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Several previous field studies in temperate regions have shown decreased soil respiration after conventional tillage compared with reduced or no-tillage treatments. Whether this decrease is due to differences in plant residue distribution or changes in soil structure following tillage remains an open question. This study investigated (1) the effects of residue management and incorporation depth on soil respiration and (2) biological activity in different post-tillage aggregates representing the actual size and distribution of aggregates observed in the tilled layer. The study was conducted within a long-term tillage experiment on a clay soil ( Eutric Cambisol) in Uppsala, Sweden. After 38 y, four replicate plots in two long-term treatments (moldboard plowing (MP) and shallow tillage (ST)) were split into three subplots. These were then used for a short-term trial in which crop residues were either removed, left on the surface or incorporated to about 6 cm depth (ST) or at 20 cm depth (MP). Soil respiration, soil temperature, and water content were monitored during a 10-d period after tillage treatment. Respiration from aggregates of different sizes produced by ST and MP was also measured at constant water potential and temperature in the laboratory. The results showed that MP decreased short-term soil respiration compared with ST or no tillage. Small aggregates (< 16 mm) were biologically most active, irrespective of tillage method, but due to their low proportion of total soil mass they contributed < 1.5% to total respiration from the tilled layer. Differences in respiration between tillage treatments were found to be attributable to indirect effects on soil moisture and temperature profiles and the depth distribution of crop residues, rather than to physical disturbance of the soil. [ABSTRACT FROM AUTHOR]

Highlights: [•] More than 1000 experimental years were included in the analysis of yield data. [•] Crop yield on average 10% lower for no-tillage compared to mouldboard ploughing. [•] Crop yield on average 2% lower for shallow tillage compared to mouldboard ploughing. [•] Dicots were more sensitive to compaction than cereals. [•] Winter wheat yield in reduced tillage was much affected by preceding crop. [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: Few previous studies explicitly deal with the effect of tillage depth in non-inversion tillage. Swedish experiments on different tillage depths (5–10 compared with 15–20cm) in non-inversion tillage on a range of soil types (mainly classified as Eutric Cambisols) were used to study effects on soil properties and crop yield, with mouldboard ploughing as the reference. On-site measurements of penetration resistance (all sites) and saturated hydraulic conductivity (eight sites) were made in 14 experiments of three years or more. Data from a total of 115 experimental years during 2006–2011 were used to analyse interactions between tillage depth, crop, soil type and precipitation on crop yield. The three most common crops were winter wheat (Triticum aestivum L.), barley (Hordeum vulgare L.) and oilseed rape (Brassica napus L.). Data on draught requirement were also collected (in three experiments). At the selected sites, there were mainly only small differences in crop yield between tillage depths, but on two sites with clay soil yield was significantly reduced by increased tillage depth. In an overall trend, increased tillage depth slightly seemed to decrease yield on heavier soils. The reaction of different crops was little affected by tillage depth. Decreasing tillage depth generally increased penetration resistance (approximately double at 10–15cm depth for shallow discing compared to ploughing) and reduced saturated hydraulic conductivity in the topsoil. Increasing tillage depth from 5–10cm to 15–20cm more than doubled the draught requirement. Mean yield for non-inversion tillage was only 1–2% lower than for mouldboard ploughing, despite a large increase in penetration resistance. There was also a poor correlation between penetration resistance and crop yield relative to mouldboard ploughing. There was no clear interaction between precipitation and tillage treatment in the effect on crop yield. Overall, on Swedish soils, there seems to be little need for soil loosening in non-inversion tillage. A shallow working depth can be recommended, especially on heavier soils. [Copyright &y& Elsevier]

We compared earthworm density, depth distribution and species composition in three soil cultivation experiments including the treatments ploughless tillage and mouldboard ploughing. Sampling was done in September 2005 and for one experiment also in 1994. By yearly sampling 1995–2005, earthworms in an energy forest of Salix viminalis were compared with those in an adjacent arable field. Sampling method was digging of soil blocks and hand sorting and formalin sampling in one cultivation experiment. Both methods were used in the energy forest and arable land comparison. In two soil cultivation experiments, highest abundances or biomass were found in ploughless tillage. Earthworm density was higher in the upper 10 cm, especially in the ploughless tillage. Earthworm density was significantly higher in the energy forest than in the arable field. Formalin sampling revealed c. 36% of the earthworm numbers found by digging in the energy forest and gave almost no earthworms in the arable field. In all treatments with soil cultivation, species living and feeding in the rhizosphere and soil dominated. One such species, Allolobophora chlorotica, was more abundant under mouldboard ploughing than ploughless tillage. Lumbricus terrestris, browsing on the surface and producing deep vertical burrows, was more common in the ploughless tillage. Species living and feeding close to the soil surface were almost only found in the energy forest, which had not been soil cultivated since 1984. The findings support earlier studies pointing out possibilities to encourage earthworms by reduced soil cultivation. This is one of the first published studies that followed earthworm populations in an energy forest plantation during several years. Explanation of earthworm reactions to management and environmental impacts should be done with consideration of the ecology of species or species groups. Earthworm sampling by formalin must always be interpreted with caution and calibrated by digging and hand-sorting sampling. [ABSTRACT FROM AUTHOR]

