Crop Rotation

Fallow Link

Fallow link of a crop rotation — this is primarily clean fallow. Common fallow links:

• fallow — winter crops — winter crops;
• fallow — spring grain crops — spring grain crops;
• fallow — winter crops — spring grain crops;
• fallow — winter crops;
• fallow — spring grain crops.

Grain-fallow crop rotations are essentially different combinations of fallow links.

Grain Link

The grain link is based on a grain crop — winter or spring rye, wheat, barley, oats — and a grain-legume or groat predecessor of continuous sowing. Grain links make it possible to build field crop rotations of grain specialization in combination with fallow links. For example:

• 1 — clean fallow, 2–3 — spring wheat, 4 — millet, 5 — spring wheat.

In alternation with other links, they allow more effective implementation of the principles of crop alternation, specialization, compatibility, and others.

Row-Crop Link

The main group of crops in row-crop links are row crops, which are predecessors of grain crops, grain legumes, and cereal crops. For example:

• potato — barley;
• maize for silage — winter wheat;
• maize — pea — winter wheat;
• sugar beet — barley, etc.

Combinations of fallow, row-crop, and grain links form various grain-fallow-row crop rotations. Due to the possibility of combining these three links with different numbers of crop fields, it gives unlimited possibilities for constructing field crop rotations. A crop rotation link with row crops is comparable in effectiveness in its effect on weeds to clean fallow.

As the main grain crops, depending on soil-climatic conditions, various crops may be chosen; for example, for the Non-Black Earth, forest-steppe, and steppe zones of the European part of the country and the North Caucasus, winter wheat is used, whereas in the east of Russia — the Southern Urals, Western Siberia and Trans-Urals, Altai — spring wheat. In the Southeast, in the Lower and Middle Volga region, as well as some forest-steppe regions of the country, winter grain crops are combined with spring grain crops. In this case, winter rye or wheat is placed after clean fallow, and spring wheat after row crops and winter crops. For example:

• 1 — clean strip fallow, 2 — winter grain crops, 3 — spring wheat, 4 — row crops, 5 — spring wheat, 6 — spring grain fodder crops (barley or oats).

Grass Link

The grass link is based on perennial grasses, which, as a rule, are used for fodder and seed for 2–3 years. Examples of grass links:

• 1–2 — perennial grasses, 3 — winter crops;
• 1–2 — perennial grasses, 3 — fiber flax.

Due to the aftereffect of perennial grasses on subsequent crops for 2–3 years, grass links may have longer variants:

• 1–2 — perennial grasses, 3 — winter grain crops, 4 — fiber flax;
• 1–2 — perennial grasses, 3 — winter grain crops, 4 — spring grain crops;

the turnover of sod may be used for row crops:

• 1–2 — perennial grasses, 3 — winter crops, 4 — row crops. In this case, a transition to a row-crop link occurs.

Grass links are constituent parts of grain-grass-row crop and crop-alternation rotations in areas of sufficient moisture.

In the south of Russia, in field crop rotations, a grass link of alfalfa is used:

• 1–2 — alfalfa, 3 — winter wheat, 4 — spring grain fodder crops;
• 1–2 — alfalfa, 3–4 — winter wheat;
• 1 — alfalfa (withdrawn field), 2 — winter wheat.

The turnover of sod may also be used for row crops:

• 1–2 — alfalfa, 3 — winter wheat, 4 — sugar beet or maize.

In Transcaucasia, on irrigated lands, the grass link with alfalfa is part of alfalfa crop rotations. Due to 2–3-year cultivation of alfalfa in 7–8-field crop rotations, 4–5-year continuous crops of cotton are successfully used.

Importance

Clean fallows allow:

• accumulating moisture, preserving, and rationally using soil moisture;
• mobilizing nutrients in the soil;
• carrying out measures to combat weeds, pests, and pathogens of crop diseases.

The entire complex of agrotechnical practices that make it possible to improve the fertility of fallow soils and create optimal conditions for plant growth and development makes them a most valuable predecessor for all crops, primarily the most demanding grain crops — winter and spring wheat and winter rye.

Clean fallow, on the one hand, leads to intensive decomposition of soil organic matter, on the other hand it enriches it with nutrients in forms available to plants, provided there are no weeds, which is especially important with deficient fertilizer application for obtaining high wheat yields, especially phosphorus, with which chestnut and chernozem soils of the steppe zone are poor.

