providing more negative charges to the clay system, n SCGs stimulated and favoured clay dispersal. The edge surface of clays and Fe oxides may play a central role in promoting soil particles association, but this effect was likely weakened in the presence of n SCGs. In ge n eral, it can be inferred that the utilization of SCGs may have adverse impacts such as soil/clay losses or soil structural changes, and these impacts need to be considered. [Display omitted] • Nanosized spent coffee grounds (n SCGs) occur in soils due to soil application. • n SCGs were found to carry negative charges over the pH range of ∼3 to ∼9. • n SCGs added to clay suspensions make the surface charge of the system more negative. • n SCGs were found to promote the dispersal of clay. • The colloidal properties of n SCGs are strongly governed by pH and IS. [ABSTRACT FROM AUTHOR]

Soil compaction combined with water deficit may cause a significant decrease in microbial functions. Two texture-contrast sugarcane soils were exposed to the combined stresses of compaction and drought, and microbial responses were investigated going into stress (phase I) as well as their response coming out of stress (phase II). We artificially applied a gradient of bulk densities (0.9–1.5 g cm−3) and water-filled pore space (WFPS, 21–100%) to simulate compaction and drought conditions. PCA results clearly demonstrated the separation of impacts of soil types and the moisture treatments. Additionally, it is evidenced that soil texture can strongly regulate soil microbial response to compaction, as finer texture provides a better local environment for soil microbial community growth, supported by two folds higher microbial biomass carbon content and significantly higher CO 2 respiration in Nitisol (clayey soil) than Planosol (sandy soil). The Structural Equation Modelling (SEM) analysis showed a strongly direct negative effect (path coefficient= −0.59 to −0.61, p < 0.01) of WFPS on the labile C at Phase I and Phase II in both Nitisol than Planosol. Further, soil moisture would govern microbial respiration cross soil types, particularly after removal of compactions which supported by the SEM result (path coefficient= −0.36 to −0.47, p < 0.05). Results from this study have implied the importance in considering the combined effects of soil texture and moisture in assessing compaction impacts and developing associated management regimes. [Display omitted] • Microbial response to compaction varied with soil moisture levels and texture. • Water filled pore space regulates microbial activity at the low moisture level. • Clayey soil showed a greater microbial response to compaction and moisture level. • Clayey soil showed higher resistance to compaction in comparison to sandy soil. [ABSTRACT FROM AUTHOR]

Recent studies have shown that long-term irrigation with treated wastewater (TWW 1 1 Treated wastewater irrigation (TWW): Freshwater (FW): Blended TWW:FW in a 1:1 ratio (MIX): Low-frequency TWW-irrigation (LFI): TWW irrigated tuff trenches (TUF)) can lead to land degradation and reduction of crop performance in clayey soils due to additions of salts and organic compounds. This study investigated the effects of two remediation and two mitigation methods intended to alleviate the damage to soil properties following long-term irrigation with TWW. The experiment was conducted in a 'Hass' avocado orchard (Persea americana Mill.) grown on a clayey soil irrigated with TWW since 2009. The treatments implemented in 2016 included: TWW (control), freshwater (FW), blended TWW:FW in a 1:1 ratio (MIX), low-frequency TWW-irrigation (LFI), and TWW irrigated tuff trenches (TUF). The results showed that FW and MIX significantly reduced total salinity, salinity-related ions (Na and Cl), and sodium adsorption ratio (SAR) to (i) depths of 90 cm and 30 cm under drippers, respectively, and (ii) depths of 60 cm (except for chloride) and 30 cm between drippers, respectively, compared with TWW. TUF and LFI reduced soil salinity and sodicity under drippers but not between drippers compared with TWW. Moreover, FW significantly increased aggregate stability to a depth of 30 cm. TUF had the highest oxygen concentration in the root zone (35 cm depth), followed by FW. Considering the scarcity of freshwater, MIX and TUF are suggested as possible measures for reducing soil salinity and sodicity, and increasing aeration of clayey soils under long-term irrigation with TWW, respectively. Our findings contribute valuable insights into strategies for remediating and mitigating the detrimental effects of TWW irrigation on soil, thus promoting sustainable agriculture in regions facing water scarcity. • FW reduced EC, Na and SAR than TWW both under and between drippers to 60 cm depth. • FW reduced salinity and sodicity at 15 cm away from drip laterals to 30 cm depth. • MIX significantly reduced EC, Na and SAR than TWW to 30 cm depth under drippers. • TUF increased oxygen concentration to 35 cm depth than all treatments. • TUF effects on EC and SAR was restricted to the wetted area bellow the drippers. [ABSTRACT FROM AUTHOR]

To achieve sustainable agricultural activity, phosphatase determination is an important practice for improving the efficiency of phosphorus (P) management in tropical agriculture. The objective of this study was to evaluate acid phosphatase activity in different soil textures and P stress levels affecting the nutritional, chemical, biochemical, and agronomic aspects of soybean. Treatments resulted from factorial combination in a 3 × 3 factorial scheme, consisting of three soil textures (clay, medium, and sandy) and three P stress levels (severe, moderate, and control) with four replications. Three different soil textures were used in the research: Latossolo Vermelho Distrófico (LVd) with clay texture, collected in the native forest, equivalent Oxisol (Soil Taxonomy); Cambissolo Háplico Tb Distrófico (CXbd) with medium texture collected in the natural field equivalent Inceptisols (Soil Taxonomy); and Latossolo Amarelo Distrófico (LAd) with sandy texture collected in the natural field equivalent Oxisol (Soil Taxonomy). Soil electrical conductivity, P available (method Mehlich-1), and acid phosphatase activity (ρ-nitrophenol released) (μg h−1 g−1 soil) were analyzed and the samples were collected at a depth of 0–20 cm. Also evaluated were the height of plants, number of leave and branches, dry mass (root, leave, and stem), P total concentration in leaf, and P translocation (transport from root to shoot) of soybean plants 45 days after sowing. Results showed the clayey textured soil provided the best results for plant growth, root, stem, and leaf dry matter content, P total concentration of P in leaf, P translocation (transport from root to shoot), P available in the soil, and higher acid phosphatase activity of under P stress. Results showed that the Latossolo Vermelho Distrófico (LVd) provided the best results in managing P in different soil textures. However, based on growth and development results, a reduction in phosphate fertilization (P stress moderate) may favor acid phosphatase activity. Acid phosphatase activity can be used as an option in the management of P soluble activity in different soil textures. However, in front of the complexity of soil–plant–P–environment interactions, further research needs to be conducted to investigate better these effects of the da acid phosphatase on different soil textures. • Different soil textures affect acid phosphatase activity. • Phosphatase is an important practice to improve phosphorus efficiency. • Different soil textures affect root and dry matter production in soybean. • Moderate P stress may favor acid phosphatase activity. [ABSTRACT FROM AUTHOR]

• Organic matter amendments increase PAW in sand but reduces PAW in clay. • Xeric tree species has improved growth with organic matter amendments in sand but not clay under water deficit. • Biochar no better than compost for improved tree performance. • No synergy found between compost and biochar as a soil amendment. Organic matter is often used as an amendment to attempt restoration of degraded soils to improve tree establishment and growth. One key aim is to increase plant available water in the soil profile. The texture of the soil, the type of organic amendment (e.g. compost or biochar), and the native environment of the tree (mesic or xeric) will impact how successful restoration efforts are. We aimed to determine whether compost and biochar amendments, either individually or in combination, would improve plant available water (PAW) in both clay and sand soils. We then aimed to measure whether changes in PAW would translate into increased water use and plant growth of both mesic (Corymbia maculata) or xeric (Eucalyptus torquata) tree species under well-watered (WW) or water deficit (WD) conditions. Clay and sand soils were amended with compost, biochar or a compost and biochar mix, whilst unamended soils acted as controls. Soil moisture characteristics of the soil mixes were determined with samples in the laboratory. Fifteen replicate pots (6 l) of each soil treatment were then planted with either mesic and xeric tree species. All pots and trees were subjected to either a WW or WD irrigation regime for 7 weeks. WD irrigation was a set percentage of the daily WW evapotranspiration (ET). ET was calculated as total pot mass one hour after irrigation (to allow for drainage) minus the total pre-dawn pot mass of the subsequent day. The tree biomass, biomass partitioning, ET, and tree water status were measured throughout the experiment to understand growth and stress responses. The xeric tree species (E. torquata) grown in sand soil had a significant increase in growth with all three OM amendments but did not when grown in clay soil. In contrast, we found no significant growth response for the mesic tree species (C. maculata) when grown in either clay or sand amended with any OM treatment. The ET of the xeric tree species was greater for all the OM amended soils for both WW and WD plants in the sand soil. This study shows that OM amendments may improve the soil water properties of sand-based soils which in turn can increase the growth of xeric tree species. However, more expensive organic amendments may not be necessary, nor mixing of OM types, as we found no tree growth differences amongst the three different OM treatments. [ABSTRACT FROM AUTHOR]

