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Aims: This study assessed the impact of combined lime and phosphorus application on soil pH, plant availability of added phosphorus and crop yield over time. Methods: In a series of long-term field trials started in 1936 on a clayey soil in south-west Sweden, acidic superphosphate and basic Thomas phosphate were tested in combination, with and without an initial high dose of lime. Results: Liming did not lower phosphorus availability in soil. Crop yield was increased throughout by addition of phosphorus together with lime. A single dose of lime, equivalent to 6 Mg CaO ha−1, increased yield over decades and crop yield was positively correlated with pH(aq) increases up to 7.5. In plots receiving no phosphorus for 80 years, the clay soil was able to supply phosphorus to crops, resulting in up to 80% of the phosphorus-fertilised yield. Vanadium in the basic slag product (Thomas phosphate) elevated levels in soil. Conclusions: In the present study, we found that, even above pH 7, interactions between P and lime were positive and not negative. No differences in phosphorus availability were found on applying phosphorus fertiliser at the normal dose on a regular basis, or as a bulk dose at longer intervals. The data support a new target pH value up to 7.5 for optimal crop production. [ABSTRACT FROM AUTHOR]

Phosphorus (P) losses from clay soils can be mitigated by introducing measures for improving soil structure. These include structure liming, where a mixture of CaO or Ca(OH)2 and CaCO3 is added to the soil. In a field experiment with separately tile-drained plots on a clay loam in Sweden, we examined the effects of structure liming on leaching of total-P, phosphate P (PO4-P) and total nitrogen (N) during three years after initial application. The treatments included two application rates (8 and 16 t ha−1) of a common product in comparison with a control (no lime). Effects of structure liming emerged during the second and third year after application, with 45 and 38% lower total-P leaching than in the unlimed control. A significant effect of the application rate was found in the third year. Nitrogen leaching and crop yield were not affected. As expected, soil pH raised following structure lime addition. Measurements of aggregate stability did not confirm the reduction in P leaching, indicating that it is important to measure P concentrations in drainage water directly when assessing the effect of structure liming. [ABSTRACT FROM AUTHOR]

Liming before cultivation of sugar beets is favourable even on alkaline soils but knowledge of response in other crops is lacking. Therefore, effects of ground limestone (GL) and structure lime (SL1 slaked lime or SL2 mix of ground limestone and slaked lime) were evaluated in southern Sweden on soil structure, growth and nutrient concentration in barley under four fertilisation strategies 1.5–2 years after application. All lime products increased aggregate stability, but with variations between locations. A lower proportion of large aggregates was found in both limed treatments, and a higher proportion of small aggregates in SL. In barley, grain yield was unaffected while shoot numbers and biomass in first node stage increased for GL and biomass increased further for SL. Structure lime increased potassium concentration in plants in first node stage, due to more potassium in the product. Both lime types increased molybdenum concentration. Ground limestone reduced zinc concentration compared with no liming. Finer seedbed tilth and increased aggregate stability may explain increased biomass for GL. Higher potassium content in SL might be a further explanation. No interactions between liming and fertilisation were found. In conclusion, on the soil types studied, no change of fertilisation strategy is needed due to liming. [ABSTRACT FROM AUTHOR]

A model for the one-dimensional consolidation of saturated clayey soils, considering creep, is proposed, based on the consolidation mechanism idealized by Terzaghi (1941). The effective vertical stress is divided into two parts: one corresponding to the "solid" contacts, and other relating to the "viscous" contacts, the void ratio changes being caused by variations solely in the solid portion. Based on experimental evidence, a non-linear viscosity law was adopted, described by a hyperbolic function, in addition to its dependence on the void ratio. The resulting differential equation system is solved through the Finite Difference Method. The main "secondary effects of time" – experimental deviations from the classical Terzaghi (1925) theory – were able to be reproduced using the model, as well as experimental results that support other categories of consolidation models, such as the isotache- and C α / C C -based models. A good fit was obtained for the results of long-term laboratory tests in clays from different parts of the world that reached the end of secondary consolidation. A good prediction was also reached for the evolution of settlements from the experimental embankment on the soft soils of Lilla Mellosa, monitored since 1947 in Sweden. [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]

