Problems of Energy Saving and Soil Compaction

Harm Caused by Excessive Soil Compaction

The use of heavy tillage machines and transport vehicles under the existing multi-operation technology of soil and crop care leads to excessive soil compaction under the impact of running systems.

Soil compaction leads to:

• a decrease in water permeability and waterlogging of the upper layer, which intensifies water erosion;
• the formation of a surface crust when compacted soil dries;
• deterioration of gas exchange;
• poor seed placement and reduced field germination; for example, germination of barley decreases by 27-30%, winter wheat — by 23.4%;
• a reduction in the number of beneficial microorganisms;
• slowing of microbiological and redox processes, thereby reducing the availability of nutrients to plants;
• a decrease by 24-30% in effectiveness of fertilizers.

Grain yield losses per hectare due to compaction amount to 0.82-1.24 t, and diesel fuel overconsumption — 2.5-3.5 kg. The most noticeable losses are in moist areas.

A single pass of a tractor compacts the soil to a depth of up to 45 cm; with multiple passes, especially a K-700 tractor, up to 50-60 cm. The consequence of compaction persists for several years, especially in subsurface layers.

When growing crops, machine-tractor units make 5-15 passes over the field, compacting the arable and subsurface soil layers. Only during pre-sowing tillage and sowing do the running systems of machinery cover up to 80% of the field area, and plantings of potatoes, sugar beet, and other row crops during the spring period alone are subjected to 3-5-fold impact by units. The total area of their tracks when performing the entire complex of field work reaches 100-200% of the field area.

When sowing using DT-75 tractors, 21.6% of the field area is subjected to direct and indirect deformation; with T-150K tractors — 29.4%; with K-700 tractors in aggregation with three seeders — 39% (Department of Agriculture, MAA). The density of sod-podzolic soil along the wheel track of wheeled tractors increases by 0.1-0.3 g/cm³, reaching 1.35-1.55 g/cm³, which is substantially higher than the optimal soil density for field crops. Crop yield in the grain-row crop rotation vetch-oat mixture — winter wheat — barley — potato decreased on average over 10 years by 6-22% due to the compacting impact of tractors. The greatest decrease was observed with wheeled tractors T-150K and K-700.

During fall plowing to a depth of 20-22 cm of sod-podzolic medium loamy soil in the Non-Chernozem zone, at a depth of 20-80 cm the density over 10 years of use of T-150K and K-700 tractors increased by 0.1-0.15 g/cm³, reaching 1.38-1.62 g/cm³ (MAA named after K. A. Timiryazev).

According to data from long-term experiments of the North Caucasus branch of the ARRI of Agricultural Mechanization, on chernozems the specific soil resistance when plowing to 20-22 cm along the tracks of light wheeled and tracked tractors is 12-15% greater than outside the tracks, and along the tracks of T-150K and K-701 tractors — by 44%. At the same time, the quality of soil clod crumbling worsened: outside the tracks the degree of clod crumbling was 87%, and along the tracks of T-150K — 83%, K-701 — 56%. The compacting impact of these tractors extends to a depth of 40-60 cm, maximum — up to 1 m.

The permissible specific pressure for most soils is 0.4-0.5 kg/cm², maximum — 1.0-1.5 kg/cm². However, high-power wheeled tractors have an indicator of up to 3-4 kg/cm² and more. By the level of compacting impact on soil, domestic tractors can be arranged in the following order: DT-75 < MTZ-52, MTZ-100 < MTZ-82 < T-150K, K-700 < K-701.

Soil overcompaction leads to deterioration of agrophysical, biological, and agrochemical properties. At a constant depth of the cultivated layer, a plow sole forms — an excessively compacted layer that negatively affects the water, air, and thermal regimes of the soil.

The most severe overcompaction occurs at increased soil moisture. For this reason, the optimal state for tillage is physical ripeness, which is within the moisture limits for sod-podzolic soils — 12-21%, gray forest soils — 15-23%, chernozem soils — 15-24%. For all soil types, the recommended moisture for tillage is not higher than 65-70% FC. The permissible pressure on moist soil at 60% FC for early spring harrowing is 0.3-0.4 kg/cm², during pre-sowing tillage — 0.5-0.6 kg/cm², main tillage — not higher than 1-1.5 kg/cm². Yield loss of field crops in the link of the grain-row crop rotation vetch-oat mixture — winter wheat — barley — potato on average over two rotations was 6-22% depending on the compacting action of tractors. The greatest decrease was noted when using T-150K and K-700 tractors.

Total yield losses of cereal crops from soil overcompaction in Russia reach 13-15 million t, sugar beet — more than 2 million t, maize grain — about 0.5 million t (V. V. Dokuchaev Soil Institute, calculation).

