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Different types of soil macropores respond differently to various tillage practices, owing to disparities in origin, scale, morphology, and function, consequently exerting distinct effects on soil structure. This study aimed to investigate the response mechanisms of three different soil pore types (total macropores, non-biopores, and biopores) to two distinct tillage practices: smash-ridging tillage (T) and no-tillage (NT) in sugarcane fields. The parameters characterizing soil pore treatments in two and three dimensions were obtained using X-ray computed tomography scanning technology. ImageJ and MATLAB software were employed to analyze the data and separate soil macropores into biopores and non-biopores categories. The results showed that non-biopores predominated in two-dimensional cross-sectional areas in NT treatment, whereas biopores were more dominant in T treatment. Biopores in T treatment had a higher proportion of two-dimensional pores compared to NT treatment. A three-dimensional analysis indicated that total macropores had larger mean diameters (MD) and macroporosity, with more continuous tubular pores in T treatment than that in NT treatment. However, NT treatment had more numerous non-biopores with broader spatial distribution and complex morphology. Additionally, biopores in T treatment had larger MD and branching length density (LD). These vertically developed biopores, along with high macropore connectivity and under smash-ridging tillage, could improve soil water and pore conductivity. Therefore, smash-ridging tillage was more beneficial for sugarcane growth compared to no-tillage in Guangxi of China. [ABSTRACT FROM AUTHOR]

Soil tillage is widely acknowledged to affect soil characteristics and agricultural productivity. This research investigates the short‐term effects of various tillage methods on soil physical properties and crop yields at a Central German field site with a dry climate (mean temperature 9.5°C; annual precipitation 470 mm). Three tillage approaches were evaluated: conventional plough tillage (25 cm depth), cultivator tillage (18 cm depth), and double‐layer plough tillage (15 and 30 cm depth). We assessed soil physical properties through standard laboratory analyses, compression tests, soil pore structure via X‐ray computed tomography (X‐ray CT) and crop yields over 3 years. The results indicate that cultivator tillage approach increased soil bulk density relative to conventional tillage, especially in the second year, though this effect diminished over time. Double‐layer plough tillage emerged as a viable short‐term alternative to conventional tillage, achieving comparable soil bulk density. Saturated hydraulic conductivity values were generally higher for soils under conventional tillage or double‐layer plough tillage than for cultivator tillage, highlighting their soil loosening effect. Classical soil analysis methods combined with X‐ray computed tomography provided valuable insights into tillage induced changes to soil structure. Cultivator tillage resulted in a distinct pore structure with reduced macroporosity and pore connectivity. Despite notable soil property variations, crop yields remained consistent across the tillage methods. Overall, double‐layer plough tillage presents a sustainable option, moderately improving soil physical properties while maintaining crop yields. This study highlights the need to assess the short‐term effects of tillage on soils and contributes to the broader dialogue on optimizing tillage strategies for effective soil management and crop production. [ABSTRACT FROM AUTHOR]

Sugarcane areas show a reduction in soil physical quality. However, few studies demonstrate the effect of sugarcane straw maintenance on soil physical quality along the crop cycle. This study aimed to evaluate and compare the soil physical quality in areas cultivated with sugarcane where straw was kept on soil, after the first and fourth harvests, with that of an area under native forest. Two areas cultivated with sugarcane, representative of the beginning and end of the production cycle, were evaluated in a clayey Oxisol. One area was evaluated after the first mechanical harvest (C1), while the other was evaluated after the fourth harvest (C4). These areas were compared to an area of native forest (NF). The data were subjected to multivariate principal component analysis. Agricultural areas cultivated with sugarcane showed reduction in soil physical quality compared to NF, presenting higher soil penetration resistance (SPR), soil bulk density (Sd) and microporosity (Mic). Sd was 13.7% higher in the C1 area, while in the C4 area such increase was only 5.1% compared to NF. The negative impact of sugarcane cultivation on soil physical quality is reduced after four harvests in areas with mechanical harvesting and where straw was kept on the soil, especially in the 0.00–0.20 m layer. [ABSTRACT FROM AUTHOR]