• A relationship between soil carbon, soil clay, and median soil aggregate size is derived. • A model of eroded sediment aggregation responsive to land management is proposed for RUSLE2. • Modeled macro-aggregation changes over time are compared to published observations. Land management that improves soil quality is known to increase the amount of water-stable soil aggregates, but many current soil erosion models do not consider land management effects when estimating the size distribution of eroded sediment. Our objective was to develop a method to improve eroded sediment size estimates in response to alternative land management practices using information available within the RUSLE2 model and its database. We conducted a literature search identifying 274 soil aggregate size distributions where soil clay and soil organic carbon were also reported. The median value and log-normal standard deviation were estimated for each distribution. Median value was found to be linearly related to soil clay fraction and quadratically related to soil carbon content. However, the 10% of samples with observed median aggregate sizes greater than 3 mm were all underestimated by the regression model. All these samples were collected from soils under land use described as grass, pasture, or forest. To then determine whether incorporating management impacts on size distribution could better fit field data than this simple approach based purely on clay and carbon, algorithms termed MAS (Model of Aggregated Sediment) were derived and applied with default values in the RUSLE2 soil erosion model to estimate a coarser sediment size distribution at the point of detachment for land management with increased biomass inputs and reduced tillage disturbances. The MAS estimates of macroaggregated sediment (>0.212 mm) mirrored fragment size observations made over 10 yr when cropland was converted to prairie in the central U.S.A. Thus, MAS estimated dynamic land management effects on aggregation better than regression relationships based solely on soil clay and carbon contents. More aggregate and sediment size datasets that include historical land use information will be needed to fully assess the generality of the MAS algorithms and parameter estimates. [ABSTRACT FROM AUTHOR]

Since tillage is one of the processes requiring high power, energy consumption in field operations is of great concern to farmers and researchers. A combined tillage tool has been recognized as one measure to reduce the power requirements in field preparation. In this research work, a combined tillage tool consisting of a subsoiler and rotary harrow (joined using four different linkage configurations) were tested under actual field conditions. The test parameters consisted of: tillage tools (combined tillage tool with four different linkages, a sole subsoiler and a sole rotary harrow), forward speeds (1.79, 2.67, and 3.33 km h −1 ), and rotational speeds of the rotor (299 and 526 rpm). The experiment site was located at 14.00 °S and 99.58 °E having a clay soil type and bulk density in the range 1.5–1.7 g cm -3 with an average water content of 16.6% (db). The results indicated that the combined tillage tool was able to reduce the draft for subsoiling by 4.4–11.3% depending on the linkage configuration compared with the same sole subsoiler used alone. There were significant effects of the rotational speed of the rotary harrow and the forward speed on the drawbar power, the PTO power, and the total power. The combined tillage tool with linkage IV consumed the least total power. The combined tillage tool with linkages I to IV used less total power by 13.7, 12.2, 10.5, and 15.3%, respectively, compared with the combined power required by the sole subsoiler and sole rotary harrow working separately. [ABSTRACT FROM AUTHOR]

Conservation agriculture (CA), with reduced tillage, permanent soil cover and diversified cropping systems, is advocated in southern Africa to improve soil quality, reduce input costs and mitigate climate-induced risks. However, improvements in terms of yield and soil organic carbon (SOC) under CA are slow and variable and many small-scale farmers are unable to buffer themselves against potential short-term financial losses. In this study we examined the effects of CA-related management practices on SOC sequestration and productivity at two medium-term sites on a sandy soil (eight year trial) and clay soil (six years) in maize producing areas of South Africa. Using field data, current input costs and market prices for crops, we calculated the gross margin for each system. Treatments compared conventional ploughing under maize monoculture with reduced tillage, intercropping and crop rotation. On the clay soil, SOC was increased under reduced tillage (57.6 t C ha −1 ) compared to conventional tillage (54.9 t C ha −1 ) while there was no difference for the sandy soil (19.7 t C ha −1 average across treatments). Profitability was most strongly influenced by seasonal rainfall, but was higher on the sandy soil than the clay soil, with an average gross margin of R11,344 ha −1 and R5,686 ha −1 , respectively. This study has demonstrated that while certain CA practices can create site-specific benefits for farmers, it is highly dependent on local weather and soil conditions. For the clay soil an additional payment scheme would be required to reward farmers in southern Africa for C-sequestration to make CA profitable and achieve increased C-mitigation through soil sequestration. [ABSTRACT FROM AUTHOR]

Biochar is anticipated to be an effective option for mitigating nitrogen (N) leaching and improving the hydraulic characteristics of soil, particularly sandy soil. However, little attention has been paid to understanding the effect of biochar on N leaching and hydraulic conductivity ( K ) in fine-textured soil. Additionally, whether different biochar application methods have different effects on N leaching and K remains unclear. Therefore, our objective in this study is to determine the effects of biochar with different application methods on nitrate/ammonium leaching and K in silty clay soil. The three biochar application patterns were as follows: A, biochar was mixed into 0–10 cm of surface soil; B, biochar was mixed into 10–20 cm of subsurface soil; and C, biochar was mixed evenly into 0–20 cm of plow layer soil. In addition, biochar was added at three rates, namely, 1%, 2% and 4% (mass ratios), and a soil column without biochar addition served as the control (CK). Our results demonstrated that the choice of biochar application method significantly influenced N leaching and soil K and balance between the soil K and N leaching, particularly for nitrate. Additionally, the leaching of N in silty clay soil occurred mainly in nitrate form. Compared with the CK, all 1% biochar treatments increased nitrate leaching (except C1%, which showed no differences from the CK) and tended to decrease K. However, all 4% biochar treatments increased nitrate leaching due to a high K . All 2% biochar treatments significantly reduced nitrate leaching by 8.3–17.0%, and B2% significantly increased the saturated hydraulic conductivity ( K sat ) of soil by 20.9%. Hence, the mixing of biochar at a rate of 2% into the subsurface soil effectively mitigated N leaching and increased K in silty clay soil. These findings could have some implications for the field application of biochar. For instance, the combination of subsurface biochar application with that of fertilizer to roots in orchards or with deep tillage in fields, which would mimic the B2% model, would yield multiple benefits, including lower costs. [ABSTRACT FROM AUTHOR]

Despite numerous individual studies evaluating the impact of straw return on soil organic carbon (SOC) stock in upland wheat and maize croplands in China using no-tillage (NTS), rotary tillage (RTS), and deep tillage (DTS) practices, the results have shown inconsistency. In addition, several factors influence the effects of various tillage practices with straw return on SOC stock that are not well understand. In this study, we conducted a meta-analysis of 764 comparisons to determine the combined impact of SOC stock in the topsoil (0–20 cm) and subsoil (20–40 cm) layers, while considering factors such as climate conditions, management practices, and initial soil properties. The results indicate that straw return with different tillage practices significantly improved SOC stock in both soil layers compared to straws removal. The increase in topsoil SOC stock was nearly identical for NTS (7.38 %) and DTS (7.17 %), compared to the RTS. However, the increase in subsoil SOC stock was significantly higher for DTS (28.8 %). According to subgroup analysis, NTS has been more effective in increasing topsoil SOC stock in regions with medium temperature (10–15 °C) and low precipitation (<400 mm), when used in a single cropping system. However, in regions with higher temperature (>15 °C) and precipitation (>800 mm), DTS is more effective in increasing SOC stock in both topsoil and subsoil layers in a double cropping system. Long-term (11–20 years) DTS resulted in a significant increase in SOC stock in the topsoil (19.2 %) and subsoil (18.5 %), while the increased effects of NTS on SOC stock were only in topsoil layer (17.1 %). The effects of straw return on SOC stock were also found to be associated with soil texture, with NTS having a greater impact on sandy to loam soils, and DTS having a greater impact on clay soils. Furthermore, a significant (P < 0.01) positive linear relationship was observed between annual carbon (C) input and SOC sequestration in the topsoil under NTS, as well as in both soil layers under DTS. These findings have important implications for enhancing SOC in Chinese upland wheat and maize cropland soils through optimizing straw return, given that more than 518 million tons of crop straw are produced annually. • Effect of straw return and different tillage practices on SOC stock was analyzed. • Topsoil SOC stock increased more in NTS than RTS in semi-arid regions. • DTS has greater effects on subsoil SOC stock than RTS and NTS. • C inputs contribute to SOC accumulation in topsoil and subsoil layers. [ABSTRACT FROM AUTHOR]

