Increasing the thickness of the arable layer and improving its physical properties and aeration while deepening contribute to:

• Deeper penetration of the plant root system into the lower soil layers, allowing better use of water and nutrients in the root zone. 
• Accumulation of water in the soil from precipitation and melt water. According to calculations of K.I. Boltyan, deepening of arable layer of sod-podzolic soil from 20 to 30 cm increases stocks of available water by 110 t/ha, or 11 t of water for each additional 1 cm of layer. Potential reserves of available water for plants in 10 cm illuvial layer are 16 mm (l/m²) for light loamy and 21 mm – for heavy loamy. The deepening of the arable layer allows plants to better withstand short-term spring-summer droughts.
• Increasing the porosity and air capacity of the soil, improving gas exchange, which allows plants with a strong root system to use subsoil layers more fully.
• Effective control of weeds, diseases and pests. Cutting the roots of weeds to a great depth contributes to their death. Deep embedding of seeds and vegetative organs of weed reproduction hinders their germination, accelerates the death of pests and pathogens, in general it allows to reduce by 60-70% of the soil infestation and improve its phytosanitary condition. 
• Loosening of the subarable horizon and destruction of the plow pan, which is formed during the annual plowing at the same depth and which significantly worsens the water and air regimes of the subarable horizon, that is especially undesirable on clay soils. As a consequence of deepening the arable layer, water runoff, washout of soil and nutrients are reduced, the risk of erosion processes is reduced and the efficiency of fertilizers and chemicalization increases.
• Reduced soil deformation and greater resistance to excessive compaction under the influence of the driving systems of tractors, tillage implements and transport vehicles.
• Sustainable functioning of the agro-ecosystem due to the potential increase of organic matter and energy accumulation in the soil.

The need for minimum tillage is due to the reduction of energy and labor costs for its implementation. In modern technologies of crop cultivation, tillage accounts for up to 25% of labor and 40% of energy costs.

Intensification of arable farming requires increasing tractor capacity, working width of implements, but reducing the weight and pressure on the soil. For example, a tractor К-701, weighing 12 tons, has a wheel system pressure of 1.7-1.8 kg/cm². Permissible load on the soil in the state of physical ripeness during plowing is 1.0-1.2 kg/cm². Excessive compaction leads to deterioration of agrophysical properties of the soil, reducing, for example, field germination of winter wheat seeds by 25% and yields by 12-30%.

The use of intensive tillage in crop rotations with the predominance of annual plowing activates the microbiological processes of humus decomposition. Black-earth soils at the mouldboard tillage lose 0.8-1.2% of humus for 30 years, which negatively affects the balance of organic matter and leads to significant losses of nutrients and energy. Accelerated decomposition of humus contributes to the development of erosion processes, especially on sloping lands. For this reason the minimum tillage is considered as the most important condition of keeping the potential and increasing the effective fertility, protecting the soil from erosion by improving the humus balance and reducing losses of nutrients. At the same time it significantly reduces energy costs for processing and the time of field work.

The most important conditions for the effective use of minimum tillage are:

• high technological level of cultivation of crops,
• qualitative mechanized field works in optimal terms,
• provision of the farm with effective means of plant protection and fertilizers.

Minimization of tillage is achieved by high technical equipment of the farm with combined tillage and seeding aggregates that combine up to 4-5 technological operations, for example, tillage, application of fertilizers, herbicides, seeding.

Minimum tillage is primarily required on black earth, chestnut, gray forest and well-cultivated sod-podzolic soils with agro-physical properties optimal for plants, fields clean from perennial weeds. For example, reduction of deep tillage on black earth, chestnut, gray forest and other soils is possible if the equilibrium density is approximately equal to the optimum and does not exceed 1.2-1.3 g/cm³ for cereal crops and the air content is at least 13-15% of soil volume.

The suitability of soils for minimum tillage is determined by a number of fertility indicators:

• humus content,
• water-retentive structure,
• porosity coefficient,
• degree and type of weediness of the field.

Suitable, for example, sod-podzolic soils are considered with a humus content of at least 2%, water-retentive aggregates, that is, particles smaller than 0.25 mm, more than 25-30% and a porosity coefficient of more than 0.9. Soils with porosity coefficient less than 0.9 are unstable and prone to compaction, which negatively affects yields.

The main directions of minimum tillage include:

• reducing the number and depth of main, pre-sowing and inter-row tillage in crop rotations on highly fertile soils and favorable agrophysical properties, subject to the use (if necessary) of herbicides;
• replacement of the deep main tillage for some crops of the crop rotation by surface and shallow tillage at the expense of the use of wide-blade flat-cutting, chisel, disk and other tools, especially for winter and spring grain crops;
• combination of several technological operations and methods in one working process through the use of combined tillage and seeding aggregates;
• use of direct sowing of cereals, corn without preliminary, strip (in the area of the row) pre-sowing tillage when growing row crops.

The choice of minimum tillage methods depends on fertility level, moisture zone, biological characteristics of the crop and the degree of weeding of the fields. For example, on moist lands of the North-West region of the Non-Black Soil Zone due to soil compaction the autumn plowing for potatoes is replaced by shallow disc tillage to a depth of 10-12 cm.