Abstract: The energy efficiency of different implements and tillage systems for winter wheat in Sweden was examined. Mouldboard ploughing was compared with different ploughless tillage systems (chisel plough, disc, disc-press) and direct drilling on a clay and a silt loam soil during three years. Fuel consumption was measured for all tillage operations, including seedbed preparation and sowing. Energy balances were calculated, based on the direct and indirect use of fossil fuels in crop production. Specific draught (draught per cross-sectional area of soil) was highest for the disc-press implement, while mouldboard ploughing gave the lowest specific surface (surface area per kg soil). Total energy requirement for tillage ranged from 0.6 to 2.8GJha−1 on the clay soil and 0.5 to 1.5GJha−1 on the silt loam. Yield of winter wheat in the ploughless tillage and mouldboard ploughing systems was similar when oats or barley were grown as preceding crops. Growing winter wheat after winter wheat caused yield losses in treatments with reduced tillage intensity, especially direct drilling. Overall energy use in tillage as a proportion of total energy use for crop production ranged from 5% for direct drilling on the silt loam soil to 25% for mouldboard ploughing on the clay. The energy input in tillage was low compared with the energy in the harvested crop and thus energy efficiency, expressed as energy gain, depended mainly on crop yield and not on tillage intensity. For Swedish conditions, a small increase in energy gain might be expected for ploughless tillage compared with mouldboard ploughing when winter wheat is grown with a good preceding crop, but a lower energy gain when winter wheat is grown after winter wheat. [ABSTRACT FROM AUTHOR]

Abstract: This study measured the specific draught (force per cross-sectional area of worked soil) and the energy use for soil fragmentation and straw incorporation using different tillage implements (mouldboard plough, 80mm tine with and without wings, 210mm sweep share, 80mm rigid and vibrating tines) on a clay and a loam soil. Tine widths of 50, 65, 80 and 120mm were compared in a separate experiment. Draught was calculated from measurements of fuel consumption and driving speed during tillage, while tillage depth was determined by weighing the loosened soil, which was also sieved to determine the aggregate size distribution and surface area. Measured values of specific draught were compared with model computations. Specific draught was much higher for the rigid 80mm tine than for the mouldboard plough and sweep share. On the clay soil, specific draught was 65kNm−2 for the mouldboard plough, 140kNm−2 for shallow tillage with the rigid tine, 98kNm−2 for the vibrating tine and 65kNm−2 for the sweep share. The vibrating tine had a much lower energy use for soil fragmentation than the rigid tine. The sweep share also had a low energy use for fragmentation, but the poorest incorporation of straw. On the loam, differences between treatments were generally smaller than on the clay. There were small differences in specific draught and soil fragmentation for different tine widths. For the different tines and shares, the measured specific draught was considerably higher than values from model computations. Overall, there were great differences in draught requirement and tillage outcome for the different tillage tools. The results show the importance of adjusting the tillage tool to achieve the desired tillage outcome in terms of soil loosening, soil fragmentation or incorporation of plant residues. [Copyright &y& Elsevier]

Abstract: Tillage experiments were carried out in order to study the effect of water content on the aggregate size distribution produced by tillage, and to investigate the relationship between the soil structures produced by tillage and Dexter''s index of soil physical quality, S. Tillage with a mouldboard plough was done on four different soils over a range of naturally occurring water contents. The aggregate size distribution and the specific surface area produced by tillage were obtained by sieving. We define the optimum water content for tillage, θ OPT, as the water content at which the specific surface area of the aggregates produced is maximum. This is consistent with the water content at which the amount of small aggregates produced is greatest and the proportion of clods produced is smallest. For the four investigated soils, θ OPT was found to be close to the water content at the inflection point of the water retention curve, and in the vicinity of 0.8θ PL (where θ PL is the lower plastic limit). At water contents either lower or higher than θ OPT, the specific surface area produced was smaller. The specific surface area produced at θ OPT was found to be strongly correlated with the index of soil physical quality, S. The specific surface area produced is larger the greater S, i.e. the better the soil physical quality. Consistently, the proportion of small aggregates produced at θ OPT is larger and the proportion of clods produced at θ OPT smaller, the greater S. No clods (>50mm) are produced on soils with good physical quality. [Copyright &y& Elsevier]