Clean fallows perform a phytosanitary function in combating weeds, pests, and pathogens of agricultural crop diseases, increase the biological activity of soils, accelerating the processes of mineralization of organic matter. Clean and occupied fallows reduce the number of viable weed seeds by 2–3 times.

Clean fallows make it possible to accumulate significant moisture reserves, allowing stable yields of good-quality wheat, especially in steppe arid regions: the Volga region, North Caucasus, Southeast of Russia, where wheat yield after clean fallow increases by 1.5–2 times compared with other predecessors; and also in arid regions of the steppe and forest-steppe of the Southern Urals, Trans-Volga, Trans-Urals, Altai, and Western Siberia — by 30–50%.

The effectiveness of fallow fields strongly depends on soil-climatic conditions, applied fertilizers, and the plant protection system. In modern farming systems using advanced soil tillage systems, crop rotations without fallow fields can be more productive.

In grain crop rotations, the share of grain crops can account for up to 30–50% of arable land. A smaller amount of land is allocated to clean fallows, therefore repeated crops are often resorted to. The remaining share of grain crops is placed after annual and perennial grasses, grain legumes, maize for silage, and some other crops.

Types of Clean Fallow

Clean fallow may be: black, early, late.

Black fallow — clean fallow, the deep primary tillage of which is carried out in autumn after harvesting the preceding crop.

Early fallow — clean fallow, the primary soil tillage of which is carried out in spring, in the year of fallowing. It is used in regions with a short autumn period or when there is no time left for soil tillage after harvesting spring crops, for example, in Northern Kazakhstan and Siberia. In addition, leaving stubble makes it possible to reduce the effect of wind erosion and increase snow accumulation.

Black fallows almost always have an advantage over early fallows, since they allow accumulating more moisture during the autumn-winter and spring periods, as well as longer use of destructive measures.

Strip fallow — black or early fallow in which tall crops are planted in strips: sunflower, maize, mustard, and other plants with a strong stem. Most often used in arid steppe regions with strong winds.

Strip fallow performs three functions: snow retention, protection of winter crops from unfavorable conditions in the winter period in low-snow and arid regions, and protection of soils from wind erosion. Strips make it possible to retain even the first snow, whereas snow banks can be made only when the snow cover height is 12–15 cm. An increase in snow cover thickness promotes moisture accumulation, protection of winter crops from freezing and sharp temperature fluctuations in the spring, and prevention of wind erosion. Strip fallows serve as a good predecessor for winter and spring wheat and increase yield by 0.3–0.4 t/ha.

Strips are placed across the direction of prevailing winds, with a distance between them equal to 3–5 times the working width of seeders or 8–24 m. Strip crops are sown during fallow cultivation, for example, with cultivators combined with seeders. With summer dates of sowing strips (for arid regions — late June — early July), they do not have time to gain sufficient height, which allows sowing winter crops across the strips. Damage to plants during the passage of seeders is relatively small; before winter they have time to strengthen sufficiently and, with the onset of frosts, produce a stable stem.

Late, or peasant, fallow — clean fallow, which in the three-field farming system of Russia was used in the spring-summer period for livestock grazing. In peasant farms, where there were not enough forces and means for simultaneous performance of spring-summer field work and cultivation of clean fallow, late fallow cultivation began only in the second half of summer, before sowing winter grain crops. For this reason, its effectiveness is significantly lower than black or early fallow, and in modern farming it is rarely used.

Geographical Features

In the intensity of use of clean fallows in crop rotations there is a certain geographical regularity, in which water plays the decisive role: as the amount of atmospheric precipitation changes, the leaching water regime of soils changes to a non-leaching one, and as climate continentality increases, the share of clean fallows in the structure of sown areas increases to 10–20%. This increase is observed from west to east and southeast of Russia.

In the steppe zone, in the meter-deep soil layer after clean fallow, 1.5–2.5 times more water accumulates than after non-fallow predecessors. In the forest-steppe zone — up to 1.3–1.4 times; in regions of the Non-Black Earth zone with sufficient moisture, there is practically no increase. For example, in Nizhny Novgorod Oblast, under winter wheat crops after clean fallow, moisture reserves were the same as after occupied fallows (lupine and vetch-oat). No significant difference in wheat yield after these fallows was noted (3.83 and 4.1 t/ha). On the contrary, in the conditions of the dry steppe zone of Western Siberia (Omsk Oblast), productive moisture reserves in the meter-deep soil layer after black fallow before sowing spring wheat were 143 mm with a grain yield of 2.11 t/ha, whereas with continuous sowing moisture reserves were only 76 mm with a yield of 1.1 t/ha.