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]

• Manure rate had little influence on the improvement of soil physical properties. • Improvement in soil gas transport and Ksat by manure varied with soil and crop type. • Silty soil had better improvements by manure addition than sandy and clayey soil. Manure application and crop rotation are common agricultural practices that can alter soil physical properties and affect soil functions. In this study, we assessed the effect of long-term manure fertilization (24 to 126 years) and crop type on soil hydraulic, aggregate and pore structural properties. Samples were collected from three long-term experiments (LTEs) in Sweden (silty clay, SiC), Germany (silt loam, SiL) and Denmark (sandy loam, SL). Measurements included water retention, air permeability and gas diffusivity measured at five matric potentials −3, −5, −10, −30 and −50 kPa, saturated hydraulic conductivity (K sat), bulk density (ρ b), and water-stable aggregates (WSA). The treatments at the three LTEs included various manure rates and crop sequences (winter wheat, maize, spring barley, and grass/clover). Results showed that long-term manure addition reduced ρ b by an average of 3–6% for all three sites, and improved soil water retention, plant available water and WSA for most investigated plots. However, increasing manure rates for the SiL and SL sites did not result in further improvements in soil water retention, ρ b and water-stable aggregates. The effect of manure on soil pore size distribution, gas transport, and K sat varied with soil and crop type. Manure increased the porosity of pores < 30 µm in the two fine-textured sites and increased the porosity of pores > 30 µm for wheat and maize plots in the SL site. Manure improved gas transport and K sat in the wheat plots and decreased these properties in the barley plots regardless of soil texture. The maize plots in the SL site had well developed pore structure, while the pore structure in the SiL site was relatively poor. Grass plots had poorer gas transport than maize plots in the SL site despite the manure addition. The study shows that improvements in soil physical and chemical properties arising from manure application largely depend on the crops grown and the soil texture. [ABSTRACT FROM AUTHOR]

Within-field variations in the mycotoxin deoxynivalenol (DON) in oat grain were investigated at two farms in south-west Sweden. At Sarestad farm (sampled 2012), where one of two fields studied was ploughed annually and the other was under no-till cultivation, the DON concentration varied between 28 and 1 755 ppb. The level was higher (270-5 000 ppb) at Entorp farm (sampled 2013). Within-field prediction models for DON were constructed using a data mining method (multi-variate adaptive regression splines) with satellite data, an ECa sensor and airborne laser scanning. At Sarestad, the no-till field had higher DON content, with the highest values in silty patches in the otherwise clayey soil. Sensor data related to soil and crop conditions had the potential to describe the DON variability within fields. The covariance between DON content and auxiliary data differed at Entorp farm, where high DON values (>2 000 ppb) were found in clayey parts of the field. This pattern was attributed to poor drainage with recurring waterlogging. Within these clayey parts, the highest DON contents coincided with the highest biomass density. South-west Sweden received much less rainfall in 2013 than in 2012, which may have resulted in different DON patterns in relation to soil types. In 2012, more permeable silty soils apparently promoted growth, biomass production and DON production, whereas in 2013 a poorly drained clayey soil with high water-holding capacity favoured development of high DON concentrations. [ABSTRACT FROM AUTHOR]

