Johan Arvidsson

Nutrient uptake and growth of barley as affected by soil compaction

A field experiment with different levels of compaction was carried out on a mouldboard ploughed silty clay, with the objective of studying the effects on plant nutrient uptake and growth. Soil from the field was also used in laboratory studies of carbon and nitrogen mineralization, and plant uptake of water and nutrients.In the field, low as well as high bulk densities reduced biomass production and nutrient uptake of barley (Hordeum vulgare L.) compared to intermediate bulk densities, where grain yield was approximately 20% higher. In the beginning of the growing season, the concentration of phosphorus and potassium was lowest in plants grown in the loosest and in the most compacted soil, and suboptimal for plant growth. The uptake of nutrients transported by diffusion was more affected by compaction than for nutrients transported by mass flow. The reasons for lowered uptake in loose compared to moderately compacted soil could be reduced root-to-soil contact, a low diffusion coefficient for nutrients and/or reduced mass transport of water to seed and roots. Differences in plant nutrient concentrations between treatments gradually declined until harvest. Immediately after compaction there was probably oxygen deficiency in the compacted soil since the air-filled porosity was critically low, but as the soil dried out, mechanical resistance to root growth may have become a more important growth-limiting factor.In the laboratory study, severe compaction reduced carbon mineralization and uptake of water and nutrients by roots, and caused denitrification. There were only small differences between loose and moderately compacted soil in carbon mineralization, nitrogen concentration in the soil, uptake of water and nutrients and dry matter yield.The large yield increase due to recompaction in the field was not reproduced in the laboratory. Possible reasons are differences in soil temperature between the field and laboratory, in the sowing and fertilizing methods, the pretreatment of the soil and in the spatial variability of bulk density. It is possible that recompaction is needed only in the uppermost part of the soil, which is the loosest, dries out first, and is where the seed as well as the fertilizer are placed.

A model for estimating crop yield losses caused by soil compaction

A computerized empirical model for estimating the crop yield losses caused by machinery-induced soil compaction and the value of various countermeasures is presented, along with some examples of estimations made with it. The model is based mainly on results of Swedish field trials, and predicts the effects of compaction in a tillage system that includes mouldboard ploughing. It is designed for use at farm level and predicts four categories of effects: (1) Effects of recompaction after ploughing. The calculations are based on the wheel track distribution in the field and the relationship between “degree of compactness” of the plough layer and crop yield. (2) Effects of plough layer compaction persisting after ploughing. Crop yield losses are estimated from traffic intensity in Mgkm ha−1 (Mgkm = the product of the weight of a machine and the distance driven), soil moisture content, tyre inflation pressure and clay content. (3) Effects of subsoil compaction. The calculations are similar to those presented under point (2), but only vehicles with high axle load are considered. These effects are the most persistent. (4) Effects of traffic in ley crops. The estimations are based on wheel track distribution, soil moisture content and several other factors.

Introduction to the special issue on experiences with the impact and prevention of subsoil compaction in the European Union

Abstract The papers in this special issue present results of the European Union (EU) concerted action “Experiences with the impact of subsoil compaction on soil crop growth and environment and ways to prevent subsoil compaction”. The results and conclusions of earlier research on subsoil compaction are memorized and it is emphasized that the conclusions are still sound: high axle load traffic on soils of high moisture content causes deep and persistent subsoil compaction. The concerted action on subsoil compaction in the EU and an almost identical concerted action on subsoil compaction in central and eastern Europe are briefly introduced. This special issue presents a selection of papers of the concluding workshop of the concerted action on subsoil compaction in the EU. It includes three papers on modeling the impact of subsoil compaction on crop growth, water availability to plants and environmental aspects; three papers on modeling of subsoil compaction by heavy machinery; four papers on measurement of soil mechanical and physical properties in relation to subsoil compaction and four papers on methods to determine the risk of subsoil compaction and to identify prevention strategies. The trends in agriculture in relation to subsoil compaction are discussed. A positive trend is that policy makers in the EU and worldwide recognize soil as a vital and largely non-renewable resource increasingly under pressure. A negative trend is that wheel loads in agriculture are still increasing causing severe damage to subsoils. The conclusion is that European subsoils are more threatened than ever in history. Manufactures, agricultural engineers and soil scientists should collaborate and research should be initiated to solve this problem and find solutions. Subsoil compaction should be made recognized by all people involved from farmer to policy maker. Therefore an assessment of the existence and seriousness of subsoil compaction throughout Europe should be initiated.