Soil tillage is a high-cost operation in the replanting of sugarcane fields. Thus, measures to reduce this cost are desirable, provided that they promote good physical conditions for sugarcane development. The objective of this study was to evaluate the effect of chiseling in total area and in the planting row on the physical attributes of Oxisol and Ultisol after soil tillage and after sugarcane planting. The experimental design was in large and uniform plots, with two treatments and ten replicates. The Oxisol and Ultisol had clay contents of 590 and 168 g kg−1 in the 0.00–0.40 cm layer. Treatments consisted of soil tillage with chiseling in the planting row and with chiseling in total area. After soil chiseling and after planting, undisturbed soil samples were collected in each experimental plot, in three layers (0.00–0.10; 0.10–0.20 and 0.20–0.40 m) and at two sampling sites (row and interrow). In both soils, chiseling in total area was efficient to reduce soil density and increase macroporosity in sugarcane interrows, compared to chiseling in the row. The values of the physical attributes of the soils evaluated, in rows and interrows, were similar in the areas with chiseling in total area and row chiseling after sugarcane planting. Changes in Oxisol and Ultisol structure due to chiseling did not persist after sugarcane planting. The soil under row chiseling system has physical quality similar to that of the soil under total area chiseling system, regardless of texture. [ABSTRACT FROM AUTHOR]

Cover crops promote nutrient cycling, and lime and gypsum can alter the soil physical attributes. This study aimed to evaluate the effect of lime and gypsum rates applied to a no-tillage system with addition of residues of three cover crops on the soil physical attributes. This experiment was carried out in chapadão do sul-ms. The treatments were comprised of three cover crops (Urochloa ruziziensis, fallow, and Pennisetum glaucum), with gypsum (0, 2.3 and 4.6 Mg ha-1) and lime applied at a dose of 0, 2, 4, 6 Mg ha-1).The attributes evaluated were: soil density, macroporosity, microporosity, total porosity and penetration resistance. The soil of the experiment was classified an Oxisol. Cover crops and lime and gypsum improved macroporosity, microporosity and total porosity at all depths, 0-0.2 m. Millet presented lower values for penetration resistance with the lime application and without gypsum application. No residual effect on soil density was detected for lime and gypsum application or cover crops in the 0.1-0.2 m layer. Brazilian Cerrado producers will have a well-defined management system to follow aiming at improving the soil physical attributes. [ABSTRACT FROM AUTHOR]

Abstract Zero-tillage (ZT) is being increasingly adopted globally as a conservationist management system due to the environmental and agronomic benefits it provides. However, there remains little information on the tillage effect on soil pore characteristics such as shape, size and distribution, which in turn affect soil physical, chemical and biological processes. X-ray micro Computed Tomography (μCT) facilitates a non-destructive method to assess soil structural properties in three-dimensions. We used X-ray μCT at a resolution of 70 μm to assess and calculate the shape, size and connectivity of the pore network in undisturbed soil samples collected from a long-term experiment (~30 years) under zero tillage (ZT) and conventional tillage (CT) systems in Botucatu, Southeastern Brazil. In both systems, a single, large pore (>1000 mm3) typically contributed to a large proportion of macroporosity, 91% in CT and 97% in ZT. Macroporosity was higher in ZT (19.7%) compared to CT (14.3%). However the average number of pores was almost twice in CT than ZT. The largest contribution in both treatments was from very complex shaped pores, followed by triaxial and acircular shaped. Pore connectivity analysis indicated that the soil under ZT was more connected that the soil under CT. Soil under CT had larger values of tortuosity than ZT in line with the connectivity results. The results from this study indicate that long-term adoption of ZT leads to higher macroporosity and connectivity of pores which is likely to have positive implications for nutrient cycling, root growth, soil gas fluxes and water dynamics. Highlights • Soil macro-porosity was higher under zero-tillage than conventional tillage. • Conventional tillage increases the number of pores but decreases the connectivity between them. • Zero-tillage presented lower values of pore tortuosity, indicating better connectivity. • Long term zero tillage improves soil pore connectivity. • 3D analyses of pore shape indicated difference between tillage systems. [ABSTRACT FROM AUTHOR]