Clean fallow has a positive effect on the water regime of the soil not only for the first but also for subsequent crops of the crop rotation. Therefore, in the steppe zone crop rotations alternating clean fallows with repeated wheat crops have become widespread:

• in the eastern part of the steppe zone: 1 — clean fallow, 2 — spring wheat, 3 — spring wheat;
• in the European part: 1 — clean fallow, 2 — winter wheat, 3 — winter wheat;
• in the Volga region (transitional zone): 1 — clean fallow, 2 — winter wheat, 3 — spring wheat.

Under conditions of unstable moisture in the steppe zone of the North Caucasus (Krasnodar and Stavropol Krais, Rostov Oblast), the moisture reserve in the upper 20-centimeter layer before sowing is of great importance for obtaining stable high yields and good overwintering of winter wheat. Clean fallows make it possible to increase the moisture reserve by 15–25% compared with non-fallow predecessors.

In order to increase moisture reserves from meltwater, strip fallows are used. For example, in Altai Krai strips make it possible to increase snow cover thickness by 3 times, which contributes to an increase in moisture reserves by 20–25%.

Importance

Occupied fallow plays an important role in increasing grain and feed production. They have become widespread in zones of sufficient moisture: the Non-Black Earth and forest-steppe zones, as well as in zones with sufficient moisture of the North Caucasus, Siberia, and the Central Black Earth zone, in which cultivation of fallow-occupying crops with sufficient moisture does not lead to a decrease in the yield of winter grain crops sown after fallow, which makes it possible, with proper agrotechnics, to obtain additional amounts of green fodder, hay, silage, and potato. Occupied fallows are also used under irrigation and with a high standard of farming.

The fallowing time in occupied fallow is significantly less than in clean fallow. They are introduced, as a rule, on weed-free fields with sufficient fertilizer application.

Winter crops are placed after occupied fallows; in the Non-Black Earth zone they yield 5–15% lower than after clean fallow, however, due to the products obtained from the fallow-occupying crop, the effectiveness as a whole remains higher. This is especially noted if legumes and green manures are used as the fallow-occupying crop.

Fallow-Occupying Crops

The fallow-occupying crop should ripen early and suppress weed growth. They are predominantly represented by leguminous crops. Non-fallow predecessors are crop rotation crops with a late harvesting date that do not have a fallowing period.

On occupied fallows, crops of continuous sowing can be sown, for example vetch-oat, pea-oat, pea-barley, or other mixtures of annual crops, as well as some perennial grasses for hay, green fodder, or silage, maize, and early potato. Such crops are called annual grasses and are harvested for fodder in the budding phase — beginning of flowering of the legume component.

After harvesting the crop, the soil is treated as fallow and the field is prepared for sowing winter or spring crops.

Types of Occupied Fallows

Continuous occupied fallow — occupied fallow in which the fallow-occupying crop is of continuous sowing, that is, annual and perennial grasses, grain crops, legumes, and their mixtures.

Row-crop occupied fallow — occupied fallow in which the fallow-occupying crop is an early-ripening row crop, for example early potato, in southern regions — maize, sunflower for green fodder or silage, etc.

Due to the fact that in row-crop fallow crops are planted with row spacings of 45–60–70 cm, this makes it possible, unlike continuous fallow, to carry out summer soil tillage.

Green-manure fallow — occupied fallow in which the fallow-occupying crop is a green manure. Most often legumes act in this role, their green mass being plowed into the soil as green fertilizer. On lighter soils it is more expedient to grow lupine as a green manure, and on more cohesive calcareous soils — sweet clover. Green-manure fallows are often used in the zone of sufficient moisture on light sandy soils poor in organic matter. On heavy clay soils they contribute to structuring and creating better looseness and water permeability.

Half fallow — a fallow field remaining after harvesting grain crops, grain legumes, and some other crops, which is repeatedly treated as fallow. As a rule, fallowing is 2–3 months. Half fallow is more often used in steppe regions of the European part of Russia.