Do effects of soil compaction persist after ploughing? Results from 21 long-term field experiments in Sweden

Abstract The extent and persistence of the effect of soil compaction in a system with annual ploughing were investigated in 21 long-term field experiments in Sweden with a total of 259 location-years. Crop yield, soil physical properties and plant establishment were determined. All experiments had two common treatments: control (no extra traffic) and compacted (350 Mg km ha −1 of experimental traffic in the autumn prior to ploughing), using a tractor and trailer with traditional wheel equipment and an axle load restricted to 4 Mg. During the rest of the year, both treatments were conventionally and equally tilled. The compaction was repeated each autumn for at least 7 years, and the yield was determined each year until 5 years after the termination of the compaction treatment. Compaction decreased the porosity and the proportion of large pores and increased the tensile strength of dry aggregates. On clay and loam soils, it decreased the proportion of fine aggregates in the seedbed and the gravimetric soil water content in the seedbed. The yield in the compacted treatment declined compared with the control during the first 4 years, after which it reached steady state. During this steady state, the compaction treatment caused a yield loss of 11.4%, averaged over 107 location-years. Within 4–5 years after the termination of the compaction treatment, the yield returned to the control level. The average yield loss at individual sites increased with increasing clay content. Results from additional treatments indicated that yield loss was linearly correlated with the amount of traffic up to 300–400 Mg km ha −1 . With greater ground contact pressure or a greater soil water content at time of traffic, there was a greater yield loss. Soil compaction effects on yield were similar for all spring-sown crops, and the percentage yield loss seemed to be independent of the yield. In a few location-years with winter wheat there was on average no yield decrease. There were 5.1% less plants in the compacted treatment than in the control. The yield decrease was significantly correlated with the number of plants. Between years results were highly variable, and no consistent correlations between yield loss and soil water content at the time of traffic or the weather conditions during the growing period were found. Soil compaction affected yield during years with good as well as poor conditions for crop growth.

Subsoil compaction caused by heavy sugarbeet harvesters in southern Sweden; II. soil displacement during wheeling and model computations of compaction

Traffic with high wheel loads in combination with high inflation pressure implies a risk for subsoil compaction, but effects will depend on the soil strength. Soil displacement during traffic with a heavy sugarbeet harvester (total load approximately 35 Mg on two axles) was determined at 0.3, 0.5 and 0.7 m depths during harvesting in the autumn. Measurements were made on one occasion on a clay loam (Eutric Cambisol) and a sand (Haplic Arenosol), and at different water contents on a sandy clay loam (Eutric Cambisol). Soil mechanical properties (precompression stress and shear strength) were determined for each traffic occasion. Field measurements were also compared with model computations of soil compaction, based on calculation of soil stresses and on the mechanical properties measured. On the sandy clay loam in the driest condition, displacement occurred only at 0.3 m depth, while it was registered down to 0.7 m depth in the wettest condition, when soil moisture was around field capacity. On the clay loam and the sand there was displacement down to 0.5 and 0.7 m depth, respectively. Model predictions of compaction correlated well with the depth to which displacement was measured in the field. One important task in subsoil compaction research is to define methods to determine soil mechanical properties that are easy to use and that still make it possible to predict compaction. The results clearly demonstrate that heavy sugarbeet harvesters may cause compaction to more than 0.5 m depth during normal field conditions in the autumn, with soil water content as the most decisive factor.

Review of modelling crop growth, movement of water and chemicals in relation to topsoil and subsoil compaction

Soil compaction influences crop growth, movement of water and chemicals in numerous ways. Mathematical modelling contributes to better understanding of the complex and variable effects. This paper reviews models for simulating topsoil and subsoil compaction effects. The need for including both topsoil and subsoil compaction results from still increasing compactive effect of vehicular pressure which penetrates more and more into the subsoil and which is very persistent. The models vary widely in their conceptual approach, degree of complexity, input parameters and output presentation. Mechanistic and deterministic models were most frequently used. To characterise soil compactness, the models use bulk density and/or penetration resistance and water content data. In most models root growth is predicted as a function of mechanical impedance and water status of soil and crop yield-from interactions of soil water and plant transpiration and assimilation. Models for predicting movement of water and chemicals are based on the Darcy/Richards one-dimensional flow equation. The effect of soil compaction is considered by changing hydraulic conductivity, water retention and root growth. The models available allow assessment of the effects of topsoil and subsoil compaction on crop yield, vertical root distribution, chemical movement and soil erosion. The performance of some models was improved by considering macro-porosity and strength discontinuity (spatial and temporal variability of material parameters). Scarcity of experimental data on the heterogeneity is a constraint in modelling the effects of soil compaction. Suitability of most models was determined under given site conditions. Few of the models (i.e. SIBIL and SIMWASER) were found to be satisfactory in modelling the effect of soil compaction on soil water dynamics and crop growth under different climate and soil conditions.

Stress distribution and soil displacement under a rubber-tracked and a wheeled tractor during ploughing, both on-land and within furrows