Liming with 'structure lime', comprising approximately 80–85% ground limestone and 15–20% slaked lime, has been promoted in subsidised environmental schemes in Sweden since 2010 to increase clay aggregate stability and mitigate particulate phosphorus losses to surface waters. To date, approximately 65,000 ha have been structure-limed. Apart from stabilising aggregates, liming may also improve other physical properties, such as soil strength. This study examined the effect of increasing application rate (0–16 t ha-1) of structure lime on soil strength, approximated by horizontal (draught requirement) and vertical (penetrometer resistance) measurements, in eight field soils (clay content 26–38%) to which structure lime had been applied two, three, four or six years previously. Draught requirement when cultivating with a multipurpose cultivator significantly decreased (by 11%) with the highest application rate of structure lime (16 t ha-1) compared with an unlimed control. This reduced the wheel power requirement by 7.1 kW and diesel consumption by 1.2–1.4 L ha-1, and lowered CO 2 emissions by 3–4 kg ha-1. To clarify the general effect of structure liming, the mean value of all limed treatments was compared with that of the unlimed control. This showed that structure liming in general significantly reduced the draught requirement (by 7%). However, penetrometer resistance measurements revealed no significant effects of structure liming and no relation between draught requirement and penetrometer resistance measurements. Overall, the results indicate that structure liming can reduce fuel consumption, due to easier soil tillage, and thus lower CO 2 emissions. • Cultivator draught requirement was measured in structure limed field trials. • A towing eye with sensors that can measure forces in three directions was used. • Structure liming reduced horizontal draught requirement by 7%. • Reductions corresponded to decreases of 1.2–1.4 L diesel ha-1 and 3–4 kg CO 2 ha-1. • Structure liming did not affect penetrometer resistance in this study. [ABSTRACT FROM AUTHOR]

Soil structure is essential for soil function and environmental quality. Therefore, adequate evaluation of management systems is essential to ensure the preservation and regeneration of soil structure. Techniques such as X-ray microtomography and automated soil particle size analysis based on gamma-ray attenuation provide rapid quantification of soil physical properties and allow for the evaluation of soil structure. The aim of this study is to determine soil physical parameters using unconventional analytical tools to characterize and evaluate the geometric characteristics of soils with different structures at high accuracy. Soil samples extracted from the UNESP experimental farm (Brazil) were separated into two different management groups according to their textural similarity. The following results were obtained from the analysis: 1) Microtomography can be used to extract soil porosity, including soil microporosity. 2) The shape factor indicates the geometric organization of the soil structure, which is relevant and valid for evaluating the degree of soil degradation. 3) The fractal dimension is related to the soil particle and aggregate size distribution but was not sufficient for describing the soil geometric properties when used alone. 4) Coupling the fractal dimension with the lacunarity provides an important tool for estimating the soil structure. Finally, the application of the physical parameters from the unconventional method provided new insights for understanding soil geometric structure, which can support future investigations of flow phenomena in the soil. [ABSTRACT FROM AUTHOR]

The structure of agricultural topsoils varies considerably throughout the year due to interactions between climatic and biological factors and agricultural management practices. Tillage generally decreases soil density and increases macroporosity, but the resulting arrangement of clods and aggregates is unstable and the soil eventually reverts back to its denser pre-tillage condition. Accounting for post-tillage changes in soil structure and related hydraulic properties could greatly improve model predictions of hydrological and transport processes. Model testing, development and parameterization is, however, currently hampered by a lack of direct measurements of the changes occurring in the structural pore system. We subjected repacked samples of soil collected from the harrowed layer of nine different fine- and medium-textured Swedish mineral soils to subsequent wetting and drying cycles in the laboratory. Initial wetting and equilibration at −30 cm pressure potential was followed by three cycles of simulated rainfall (5 mm h −1 for 4 h) and equilibration. X-ray tomography was used to quantify changes in surface and total porosity, pore size distribution (PSD) and connectivity of structural pores. Total porosity decreased (by 2–24%) in all soils except for two clay soils where in one case the porosity increased slightly (3%) and remained unchanged in the other. In six of the soils, the PSD shifted significantly towards smaller pore sizes, and in four of these soils the connectivity of the pore network decreased. Soil surface porosity decreased most markedly in two silt loam soils (by 73% and 75%). For the nine soils changes were strongly correlated with silt content. Only weak correlations were found between the changes in total porosity and soil texture and organic carbon content. Changes in the PSD appeared to be mainly controlled by the initial structure of the sample created at the time of tillage and sample preparation. [ABSTRACT FROM AUTHOR]

One of the main limitations in applying fertilisers at a variable rate according to soil requirements is the number of samples required to spatially represent soil attributes. Currently, to map soil attributes with high accuracy, a high sample density is needed, which is often unfeasible. One technique that minimizes the number of samples required is the use of maps that have prior information of the soil spatial variability, making it possible to identify representative sampling locations in the field. Soil apparent electrical conductivity (ECa) is a powerful indicator of the characteristics of the soil matrix, and it can be easily measured. The objectives of this study were to determine the efficacy of ECa for mapping the spatial variability of soil properties using a targeted and reduced number of samples (which is economically feasible for growers). A high sampling density was applied in an experimental sugarcane field to assess the spatial variability of soil attributes, and ECa was read by a direct contact sensor. Thematic maps of important agronomic attributes were generated using the high sample density and compare with a targeted and reduced sampling helped by ECa measurements. The methodology used to obtain the spatial variability maps of soil chemical and physical properties indicated that it was possible to obtain maps of acceptable accuracy (r = 0.82 and 0.59 for clay and pH, respectively) that could be used to formulate lime recommendations for variable-rate applications. The total lime spent (28 tons) based on the application maps generated by a targeted sampling mesh (20 sampling points) was very similar to that (30 tons) obtained based on high-density sampling (204 sampling points), representing a large improvement in soil sampling methodology. Here we demonstrated that ECa can improve prediction maps and enables efficient sample orientation. This approach provides an interesting way to map soil properties over large areas using a feasible sampling method and can help farmers in crop management while respecting environmental and soil requirements. [ABSTRACT FROM AUTHOR]

The determination of soil hydraulic properties is laborious and expensive, especially in large-scale applications. One often used substitute for measured hydraulic properties are pedotransfer function (PTFs) estimates. Most PTFs, however, are statistical models that tend to produce biased results for data outside their –often limited– calibration databases. In addition, most PTFs have been established on data derived from temperate regions causing the question whether such models are applicable to soils in tropical regions. This work aimed to evaluate the performance of the Splintex PTF to predict the hydraulic functions for sandy and clayey soils from several tropical and subtropical Brazilian datasets. Splintex is somewhat unique in that it is based on physical principles using a modification of the Arya-Paris method while allowing the estimation of van Genuchten parameters from limited data. In addition, Splintex has an option to include measured soil water retention points, in principle allowing it to produce accurate estimates for a variety of soils. Estimates by Splintex were compared with the empirical Rosetta PTF, which also has an option to use one (or two) retention points. Estimates by both PTFs were compared to observed retention data and field capacity, available water capacity, hydraulic conductivity, and diffusivity using metrics such as Pearson correlation ( r ), mean absolute error (MAE) and root mean square error (RMSE). Both Splintex and Rosetta yielded similar results and sometimes produced significant biases in estimated quantities. In the majority of cases it appears that Splintex produced somewhat better estimates than the 2001 version of Rosetta , indicating that Splintex is a viable, physically-based, alternative to estimating hydraulic properties. [ABSTRACT FROM AUTHOR]

Efficient mitigation of environmental loads from agricultural fields to surface waters requires sufficient knowledge of dominating erosion processes and sediment transport pathways. Computational models are often applied in sediment load assessments but their structure inherently includes assumptions and uncertainties, which can hinder their predictive and explanatory capabilities. In this study, a 3D dual-permeability model was applied with field-scale data from a high-latitude site to investigate sediment balances and structural uncertainties in sediment transport components. The two-year data encompassed hourly records of water flow and sediment concentration composite samples from tillage layer runoff and drain discharge in two adjacent clayey fields with different slopes (1% and 5%). Three model structures with different assumptions of sediment transport pathways were built to test their performance against the data. The simulations demonstrated how different model structures can reproduce the data with varying results on sediment balance. The varying results revealed the importance of flow, erosion, and sediment transport observations from the fields to improve the simulations. Structural uncertainty analysis revealed uncertainties which parameter sensitivity analysis could not describe. Concentration data was shown to include more information about erosion and sediment transport processes than solely the load data. The results suggest that a major part (48–69%) of the detached particles remained in the field and that lateral subsurface transport contributed to load generation (10–21% of total loads) especially in the steeper field. The results demonstrated that the majority (84–87%) of sediment loads occurred via subsurface drain discharge and groundwater outflow with the slope gradient of 1–5%, which suggests that load mitigation measures should also be directed to decrease loads via subsurface transport pathways. The simulations demonstrated how transport processes were controlled not only by water flow but also by soil structure. [ABSTRACT FROM AUTHOR]