Delaying tillage and incorporation of arable crop residues in autumn may limit accumulation of soil mineral nitrogen (SMN) and reduce nitrogen (N) leaching. However, on clay soils, high water content during late tillage can impair soil structure and fertility. This study investigated the effects of tillage timing on SMN (0–90 cm depth), soil physical properties in the topsoil and yield in two Swedish clay soils differing in clay content. SMN generally increased during autumn and also with earlier tillage. On a heavy clay soil (Ultuna; ∼60% clay), SMN increased throughout winter until spring and the amount of N leached was probably small. In contrast, on a clay loam soil in southernmost Sweden (Rydsgård; ∼35% clay), SMN decreased during winter by up to 26 kg ha−1. In general, measured soil water content (w) was lower than 0.9 × plastic limit (PL) at the time of early tillage (mouldboard ploughing or stubble cultivation), while it exceeded 0.9 PL at the time of normal and late tillage. The proportion of small aggregates produced by tillage was negatively correlated to relative soil water content at the time of tillage (w/PL). Conventional methods to determine soil physical qualities (bulk density, saturated hydraulic conductivity, aggregate tensile strength) did not show any clear differences between treatments. However, plant emergence and yield were significantly reduced after late compared with early tillage at Ultuna, a trend that has persisted from 2000 until the present. These results suggest that the suitability of delayed autumn tillage as a means to reduce SMN accumulation and N leaching varies between Swedish clay soils. A reduction in N leaching can be achieved on lighter clay soils in warmer and moister areas, whereas the effects may be small on heavier clay soils in central Sweden, where repeated late tillage carries a risk of yield reduction. [ABSTRACT FROM AUTHOR]

Reduced tillage is proposed as a method of C sequestration in agricultural soils. However, tillage effects on organic matter turnover are often contradictory and data are lacking on how tillage practices affect soil respiration in northern Europe. This field study (1) quantified the short-term effects of different tillage methods and timing on soil respiration and N mineralisation and (2) examined changes in aggregate size distribution due to different tillage operations and how these relate to soil respiration. The study was conducted on Swedish clay soil (Eutric Cambisol) and compared no-tillage with three forms of tillage applied in early or late autumn 2010: mouldboard ploughing to 20-22 cm and chisel ploughing to 12 or 5 cm depth. Soil respiration, soil temperature, gravimetric water content, mineral N and aggregate size distribution were measured. The results showed that respiration was significantly higher ( P < 0.001) in no-till than in tilled plots during the 2 weeks following tillage in early September. Later tillage gave a similar trend but treatments did not differ significantly. Soil tillage and temperature explained 56 % of the variation in respiration. In the early tillage treatment, soil respiration decreased with tillage depth. Mineral N status was not affected by tillage treatment or timing. Soil water content did not differ significantly between tillage practices and therefore did not explain differences in respiration. The results indicate that conventional tillage in early autumn may reduce short-term soil respiration compared with chisel ploughing and no-till in clay soils in northern Europe. [ABSTRACT FROM AUTHOR]

Abstract: The study investigated proximal sensor data fusion for topsoil clay mapping on a 22hectare agricultural field in southwest Sweden. Eight different predictor sets and two different prediction methods were tested in an orthogonal design. The predictor sets were different combinations of proximally measured gamma (γ) ray spectrometry and apparent electrical conductivity (ECa), four terrain attributes (elevation, slope and the cosine and the sine of the aspect) and the digital numbers (DNs) of an aerial photo. The two prediction methods were partial least squares regression (PLS-R) and k nearest neighbor prediction (kNN). It was found that the γ ray spectrometry variables (232Th, 40K and total count of decays) were good predictors of topsoil clay content (mean absolute error of about 1.5% clay) and predictions were neither much improved nor deteriorated by addition of any of the other predictors. The ECa measurements, which are affected also by the subsoil, did not perform as well. Predictions were improved when the ECa data were integrated with the aerial photo DN but were deteriorated by addition of elevation data. The kNN method yielded slightly better predictions than the PLS-R method but overall it was more important which input data were used than how the predictions were made. It was observed that even though dense soil sampling was used for calibration (three samples per hectare), use of proximal soil sensor data was almost always better than mere interpolation of the calibration samples. [Copyright &y& Elsevier]