Ploughing is a field operation considered to be associated with severe soil compaction. Two experiments were carried out in Denmark on Eutric Cambisols with a Claas Challenger 2-65 E rubber-tracked tractor with a total weight of 185 kN. In Experiment A, the vertical stress under the track during ploughing was measured by stress sensors at 0.1 m depth in order to study stress distribution. In Experiment B, the vertical soil displacement and vertical normal soil stress during ploughing were measured simultaneously at three different depths. The tracked tractor was compared to a wheeled tractor with a total weight of 97 kN. The rubber-tracked tractor and the wheeled tractor were pulling a plough with 12 and 7 bodies, respectively. The tracked tractor ploughed on-land, whereas the wheeled tractor ploughed both on-land and conventionally (two wheels running in the furrow). In Experiment A, vertical stress was found to be much higher under the rear than under the front part of the tracks. It was caused by unsuitable adjustment of the plough to the tractor for given field conditions. By lowering the point of application of the draught force induced by the plough, maximum vertical stress was reduced from 304 to 158 kPa. However, the vertical stress was concentrated under the supporting rollers and wheels as well as under the centre line of the track, so that maximum stress was 3.8 times higher than average stress. In Experiment B, the vertical stress was higher below the wheeled tractor than below the tracked tractor, which had been adjusted as in Experiment A. No significant difference in maximum vertical soil stress was found between the tracked tractor and the wheeled tractor ploughing on-land at any depth. The vertical stress at 0.3 and 0.5 m depth was significantly higher during conventional ploughing (i.e. under the in-furrow wheels) than during on-land ploughing. The higher vertical stress also resulted in larger vertical soil displacement at 0.3 m depth under the in-furrow wheels when ploughing conventionally than under the on-land ploughing tractor. At 0.5 m depth, no residual vertical soil displacement occurred because the soil strength was very high. The results clearly demonstrated that on-land ploughing may reduce the risk for subsoil compaction compared to conventional ploughing. Using tracks instead of wheels may further reduce this risk. However, this is only the case if the tractor is well balanced. Thus, each particular tillage tool should be adjusted to the tractor, also with respect to the soil type and the field conditions.

Soil stress and compaction effects for four tractor tyres

Abstract Compaction effects and soil stresses were examined for four tractor tyres under three inflation pressures: 67, 100 and 150% of the recommended pressure. The four tyres were 18.4 R 38, 520/70 R 38, 600/65 R 38 and 650/60-38 and they carried a wheel load of 2590 kg. The 650/60-38 was a bias-ply tyre while the other three were radial tyres. Increased inflation pressure significantly increased all measured parameters: rut depth, penetration resistance and soil stress at 20 and 40 cm depth. The 18.4 R 38 caused a greater rut depth and penetration resistance than the other tyres, which did not differ significantly from each other. The soil stress was highest for the 18.4 R 38, followed by the 650/60-38. The low-profile tyres decreased compaction compared with the 18.4–38 tyre, mainly by allowing a lower inflation pressure. The use of low-profile tyres did not reduce compaction if not used at a lower inflation pressure. The bias-ply tyre caused a higher stress in the soil than the radial tyres when used with the same inflation pressure, but the compaction effects in terms of rut depth and penetration resistance were not greater for this tyre than for the radial low-profile tyres.

Application of the Kinect sensor for dynamic soil surface characterization

Agricultural soil roughness is pertinent to important agricultural phenomena, such as evaporation, infiltration or compression. Monitoring roughness variations would make possible the improvement of tillage operations. In the present work, implementation of the Microsoft Kinect™ RGB-depth camera for dynamic characterization of soil micro-relief is proposed and discussed. The metrological performance and the effect of the operating conditions on three-dimensional reconstruction was analyzed considering both laboratory tests on calibrated reference surfaces and field tests on different agricultural soil surfaces. Data set analysis was made on the basis of surface roughness parameters, as defined by ISO 25178 (2012) series: average roughness, root mean square roughness, skewness and kurtosis. Correlation between different tillage conditions and roughness parameters describing soil morphology was finally discussed.

Early sowing - a system for reduced seedbed preparation in Sweden.

Conventional seedbed preparation for spring sown crops in Sweden includes 3‐4 harrowings followed by sowing, but there is a great interest among farmers to reduce this tillage. Since the soil is normally at field capacity after winter, the conventional system implies a major risk of soil compaction and the farmer has to wait for the soil to dry before seedbed preparation can be started. A new technique that has been made possible by new types of seed drills and improved tyre equipment is early sowing of spring cereals without harrowing. It was tested in 74 field experiments in Sweden during 1992‐1996, on soils with clay contents ranging from 6 to 57% (typically Eutric or Gleyic Cambisols). On an average, early sowing increased yield by 1% compared with that of conventional sowing. When early sowing was made more than 30 days before conventional sowing it increased yield by an average of 11%. There was no clear relation between yield response to early sowing and soil type. In four long-term experiments, there were no significant differences in bulk density or in saturated hydraulic conductivity between early and conventional sowing. As an average for all experiments, number of emerged plants was 6% lower for early than that for conventional sowing, but this factor did not seem to be decisive for crop yield. In an experiment, when barley (Hordeum vulgare, L.) was grown after barley, there was a higher occurrence of leaf scald (Rhyncosporium secalis (Sacc.) Shoemaker) and net blotch (Dreschlera teres (Oudem) J.J. Davies) in early sown treatments, however, when all results are considered, the risk of increased plant pests due to early sowing seems small. In total, early sowing of spring cereals without harrowing may be beneficial to farmers since it reduces the cost of tillage and increases crop yield potential by lengthening the growing period. # 2000 Elsevier Science B.V. All rights reserved.