Slow- and controlled-release (SCR) nitrogen (N) fertilizers improve crop production and N utilization efficiency. However, responses of biological soil characteristics to the long-term application of N fertilizer have received little attention. In this work, a five-year field experiment was performed to assess the influence of different N fertilizer treatments (no N fertilizer application [CK] and applications of polymer-sulfur coated urea [PSCU], conventional prilled urea [PU], and urea-formaldehyde [UF]) on soil microbial communities in yellow clayey paddy soils in southern China. The types of N fertilizers had a stronger impact on soil bacterial diversity and community structure than fungal diversity and community structure. The soil microbial communities of PU and UF treatments did not differ from those of CK regarding alpha diversity indices. However, the PSCU treatment significantly decreased the Shannon index by 2.16% for bacteria but had no significant effect on the Shannon index of fungi. This might be due to the application of PSCU significantly reducing the soil pH by 0.16 units compared to CK and leading to soil acidification. Co-occurrence network analysis determined the keystone species mainly belonging to Proteobacteria and Ascomycota. Notably, these keystone species played an important role in PSCU-treated soils. Soil Ca2+, Na+, and NH 4 + were the main determinants of microbial network stability. These results contribute to our understanding of how SCR-N fertilizers impact soil microorganisms. • The application of polymer-sulfur coated urea significantly reduced soil pH. • Nitrogen fertilizer types had more significant effects on soil bacterial diversity. • Nitrogen fertilizer types significantly affected soil bacterial community composition. • Soil nutrient availability played critical role in driving microbial community change. [ABSTRACT FROM AUTHOR]

Phosphorus (P) interacts with soil constituents in many ways, forming compounds of distinct stabilities in a number of chemical inorganic and organic forms. The identification of these P compounds in tropical agro-ecosystems is especially relevant to understanding potential P availability in these common P-fixing soils, providing information to improve P use efficiency. In this study, we investigated P partitioning and speciation in Brazilian Cerrado Oxisols under different management systems using a combination of sequential chemical P fractionation (SPF), P K-edge XANES and 31P NMR spectroscopy. Topsoil (0–10 cm) samples were obtained from soils under three management regimes, including native vegetation (Cerrado), no-tillage (NT), and conventional tillage (CT) agriculture. Four representative agricultural sites in the Brazilian Cerrado were selected: Ox-1 (Costa Rica-MS), Ox-2 (Sapezal-MT), Ox-3 (Cristalina-GO) and Ox-4 (Tasso Fragoso-MA). In all sites, the soils are classified as Typic Hapludox, varying in cultivation time, soil clay content and oxide types. Long-term cultivation in NT and CT led to large P accumulation in the soil. Chemical P fractionation indicated that labile P was the smallest pool at all sites. P K-edge XANES showed that P is mostly sorbed to the Fe and Al hydr(oxides), goethite, hematite and gibbsite. It also showed that phytate was the predominant organic P species, depleting in sequence from native vegetation to NT and CT management systems. 31P NMR showed that monoester P was present in all soils and management systems, whereas diester-P was found only in soils under native vegetation. The combined use of SPF, XANES and 31P NMR data was necessary to fully understand inorganic and organic P chemistry and reactivity in these tropical agricultural croplands. • Soil P fractionation (SPF) was useful to identify labile P. • Like SPF, P K-edge XANES detected the majority of P sorbed on Fe/Al oxyhydroxides. • 31P NMR identified recalcitrant monoester-P as the major form of organic P. • 31P NMR identified diester-P only in the soils under native vegetation. • SPF, XANES and NMR should be combined for a clearer image of P in tropical soils. [ABSTRACT FROM AUTHOR]

Rapid transport of water and solutes through desiccation soil cracks can lead to crop water and nutrient stress. The challenge of irrigation management of cracking soils is to take advantage of the rapid water intake rate of a dry, cracked soil, while keeping plant water stress at a minimum. Therefore, mitigation not suppression of desiccation cracks is imperative and considered our objective of this study. A laboratory experiment was carried out to investigate the effects of sugarcane pith additive on mitigating desiccation cracks, the volumetric shrinkage strain, the total porosity, and water retention at field capacity of clay soils. The clay soil was treated with the sugarcane pith at dosages of 1, 2, 3, 4 and 5% on dry weight basis. Various experimental methods were used to determine the variations in volumetric shrinkage, total porosity and water retention at field capacity. The characteristics of crack patterns were studied using an image processing technique. Compared with the untreated soil, the results showed that the sugarcane pith can increase the total porosity and water content at field capacity, while reducing volumetric shrinkage strain, and consequently, mitigating the development of desiccation cracks. Therefore, results suggested that the modification of clayey soil by the addition of the sugarcane pith by rates up to 2% on dry weight basis can be a viable and innovative method to mitigate the development of desiccation cracks. In addition, this application will enhance recycling efforts by converting sugarcane pith waste into usable amendment to mitigate cracks in clayey soil. [ABSTRACT FROM AUTHOR]

Subsurface drain trenches are important pathways for water movement from the field surface to subsurface drains in low permeability clayey soils. The hydrological effects of trenches installed with well conducting backfill material and gravel inlet patches are difficult to study with only experimental methods. Computational three-dimensional soil water models provide additional tools to assess spatial processes of such drainage system. The objective was to simulate water flow pathways with 3-D FLUSH model in drain spacing and trench depth scale with two model configurations: (1) the total pore space of soil was treated as a single continuous pore system and (2) the total pore space was divided into mobile soil matrix and macropore systems. Both model configurations were parameterized almost solely with field data without calibration. Data on soil hydraulic properties and drain discharge measurements were available from a clayey subsurface drained agricultural field in southern Finland. The effect of soil hydraulic variability on water flow pathways was assessed by generating computational grids in which the hydraulic properties were sampled randomly from five measured soil sets. Both model configurations were suitable to describe the recorded drain discharge, when model was parameterized in finer scale than drain spacing and the parameterization described highly conductive subdomains such as macropores in a dual-permeability model or the trench in a single pore system model. Models produced similar hourly discharge and water balance results with randomly sampled soil hydraulic properties. The results provide a new view on consequences of soil heterogeneity on subsurface drainage. The practical implication of the results from different drainage scenarios is that gravel trench appears to be important only in soils with a poorly conductive subsoil layers without direct macropore connections to subsurface drains. Solely drain discharge data was not sufficient to determine the differences in water flow pathways between the two model configurations and more output variables, such as groundwater level, should be taken into account in making assessments on the effects of different drainage practices on field drainage capacity. [ABSTRACT FROM AUTHOR]

In a two year minirhizotron study (2011 and 2012), the root growth, yield and fruit quality responses of six melon genotypes to two locations with different soil types were investigated. The field experiments were conducted in south Texas at two locations viz. Uvalde with clayey (hyperthermic aridic calciustolls) and Weslaco with sandy loam (hyperthermic typic calciustolls) type soils, with subsurface drip irrigated using black plastic mulch. Root length intensity ( L a , cm cm −2 ), marketable (MFY), total fruit yield (TFY; t ha −1 ), fruit firmness (N) and soluble solids content (SSC; °Bx) of four TAMU inbreds and two commercial hybrids, Mission and Journey were measured. Root length intensity was lower in 2011 than in 2012, possibly due to the variations in climatic, and soil conditions, and minirhizotron tube artifacts. Sandy loam soil produced 77% higher L a (1.6 vs. 0.9 cm cm −2 ) as compared to clay soil. Under sandy loam soils, root growth distribution was deeper (40–70 cm) while it was confined at the depth of drip tape (<30 cm) in clay soils, which indicated that root growth distribution varies with soil type even under same irrigation system. Clay soils produced 40% and 24% higher MFY and TFY respectively as compared to sandy loam soils, most likely due to longer growing season at Uvalde. Texas A&M melon inbreds had similar L a to most popular commercial cultivar Mission and higher L a than Journey. These results reveal that under high input intensive production systems large root systems may not be required for high yielding potential, however under sandy loam soils cultivars vary in their root distribution patterns across soil depth. Further, the great rooting ability of TAMU breeding lines under different soil types and equivalent yield potential to commercial hybrids confirms their suitability as a potential parent for developing genetically improved and stable cultivars for a wide range of environments. [ABSTRACT FROM AUTHOR]

The shrinkage and swelling behaviors of clayey soils could lead to cracks and erosions inducing severe damages to agricultural lands and engineering projects. Thus, improving the understanding of shrink-swell characteristics is crucial to nonrigid soils. However, it remains difficult for in-situ monitoring of soil shrink-swell processes continuously and nondestructively. The objective of this study was to present a thermo-time domain reflectometry (thermo-TDR) technique for determination of soil shrinkage and swelling dynamics and hydro-thermal regimes in-situ during wet-dry cycles. A field experiment on two clayey soils (a paddy soil and an alluvial soil) was conducted to evaluate the performance of the thermo-TDR method for in-situ determination of soil volume changes and associated hydraulic and thermal properties during wet-dry cycles. The results showed that both soils experienced considerable shrinking and swelling processes with maximum vertical deformations of 2.4 and 1.8 cm for the paddy soil and alluvial soil, respectively, and with maximum horizontal deformations of 370 and 280 cm2 for the paddy soil and alluvial soil, respectively, during a 36-day period. The thermo-TDR method provided volume change values (shown as the bulk density) agreed well with independent core-sampling measurements with an average RMSE of 0.15 Mg m−3 and a R2 of 0.46. A better agreement was observed between thermo-TDR measured bulk densities and values from the ruler-image processing method with an average RMSE of 0.07 Mg m−3 and a R2 of 0.77. Besides, the thermo-TDR method gave consistent in-situ soil shrinkage curve and water retention surface measurements by combining with soil matric potential sensors. Unlike rigid soils, the paddy and alluvial soils showed complicated hydro-thermal regimes in response to the shrink-swell processes. We conclude that the thermo-TDR technique is a reliable tool for continuous in-situ determination of soil shrink-swell processes. Future studies should focus on development of comprehensive soil heat and water transport models accounting for both moisture content and volume changes. • A thermo-TDR technique determines soil shrink-swell behaviors accurately in- situ. • New approach produces in- situ shrinkage curves and water retention surfaces. • Shrinkage and swelling have significant effects on soil hydro-thermal regimes. • Paddy soil is susceptible to the shrink-swell behavior than alluvial soil. [ABSTRACT FROM AUTHOR]