Abstract: Soil water content during tillage can have a large impact on soil properties and tillage outcome. Measurement of soil relief in relation to fixed elevation points provides a non-destructive method of monitoring loosening/compacting processes during the year. The main objective of this study was to determine the effect of soil water content during primary tillage on soil physical properties. The treatments included mouldboard and chisel ploughing of a clay soil on three occasions in the autumn, with gradually increasing water content (0.76, 0.91 and 1.01×plastic limit). Soil surface height was measured by laser within a 0.64m2 area from fixed steel plates after each tillage occasion, and before and after seedbed preparation in the following spring. The measurements of surface height were compared with measurements of other soil physical properties, such as bulk density, saturated hydraulic conductivity and seedbed properties. Tillage at the lowest water content (0.76×plastic limit) produced the greatest proportion of small aggregates, and generally the most favourable soil conditions for crop growth. Soil loosening, as measured by increase in soil height during primary tillage, was highest for mouldboard ploughing and for tillage at the lowest water content. Differences between tillage treatments decreased with time, but were still significant after sowing in the spring. Natural consolidation during winter was smaller than the compaction during seedbed preparation in the spring. No significant differences in bulk density were found between treatments, and thus soil surface height was a more sensitive parameter than bulk density determined by core sampling to detect differences between treatments. Late tillage under wet conditions caused a greater roughness of the soil surface and the seedbed base, which was also found in the traditional seedbed investigation. The effect of tillage time on seedbed properties also resulted in a lower number of emerged plants in later tillage treatments. The laser measurements were effective for studying changes in soil structure over time. The results emphasize the need to determine changes in soil physical properties for different tillage systems over time in order to model soil processes. [Copyright &y& Elsevier]

Abstract: Autumn tillage strategies designed to reduce leaching losses of nitrogen (N) from arable fields were examined on a medium clay soil (approx. 40% clay) in terms of their effects on accumulation of soil mineral N (SMN) during autumn and winter, crop N uptake, grain yield (spring-sown cereals) and soil structure over the long term (1997–2004). Tillage strategies included mouldboard ploughing (20–25cm depth) and stubble cultivation (10–12cm depth) in different combinations and timing, together with different options for straw management and catch crops. Postponing mouldboard ploughing from early September to early November significantly decreased SMN content during autumn and winter, although levels were generally low in all treatments. On average, the soil profile down to 90cm depth contained 30kgNha−1 in November and 27kgNha−1 in December with early mouldboard ploughing, while the corresponding figures for late mouldboard ploughing were 16 and 21kgNha−1. Stubble cultivation stimulated N mineralisation but the increase in SMN from tillage in September to November was only 3kgha−1 after stubble cultivation, compared with 8kgha−1 after mouldboard ploughing. Stubble cultivation before late mouldboard ploughing resulted in 6kgha−1 higher SMN during autumn than late ploughing without preceding cultivation. Postponement of mouldboard ploughing significantly decreased grain yield by on average 11% and this negative effect accumulated over time. A catch crop compared with no catch crop reduced SMN during autumn and winter by 3–5kgha−1 and had no significant yield effect. Effects of straw incorporation were small and could not be significantly proven either for SMN or yield. Transport of SMN to deeper layers was generally limited and SMN did not decrease during winter, indicating a minor impact of tillage time on N leaching risk. No significant changes in soil physical parameters were detected, but the results indicated poorer soil structure after tillage in late autumn compared with early autumn in terms of higher soil bulk density, lower aggregate stability in water, and lower infiltration rate. Overall, considering the short-term and long-term negative effects on yield and possibly soil structure, the benefit of delaying tillage seems small on this clay soil. [Copyright &y& Elsevier]

Abstract: Soil disturbance by tillage and traffic often adversely affects aggregate stability, leading to colloid and particle mobilisation, which may result in crusting, low water infiltration rate and sediment transport. Hence, minimising soil tillage is an important step in conserving soil quality. This study investigated readily dispersible clay (RDC) and particle transport as affected by shallow tillage or mouldboard ploughing in five Swedish long-term reduced tillage experiments that had been underway for 15–31 years at the time of soil sampling. The soils of the experimental sites are Eutric and Dystric Cambisols. RDC of soil samples, collected in 0–10cm and 12–17cm depth, from mouldboard ploughed (MP) and shallow tillage (ST) plots was compared by measuring turbidity. Particle transport was also determined in undisturbed soil columns (20cm in diameter and 20cm high) from these treatments. RDC and particle transport were significantly lower for ST than for MP at three sites where clay content was above 30%. Particle transport in two soils (clay content above 40%) increased with irrigation events, indicating that preferential transport dominated in unsaturated soil columns, but matrix flow and, consequently, particle dispersion increased as the soil approached saturation. Despite more organic C accumulation in the upper 0–10cm of ST than in the 12–17cm soil layer, clay dispersion was lower in the latter. Particulate P (Total P−dissolved P) was well-correlated to turbidity, suggesting that analysis costs often can be cut by only measuring turbidity. Shallow tillage generally produced positive environmental effects without negative effects on crop yield, especially on soils with high clay content. [Copyright &y& Elsevier]