Tillage of compacted soils is associated with increased energy costs. According to calculations, fuel consumption during the tillage of compacted soils sharply increases; for example, during plowing by more than 1 million t per year.

The main reason for reduced crop yields under soil compaction is deterioration of the conditions for the formation of a powerful root system and its active functioning. According to data from the Agricultural Experiment Station of the State of Minnesota (USA), an increase in the density of loamy soil from 1.16 to 1.38 g/cm³ leads to a decrease in root length of peas by 6.2 times, and mass — by 1.9 times. Soil compaction causes the formation of a surface root system, which affects mineral plant nutrition, which worsens by 36-42% even with sufficient moisture supply.

Measures to Reduce Soil Compaction

The basis of the system of measures to limit the level of impact of heavy machinery on soil are preventive measures aimed at reducing the number of passes of machinery and loosening the soil during its tillage, applying increased rates of organic fertilizers and enriching with organic matter, liming or gypsuming, and improving structure.

To prevent overcompaction, soil is tilled upon reaching physical ripeness. On all soil types, tillage is performed at moisture not more than 60-70% FMC.

The permissible load limits on moist (60% FC) sod-podzolic loamy soil during early spring harrowing are 0.3-0.4 kgf/cm², during pre-sowing tillage — 0.5-0.6, during main tillage — 1.0-1.25 kgf/cm² (RAAS). For typical heavy loamy chernozem, pressure on the soil during main tillage should not exceed 0.8-1.0 kgf/cm², during sowing and pre-sowing tillage — 0.4-0.6 kgf/cm².

To reduce soil overcompaction during early spring works, for example, harrowing of fall-plowed land, sowing, and pre-sowing cultivation, it is necessary to use tracked tractors or tractors with dual tires, pneumatic tracks and, if possible, avoid the use of wheeled tractors type T-150K, K-701. Especially great damage is caused by the running parts of tractors to sowings of winter cereals and grasses during early spring top dressing with nitrogen fertilizers. Heavy fertilizer spreaders compact the soil, therefore for top dressing it is advisable to use aviation or tractors with pneumatic tracks.

When using wheeled tractors, they are aggregated so that the tractor track coincides with the track of the trailed implement. The track of the tractor and trailed implement during pre-sowing works is additionally loosened, and the depth along the track is increased by 3-4 cm. Refueling units with seed material, fertilizers, herbicides, or fuel is performed outside the field or on specially designated roads.

Optimization of routes of agricultural machinery movement over the field is an important preventive measure to prevent excessive soil overcompaction. For this, permanent routes (tramlines) of unit movement are established during sowing and crop care. Movement of machinery along permanent routes when using the same brands allows reducing the area of soil compaction by 1.7-2.7 times compared with uncontrolled movement.

When caring for row crops, repeated movement of machinery should be along the same tramline along which planting was performed. Failure to observe this rule leads to damage of plants by the working parts of the cultivator, since the width of butt row spacings is not always maintained during sowing.

Minimization of tillage envisages a reduction in the number of passes of machinery over the field, achieved by combining several technological operations and methods and performing them in one working process. Such an approach allows reducing the number of passes over the field by 2-3 times.

Reduction of soil compaction is achieved by replacing or reducing the number of deep tillages with surface and shallow ones through the use of wide-span high-performance units on slightly infested fields. Thus, in the conditions of the steppe zone, fall plowing for early spring cereals is replaced by flat-cutting tillage using wide-span units, for example, KPSH-9, KPSH-5, KPSH-11.

Loosening of the soil by mechanical tillages is achieved by different-depth tillage in crop rotation; a combination of moldboard and moldboardless tillage; flat-cutting, disk, chisel, etc. Such systems allow reducing the load on the soil and the area of compaction by 30-40%.

An effective method of loosening the subsurface horizons is periodic chiseling to a depth of 30-40 cm, carried out once every 3-4 years. Deep chiseling destroys the plow sole, loosens the compacted subsurface layer, and improves water and air permeability. For this, chisel deep looseners PCh-2.5, PCh-4.5, plows-looseners PRPV-5-50, flat-cutting deep looseners, implements for moldboardless tillage type paraplow, and plows with cut-out bodies are used.

The greatest effectiveness of deep loosening of subsurface layers is achieved in the cultivation of row crops: maize, potato, sugar beet, and others, as well as winter crops. The yield of row crops increases by 15-20%.

Methods of deep loosening are also performed in the system of contour-reclamation farming. On soils subject to the risk of water erosion, deep loosening across the slope promotes the conversion of water runoff over the surface into intrasoil runoff, increasing water reserves and reducing soil washout.