There is a long-lasting debate about the effects of tillage practices on soil structure and structure-mediated ecosystem properties like hydraulic conductivity and crop productivity. This is investigated in a long-term field experiment on tillage practices at the Westerfeld trial in Bernburg, Germany (25 years of different management). Here we combine soil structure information obtained by X-ray microtomography with bulk properties like bulk density, air capacity and saturated hydraulic conductivity, as well as integrative, ecological properties like earthworm abundance and crop yield. This study goes beyond previous studies in that the soil microstructure is investigated in two different depths, within (13–23 cm) and underneath (28–38 cm) the plow horizon. Furthermore the microstructure is investigated at two different resolutions (60 μm and 20 μm) by employing a nested sampling design. The plowed horizon in the conventional tillage plots differs from the undisturbed soil underneath the cultivator depth (13–23 cm) in the reduced tillage plot by lower bulk density, higher air capacity, higher saturated hydraulic conductivity, higher macroporosity and pore connectivity. After 25 years of reduced tillage saturated hydraulic conductivity only marginally recovered in the abandoned plow pan (28–38 cm). Macropore density and connectivity did not change significantly as compared to the current plow pan under conventional tillage. The topsoil underneath the cultivator depth in the reduced tillage plot developed a “no-till pan”, as porosity and pore connectivity where smaller than in greater soil depths. Image-based macroporosity and laboratory-based air capacity showed good agreement. Overall, the combination of hydraulic measurements and X-ray CT imaging of soil microstructure at different resolutions provides a comprehensive view on soil structure modification by tillage practices. The change from conventional to reduced tillage led to a compaction of soil that was not compensated by higher bioturbation as reported for other sites. This is explained by unfavorable conditions for anecic earthworms (frequent dry periods with severely impaired penetrability of the loess substrate) as well as the absence of very deep rooting, perennial crops in crop rotation. [ABSTRACT FROM AUTHOR]

Tillage influences first soil structure and then soil organisms such as earthworms, which are highly involved in the creation of soil macroporosity. This study assessed the temporal dynamics of earthworm-related macroporosity in two ploughed and one unploughed cropping systems. Three sampling dates were chosen: one month before ploughing, and one and five months after the event. Earthworm communities, able to rebuild the macroporosity, were sampled one and five months after ploughing. Before ploughing, the burrow continuity, i.e., the number of burrows with a vertical length greater than 5 cm, was not significantly different in the three systems. It was stable between the three sampling dates in the unploughed system but it decreased by 65% and 46% after ploughing (i.e., in two months) in the organic and the conventional systems, respectively. Five months after ploughing, the burrow continuity remained between two and four times lower than in the unploughed living mulch cropping system. Earthworm biomass was higher and burrow system characteristics (i.e. burrow volume and continuity) were more stable over time in the non-tilled with a living mulch cropping system than in the tilled systems. Earthworm-produced macroporosity was thus substantially decreased after ploughing in conventional and organic systems and had still not totally recovered 5 months later. This can lead to large functional consequences on soil structure and thus on air and water fluxes in the soil. [ABSTRACT FROM AUTHOR]