Tillage and nitrogen (N) fertilization have been shown to affect soil abiotic and biotic properties, but it is unclear how these impact long-term tillage systems in subtropical climates. We studied a 48-y wheat cropping trial in semi-arid, subtropical Australia that applied different tillage practices (no-till [NT] and conventional till [CT]) and N fertilization rates (0 and 90 kg N ha-1, 0 N and 90 N, respectively) in a Vertisol from 0 to 10 cm soil depth. Total organic carbon (TOC) significantly increased only when N fertilizer was applied under NT. Total nitrogen (TN) concentrations increased when N fertilizer was applied but were unaffected by tillage. N-acetyl-β- D -glucosaminidase (NAG) activity was highest when N was applied and α-glucosidase (α-Glu) activity was lowest in the NT and 0 N treatments. Activities of β-glucosidase, phenol oxidase and phosphatase were unaffected by the management practices. While the bacterial community composition appeared most distinct in NT and 0 N conditions, fungal community composition, and bacterial and fungal alpha diversity remained unaffected by the treatments. Although wheat yield was only significantly influenced by N fertilization rates, both NT and N fertilization may be preferable for management as these soils had the most favorable TOC, TN, and enzymatic activity. These differences seen between treatments here are less pronounced than reported elsewhere, with this likely a result of the high clay content of the soil which can have a buffering capacity, or that these treatments have less of an impact over longer time scales. Nevertheless, we conclude that no-tillage and N fertilization remain important in influencing soil properties and functioning over decades in this Vertisol in a semi-arid subtropical region. • Total organic carbon significantly increased when N was applied under no-till (NT). • Total N increased when N fertilizer was applied but there was no effect of tillage. • N-acetyl-β- D -glucosaminidase activity was highest when N was added. • Bacterial community composition was most distinct in NT and no N addition treatment. • Fungal community composition and bacterial alpha diversity were not affected. [ABSTRACT FROM AUTHOR]

The expansion of irrigation infrastructure in Tasmania, Australia, has led to intensified irrigated crop production, including for vegetables. This has resulted in increased irrigation of texture contrast soils, and other soils with high clay content in the subsoil. Widely used for rain-fed grain production in other parts of Australia, these soils have been subject to a range of soil amelioration approaches in an effort to improve their soil physical characteristics and capacity to produce crops. Subsoil manuring – the process of placing organic soil ameliorants at a target depth using a specially modified deep ripper – has proven to be successful in increasing yields of rain-fed grain crops. Locally available organic materials (chicken manure and poppy seed meal) were placed in the upper zone of a clay subsoil at three sites used for irrigated vegetable production. The crops grown were green peas for processing and carrots for seed production. Normal grower management practices were the reference against which treatments were compared. Subsequent measurements showed no consistent or significant benefit from subsoil manuring one year after treatment under the soil and crop management conditions used in this research. • Subsoil manuring has shown productivity benefits in rain-fed grain production. • Irrigated vegetables were grown on treated texture contrast and high clay soils. • No significant differences were found as a result of subsoil manuring treatments. [ABSTRACT FROM AUTHOR]

Adhesion between metal surfaces and soil can have significant effects on soil-tool interaction. The cone pull-out test (CPT) and piston pull-out test (PPT) for adhesion assessment were used in this study on smectite, illite and kaolinite clays at different water contents. In the CPT, the tangential adhesion stress (TAS) and cone adhesion (CA) were measured. In the PPT, the normal adhesion stress (NAS) and piston adhesion (PA) were measured. The results showed that the NAS and TAS depended on the type of clay. The ratios of NAS to TAS for smectite and kaolinite had the largest and smallest values, respectively. For all three types, NAS and TAS decreased as the water content (W) decreased. An increase in the thickness of the water film at the soil-metal contact surface reduced the stress required to separate the metal from the soil. The relationship between CA-W and PA-W for the three clay types differed. For smectite, a change in water content had no effect on CA or PA. For illite, an increase in water content decreased the CA and PA. For kaolinite, a bell-shaped curve formed such that, as water content increased, where WLL, CA and PA decreased. For all three clay soil types, NAS and PA were higher than TAS and CA at a specific water content. This demonstrated the effect of the metal-to-soil contact geometry on the adhesion parameters. The NAS and TAS values were classified in terms of clogging potential. Clogging potential is the adhesion of soil to the cutting tools or conveying system. The selection of the use of the CPT or PPT for adhesion assessment depended on the phenomenon being studied. • The metal-to-soil contact geometry does affect on adhesion parameters. • The normal adhesion stress (NAS) was higher than the tangent adhesion stress (NAS). • The piston adhesion (PA) was higher than the cone adhesion (CA). • The NAS and TAS decreased as the water content decreased. • There is linear relationship between NAS and TAS. [ABSTRACT FROM AUTHOR]

Organic wastes, fertilizers, organominerals, and minerals contain nutrients essential to crops and contribute to increase productivity. However their use can also lead to the accumulation of copper and zinc, which changes the distribution of their fractions and enhances the risk of toxicity to plants and the environment, thereby working against the sustainable development goals. However, the effect of manure applications on clayey soils and the effects of increasing Cu and Zn contents over the years on crop productivity remain unknown. This study aimed to evaluate the distribution and the potential for contamination of heavy metals in clayey soil with a history of the application of different types and amounts of fertilizers under Cynodon spp. grazing and no-tillage system for soybeans. In Experiment 1, Cynodon spp. were cultivated for hay production and submitted to applications of the following treatments: 0, 200, and 400 kg ha−1 of total-N in the form of pig slurry and urea. In experiment 2, the soybean was grown and subjected to the following treatments: control, pig slurry, commercial granulated solid organic fertilizer, organomineral fertilizer blended with granules, and mineral fertilizer blended with granules. The dose of each nutrient source was determined based on the soil analysis and the recommendations of the liming and fertilization manual. The experiments were conducted for four agricultural crops where soil samples were collected in the layer of 0.00–0.10 m layer and submitted to chemical fractionation of Cu and Zn. The use of pig manure increased the availability of Cu and Zn in the soil, causing an increase in the distribution of copper organic (40.73% and 57.64% for PS200 and PS400 treatments, respectively, in Experiment 1; 67.33% for PS treatment, in Experiment 2) and residual fractions (10.01% and 7.60% for PS200 and PS400 treatments, respectively, in Experiment 1; 9.80% for PS treatment, in Experiment 2), while zinc was predominant in clay-mineral (61.04% and 92.01% for PS200 and PS400 treatments, respectively, in experiment 1; 278.90% for PS treatment, in Experiment 2) and residual fractions (2.36% for PS200 treatment in experiment 1; 9.90% for PS treatment, in Experiment 2). Additionally, the use of swine manure increased the Cu and Zn contents in the exchangeable fraction, which may potentiate the toxicity to plants and increase the potential for contamination of subsoil water. However, the increased bioavailability of Cu and Zn did not caused a loss of crop productivity but instead increased dry mass production and crop yield. • Use of PS in the highest dose increases Cu and Zn available contents in the soil. • Use of PS accumulates Cu in the organic and residual fractions. • Use of PS accumulates Zn in the mineral and residual fractions. • There was no harm to Tifton 85 DM the accumulative production over the years. • There was no harm to soybean DM accumulative production and productivity over the years. [ABSTRACT FROM AUTHOR]

Cement and other traditional materials are frequently used to improve the properties of soil in the Yellow River Basin, the ecological environment has become severely polluted. To promote the environmental protection strategy of sustainable development, environmentally friendly biopolymers were used to treat typical silt samples collected from the Yellow River Basin. The water retention characteristics and vegetation growth of the treated silt were evaluated, and the microscopic mechanism of the water retention characteristics was investigated. The results show that the water retention capacity of the treated silt increased upon increasing the ratio of xanthan gum, gellan gum, and guar gum, with gellan gum performing better than the other two gums. The biopolymers had no discernible effect on the vegetation germination, but effectively promoted vegetation growth with a significantly lower wilting rate than that of the untreated soil. The soil treated with xanthan gum had the highest germination rate and vegetation growth height, while soil treated with gellan gum had the lowest wilting rate. The superior performance of gellan gum and xanthan gum can be attributed to their hydrophilicity and adhesion. These gums directly interact with the surface of charged clay particles in the soil pore space to closely connect the particles, reduce water loss, and increase the water retention capacity. The better soil water retention capacity is associated with improved germination and vegetation growth. • Water retention characteristics of biomolymer-treated soil in wide suction range. • Different biopolymers' effects on vegetation growth in treated soil. • The water retention capacity of treated silt increases as the ratio increases. • The water retention capacity of gellan gum was better than xanthan gum and guar gum. • The rate of wilting in treated soil was significantly lower than in untreated soil. [ABSTRACT FROM AUTHOR]