The use of herbicides reduces the number of inter-row tillage in row crops. On light soils, there is a pre-sowing harrowing for early spring crops, and in the system of main tillage deep plowing is periodically replaced by shallow plowing or discing by 10-12 cm.

Cultivation of potatoes, root crops and vegetable crops on fields without perennial weeds exclude autumn plowing or replace it with discing. This method is effective on light granulometric composition of sod-podzolic soils, dark gray forest and other well-cultivated soils.

A good mixing of soil with fertilizers is achieved in spring pre-sowing milling with the use of tools with active working tools, such as КФГ-3,6, ПР-2,7, which improves the quality of processing and increases yields by 10-20%.

According to the Ryazan State Agricultural Academy, plowing in the first year with the embedding of organic fertilizers is enough for repeated corn cultivation on gray forest soils, in the next three years it is acceptable to replace it by discing to a depth of 10-12 cm.

Minimum tillage is especially effective on the black earth soils of the Central Black Earth zone, the North Caucasus, the Volga region in the cultivation of winter wheat, following the leguminous, annual grasses, corn for silage.

Plowing is replaced by shallow loosening to a depth of 10-12 cm using disk and polydisc tillers, flat-cut cultivators such as КПШ-9, КПШ-11, equipped with needle harrows БИГ-3А and ring-spurring rollers.

Bare fallows are widespread in arid areas, in zones of unstable moisture, as well as after sunflowers, millet, barley, and other crops that clog fields because of their poor competitiveness with weeds.

In the steppe regions of Siberia and Kazakhstan, which are characterized by harsh snowless winters, winter cereals are almost not cultivated, and after fallow, spring wheat is sown. In this case the fallow field is cultivated for a longer period, including the spring of the year of spring wheat sowing.

Summer-autumn (also autumn) tillage – tillage in summer-autumn period for sowing spring crops in the following year. It may include one or more techniques performed in a certain sequence. Methods of autumn tillage depend on soil and climatic conditions: moisture of zone, soil type, granulometric composition, thickness of arable layer, probability of erosion, reaction of crops to tillage depth, preceding crops, weed infestation and other conditions.

Depending on the purpose of tillage systems can be divided into:

• main;
• pre-sowing;
• post-sowing, on care of the crop.

The choice of techniques that make up a particular system of tillage is determined by landscape conditions, type and condition of soil, zonal climatic features, weediness of fields, preceding crops and their biological characteristics, fertilizer system in the crop rotation. It should provide optimal timing and high quality of work.

Currently the following systems of mechanical processing are used:

• The system of tillage for spring crops, is determined by the preceding crop, for example, annual non-row crops of continuous seeding, row crops, seeded perennial grasses, bare or strip fallows, tillage for intermediate crops and after their harvesting.
• Tillage system for winter crops includes tillage of bare, strip or seeded fallows and tillage after non-fallow predecessors.

Tillage systems for specific crops are combined into technological complexes or systems of tillage in the rotation.

According to the method of main treatment of certain crops systems are divided into:

• moldboard,
• non-moldboard,
• combined,
• minimum,
• combined, include two or more methods of tillage.

For example, if the rotation is dominated by moldboard as well as chisel tillage, the system is called the moldboard-chisel system. If flat-cutting predominates in the rotation and alternates with the moldboard, the system is called flat-cutting-moldboard.

All systems of tillage for individual crops are inextricably linked with each other in the rotation and based on a scientifically sound combination of deep and shallow, moldboard and no-moldboard and other types of tillage in each field, for a particular crop. Taking into account the level of fertility, weediness of fields and other conditions determine the possibility of reducing the depth and number of main tillage, if there is a risk of erosion, soil protection tillage is used.

Depth is the key parameter of tillage, which affects the incorporation of fertilizers, seeds and vegetative organs of weeds, the quality of crumbling. Depending on the depth, a distinction is made between:

• surface – to a depth of up to 8 cm;
• shallow – to a depth of 8 to 16 cm;
• normal (medium) – to a depth of 16 to 24 cm;
• deep – to a depth of 24 to 40 cm;
• plantage – to a depth of more than 40 cm.

Two-tier (two-layer) plowing is a special method of main tillage to a depth of 35-40 cm with turning the upper part of the arable layer and simultaneous loosening of the lower part or moving the upper and lower layers vertically. Two-tier plowing allows loosening the upper part of the arable layer with overturning the lower one. It provides deep embedding of seeds and vegetative organs of weeds reproduction, turf, plant residues, slowing down their decomposition. Deep embedding of weed seeds, pest larvae and fungus spores reduces crop infestation by 60-70%.

Two-tier plowing is used for cultivation of sod-podzolic soils, plowing of alfalfa layer, for pre-sowing soil preparation for sugar beet and other technical crops. Two- and three-tier ploughs ПД-3-35, ПНЯ-4-40, ПНЯ-6-40 and ploughs with notched bodies are used for it.