• Crop intensification enhances soil macropores hydraulic conductivity compared to mono-cropping. • Long-term NT improves soil structure and water transport properties. • Soil water flux and pore continuity are greater within than between crop rows. • Intensive tillage creates non-persistent changes on soil hydro-dynamic properties. Soil hydraulic properties and pore continuity are important parameters of soil quality and may differ among tillage systems, crop rotations, and change over time. However, there are some contrasting results, depending on soil type, climate and cultivation history on the spatial and temporal variations. The objective of this study was to determine spatio-temporal dynamics of soil hydraulic properties and pore characteristics (i.e., pore volume, effective porosity, and continuity) on a silt loam long-term tillage field experiment, in Agramunt, NE Spain, during two cropping years. Undisturbed soil samples were used to determine soil water retention, θ(Ψ) , and soil hydraulic conductivity, K(Ψ) , curves in two different tillage systems (intensive tillage, IT vs no-tillage, NT), two crop sequences (short fallow-maize, FM vs legume-maize, LM) and two positions (within the row of crops, W-row vs between the rows of crops, B-row). The results revealed that LM had greater specific hydraulic conductivity, K pc in its macroporosity (>1000 µm) than FM due to greater number of effective pores, N pc and effective porosity, ε pc. Soil water content, θ was greater under IT than under NT at higher soil water matric potential, Ψ (≥-3 cm H 2 O), whilst the opposite was observed at lower Ψ (≤ − 50 cm H 2 O). Long-term NT showed greater hydraulic conductivity, K at higher Ψ (≥ − 10 cm H 2 O) than IT, and no difference at lower Ψ. Although IT had greater pore volume, ϕ pc than NT in the macroporosity and coarse mesoporosity (1000–60 µm) pore size classes, NT had two times greater K pc than IT due to increased N pc , ε pc , and pore continuity, C wpc. K(Ψ) and pore characteristics showed spatial variations (W-row vs B-row). W-row had significantly greater K at higher Ψ (≥ − 3 cm H 2 O) than B-row. Temporal dynamics of soil hydraulic properties and pore characteristics were not evident under IT during crop succession. This study shows that LM increases specific hydraulic conductivity of soil macroporosity by increasing the number of effective macropores and the effective porosity. In a Mediterranean climate, this may improve the hydrological functions of agricultural soil and associated crop yield. Further, long-term NT formed a stable number of effective macropores and coarse mesopores, and showed a greater pore continuity in coarse and fine mesopores, resulting in improved soil water flux. [ABSTRACT FROM AUTHOR]

Severe treading damage to soils often occurs when cattle and sheep graze standing forage crops during winter. Soil recovery is a long process that may take several months if not years. Noninversion tillage can speed up the recovery process by improving drainage and air diffusion. This research assessed the ongoing benefit of noninversion tillage for improving soil structure relative to non-tillage. This assessment was made following a land-use transition from winter forage cropping to re-establishment of seasonal pasture that was rotationally grazed by cattle or sheep. Prior to commencement of this study, the research site had poor soil structure due to four consecutive years of cattle and sheep grazing of winter forage crops [macroporosity (0-100 mm) <0.075 and 0.113 m3/m3 under cattle and sheep, respectively]. Tillage was effective in increasing soil macroporosity to ca. 0.175 m3/m3 under both grazing classes, which was significantly higher than nontilled soils (ca. 0.140 m3/m3, 0-100 mm depth). Improvements gained from tillage generally did not persist longer than 18 months. Average annual pasture production in tilled plots was 22.1 and 20.9 tons of dry matter per hectare (t DM/ha) for respective cattle- and sheep-grazed plots, while in the nontilled plots, it was 19.1 and 18.6 t DM/ha, respectively. Results indicate noninversion tillage can provide an immediate increase in the porosity of compacted soils and improve pasture growth. However, processes involved in the formation of resilient soil aggregates are curtailed if subsequent grazing events coincide with high moisture content that causes recompaction. [ABSTRACT FROM AUTHOR]