The degree of soil compaction is affected not only by the agricultural machinery but also by the soil physical, chemical, and mechanical properties. We hypothesized that the changes in the soil physical (clay content) and chemical properties (soil organic matter, SOM) due to long-term tillage operations would cause corresponding variations in the soil mechanics properties. The in-situ undisturbed soil samples were firstly adopted to detect soil properties as affected by long-term conventional tillage of Mollisol (black soil), and explore the relationship between soil physico-chemical properties and mechanical properties with 4 different cultivation duration croplands (0, 17, 30, and 40 yr). Then, artificial modified soil samples were further used to verify this relationship and confirm the predominate factor influencing compression-rebound behavior at 3 levels of SOM and clay contents, respectively, at 2 levels of gravimetric water contents. The compression index (C c) and rebound index (C r) were determined using a fast oedometer test. We found that with cultivation duration extending, the clay content and soil bulk density increased, while the SOM, C c and C r gradually decreased. The laboratory simulation tests also showed that the compressibility was higher when SOM or clay content was higher; while the soil resilient capacity was lower when the SOM was lower or clay content was higher. In conclusion, the decrease of SOM and the increase of clay content due to long-term cultivation could increase the risk of soil compaction and weaken its recovery capacity. SOM is predominant in influencing the soil mechanical properties relative to clay content. Maintaining and/or increasing SOM may improve the mechanical properties of arable Mollisols. • Long-term conventional tillage decreases SOM and increases clay content. • Both SOM and clay content affect the compression and rebound behavior. • SOM is predominant in governing the mechanical properties of Mollisols. • SOM acts as an early warning signal for evaluating mechanical properties. • In-situ and indoor simulated test can be complemented and verified mutually. [ABSTRACT FROM AUTHOR]

Erosion and colloidal particle loss from cultivated clay soils in cool humid climate pose a risk to soil productivity and surface water quality. To enhance soil management practices that effectively reduce clay soil erosion, we need to understand the interrelations between the key variables on which clay soil aggregate structure depend. The objective of our study was to quantify the relative importance of OC content, land use and soil wetness, for the aggregate stability of post-glacial clay soils. We estimated the potential effect of five different land uses (cereal cropping with variable tillage and crop rotation, permanent grassland and forest as a control) on clay soil aggregate stability as measured by the percentage of water-stable aggregates (WSA% of 2–5 mm fraction) and colloid detachment (turbidity, NTU%), after controlling for the differences in organic carbon content (OC%) and Clay%/OC% ratio between the land uses through covariance analysis. Further, we assessed how aggregate structure in differently managed soils with different OC% tolerates the varying moisture conditions. The higher OC% was reflected in all cultivated soils by increased aggregate stability, implying that OC inputs may positively affect soil structure even in low additions. When compared at equal OC%, the mean WSA% was lower in cereal cropping than in soils under forest or permanent grass, clearly showing the negative effect of tillage frequency on the aggregate stability. The detachment of colloidal particles from aggregates was higher in soils with a high Clay%/OC% ratio, and thus the Clay%/OC% ratio may offer an easily measurable indicator for the risk of clay dispersion, and thereby soil erosion and the export of particle-bound nutrients from cultivated fields. When compared at an equal Clay%/OC% ratio, colloid detachment from aggregates representing cereal fields was two- to threefold as compared to permanent grassland. Cultivated soils with less than 4–6% OC were very sensitive to waterlogging, highlighting the role of proper drainage in erosion control. The results demonstrate that an increase in OC content and proper drainage would help to improve the aggregate stability of cultivated clay soils in cool humid climate, but the effective improvement of the present situation would require drastically reduced soil disturbances for areas with the highest erosion risk. [ABSTRACT FROM AUTHOR]

Soil compaction by vehicular traffic modifies the pore structure and soil hydraulic properties. These changes potentially influence the occurrence of preferential flow, which so far has been little studied. Our aim was to study the effect of compaction on soil hydraulic and transport properties in subsoil. A randomized block design trial at two sites on a well-structured clay soil in central Sweden was established. Plots with two levels of compaction were created at both sites, in the following referred to as trafficked and control. The trafficked treatment was created by 4 passes track-by-track with a three-axle dumper with a maximum wheel load of 5.8 Mg. After one year, undisturbed soil columns (20 cm height × 20 cm diameter) from both trafficked and control plots at a depth of 30–50 cm were sampled. The columns were analyzed using X-ray CT imaging, together with measures of the degree of preferential transport derived from non-reactive tracer breakthrough curves and measurements of saturated hydraulic conductivity ( K s ) and air permeability at the field moisture content ( K a ). Although the traffic treatment did not cause any compaction effects at one of the two sites, it did result in significant reductions in saturated hydraulic conductivity, air permeability and number of macropores at the second site. At this site, the traffic also significantly reduced the strength of preferential flow, presumably due to compaction-induced disruption of macropore continuity. In apparent contrast, some previous studies have shown increases in the strength of preferential flow as a result of compaction. We propose a conceptual model to explain these apparently contradictory results, which suggests that preferential flow should be strongest at some intermediate level of compaction. [ABSTRACT FROM AUTHOR]

Biochar represents a soil conditioner that can change the physical and hydraulic properties of the soil. To date, little information is available about the biochar-induced changes on physical and hydraulic properties of fine textured soils. Therefore, an evaluation of its effects before the field use is advisable. The main objective of this investigation was to evaluate the impact of biochar addition on saturated ( K fs ) and unsaturated ( K ( h )) hydraulic conductivity, water retention, capacitive indicators such as macroporosity ( P mac ), air capacity (AC), plant available water (PAWC) and relative field capacity (RFC, equal to the ratio between field capacity and saturated soil water content), dry bulk density ( ρ b ) of a repacked clay soil. Biochar effects on simulated wheat yields were also evaluated using the DSSAT model. Five levels of amendments (0–5–10–20–30 g biochar per kg −1 soil) were used and the soil columns remained in the field for about 30 months until undisturbed soil conditions were reached. No significant differences of the K fs values were detected between amended and unamended soils and the ratio between K fs values was, on average, equal to a factor of 1.01–0.93–0.98–1.25 (respectively for C5–C10–C20–C30). In the same way, biochar did not affect appreciably the K ( h ) values. Depending on the applied pressure head or the biochar concentration, the differences were within a factor of 0.83–0.39. On the contrary, significant increases of soil water retention were detected close to water saturation (0 < h < −10 cm) for the highest biochar concentration. This behavior resulted in an imbalance between the liquid and gaseous phases of the soil. The relative field capacity, that gives an account of the optimal balance between water capacity and air capacity of the soil, was lower than the critical limit of 0.6, suggesting excessive soil aeration. Since these results are coupled to non-significant differences in ρ b values, our results confirm that small decreases in bulk density (on average, 0.014 g cm −3 ) may result in appreciable modifications in soil water retention close to water saturation. The simulations carried out with DSSAT suggested that a moderate addition of biochar to a clay soil (not higher than 10 g kg −1 ) has the potential to increase the production of durum wheat (mean increase ± standard deviation, 236 ± 126 kg ha −1 ). These findings will have to be verified under field conditions. [ABSTRACT FROM AUTHOR]

Sustainable agriculture intensification requires optimization of agriculture resources such as new fertilizers with higher nutrient use efficiency. Biochar has been a promisor alternative not only as a P source but also as a matrix to host P fertilizer to improve its use efficiency by intrinsic features. In our previous work, biochar enriched with P lead to higher sugarcane biomass yield and P use efficiency than conventional P fertilizer in a greenhouse trial, however, the effects of biochar enriched with P in the fate of available-P were not plenty understood. In this work, we investigated the superior P availability after fast-pyrolysis biochar-P fertilizer (BioFert) over the incubation time of 240 days in three distinct soils (sandy, loamy and clayey), evaluating the available-P by an anionic exchangeable membrane (AER) and bicarbonate solution extractions, as also solid P speciation by X-ray Absorption Near Edge Structure (XANES) analysis performed at a Synchrotron source. The AER results showed that available-P in BioFert treatment was, on average, 14% superior in sandy, 56% in loamy, and 72% in clayey soil than triple superphosphate (TSP). XANES results pointed out Al- and Fe-phosphates as the main P-sink for all soils, however both fertilizers introduced P-Ca in the system. The superiority of BioFert was associated with its capacity to buffer the soil pH in values higher than 7 potentially reducing P immobilization. In summary, results support the higher efficiency of BioFert than TSP observed in previous work because it supplies more available P synchronized to plant demand over time. [Display omitted] • Available-P in Biofert was, in average, 14% superior in sandy, 56% in loamy and 72% in clayey soil than TSP • Superiority of Biofert was associated to its capacity to buffer the soil pH. • Al- and Fe-phosphates are the main P-sink for all soils, however both fertilizers introduced P-Ca in the system. • The higher efficiency of Biofert than TSP because it supplies more available P synchronized to plant demand over the time. [ABSTRACT FROM AUTHOR]