Rolling is carried out simultaneously with sowing or after it, before sprouting in dry weather, especially on loose soils. Rolling allows to compact the soil of the sowing layer and improve the contact of seeds with the solid phase of the soil. Excessive looseness of the sowing layer prevents water absorption by seeds, the top layer dries up quickly, which reduces field germination of seeds and slows down the emergence of seedlings. Lack of moisture in the period of bushing node formation negatively affects the formation of the secondary root system of cereal plants.

Post-sowing packing also reduces air content in the soil; it improves its warming, which ensures earlier sprouting. It is especially effective for sowing leguminous crops as well as cereals and grasses when they are sown in dry soil. Post-sowing consolidation of tilled crops, such as corn and sunflower, increases field germination and accelerates seedling emergence.

Rolling has negative features: continuous soil rolling also stimulates weed seed germination, soil compaction reduces its water permeability and moisture absorption of precipitation, soil crust is formed when drying. Therefore, with sufficient soil moisture and good pre-sowing tillage, rolling is inexpedient. When sowing small-seeded crops, packing is combined with sowing.

In order to avoid continuous rolling grain seeders СЗС-2,1, СЗП-3,6А are used, equipped with special rollers, which compact the soil only in the rows of sowing and well close the rows. As a result, a dense seed bed is created and field germination of the seeds increases.

Post-sowing rolling is carried out by smooth rollers of ЗКВГ-1,4, СКГ-2 type with additional loosening of the surface by light seed harrows or ploughs. This creates a loose layer on the surface and prevents emergence of soil crust. In legume crops that bring the cotyledons to the surface, the soil crust hinders emergence of seedlings. For this reason, rolling is carried out during the pre-sowing cultivation or combined with sowing.

In the steppe arid zone, the soil is rolled after sowing, while in regions with sufficient moisture the soil is rolled before sowing.

Nutrition area is the area occupied by one plant, which provides optimal conditions for growth and development, hence the highest yield.

It depends on:

• the species and density of the plants, i.e. their number per 1 m2 or 1 ha;
• the degree of tillering and branching;
• the moisture content of the area;
• the duration of the growing season.

Thus, late-ripening varieties require a larger nutrition area compared to early-ripening varieties. In warm and arid climates, the nutrition area should be larger, and hence the seeding rate. For example, for the Non-Black Soil Zone, the optimal feeding area per plant of winter wheat is 20 cm², for the left bank of the Volga region – 25 cm². On soils with a high level of fertility the nutrition area is less than on less fertile soils. In conditions of irrigated agriculture it is possible to increase the density of plant standings.

The highest productivity of plants is achieved with the optimal nutrition area, which is close to a square in shape.

Nutrition area is determined for each crop and variety experimentally in relation to specific conditions of cultivation.

Disking^[1]There is no exact analogue of the Russian concept of “лущения” in English. The closest translations: discing, stubbling [as applied to the fall application of the technique, also … Continue reading – method of soil treatment, which provides loosening, mixing, partial wrapping and cutting of weeds. Disking allows to cover a part of stubble, weed seeds, which in the wet soil give seedlings and sprouts that are destroyed by subsequent tillage. It partially eliminates pests and pathogens that live on stubble. Disking creates a loose, mulching layer of soil on the surface of the field to reduce soil moisture evaporation.

Disking of the dried up compacted soil after harvesting cereal crops creates more favorable conditions for the subsequent plowing, making it easier and preventing further drying.

Stubble dicking, which is carried out after harvesting cereals, leguminous and other crops of continuous sowing, and soil discing are differentiated. Stubble dicking with flat discs are used for disker in steppe areas, and with spherical (concave) discs in areas with sufficient moisture content. The discs are good at cutting horizontal rhizomes and shoots of roots of perennial weeds, stimulating their sprouting.

The depth of discing depends on the degree of weed infestation and species of weeds, soil moisture at the time of treatment and the preceding crop. When weed infestation by annual weeds the depth of discing is 4-5 cm, rhizomatous – up to 8-10 cm. On dried soils the working depth is increased by additional weights or by increasing the angle of attack to 30-35 °, which allows well cut and crush layers, incorporate vegetable residues and weed seeds. Stubble discing is carried out across the direction of harvesting units movement at a speed of up to 10 km/h.

Mouldboard and disc disker for discing. Mouldboard (polydisk tiller or hull) disker are light ploughs with small bodies without skimmers, allowing to carry out loosening to a depth of 18 cm with turning the soil. Such tillage is especially effective for undercutting root-shoot weeds.

Examples of the disker^[2]The name of the tool used for discing. Also may be used: till-plow, breaker stubble, cleaner stubble, one-way disk, disker, harrow single(-disk), parer, disk topsoil, plow shallow, plow skim, plow … Continue reading: ЛДГ-5А, ЛДГ-10А, ЛДГ-15А.

Plowing is a method of main tillage, which ensures turning of the tilled layer layer by at least 135°, loosening and partial mixing of the soil, undercutting the underground part of plants, fertilizers and plant residues. Plowing changes the composition of the arable layer, giving it a loose lumpy structure.

Increased aeration of the soil during plowing increases the activity of soil microflora, part of the seeds, seedlings and vegetative organs of weeds moves to the deeper layers, losing germination or dying off.