Soil structure influences the soil hydraulic properties, aeration and resistance to root penetration. Many indicators can be used to investigate the changes of soil structure, but using a single indicator or method has limitations. This study evaluates the effects of 15-years tillage management on soil structure with soil bulk density (BD) , penetrometer resistance (PR), soil water retention curve (SWRC), least limiting water range (LLWR) and X-ray computed tomography (CT). The treatments include no-tillage (NT), rotary tillage (RT), and mouldboard plough (MP). Soil bulk density of the 0–30 cm soil profile was measured after the establishment of tillage treatments for 7, 9, 12 and 14-years. The values of PR , SWRC, LLWR, and 3-D pore geometry of the 5–10 and 15–20 cm layers were determined in the 15th year of the experiment. The greater BD in the 0–5 cm layer of NT was not observed after 9 years, but an increased BD in the 5–20 cm layer was found in most years. Tillage had no effect on PR in wet soil. When soil had dried, the NT treatment had a greater PR and it was the lower limiting factor of LLWR, ultimately leading to a narrower LLWR of NT. Both NT and RT showed lower proportions of structural but higher textural pores. The macroporosity (> 50 µm) from X-ray CT was greater than that estimated from SWRC of the 15–20 cm layer. The characteristics of pore morphology were similar under three tillage treatments. Therefore, NT resulted in a narrower LLWR due to the denser soil layer, yet similar macropores may alleviate the negative impacts on crop growth caused by lower LLWR. It was suggested that using LLWR and characteristics of macropores from X-ray CT at the same time is a suitable way to assess soil structure under various tillage practices. • After 15-years no-tillage, the physical quality is poor in 5–20 cm layer reflected by greater BD, PR, and lower LLWR. • Similar properties of macropore weak the usefulness of LLWR for assessing soil structure under no tillage treatment. • Combining LLWR with macropores from X-ray CT is a suitable way to assess soil structure under various tillage practices. [ABSTRACT FROM AUTHOR]

Highlights: [•] RZWQM assessed for atrazine transport in subsurface drainage. [•] RZWQM adequately predicted atrazine concentrations in drainage. [•] Six years of data show atrazine concentrations greater under no-till than till. [•] Atrazine in drainage sensitive to macropore flow and storm timing/intensity. [•] Atrazine in drainage also sensitive to its application rate and tillage. [Copyright &y& Elsevier]

We studied the combined effects of reduced tillage and animal manure on soil structure and hydraulic conductivity ( K) in the 2-10 and 12-20 cm layers in a loamy soil. The study was performed at the end of a 7-yr field trial and included three tillage treatments (mouldboard ploughing until 25 cm depth: MP, shallow tillage until 12 cm depth: ST, no-till: NT) and two fertilizer application treatments (mineral or poultry manure). Soil structure was assessed through bulk density ( ρb), micromorphological and macropore-space characteristics. K was measured in situ at −0.6, −0.2 and −0.05 kPa. Untilled layers had a vermicular microstructure resulting from earthworm activity, whereas tilled layers displayed a mixture of crumb and channel microstructures. Untilled layers had the highest ρb and twice as much lower total macroporosity area (pores > 240 μm in equivalent diameter) than tilled layers, reflected by the smallest area of macropores 310-2000 μm in diameter and the smallest area of large complex macropores. K under untilled layers was 12-62% lower than that under tilled layers, but differences were statistically significant only at −0.05 kPa in the 2-10 cm. No significant interaction between tillage and nutrient application treatments was detected for all properties. Compared with mineral fertilizer, poultry manure resulted in a similar ρb but 20% greater total macroporosity area and 30% higher K at −0.2 kPa. Overall, the sensitivity of soil structure and K to poultry manure were relatively small compared with tillage. We suggest that cultivation practices other than animal manure application are needed to improve physical properties under reduced tillage. [ABSTRACT FROM AUTHOR]

Abstract: Structural porosity is a decisive property for soil productivity and soil environmental functions. Hydraulic properties in the structural range vary over time in response to management and environmental influences. Although this is widely recognized, there are few field studies that determine dominant driving forces underlying hydraulic property dynamics. During a three year field experiment we measured temporal variability of soil hydraulic properties by tension infiltrometry. Soil properties were characterized by hydraulic conductivity, effective macroporosity and Kosugi's lognormal pore size distribution model. Management related influences comprised three soil cover treatment (mustard and rye vs. fallow) and an initial mechanical soil disturbance with a rotary harrow. Environmental driving forces were derived from meteorological and soil moisture data. Soil hydraulic parameters varied over time by around one order of magnitude. The coefficient of variation of soil hydraulic conductivity K(h) decreased from 69.5% at saturation to 42.1% in the more unsaturated range (−10cm pressure head). A slight increase in the Kosugi parameter showing pore heterogeneity was observed under the rye cover crop, reflecting an enhanced structural porosity. The other hydraulic parameters were not significantly influenced by the soil cover treatments. Seedbed preparation with a rotary harrow resulted in a fourfold increase in macroporosity and hydraulic conductivity next to saturation, and homogenized the pore radius distribution. Re-consolidation after mechanical loosening lasted over 18months until the soil returned to its initial state. The post-tillage trend of soil settlement could be approximated by an exponential decay function. Among environmental factors, wetting-drying cycles were identified as dominant driving force explaining short term hydraulic property changes within the season (r2 =0.43 to 0.59). Our results suggested that beside considering average management induced changes in soil properties (e.g. cover crop introduction), a dynamic approach to hydrological modeling is required to capture over-seasonal (tillage driven) and short term (environmental driven) variability in hydraulic parameters. [Copyright &y& Elsevier]