Geographical Features

Vetch-oat occupied fallow is often used in the Non-Black Earth zone, where its effectiveness in aftereffect on potato and other row crops is comparable to clean fallow.

Potato occupied fallow, in its influence on the yield of winter crops, as well as on the productivity of the link with row crops, is comparable to vetch-oat. However, in comparison with clean fallow, the productivity of the link is higher by 23–30%.

In more moisture-deficient conditions, for example in the Central Black Earth zone, the yield of winter wheat is 15–20% higher after clean fallow than after vetch-oat. However, the effectiveness of the link due to the products of the fallow-occupying crop is higher.

In regions of sufficient moisture of the North Caucasus, occupied fallows of leguminous perennial grasses — clover and sainfoin — make it possible to obtain the same yields of winter wheat as after clean fallow.

On sandy and sandy loam soils, green-manure fallows play an important role.

Importance

The qualities of perennial grasses as a predecessor are determined by the ability of leguminous plants to accumulate nitrogen in the soil and by a complex positive effect on the fertility and productivity of subsequent crops.

Due to the accumulation of a large amount of plant and root residues, perennial grasses contribute to increasing soil fertility. The mass of plant residues reaches 7–8 t/ha of absolutely dry matter. Not infrequently the group of perennial grasses, in its effect on fertility and the yield of winter grain crops and other crops, surpasses occupied and clean fallows under conditions of sufficient moisture because of high water consumption. Lack of moisture sharply reduces the yield of perennial grasses, leads to thinning and weed infestation. For this reason, perennial grasses are used in regions of sufficient moisture, as well as on irrigated lands as predecessors of winter crops. Their aftereffect persists on the second and third crops, determining their universality of use as a predecessor.

Perennial grasses perform an ecological function of protecting the soil from erosion. Due to the strong grass stand, they cover the soil from intensive atmospheric precipitation and wind. Their powerful root system creates the upper soil layer strengthened against the destructive action of water and wind.

Use of Perennial Grasses in Crop Rotations

In the first year, perennial grasses develop slowly and do not produce a large yield. During this period their root system is formed, which is preserved under the cover of the main crop. After harvesting the main crop, the grasses continue to vegetate and go into winter. In spring of the next year, vegetation resumes. Perennial grasses make it possible to carry out 2–3 cuttings of fodder mass during the summer. The period of their use may be 2–3 years in field crop rotations, and 4–5 years and more in fodder and specialized ones.

Perennial grasses in a crop rotation are most often undersown under the cover of preceding annual grasses or grain crops, or sown simultaneously with early spring crops. For this, grain-grass seeders are used. Undersowing of perennial grasses under conditions of the Non-Black Earth zone is carried out in spring under the cover of spring and winter grain crops. However, with high yields of grain crops up to 3.5–5 t/ha of grain, undersown perennial grasses are suppressed by the cover crop, which leads to their significant thinning. For this reason, perennial grasses are undersown under the cover of annual grasses, winter crops, or vetch-oat mixture for fodder.

The effectiveness of perennial grasses is influenced by moisture, dates and methods of sod cultivation, mass and composition of root and post-cutting residues, degree of infestation by diseases and pests, and weediness.

Importance

Row crops reduce the number of weeds, accumulate reserves of available nutrients in the arable layer, and some of them positively influence the water balance. The soil under row crops remains loose throughout the season, contributing to activation of soil microflora.

Most row crops are late spring crops, which makes it possible before their sowing to carry out several soil tillages and, in combination with herbicides, destroy some annual weeds and restrain the spread of perennial ones. Destructive measures are also carried out after sowing with the help of inter-row cultivation until the rows close.

The production of some row crops is especially profitable, which makes it possible to increase the profitability of enterprises. In addition, the location of enterprises around potato and sugar beet processing plants makes it possible to reduce transportation costs.

The negative qualities of row crops include: a small amount of plant residues, destructive effect on soil structure, and weak soil-protective function. Therefore, when cultivating them, high doses of organic fertilizers are applied. Another disadvantage of row crops is the large removal of nutrients, therefore they are cultivated against the background of high doses of organic and mineral fertilizers, the aftereffect of which may persist for several years.

On lands with a slope of more than 3°, the area of row crop sowings is reduced or they are completely excluded from the crop rotation. In case of sowing on sloping lands, they are placed in rows across the slope with special soil-protective measures.