Erodibility of Swedish clay soils estimated according to the existing methods is usually low, but high levels of suspended solids and attached unreactive phosphorus have been recorded in drainage water from fields and catchments dominated by clay soils. Inherent susceptibility to soil erosion is usually assessed through aggregate stability studies or dispersion tests. The latter are simple to perform and produce good results when compared against runoff lysimeter experiments. The environmental soil test to determine the potential for sediment and phosphorus transfer in runoff from agricultural land (DESPRAL) and soil suspension turbidity (SST) dispersion tests, which differ in soil–liquid ratio and shaking and settling times, were compared here for their ability to indicate the erodibility of 10 Swedish clay soils. The tests proved to be significantly correlated (r=0.78), but DESPRAL showed higher repeatability (r i =0.995) than SST (r i =0.824). Variation in soil dispersion was explained by clay, sand and organic matter content in DESPRAL and by clay and sand content in SST. An additional study on the effect of soil storage duration on dispersion (DESPRAL test) in 15 soil samples showed that storage had no effect on some soils, but significantly decreased dispersion in others after only 8 weeks. Therefore, soil dispersion tests should be performed as soon as possible after sample drying. The DESPRAL and SST tests proved to be a good option for estimating the erodibility factor K in the Revised Universal Soil Loss equation under Swedish conditions and were able to differentiate the susceptibility to sediment losses for different clay soils. They provided an indirect measure of the amounts of sediment and P mobilized, but further work is needed to calibrate them against measured values at field and catchment scale. [ABSTRACT FROM PUBLISHER]

Abstract: In order to explore the influence of site-specific soil properties on nitrogen (N) and phosphorus (P) losses between individual fields and crop sequences, 16 drained fields with clay soils were investigated in a four-year study. Mean total N (TN) loss was 6.6–11.1 from a conventional, 14.3–21.5 from an organic and 13.1–23.9kgha−1 year−1 from an integrated cropping system across a 4year period, with 75% in nitrate form (NO3–N). Mean total P (TP) loss was 0.96–3.03, 0.99–4.63 and 0.76–2.67kgha−1 year−1, from the three systems respectively during the same period, with 25% in dissolved reactive form (DRP). Median N efficiency was calculated to be 70% including gains from estimated N fixation. According to principal component factor (PCA) analysis, field characteristics and cropping system were generally more important for losses of N and P than year. Accumulation of soil mineral N in the autumn and (estimated) N fixation was important for N leaching. No P fertilisers were used at the site in either cropping system. Total P concentration in drainage water from each of the fields was marginally significantly (p<0.05) correlated to TP concentration in the topsoil (r=0.52), measured in hydrochloric acid extract (P-HCl). Mean DRP concentrations were significantly (p<0.01) correlated to degree of P saturation (DPS-AL) and soil carbon (C) content in the topsoil (r=0.63). Good establishment of a crop with efficient nutrient uptake and good soil structure was general preconditions for low nutrient leaching. Incorporation of ley by tillage operations in the summer before autumn crop establishment and repeated operations in autumn as well, increased N leaching. Crop management in sequences with leguminous crops needs to be considered carefully when designing cropping systems high efficiency in N utilisation and low environmental impact. [Copyright &y& Elsevier]

Abstract: Models for draught requirement are in most cases developed from foundation engineering, and generally include cohesion as the main parameter to define soil strength. There are also empirical models which include penetration resistance as a soil strength factor. This study examined specific draught during mouldboard ploughing as a function of soil strength and related the results to existing models. Draught requirement was measured on 37 different occasions at 15 sites with clay content ranging from 13 to 56%. Four of these sites were ploughed on several occasions in the autumn to obtain a range of water contents. Shear vane measurements were carried out on all occasions and were used to derive soil cohesion. Penetration resistance was measured on 21 occasions. Soil strength proved much more sensitive to changes in water content than draught requirement. Consequently, model predictions of specific draught were much higher than measured values in soil with high cohesion values. A possible explanation is that specific draught mainly depends on inter-aggregate strength, while the intra-aggregate strength may be considerably higher. Over all tillage occasions, specific draught was much more strongly correlated to cohesion than to penetration resistance. There was also a clear correlation between draught and soil clay content. Multiple regression including cohesion and soil water content resulted in a much higher coefficient of determination than regression with cohesion only. The results indicate that neither shear vane nor penetrometer measurements are sufficient to predict draught requirement, and it is desirable to develop a simple yet reliable field method that can be used for this purpose. More general estimates of fuel consumption can probably be made based on the soil clay content only. [Copyright &y& Elsevier]

