Effects of loosening combined with straw incorporation into the upper subsoil on soil properties and crop yield in a three-year field experiment

Subsoil management needs to be integrated into the current tillage regimes in order to access additional resources of water and nutrients and sustain crop production. However, arable subsoil is often deficient in nutrients and carbon, and it is compacted, affecting root growth and yield. In this study, crop yield and soil responses to loosening of the upper subsoil, without and with straw injection below the plough layer (25-34 cm), were studied during three crop cycles (2016-2018) in a field experiment near Uppsala, Sweden. Responses to straw injection after loosening were studied after single and triple consecutive applications of 24-30 Mg ha-1 during 2015-2017 to spring-sown barley and oats. Subsoil loosening combined with one-time or repeated straw addition (LS treatments) significantly reduced soil bulk density (BD) and increased porosity, soil organic carbon (SOC) and total nitrogen (N) compared with loosening (L) alone (one-time or repeated annually) and the control. In treatment L, the soil re-compacted over time to a similar level as in the control. Field inspections indicated higher abundance of earthworms and biopores in and close to straw incorporation strips. Aggregates readily crumbled/fragmented by hand and casts (fine crumbs) were frequently observed in earthworm burrows. The treatment LS improved soil properties (SOC and porosity) and water holding capacity, but had no significant influence on crop yield compared with the control. Crop yield in all treatments was 6.5-6.8 Mg ha-1 in 2017 and 3.8-4.0 Mg ha-1 in 2018, and differences were non-significant. Absence of yield effect due to treatments could be possibly due to other confounding factors buffering expression of treatment effects on yield. Lower relative chlorophyll content in leaves in the loosening with straw treatment during early growth stages, did not affect final crop yield. Subsoil loosening performed three times gave no further improvement in soil properties and grain yield compared with one-time loosening. There was no difference in yield between repeated subsoil loosening + straw and one-time treatment. It will be interesting to study the long-term effects of deep straw injection and evaluate its impact under other soil and weather conditions

Liming with CaCO3 or CaO affects aggregate stability and dissolved reactive phosphorus in a heavy clay subsoil

A 22-month incubation experiment was conducted to study the effect of lime on clay dispersion, wet aggregate stability (WAS) and dissolved reactive phosphorus (DRP), using a heavy clay subsoil with an initial pH of 7.0 and 7.3 g kg(-1) of soil organic carbon. Lime was applied to achieve soil pH values of 7.5, 8 and 8.4. Clay dispersion decreased linearly with increased pH (corresponding to an increase in lime amount) for both lime types (R-2 = 0.44 for CaO; R-2 = 0.53 for CaCO3, P < 0.05), with a decrease of 2-16 % (CaO) and 3-17 % (CaCO3) compared with the control.Both WAS and DRP followed piece-wise linear functions, with an increase and peak around pH 7.5-7.8, and a decline at higher pH (WAS: R-2 = 0.73 for CaO, R-2 = 0.68 for CaCO3, P < 0.001; DRP: R-2 = 0.84 for CaCO3, R-2 = 0.33 for CaO, P < 0.001). Wet aggregate stability increased on average by 13 % and 11 % at the lowest and intermediate levels, respectively, compared with the control. At the highest lime application rate, WAS was 6 % (CaO) and 8 % (CaCO3) lower than in the control. These differences were probably caused by changes in electrical charge and in concentrations of soluble calcium and dissolved organic carbon (DOC) as the pH increased. More studies are needed to understand the processes in detail and to draw conclusions that are more robust

Evaluation Of Onion Production On Sandy Soils By Use Of Reduced Tillage And Controlled Traffic Farming With Wide Span Tractors

Growing of vegetables is often characterised by intensive field traffic and use of heavy machines. By implementing controlled traffic farming (CTF), compaction of the growth zone can be avoided. An experiment was established in an onion field on a coarse sandy loam. Treatments were applied in the field that for five years had been managed by seasonal CTF (SCTF), where harvest is performed by random traffic due to lack of suitable harvest machines. The main treatment was compaction with a fully loaded potato harvester. The split treatment in the crossed split plot design was mechanical loosening. Bulk density, macroporosity, penetration resistance, water retention characteristics and yield were measured. Mechanical loosening caused improvements in the physical soil measurements and more roots were found in the upper soil layers. The highest yield was however found in the CTF simulation plots (19% higher than in the SCTF simulated plots). Using wide span tractors as a harvest platform will enable CTF in vegetable production. Avoidance of compaction will enable reduced tillage intensity and productivity can be improved both through higher yield of the area that is cropped and by a larger percentage of fields can be cropped area as less area will be needed for tracks

The contribution of tyre evolution to the reduction of soil compaction risks

The use of today’s heavy machinery in agriculture poses a great risk to soil in the form of compaction. Subsoil compaction has been found to persist for decades, thus reducing the risk is extremely important. The stress distribution in the contact area between the tyre and the soil is of primary importance for the propagation of stress in the soil. The characteristics of the tyre therefore affect soil stress. The objective of this study was to compare effects of five generations of tyres (introduced from before the 1970s to 2018) on soil stress and soil structure, including two standard narrow tyres and three larger low-aspect-ratio tyres. Wheel loads of 2900 and 4300 Mg were chosen for the front and rear axles respectively, and the load-rated inflation pressure ranged from 240 to 60 kPa. The contact stress distribution was estimated using the FRIDA model and was used as input for calculation of the vertical stress through the soil profile. Mean normal stress and physical properties were quantified in a field experiment on a clay soil in Clermont-Ferrand, France. The results show that for a given wheel load, the tyre-evolution reduced soil stress when the development included an increase in the tyre-soil contact area and an associated decrease in the tyre inflation pressure. FRIDA model calculations indicated a reduction in soil stress for newer tyres due to a more even contact stress distribution, and were confirmed by the mean normal stress measurements. Although the difference in soil stress between the various tyres decreased with depth, a significant reduction was measured even at 0.6m depth beneath the centreline of both front and rear tyres. We found only a very limited effect of the traffic on the dry bulk density and air permeability at 0.3m depth below the centre of the tyres

Corrigendum to : "The numeric visual evaluation of subsoil structure (SubVESS) under agricultural production"

Erratum de "The numeric visual evaluation of subsoil structure (SubVESS) under agricultural production" http://prodinra.inra.fr/record/294601International audienc

Sustainable soil management: Soil knowledge use and gaps in Europe

International audienc