Row Crops in Crop Rotation

The reaction of row crops to predecessors and the order of alternation in a crop rotation are different. The best predecessors of row crops are considered winter crops following clean fallow, then winter crops following occupied fallow. In regions with sufficient moisture, good predecessors include winter and spring grain crops following sod of perennial grasses.

With a large share of row crops in the structure of sown areas, under conditions of high fertility and good application of organic and mineral fertilizers, some of them can be sown after other row crops. Grain legumes, as a more valuable predecessor, are used mainly for grain crops.

Despite satisfactory results of repeated crops for some row crops, sowing in the same place should be avoided, especially on soils in regions subject to wind and water erosion.

Row crops can be considered valuable predecessors, after which cultivation of many agricultural plants is possible, including row crops belonging to other botanical families. Late-harvested row crops are used as predecessors for spring crops. After row crops, clean and occupied fallows are not placed, just as vice versa, including because after row crops the soil in clean fallow is strongly pulverized. In regions with a threat of wind and water erosion, for the same reason, repeated crops of row crops are not used.

Importance

Most agricultural crops occupy the field for 50–70% of the warm period of the year. In the spring period, when sowing late spring crops, there may also remain enough time to obtain an additional yield of green mass of winter crops.

Intermediate crops, along with occupied fallows, are elements of intensive farming. If the replacement of clean fallows by occupied ones under conditions of sufficient moisture makes it possible to increase the coefficient of arable land use to unity, then the use of intermediate crops makes it possible to make it higher than unity. The use of fertilizers, irrigation, and modern soil tillage technologies makes it possible, through intermediate crops, to increase the productivity of 1 ha of arable land in the Volga region and Kuban to 20–25 thousand FU, in the Non-Black Earth zone — to 10 thousand FU

Due to the use of intermediate crops in the southern regions of Russia under irrigation conditions, it is possible to obtain up to three harvests per year, increasing the productivity of arable land by 1.6–2.6 times and reducing the cost of production by 15–25%. The degree of saturation of crop rotations with intermediate crops can reach 30–80%.

Intermediate crops are an important source of feed and a link in the green conveyor. They make it possible to obtain green fodder during a period when the main fodder crops have not yet reached fodder ripeness (in spring) or have been harvested (in autumn). They can serve as high-quality raw material for preparing feed for the stall period. In southern regions they also make it possible to obtain grain, for example, with stubble sowing of buckwheat, or tubers with stubble or post-cutting planting of potato. Crops of green-manure intermediate crops can be used for green fertilizer.

The All-Russian Research Institute of Feeds has developed a technology for producing green fodder for farmstead crop rotations, making it possible to obtain from a combination of winter intermediate and undersown crops up to four harvests of fodder during the year under conditions of the Non-Black Earth zone. This became possible due to the widespread use of mineral fertilizers and liquid manure, irrigation, and other methods of intensifying farming.

In specialized crop rotations, intermediate crops make it possible to mitigate negative phenomena and compensate for dropped links of crop alternation.

Intermediate crops have a versatile effect on agrophytocenosis. Their use makes it possible to reduce weed infestation in subsequent links by 30–50%, and damage by root rots by 1.5–2 times. The positive effect of intermediate crops is due to the density of the stand, which suppresses weeds, and plant residues plowed into the soil enhance the activity of soil biota, which suppresses root rot pathogens and weed seeds.

The introduction of intermediate and green-manure crops into a crop rotation makes it possible to additionally increase the input of plant residues. In southern regions under irrigation conditions, they leave up to 10 t/ha of residues per crop rotation, in the southwestern and central part of the Non-Black Earth region — 3–5 t/ha.

Influence of Intermediate Crops on Soil Fertility

Intermediate crops have a comprehensive effect on soil fertility, the water regime of soils, the yield of subsequent crops, and the productivity of the crop rotation.

Under conditions of sufficient moisture of the Non-Black Earth zone, intermediate sowings of winter rapeseed and white mustard with a green mass yield of 25–30 t/ha do not have a negative effect on the water balance, which is explained by their replenishment from autumn-winter precipitation and meltwater. In southern regions, intermediate crops protect the soil from overheating, reduce the surface wind speed, and create a favorable water regime. Under conditions of the Volga region, stubble sowings of maize reduce soil temperature from 45–48 to 24–25 °C in the absence of irrigation and to 18–20 °C under irrigation (A. M. Gavrilov). Wind speed in stubble sowings of maize and Sudan grass decreases from 3–5 to 0.1–0.2 m/s, which helps preserve relative air humidity in the crops at 95–98% versus 34–36% in open areas.

