Intermediate crops – crops of the crop rotation, sown in the field after harvesting the main crop in the same year, in order to obtain additional yields.
Most crops occupy the field during 50-70% of the warm period of the year. For example, in the Non-Black Soil Zone, after harvesting spring and winter cereals, fields remain unoccupied for two to three months. During this period 100-150 mm of precipitations fall and the sum of active temperatures reaches 1000 °С, or 30-40% of agroclimatic resources of warm period of the year. The number of frost-free days can reach 65-70 days. This is enough to produce an additional yield of stubbles, single-cut (after mowing the grass), sub-sowing or sideral crops to be used as green forage or green fertilizer. There may also be enough time left in the spring when sowing late spring crops to get an additional crop of green mass of winter crops.
Types of intermediate crops
A stubble crop is an intermediate crop sown after the main cereal crop has been harvested.
Post-mowing crops (single-cut) are intermediate crops sown after the main crop is harvested, such as winter rye, annual grasses used for green fodder, hay, or silage. As a rule, post-mowing crops are sown earlier than stubble crops.
The same crops as for stubby crops are used as post-mowing crops as well as fodder rutabaga and cabbage (by sprouting), annual legume mixtures, pea or bean mixtures with mustard, etc.
Winter intermediate crops are crops sown after the main crop is harvested in autumn to provide green fodder in early spring. These include rye, triticale, colza, vetch, winter peas or mixtures of winter rye and vetch.
Overseeding crops are intermediate crops that are sown in the spring under the cover of the main crop, for example, winter or spring cereals, annual legume mixtures. Overseeding crops remain in the field after the main crop is harvested and give a crop of green mass for the rest of the season. Winter and spring vetch, seradella, annual ryegrass, lupine, peas, clover, sainfoin, and melil are used as overseeding crops.
The importance of intermediate crops
Intermediate crops, along with seeded fallows, are elements of intensive farming. Replacement of bare fallow with seeded fallow in conditions of sufficient moisture can increase the coefficient of utilization of arable land to unity, the use of intermediate crops make it higher than unity.
Wide use of fertilizers, irrigation, modern cultivation technologies enables to increase productivity of one hectare of arable land in Volga and Kuban regions up to 20-25 thousand fodder units, in Nonchernozem zone – up to 10 thousand fodder units.
Table. Efficiency of arable land use under irrigation in Kuban (Zubenko, 1980)[1] Farming. Textbook for universities / G.I. Bazdyrev, V.G. Loshakov, A.I. Puponin et al. - M.: Publishing house "Kolos", 2000. - 551 p.
| One | Corn, green mass | |||
| Two | Winter barley: grain straw | 7.38 | 2.4 | |
| Corn stubble, green mass | ||||
| For a total of two harvests | ||||
| Three | Winter vetch-rye mixture, green mass | |||
| Corn post-mowing, green mass | ||||
| Pea-sunflower mixture post-mowing, green mass | ||||
| For a total of three harvests |
Due to the use of intercrops in the southern regions of Russia under irrigation conditions it is possible to get up to three harvests per year, increasing the productivity of arable land in 1.6-2.6 times and reducing the cost of production by 15-25%. The degree of saturation of crop rotations with intercrops can reach 30-80%.
Intermediate crops are an important source of fodder and a section of the green conveyor. Because of their use, it is possible to obtain green fodder in the period when the main fodder crops have not yet reached fodder ripeness (in spring) or are harvested (in autumn). They can serve as a high quality raw material for stockpiling fodder for the stabling period.
In the southern regions, they produce not only green fodder, but also grain, for example, in the stubble planting of buckwheat, or tubers in the stubble or post-mowing of potatoes. Seeded intermediate crops can be used for green fertilizer.
Intermediate crops are cultivated in pure form or in mixtures. For example, mixtures of lupine with oats and sunflowers, oats with peas, corn or Sudan grass with peas or lathyrus, vetch or lathyrus. Mixtures of winter wheat and winter rye with winter vetch or wintering peas produce greater yields than their pure crops. Mixtures of cover crops such as winter vetch and annual ryegrass sown under winter rye cover for green fodder are no less effective.
Peculiarities of the use of intermediate crops in the regions of Russia
Cultivation of intermediate crops without irrigation is possible in most regions and republics of Russia located south of the line St. Petersburg-Tver-Ivanovo-Kazan-Ufa and north of the line Belgorod-Voronezh-Penza-Ulyanovsk-Ufa.
Sainfoin, melilot, annual clover, Sudan grass are sown in southern areas, while in northern areas – various types of clover, melilot, winter vetch, seradella, perennial and annual lupine, and annual ryegrass. They are sown under the cover of annual grasses or cereals.