Abstract: In cultivated soils, Soil structure mainly results from climatic, anthropogenic and biological processes. Nevertheless, few field methods evaluating the quality of soil structure consider the contribution of biological processes. In order to include earthworm biostructures in the field description of soil-structure, an original method is proposed in this paper. Soil profiles under different agricultural practices were examined to distinguish soil-structure patterns, notably those resulting from earthworm bioturbation. The relevance of naked eye observation was tested by a micromorphological approach, using image analysis on thin sections. Then, the application of this method was illustrated by mapping soil profiles. Our study led to the creation of a typology (i.e. classification system) of eleven soil-structure patterns, taking into account anthropogenic processes (e.g. compaction, soil tillage), root activity and earthworm activity. Seven patterns were attributed to earthworm activity in the form of burrows or casts. Three burrow features were distinguished, differentiating between filled burrows, or empty burrows with a brown cutan or without visible cutan. Four patterns of cast packing were distinguished, differentiating between cast aggregates that were fresh, welded, compacted, or combined with burrow features. This typology appears relevant for developing a field tool to describe and spatially quantify soil structure. [Copyright &y& Elsevier]

The variability and the spatial dependence attributes of the following plant and soil: a) the soybean yield (SY) in no-tillage and irrigated, b) the macroporosity (MA), c) microporosity (MI), d) total porosity (TP), e) and bulk density (BD), in depths of 1 (0-0.10m), 2 (0.10-0.20m) and 3 (0.20-0.30 m), in a Red Latosol of the Engineering college of the São Paulo State University (FE/UNESP) in the Ilha Solteira campus, located in Selv&#x;ria County, Mato Grosso do Sul state, Brazil, were analyzed in the agricultural year of 2004/05. The main goal was to study the variability and the linear and spatial correlations among the attributes (plant and soil), aiming to select an index of soil physical quality with good capacity to represent the soybean yield. A geostatistical grid to collect soil and plant data was installed, with one hundred and twenty four sample points, in an area of 4000m². The linear relationship between soybean yield and physical attributes of soil studied was low. So, there was a direct spatial relationship between SY and MA1 (0-0.10m), as well as between SY and MA2 (0.10-0.20m). The MA1 showed its best index of the soil physical quality, when it was destined to estimate the soybean yield on no-tillage. [ABSTRACT FROM AUTHOR]

Abstract: To test the assumption that changes to earthworm communities subsequently affect macroporosity and then soil water infiltration, we carried out a 3 year study of the earthworm communities in a experimental site having six experimental treatments: 2 tillage management systems and 3 cropping systems. The tillage management was either conventional (CT; annual mouldboard ploughing up to −30cm depth) or reduced (RT; rotary harrow up to −7cm depth). The 3 cropping systems were established to obtain a wide range of soil compaction intensities depending on the crop rotations and the rules of decision making. In the spring of 2005, the impact of these different treatments on earthworm induced macroporosity and water infiltration was studied. During the 3 years of observation, tillage management had a significant effect on bulk density (1.27 in CT and 1.49mgm−3 in RT) whereas cropping system had a significant effect on bulk density in RT plots only. Tillage management did not significantly affect earthworm abundance but significantly influenced the ecological type of earthworms found in each plot (anecic were more abundant in RT). On the contrary cropping system did have a significant negative effect on earthworm abundance (104 and 129ind.m−2 in the less and most compacted plots, respectively). Significantly higher numbers of Aporrectodea giardi and lower numbers of Aporrectodea caliginosa were found in the most compacted plots. CT affected all classes of porosity leading to a significant decrease in the number of pores and their continuity. Only larger pores, with a diameter superior to 6mm, however, were adversely affected by soil compaction. Tillage management did not change water infiltration, probably because the increase in macroporosity in RT plots was offset by a significant increase in soil bulk density. However, cropping system had a significant effect on water infiltration (119 vs 79mmh−1 in the less and most compacted plots, respectively). In RT plots, a significant correlation was observed between larger macropores (diameter>6mm) and water infiltration illustrating the potential positive effect of earthworms in these plots. [Copyright &y& Elsevier]