Under stubble sowings, the biological activity of sod-podzolic soil is 1.5–2 times higher than in the autumn-plowed control plot (MAA named after K. A. Timiryazev).

Intermediate crops increase the number of water-stable aggregates. Thus, on chernozem soils of the Volga region, undersown sweet clover led to an increase in the number of water-stable aggregates in the upper 10-centimeter layer by an average of 12–13%. Under conditions of Moscow Oblast, winter intermediate and post-cutting fodder crops increased the number of water-stable aggregates in sod-podzolic soil by 7–10%. Under conditions of irrigated farming they weaken soil salinization.

Stubble and winter intermediate crops make it possible to protect fields from erosion in the autumn and spring periods.

Intermediate crops serve as a source of organic matter for sod-podzolic and low-fertility soils. Due to them, up to 4–5 t/ha of plant and root residues enter the soil.

In intensive farming, the stubble form of green manuring is economically more expedient than a separate one, that is, the application of green fertilizer through intermediate green-manure crops, rather than separately cultivated for these purposes. As stubble green manures on sod-podzolic soils in the Non-Black Earth zone, white mustard, winter rapeseed, oilseed radish are effective; on sandy and sandy loam soils — annual lupine (as stubble) and undersowing of perennial lupine, serradella, sainfoin.

Due to additional soil tillages when cultivating intermediate crops in a crop rotation, weeds are destroyed. Weed seedlings appearing under the cover of fast-growing and dense crops are suppressed and destroyed before seed ripening during harvesting for green fodder or plowing in for green fertilizer. In some cases, root exudates and decomposition products of green mass have a suppressive effect on seeds of individual weed plants. Weed infestation of subsequent crops after stubble crops decreases by 35–50% while simultaneously reducing the amount of vegetative mass of surviving weeds (MAA named after K. A. Timiryazev). Saturation of a crop-alternation rotation up to 50% with intermediate crops reduces weed infestation of winter wheat crops by 2–3 times.

Types of Intermediate Crops

Stubble crop — an intermediate crop sown after harvesting the main grain crop.

Post-cutting crop — an intermediate crop sown after harvesting the main crop, for example winter rye, annual grasses used for green fodder, hay, or silage. As a rule, post-cutting crops have earlier sowing dates than stubble crops. The same crops are used as post-cutting crops as for stubble crops, as well as fodder rutabaga and cabbage (by seedling method), annual grass-legume mixtures, mixtures of peas or beans with mustard, etc.

Winter intermediate crops — crops sown after harvesting the main crop in autumn for the purpose of obtaining green fodder in early spring. These include rye, triticale, turnip rape, vetch, wintering pea, or mixtures of winter rye and vetch.

Undersown crops — a type of intermediate crops that are sown in spring under the cover of the main crop, for example under winter or spring grain crops, annual grass-legume mixtures. Undersown crops remain vegetating in the field after harvesting the main crop and produce a green mass yield until the end of the season. Winter and spring vetch, serradella, annual ryegrass, lupine, pea, clover, sainfoin, and sweet clover are used as undersown crops.

Predecessors of Intermediate Crops

Stubble and post-cutting crops are cultivated after harvesting winter and early spring grain crops, early grain legumes, annual grasses, and early silage crops. Undersown crops may also be used in these same fields.

Winter intermediate crops are placed in crop rotation fields after late spring crops — potato, maize, buckwheat, sorghum, Sudan grass, etc.

Cultivation

Intermediate crops are cultivated in pure form or in mixtures. For example, mixtures of lupine with oats and sunflower, oats with peas, maize or Sudan grass with peas or vetch, vetch or vetch. Mixtures of winter wheat and winter rye with winter vetch or wintering pea give a higher yield than their pure crops. No less effective are mixtures of cover crops — winter vetch with annual ryegrass, undersown under the cover of winter rye for green fodder.