Biochar is a beneficial amendment for fine-textured soils. In addition, the interaction of biochar particles with soil components influences the dynamics of water and ions, which is particularly important to remediate salt-affected soils. We investigated the effect of sugarcane bagasse (SB), orange bagasse (OB), and corncobs (CB) biochar on water movement and ion leaching in clayey soil. Non-amended soil (CT) column and soil amended with gypsum (CTG) served as controls. Water infiltration, water flow rate, cumulative leached cations, anions, and exchangeable cations (Ca2+, Mg2+, K+, and Na+) were determined. Biochar increased the water infiltration and water flow rate by 80% and 71%, respectively. The SB and CB treatments increased the ion removal from the soil by 48%, whereas the OB increased the removal by 19%. The OB´s lower surface area and water holding capacity likely influenced its performance. Biochar reduced the Ca2+ and Mg2+ concentration on the soil exchange complex by 44% and 76%, respectively, and increased K+ by 233%. However, the most exciting result was the reduction of exchangeable Na+, 90% in the SB and CB treatments and 50% in the OB treatment. Considering that a high concentration of Na+ on the exchange complex contributes to soil structural degradation, biochar application, especially SB and CB, can potentially improve soil quality and mitigate salt-affected soils. [Display omitted] • All biochars increased the water infiltration and distribution in the clayey soil. • Biochar showed a selective affinity for cations and anions in the soil. • All biochars promoted Ca2+ and K+ leaching. • Sugarcane biochar increased Na+ removal from the soil. • Biochar can potentially improve the soil´s mechanical and hydraulic properties. [ABSTRACT FROM AUTHOR]

The dynamics of soil structure is caused by biotic and abiotic processes, with the onset and magnitude of deformation controlled by soil rheological and mechanical properties. Quantification of such properties is challenging because soil behaviour changes with soil moisture, but common rheological tests are not applicable over all consistency ranges. Here, we combine oscillation shear rheometry with spherical indentation mechanical measurements of soil to obtain greater characterization over a broader range of water contents. The elastic modulus could be measured with either approach, with good agreement found for measured silt and clay textured remoulded agricultural soils. For shear rheometry, plastic viscosity, complex modulus and shear yield stress were also obtained. The spherical indentation provided measurements of hardness and yield stress. Although yield stress was correlated between approaches, the values were orders of magnitude greater for the indenter (0.54 ± 0.33 kPa vs. 34.4 ± 31.2 kPa), presumably because of different loading and failure conditions. At drier water contents, yield stress varied more between the two tests on the clay soil, which corresponded with brittle fracture creating artefacts in shear rheometry measurements. Spherical indentation has not been widely applied to the testing of soils, but the good agreement over a wide water content range between elastic modulus obtained from spherical indentation measurements (0.66 ± 0.27 MPa in wetter zone to 4.45 ± 2.53 MPa in drier zone) and shear rheometry (0.47 ± 0.11 MPa in wetter zone to 2.02 ± 0.98 MPa in drier zone) is promising. Moreover, spherical indentation can be applied to materials varying from brittle to viscous and allows testing on structurally intact soil aggregates. The geometry of a spherical indenter may more closely mimic contacting soil aggregates, so scope exists to extend the approach to explore the slumping of aggregated seedbeds produced by tillage. • Spherical indentation and shear rheometry tests on soil pastes were combined • Testing range extended to broader water contents, from viscous to brittle behaviour. • Elastic modulus measurements similar with both approaches. • Yield stress differed by orders of magnitude between tests. • Future potential to apply spherical indentation to structured soils. [ABSTRACT FROM AUTHOR]

Intensive soil disturbance by conventional tillage and heavy machinery traffic for planting, cultivation, and harvesting operations are the main causes of soil compaction and degradation of soil physical quality in sugarcane fields. However, the adoption of conservation soil tillage practices, such as no-till and reduced tillage associated with traffic control have been proposed as a key strategy to preserve soil physical quality, enhancing water availability and air fluxes. Nevertheless, the effects of reduced tillage associated with traffic control in sugarcane fields are still not well documented. A study was carried out to quantify soil water availability and air flux indicators in two soils with contrasting textures (named Sandy Loam and Clayey soil) under conventional and reduced tillage practices associated with and without controlled machinery traffic in central-southern Brazil. Soil physical parameters such as bulk density, total porosity, air-filled porosity, air permeability, pore continuity index, and the least limiting water range (LLWR) were measured. In both soils, there was no difference between conventional and reduced tillage in bulk density, air permeability, and LLWR. However, reduced tillage with non-traffic decreased bulk density and increased macroporosity, air-filled porosity, air permeability, pore continuity, and LLWR in Sandy Loam soil. In Clayey soil, the bulk density and LLWR did not change between tillage practices, but air permeability and pore continuity index were larger under reduced tillage with non-traffic. These results highlighted that soil disturbance by conventional tillage does not improve the water availability and air permeability during the crop cycle. However, the traffic control is essential to support the adoption of reduced tillage in sugarcane fields, preserving soil water availability and air fluxes for the subsequent ratoons. Reduced tillage and traffic control are two of the most important pillars for reducing soil compaction and promoting sustainability of sugarcane production in Brazil. • Reduced tillage system did not negatively impact the least limiting water range (LLWR) compared to conventional tillage. • Reduced and conventional tillage system sustain similar air-filled porosity and air permeability. • Reduced tillage associated with traffic control increase LLWR in Sandy loam soils. • Traffic control is essential to support the adoption of reduced tillage in sugarcane fields. [ABSTRACT FROM AUTHOR]

The selection of an appropriate soil tillage system for improving yields and longevity is an important decision in sugarcane cultivation. In the present study, the effects of different soil tillage systems and methods of applying lime on sugarcane stalk and sugar yield performance as well as soil fertility parameters were evaluated throughout the sugarcane crop cycle. The experiments were established in two locations in April 2015 and conducted until August 2019, corresponding to a total of 4 growing seasons. A field study with a randomized block design was established with four replicates considering 4 treatments: conventional soil tillage system (CT), deep strip-tillage system (DT) and modified deep strip-tillage system (MDT), all with the same lime rate; and a standard treatment (control, CT without liming). Immediately after harvesting plant cane (18 months (mo) after planting), first ratoon (30 mo after planting), second ratoon (42 mo after planting) and third ratoon (54 mo after planting), soil samples were collected from a depth of 0.0–1.00 m, stratified every 0.2 m. Leaf material was sampled during the period of full vegetative growth. Analyses of soil chemical fertility, leaf concentrations of elements, and sugarcane yield components were performed. MDT was found to correct soil acidity most efficiently, mainly due to the positioning of the lime application. Under high aluminum saturation (AS), especially in deeper layers, deep lime placement was more effective and resulted in the best distributions of calcium (Ca2+) and magnesium (Mg2+), the highest base saturation (BS) and the lowest AS compared with the other treatments. Lime application was more important than the tillage system for improving the sucrose concertation and total recoverable sugar (TRS), whereas the tillage system affected the stalk yield and, consequently, the yield of sugar. Compared with DT and CT, the average stalk yield was 4.1% and 9.4% higher, respectively, under MDT at Macatuba and 6.3% and 15.3%, higher, respectively, under MDT at Piraju. Similarly, MDT improved average sugar yield by 3.7% and 10.4% at Macatuba and 6.1% and 16.3% at Piraju. Overall, long-term assessments, which are important for semi-perennial crops like sugarcane, showed that the both deep strip-tillage were most effective. • Strip-tillage system is an innovative soil tillage for sugarcane plantation. • Deep liming placement is important to reach longevity for sugarcane ratoons in highly weathered clayey soils. • Soil fertility is enhanced by deep liming placement. • Sugar and stalk yield is affected by the relation of lime application and tillage systems. [ABSTRACT FROM AUTHOR]