In many regions of Russia, winter rye, wheat, barley, vetch, rape, Barbarea, winter peas, winter oats may be used as winter intermediate crops. They are characterized by good use of agroclimatic resources in autumn-winter and early-spring periods, resistance to overwintering, fast growth rate and high yields of green mass in early spring.
In the southern regions of Russia in conditions of irrigation or sufficient moisture with a long growing season, plenty of heat and naturally high soil fertility have good prerequisites for the cultivation of stubble crops in the post-harvest period. Corn, sunflower, buckwheat, Sudan grass, millet, sorghum, foxtail millet and other late spring crops are used as the intermediate crops in the southern regions.
These regional characteristics determine the choice of intermediate crops that are drought-resistant and heat-demanding for the southern regions of the country and those that are not heat-demanding, fast-growing and frost-resistant for the Non-Black Earth zone.
The efficiency of intermediate crops in the Non-Black Soil Zone depends to a greater extent on the duration of the warm period, the amount of heat, and the amount of fertilizers applied.
In this zone, post-mowing crops for green fodder, such as vetch and pea-oat mixtures after the harvest of early potatoes, are suitable. The best for these conditions is considered to be perennial lupine or clover-grass. Mustard, winter and spring rape, etc., are common as the stubble crops.
Oats, peas, lupine, Pisum arvense, fodder cabbage, turnip, white mustard, winter and spring rape, phacelia, oil radish, winter Barbarea and other fast-growing and frost-resistant plants are used as stubble and post-mowing crops in the forest-meadow zone.
In the Central Black Earth zone of Russia, corn, Sudan grass, sorghum, peas, vetch, legume-grass mixtures, winter rape, suet and others with sowing not later than mid-July are suitable as post-mowing crops. Winter rape, colza, peas, and legume-oat mixtures are used for the stubbles.
In the steppe zone of the European part of Russia, intermediate crops are cultivated: in the winter crops – rape, Barbarea, wheat, rye and their mixtures; in the post-mowing crops – corn, Sudan grass, sorghum, sunflower; in the stubble crops – spring and winter cabbage family, pea-oat mixture, triticale, mixture of winter rye with winter vetch.
In the Middle and Southern Urals and Western Siberia, oil radish, spring rape and white mustard are grown as a stubble crop and sown 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, potatoes, and corn.
Predecessors of intermediate crops
Stubble and post-mowing crops are cultivated after harvesting winter and early spring cereals, early leguminous crops, annual grasses and early silage crops. Overseeding crops may also be used in these fields.
Winter intermediate crops are placed in the rotation fields after late spring crops – potatoes, corn, buckwheat, sorghum, Sudan grass, etc.
Cultivation features
Getting additional yields by sowing intermediate crops is possible with the use of fertilizers, applied on the basis of the removal of nutrients with the planned yield. Organic fertilizers, as a rule, are applied during the main tillage under the preceding main crop. For winter intermediate organic fertilizers are applied prior to their sowing taking into account the yield of the subsequent main crop. Mineral fertilizers are applied directly under the intermediate crops and in the form of top dressing.
According to the Moscow Agricultural Academy named after K.A. Timiryazev, the yield of green mass of winter rape and crop mustard on sod-podzolic soils depends on the doses of mineral fertilizers, primarily nitrogen fertilizers. They have a positive effect on yield and the content of crude protein in green mass. Spring fertilization with nitrogen fertilizers of winter intermediate crops is effective. Phosphorus and potash fertilizers are applied to plants of the legume family.
The choice of tillage methods is determined by the density, moisture and weediness of the fields. Under the conditions of the Moscow region, plowing of loamy soil to the depth of the arable layer with pre-sowing cultivation on different fertilizer backgrounds in three years led to an increase in crop yield by 10% on average compared with double stubble plowing (disking) for 10-12 cm. However, it is economically advantageous surface treatment, which allows you to quickly prepare the soil for sowing of post-mowing and stubble crops and coincides with the technology of autumn plowing. Rolling is used to accelerate sprouting in conditions of a short vegetation period.
The most effective for cultivation of intermediate crops combined units allow fertilizing, pre-sowing tillage and seeding in one pass of the technique. Seed rates are increased by 20-25% compared with conventional seeding. In conditions of drying of the upper soil layer the sowing depth is increased by 1-2 cm.