Obtaining additional yields from intermediate crops is possible with the use of fertilizers applied calculated for the removal of nutrients with the planned yield. Organic fertilizers, as a rule, are applied during the main soil tillage for the preceding main crop. For winter intermediate crops, organic fertilizers are applied before their sowing taking into account the yield of the subsequent main crop. Mineral fertilizers are applied directly under intermediate crops and as top dressing.

The yield of green mass of winter rapeseed and stubble mustard on sod-podzolic soils depends on doses of mineral fertilizers, primarily nitrogen. They positively influence the yield and content of crude protein in the green mass. Spring top dressings with nitrogen fertilizers of winter intermediate crops are effective. Under plants of the legume family, phosphorus and potassium fertilizers are applied.

The choice of soil tillage methods is determined by its density, moisture, and weediness of fields. Under conditions of Moscow Oblast, plowing of loamy soil to the depth of the arable layer with pre-sowing cultivation against different fertilizer backgrounds on average over three years led to an increase in the yield of stubble crop by 10% compared with double stubble discing to 10–12 cm. However, surface tillages are economically profitable, making it possible to quickly prepare the soil for sowing post-cutting and stubble crops and coinciding with the technology of autumn plowing. To accelerate germination under conditions of a short growing season, rolling is used.

Combined implements are most effective when cultivating intermediate crops. Seed sowing rates compared with ordinary sowing are increased by 20–25%. Under conditions of drying of the upper soil layer, the sowing depth is increased by 1–2 cm.

Features of Using Intermediate Crops in Regions of Russia

Cultivating intermediate crops without irrigation is possible in most regions of Russia located south of the line St. Petersburg — Tver — Ivanovo — Kazan — Ufa and north of the line Belgorod — Voronezh — Penza — Ulyanovsk — Ufa. Regional features determine the choice of intermediate crops: drought-resistant and heat-demanding for southern regions of the country, and undemanding to heat, early-ripening, fast-growing, and frost-resistant for the Non-Black Earth zone.

In southern regions, sainfoin, sweet clover, annual clover, Sudan grass are used; in northern regions — various types of clover, sweet clover, winter vetch, serradella, perennial and annual lupine, annual ryegrass. They are sown under the cover of annual grasses or grain crops.

In many regions of Russia, winter rye, wheat, barley, vetch, rapeseed, turnip rape, wintering pea, and wintering oats can be used as winter intermediate crops. They are distinguished by good use of agroclimatic resources of the autumn-winter and early spring periods, resistance to overwintering, fast growth rate, and early spring return of high green mass yields.

In the southern regions of the country under irrigation conditions or sufficient moisture with a long growing season, a large amount of heat, and naturally high soil fertility, there are good prerequisites for cultivation in the post-harvest period. As intermediate crops in southern regions, maize, sunflower, buckwheat, Sudan grass, millet, sorghum, mohar, and other late spring crops are used.

The effectiveness of intermediate crops in the Non-Black Earth zone depends on the duration of the warm period, the amount of heat, and applied fertilizers. In this zone, post-cutting crops harvested for green fodder are suitable, for example vetch-oat and pea-oat mixtures after harvesting early potato. Perennial lupine or sweet clover are considered best for these conditions. As stubble crops, mustard, winter and spring rapeseed, etc., are widespread.

In the forest-meadow zone, oats, peas, lupine, field pea, fodder cabbage, turnip, white mustard, winter and spring rapeseed, phacelia, oilseed radish, winter turnip rape, and other fast-growing and frost-resistant plants are used as stubble and post-cutting crops.

In the Central Black Earth zone, maize, Sudan grass, sorghum, peas, vetch, legume-grass mixtures, winter rapeseed, turnip rape, and others with sowing no later than mid-July are suitable as post-cutting crops. For stubble crops, winter rapeseed, turnip rape, peas, and legume-oat mixtures are used.

In the steppe zone of the European part of Russia, intermediate crops are cultivated: in winter crop sowings — rapeseed, turnip rape, wheat, rye, and their mixtures; in post-cutting sowings — maize, Sudan grass, sorghum, sunflower; in stubble sowings — spring and winter crops of the cabbage family, pea-oat mixtures, triticale, mixture of winter rye with winter vetch.

In the Middle and Southern Urals and Western Siberia, oilseed radish, spring rapeseed, and white mustard are grown as a stubble crop, sowing no later than August 1. Good yields are obtained from the use of winter rye for green fodder, after which the main crop of the crop rotation is sown, for example peas, barley, potato, and maize.