Publikasjoner
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2014
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Verification of traffic-induced soil compaction after long-term ploughing and ten years minimum tillage on clay loam soil in South-East Norway T. Seehusen, T. Børresen, B.I. Rostad, H. Fleige, A. Zink and H. Riley Abstract Grain yields are presented from a 10-year field trial with four tillage regimes (annual ploughing, harrowing only, ploughing/harrowing alternate years, minimum tillage) on clay loam. We also present soil physical analyses and use the compaction verification tool (CVT) to assess compaction on plots with annual ploughing and minimum tillage, after using slurry tankers with contrasting wheel loads (4.1 Mg, 6.6 Mg) and wheeling intensities (1x/10x) in the 11th trial year, and yields monitored two years after compaction. Winter wheat yields in the period before compaction were strongly affected by tillage, with annual ploughing giving on average 24% higher yield than direct drilling. Both wheat and oats were far less affected in treatments with harrowing only or ploughing/harrowing alternate years, on average within 6% of annual ploughing. Yields after compaction were affected by both previous tillage and compaction intensity. In the first year, single wheeling after annual ploughing gave 23% yield reduction with 4.1 Mg wheel load and 28% reduction with 6.6 Mg wheel load, whilst multiple wheeling gave 14 % reduction at 6.6 Mg wheel load. Yield reductions after minimum tillage ranged from 63% (single wheeling with 4.1 Mg) to 100% (multiple wheeling with 6.6 Mg). Similar trends were found in the second year. The soil physical data indicated that all wheeling led to changes in bulk density, pore sizes and permeability in both topsoil and subsoil on both sampled tillage plots. However, effects in the subsoil were partly masked by the soil’s high initial bulk density, partly due to its high clay content. The CVT, which plots air capacity against hydraulic conductivity, suggested some harmful compaction on both plots, with the minimum tillage plot being less affected than the ploughed plot. However, yield results did not support this conclusion, indicating that other factors limited yields on the minimum tilled plot. Keywords: long term contrasting soil tillage, yield results, slurry tanker, wheel load, wheeling intensity, compaction verification tool.
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Forfattere
Randi Berland FrøsethSammendrag
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Forfattere
Till SeehusenSammendrag
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Till SeehusenSammendrag
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Till SeehusenSammendrag
Abstract The object of the first study was to evaluate effects of long-term tillage regimes (ploughing- P and minimum tillage- M) on the bearing capacity of a clay loam soil and to determine the effects of wheeling with different wheel loads (4.1 Mg; 6.6 Mg) and wheeling frequencies (1x, 10x) of two slurry tankers on the soil’s functional parameters and crop yields. Paper I includes laboratory measurements of the precompression stress (Pc) to determine soil strength at -6 kPa in top- (20 cm) and subsoil (40 and 60 cm). Further, a combined stress-state and displacement transducer system was used to determine major principal stress (σ1) and vertical and horizontal soil deformation in the field. It was the first time this technique has been used under the climatic and farming conditions in Norway. The results show that the M plot had in the topsoil 74% higher Pc than the P plot, whilst the differences were less distinct in the subsoil. Wheeling increased Pc at all soil depths. Compared to ploughing, higher Pc in the upper layer of the M plot led on average to 60% (light tanker) and 48% (heavy tanker) reductions in the σ1 values. The extent of σ1 was dependent on the ground pressure in the topsoil. The first pass of a wheel caused the greatest damage in some cases, but all wheelings led to accumulative plastic deformation in both vertical and horizontal directions. The results show that soil water content is an important factor influencing bearing capacity. Wheeling with high intensity would have exceeded Pc in all cases in moist soil (matric potential -6 kPa). Drier soil (-100 kPa), in combination with minimum tillage, limited the occurrence of stresses exceeding Pc in the upper soil layer. The effects of tillage, wheel load and wheeling intensity on the hydraulic properties of this soil are described in Paper II. Soil physical analyses and a compaction verification tool (CVT) were used in order to assess the extent of damage to soil structure. In addition, grain yields are presented for the ten years before and two years after the compaction study. The yields in the period before compaction were strongly affected by tillage, ploughing giving on average 24% higher yield than direct drilling. Yields after compaction were affected by both previous tillage and compaction intensity. In the first year, single wheeling on the P plot gave 23% and 28% yield reductions with 4.1 Mg and 6.6 Mg wheel loads, respectively, whilst multiple wheeling gave 14 % reduction at 6.6 Mg wheel load. Yield reductions on the M plot ranged from 63% (1x wheeling with 4.1 Mg) to 100% (10x wheeling with 6.6 Mg). Similar trends were found in the second year. Soil physical data indicated that all wheeling led to changes in both top- and subsoil on both tillage plots. However, effects in the subsoil were partly masked by the soil’s high initial bulk density. The CVT suggested harmful compaction on both plots, with the M plot being less affected than the P plot. However, yield results did not support this conclusion, suggesting that other factors limited yields on the M plot. The second study was part of a multidisciplinary project addressing Fusarium aspects related to crop management, plant breeding and animal productivity. The main object of Paper III was to compare effects of ploughing versus reduced tillage and straw removal versus retention, on the amounts of plant residue, weed populations, soil structural parameters and cereal yields in four 3-year tillage trials (spring oats and spring wheat) on soils (clay loam, loam and silt) representative of cereal-growing in Norway. The methods included measuring straw residue cover, analyses of soil physical parameters, weediness, as well as crop yields and quality. The results showed that the more intensive the tillage, the higher the amount of small and the lower the amount of large soil aggregates. Reduced soil tillage, and in some cases spring ploughing, gave significantly higher aggregate stability than autumn ploughing, thus providing good protection against erosion. However, decreasing soil tillage intensity generally increased the amounts of surface residues and weeds. Crop rotation with oilseeds also led to a higher amount of weeds, both in the oilseed itself and in cereals the following year. Straw treatment affected yields to only a small degree, whilst the effects of soil tillage varied between both year and soil type. There were only small yield differences between tillage systems on loam soil, whilst reduced soil tillage was superior on clay soil and inferior on silt soil. Our results suggest that shallow spring ploughing is a good alternative to autumn ploughing, as it gave comparable yields and better protection against erosion, and was nearly as effective against weeds. In Paper IV the influence of the various tillage regimes on the inoculum potential and dispersal of Fusarium spp. was evaluated. In order to assess the amount of Fusarium spp. on straw residues, samples from the previous year were collected after sowing. Inoculum potential was calculated as the percentage of the residues infested with Fusarium spp. multiplied by the proportion of the soil surface covered with residues. For the assessment of Fusarium inoculum transported over long distances, air samples were collected in spore traps. This is the first report in Norway of Fusarium species DNA collected in air samples above cereal fields. The results confirm that residues are an important source of inoculum and the inoculum potential of Fusarium spp. was significantly lower in ploughed plots compared to those with harrowing only. No differences in the inoculum potential were found between ploughing in spring and autumn, whereas harrowing in autumn generally reduced it more than did spring harrowing. Fusarium DNA was mainly detected in the samples collected from heading onwards, and the dispersal increased after rainy periods.