Abstract: The aim of this paper is to collate information on potential measures to reduce phosphorus (P) losses, with particular reference to Sweden. In Sweden, three dominant types of soils or soil profiles are at risk of suffering from high P losses through different pathways: clay soils with a naturally poor structure, usually situated on the large central plains, are prone to lose P through drain tiles; silty soils, usually situated on hilly terrain, are prone to erosion; and sandy soils with a low P sorption capacity in both topsoil and subsoil and that have had heavy applications of fertilisers, are prone to high leaching losses. Fields with such soils and landscape position with connectivity to surface waters may lose more than 0.5 kg P ha year−1 and often more than 1 kg P ha year−1. Losses of soluble reactive P (SRP) are commonly 30–50% of the total P losses. Improved soil tillage together with other measures aimed at improving soil structure are suggested to have the best potential to reduce losses, with short-term and long-term effects, for the clayey and silty soil profiles. For the silty soils, keeping the surface densely vegetated in winter and liming backfill of the drainage systems are suggested to be important ways to reduce the losses of particulate P (PartP). For sandy soils prone to P leaching, appropriate application of fertiliser and improved contact between fertiliser and the soil may be one of the few effective ways to reduce SRP losses. [Copyright &y& Elsevier]

Field traffic may reduce the amount of air-filled pores and cavities in the soil thus affecting a large range of physical soil properties and processes, such as infiltration, soil water flow and water retention. Furthermore, soil compaction may increase the mechanical strength of the soil and thereby impede root growth.The objective of this research was to test the hypotheses that: (1) the degree of soil displacement during field traffic depends largely on the soil water content, and (2) the depth to which the soil is displaced during field traffic can be predicted on the basis of the soil precompression stress and calculated soil stresses. In 1999, field measurements were carried out on a Swedish swelling/shrinking clay loam of stresses and vertical soil displacement during traffic with wheel loads of 2, 3, 5 and 7 Mg at soil water contents of between 11 and 35% (w/w). This was combined with determinations of soil precompression stress at the time of the traffic and predictions of the soil compaction with the soil compaction model SOCOMO. Vertical soil displacement increased with increased axle load. In May, the soil precompression stress was approximately 100 kPa at 0.3, 0.5 and 0.7 m depth. In August and September, the soil precompression stress at 0.3, 0.5 and 0.7 m depth was 550–1245 kPa. However, when traffic with a wheel load of 7 Mg was applied, the soil displacements at 0.5 m depth were several times larger in August and September than in May, and even more at 0.7 m depth. An implication of the results is that the precompression stress does not always provide a good indication of the risk for subsoil compaction. A practical consequence is that subsoil compaction in some soils may occur even when the soil is very dry. The SOCOMO model predicted the soil displacement relatively well when the soil precompression stress was low. However, for all other wheeling treatments, the model failed to predict that any soil compaction would occur, even at high axle loads.The measured soil stresses were generally higher than the stresses calculated with the SOCOMO model. Neither the application of a parabolic surface load distribution nor an increased concentration factor could account for this difference. This was probably because the stress distribution in a very dry and strongly structured soil is different from the stress distribution in more homogeneous soils. [Copyright &y& Elsevier]

In Sweden, 90% of the total amount of ammonia released to air originates from agriculture,e.g . manure handling. Incorporation of slurry into soil can reduce ammonia emissions after spreading. The objective of this study was to compare cattle slurry application to ley using (1) band spreading, (2) pressurized injection, and shallow injection with two different types of disc tines (3) and (4). Two years of field experiments were conducted to study slurry position after spreading, ammonia volatilization, grass yield, and silage quality. An economic analysis was also performed. Injection (2) and (3) were unable to satisfactorily incorporate the slurry, neither on a loam under dry soil conditions, nor on a clay soil. Year 1, high ammonia emissions were measured following application by all methods. Injector (3) with V-shaped disc tines gave a significantly (probability P<0·05) higher ammonia release compared to the other methods. Injector (3) also gave a significantly better silage quality than band spreading. Year 2, injector (4) with tines consisting of two-angled disc coulters resulted in the lowest ammonia losses. Certain differences in yield were observed in year 2. Computer simulations showed, that broadcast and band spreading were economically more profitable than shallow injection. [Copyright &y& Elsevier]