Prevention of soil compaction requires examining soil mechanical stability. This is usually done by applying the basic concept of the pre-compression stress σ p , assuming a fully elastic behavior for soils being loaded by stresses lower than σ p and a mixture of elastic-plastic behavior being loaded by higher stresses. However, a small cumulative plastic deformation may occur even when the applied stresses is not beyond σ p being indeterminable by current pe-compression test procedures which is not accounting for unloading steps. Therefore, we investigated an alternative approach to simultaneously determine σ p and mechanical elasticity of soil by introducing unloading steps (referred to as release compression, RC). Results were compared to the conventional procedure with continuously increasing loads (continuous compression, CC). In the case of RC, soil settlement was measured both after each loading (RC-L) and after each unloading (RC-U) phases between two consecutive pressures providing two load displacement curves. Oedometer tests were conducted with three different soils comprising different clay contents ranging from 75 to 454 g kg−1. Remolded soil was filled into steel rings and compressed under pre-determined loads in a loading frame providing test samples with known pre-compression stresses of 60 and 120 kPa. The results revealed that σ p values determined under two different applied loading paths (RC vs. CC) were significantly different. Both testing approaches resulted in an overestimation of σ p values based on stress-strain curves which was more pronounced for RC-L compared to CC paths. However, the results from RC-U paths were closer to the CC method than the RC-L path suggesting that if an unloading step is used, RC-U curve should be used to determine σ p values. The results also showed that soil with higher clay contents comprised the lowest σ p value determined from the oedometer tests among all examined soils. From release compression test, we were also able to determine the elasticity of the sample for each loading stress. Among the examined soil samples, the clay soil (with higher clay content) showed the highest elasticity index being less susceptible to soil deformation. • Determination of pre-compression stress (σ p) is stress-path depended. • Continuous multistep stress-path test predicts the known σ p with higher accuracy. • Loading-rebounding (LR) stress-path test predicts the known σ p with lower accuracy. • LR stress-path test allowed to determine soil elasticity for each stress level. • The accuracy of σ p prediction was highest for soils with higher clay contents. [ABSTRACT FROM AUTHOR]

Integrated weed management (IWM)-based cropping systems included diversified agricultural practices (i.e., diversified crop rotations with diversified sowing dates, false seed-bed technique, delayed autumn sowing and mechanical weeding) to reduce the dependence to herbicide, some of these influencing soil hydraulic properties. The aim of our study was to assess the vertical and annual variability of the near-saturated hydraulic conductivity K ( h ) for IWM-based cropping systems. The three cropping systems considered were classified as no-till cropping system S2 and moderate to intensive tillage cropping systems S4 and S5. The soil of cropping systems was a well-structured silty clay loam soil with shrink-swell behavior. Soil was studied at three depths (10, 20 and 50 cm) and during two or three annual measurement campaigns. The tension disc infiltrometer device was used to measure steady state flows at −5, −3, −2 and −1 cm pressure heads for all the cropping systems, horizons and measurement campaigns. The steady state flows were used to derive K ( h ) at each pressure head applied as well as the effective macroporosity. No vertical variability was found on K ( h ) for any of the cropping systems due to well-developed porosity networks throughout the soil profiles, confirmed by comparable average effective macroporosity values between all soil horizons and with the presence of non-equilibrium flows and water repellency behaviors at all soil horizons. The consequences for modeling the water flow of well-structured clayey soil imply taking into account comparable values of K ( h ) for all soil horizons and considerably simplifies the work of modelers. The no-till cropping system S2 presented time-invariable K ( h ) under different θ i , which was in agreement with the equally time-invariable macroporosity results. For cropping system S4, K ( h ) variability was found to be in agreement with θ i variability, which was confirmed to be inversely correlated to K ( h ). As expected, the K ( h ) of cropping system S5 was found to be stable through time, in agreement with its comparable θ i Moreover, our results allowed confirming the temporal stability of no-till cropping system S2 compared to superficially tilled cropping systems S4 and S5. [ABSTRACT FROM AUTHOR]

Soil compaction has always been a problem to the agricultural productivity, mainly in clayey soils under the no-tillage (NT). Alternatives to mitigate this problem are necessary. The aim of this study was to evaluate the effect of seeder equipped with fixed shanks openers, working at three depths, in a Ferralic Nitisol (Rhodic), under NT on the mitigation of soil compaction and corn ( Zea mays L.) plant development. The test comprised three treatments regarding the depth at which the shank openers of a seeder used to sow corn worked: openers reaching up to 0.05 m; openers reaching up to 0.07 m; and openers reaching up to 0.17 m. The effect of these treatments was evaluated in relation to the determination of soil physical parameters, and corn plant parameters. The use of a seeder equipped with fixed shanks openers up to 0.17 m depth caused an increase in soil macroporosity and total porosity, and a decrease in soil bulk density, soil resistance to penetration and degree of compactness in the layer between 0.07 and 0.17 m. The improved physical conditions of the soil in this layer led to a further development of the root system of plants in greater depth, and consequently to a better development of corn plants with higher stalk diameter, root density and root length. The use of a seeder equipped with fixed shanks openers working up to 0.17 m depth, therefore, promoted physical improvement to the soil, favoring the development of corn plants, and presenting potential to mitigate the compaction of clayey soils under NT. [ABSTRACT FROM AUTHOR]

Dissolved organic matter (DOM) plays an important role in soil biological activity and transport of pollutants and nutrients in soils, but very little information is available with regard to the long-term impact of agricultural management practices on the dynamics and fate of DOM in acidic soils. The seasonal and inter-annual variation of dissolved organic carbon (DOC) and nitrogen (DON) contents and leaching were investigated in an acidic clay soil (Ferric Acrisol) by a long-term field lysimeter experiment in subtropical China. The experiment was conducted from 2002 to 2010 with 4 fertilization treatments under maize monoculture: no manure (CK), low-rate manure with 150 kg N ha −1 y −1 (LM), high-rate manure with 600 kg N ha −1 y −1 (HM), and high-rate manure with 600 kg N ha −1 y −1 and lime at 3000 kg Ca(OH) 2 ha −1 3 y −1 (HML). Manure application resulted in a seasonal variation of soil DOC and DON, and significant effects were observed by manure DOC, microbial biomass and soil water content. Soil DOC, which was mainly determined by soil organic matter and soil water content, increased yearly until the seventh year when it was stabilized. Manure application on acidic clay soil did not alter DOC leaching, whereas DON leaching clearly increased after three years of high manure application of 600 kg N ha –1 y –1 . The average annual DON leaching losses under long-term manure application had a range of 3.8–5.4 kg ha –1 , accounting for 6–11% of total nitrogen leached. The addition of lime, combined with manure application, produced no impact on soil dynamics and leaching of DOC and DON, with the exception of increasing emission of CO 2 . [ABSTRACT FROM AUTHOR]

Highlights: [•] We studied the long term impact of no till and conventional till on solute transport. [•] Clay content was positively correlated with velocity and dispersion in no till. [•] In conventional till no correlation was found with the studied soil characteristics. [•] Dispersion was higher in the soil with the highest clay content. [•] Structure was well preserved in the most clayey soil under no till. [Copyright &y& Elsevier]

Highlights: [•] Tillage had significant impact on SOC content, SOC storage, CPOM-C, KMnO4-C, and Cmin. [•] Significant positive correlations were observed among SOC content, CPOM-C, and Cmin. [•] CPOM-C was the most sensitive C-fraction to tillage changes. [Copyright &y& Elsevier]

For decades, conservation tillage has been promoted as a measure to increase carbon stocks in arable soils. Since organic farming improves soil quality and soil carbon storage, reduced tillage under organic farming conditions may further enhance this potential. Therefore, we assessed soil organic carbon (SOC) stocks of reduced tillage compared with mouldboard ploughing in nine organic farming field trials in France, Germany, the Netherlands, and Switzerland with the same sampling and analytical protocol. We sampled soil cores until a depth of 100 cm to determine soil carbon stocks that are relevant for climate change mitigation but are often overlooked in tillage studies with shallow sampling depths. The studied field experiments were between 8 and 21 years old and comprised different soil types with clay contents ranging from 10% to 50%. SOC stocks increased with increasing clay-to-silt ratio, precipitation and organic fertiliser input. Across sites, reduced tillage in comparison with ploughing increased SOC stocks in the surface layer (0–10/15 cm) by 20.8% or 3.8 Mg ha−1, depleted SOC stocks in the intermediate soil layers to 50 cm soil depth with a maximum depletion of 6.6% or 1.6 Mg ha−1 in 15/20–30 cm and increased SOC stocks in the deepest (70–100 cm) soil layer by 14.4% or 2.5 Mg ha−1. The subsoil SOC stock increase may be linked to the inherent soil heterogeneity. Cumulative SOC stocks increased by 1.7% or 1.5 Mg ha−1 (0–50 cm, n = 9) and 3.6% or 4.0 Mg ha−1 (0–100 cm, n = 7) by reduced tillage compared with ploughing with estimated mean C sequestration rates of 0.09 and 0.27 Mg ha−1 yr−1, respectively. There was no effect of field trial duration on tillage induced cumulative SOC stocks differences. Under reduced tillage, biomass production was 8% lower resulting in a decrease of crop C input by 6%. However, this reduction may have been outbalanced by increased C inputs from weed biomass resulting from a higher weed incidence in reduced tillage, which warrants further research. Thus, reduced tillage in organic farming has the potential to increase total SOC stocks, while crop management has to be improved to increase productivity. • Reduced tillage in organic farming has the potential for carbon sequestration. • Reduced tillage in organic farming stratifies SOC stocks similarly to no-till. • SOC stocks in subsoils affect the climate change mitigation evaluation of tillage systems. [ABSTRACT FROM AUTHOR]