Effective management of soil structure and organic matter are essential in organic cropping to ensure good rooting conditions and to optimize the production of mineralized N and thus minimize greenhouse gas emissions. We investigated how mid-winter or early spring ploughing and three grazing duration treatments prior to ploughing influenced soil structure, soil organic matter and plant root growth under the first spring barley crop after a grass–clover ley. The experiment was carried out over two seasons. We also studied the soil under first-year oats in a long-term rotations experiment where 2 or 3 years of arable crops followed 3 or 4 years of grass. Pore size distribution and pore continuity, bulk density, particulate (light fraction) organic matter, readily oxidizable organic matter (ROM), aggregate size distribution and root length densities were measured. Macroporosity appeared to be the best indicator of soil physical fertility; it was sensitive to changes in soil structure arising from compaction and root growth. This, along with visual examination, revealed the loosening resulting from ploughing. The generally favourable macroporosity amongst small, stable aggregates reduced the likelihood of development of anaerobism. Macroporosity and aggregate size can be estimated from visual examination of the soil, a method that offers the advantage of being quick and of sampling a large volume. The content of ROM was high 6.1–6.4 g 100 g−1 whole soil. However, particulates formed only a small fraction (6–9%) of the ROM. Despite the favourable ROM and structure, the soil was susceptible to compaction damage during seedbed preparation in wet soil after ploughing which reduced grain yield in some plots. Grazing by sheep before ploughing and date of ploughing had minor effects on soil quality. Grazing for 2 months prior to ploughing increased root length density in the upper topsoil in the following arable crop, possibly because of the higher quality of the animal and grass–clover residues. Conservation of soil quality was related more to secondary tillage and sowing operations after ploughing than to duration and timing of grazing. [ABSTRACT FROM AUTHOR]

Abstract: A better understanding of tillage and stubble management effects on surface soil structure is vital for the development of effective soil conservation practices for the long-term. Relationships between aspects of soil structure and runoff/soil loss were investigated in 24 year old field experiment on an Oxic Paleustalf, in NSW, Australia. Two tillage/stubble management systems were compared, namely direct drilled/stubble retained (DD/SR) versus conventional tillage/stubble burnt (CC/SB). Tillage and stubble burning significantly increased bulk density and decreased the macro-aggregate stability, mean weight diameter (MWD), geometric mean diameter (GMD) and total porosity, particularly macroporosity (>60μm). For the 0–5cm layer, DD/SR had significantly higher water stability of macro-aggregates >2mm than CC/SB (165g/kg versus 78g/kg), and the volume of pore space of diameter >60μm at 0–5cm depth was significantly greater (more than 11%) for DD/SR than for CC/SB. Under simulated rainfall (100mm/h) and the removal of surface stubble, both runoff and soil loss were significantly higher under CC/SB compared to DD/SR. The infiltration rate at the end of the experiment under DD/SR was 3.7 times that of CC/SB (85mm/h versus 23mm/h). There were significant correlations between the proportion of soil particles >0.25mm measured after wetting by rain and both final infiltration rate (P <0.001) and soil loss (P <0.001). It was concluded that 24 years of direct drilling and stubble retained practices significantly reduced runoff and soil erosion hazards, due to a fundamental change in soil structure, viz. higher soil aggregate stability and higher macroporosity of the surface soil. [Copyright &y& Elsevier]