The All-Russian Research Institute of Fodder has developed a green fodder production technology for on-farm crop rotations, which allows to obtain up to four harvests of fodder during the year from a combination of winter intermediate and overseeding crops in the Non-Chernozem zone conditions. This was made possible through extensive use of mineral fertilizers and liquid manure, irrigation and other methods of intensification of agriculture.
Table. Productivity of arable land in forage crop rotations when using intermediate crops (according to the All-Russian Institute of Fodder)[2]Farming. Textbook for universities / G.I. Bazdyrev, V.G. Loshakov, A.I. Puponin et al. - M.: Publishing house "Kolos", 2000. - 551 p.
| First | Middle of May (winter rye) | ||
| Second | July 20-31 (overseeded crops) | ||
| Third | 1-10 August (regrown grass of overseeded crops) | ||
| Fourth | End of September (regrowth of grass overseeded crops) | ||
| Total | |||
Their importance in field and special crop rotations increases even more. With specialization and concentration of animal husbandry, many fodder crops are removed from field rotations and the area of grain crops is increased. Specialization of crop rotations with the maximum saturation of its leading crop leads to the reproduction of pathogens in the soil, an increase in weed infestation by specialized weeds, the spread of pests, and an increase in phytotoxicity of the soil.
Intermediate crops are even more important in specialized crop rotations, which allow to mitigate negative phenomena and make up for the dropped out links of fruit and vegetable rotation. For example, legumes and crucifers as green manure in crop rotations saturated with grain crops up to 80% and more reduce the lesion of barley and wheat by cercosporrelosis and other root rots.
According to the data of the Moscow Agricultural Academy, the infestation of plants in permanent barley crops with root rots can be reduced by 1.5 times through the use of stubble sideration, which due to the green mass plowing promotes the development of saprophytic soil microflora, some groups of which are antagonists of root rot pathogens.
Table. Root rot lesion of barley, % (according to Loshakov, 1980)[3]Farming. Textbook for universities / G.I. Bazdyrev, V.G. Loshakov, A.I. Puponin et al. - M.: Publishing house "Kolos", 2000. - 551 p.
| 1. Winter rye-potato-barley | ||||
| 2. Winter rye-barley-barley | ||||
| 3. Barley-barley-barley |
In Kuban, when the area of rice crops in crop rotations is increased to 70-75% and more, winter intermediate crops of wintering peas or other sideral crops allow to increase rice yield by 28% when permanent sowing.
Rice rotations are recommended with the following alternation: 1 – leguminous crops with alfalfa in summer, 2 – alfalfa, 3-5 – rice, 6 – rice + winter intermediate siderats, 7-8 – rice. Various forms of siderats as intermediate crops in cotton, tobacco, vegetable and other special crop rotations show high efficiency.
Influence of intermediate crops on soil fertility
Intermediate crops have an all-round effect on soil fertility, soil water regime, yields of subsequent crops, and crop rotation productivity.
In the conditions of the central part of the Non-Black Soil Zone of Russia on sod-podzolic soil, plowing the green mass of the stubble white mustard as a green fertilizer, increased the potato yield by 30-50% compared with the control, while simultaneously improving product quality – increasing starch content and reducing scab lesions.
Influence on water, thermal and air regime of soils
Under conditions of sufficient moisture in the Non-Chernozem zone intermediate crops of winter rape and white mustard with green mass yield of 25-30 t/ha have no negative effect on the water balance, which is explained by their replenishment by autumn-winter precipitation and melt water.
In southern areas, intermediate crops protect the soil from overheating, reduce the speed of surface wind and create a favorable water regime. According to Gavrilov A.M. data, in Volga region conditions corn stubble crops decrease soil temperature from 45-48°C to 24-25°C without irrigation and to 18-20°C with irrigation. Wind speed in corn and Sudan grass stubble crops decreases from 3-5 to 0,1-0,2 m/s that contributes to preservation of relative air humidity in crops at 95-98%, in comparison with 34-36% in open plots.
Influence on biological activity of soil
According to the Moscow Agricultural Academy named after K.A. Timiryazev, the biological activity of sod-podzolic soil under stubble crops is 1.5-2 times higher than on the autumn-plowing control plot.
Influence on the structure of the soil
Intermediate crops increase the number of water-retaining aggregates. For example, in the chernozem soils of the Volga region, the sowing of melilot led to an increase in the number of water-retaining aggregates in the 10-cm top layer by 12-13% on average.
Under the conditions of Moscow Region, winter intermediate and post-mowing fodder crops increased the number of water-retaining aggregates in the sod-podzolic soil by 7-10%.
In conditions of irrigated agriculture they weaken soil salinity.
Influence on erosion of the soil
Intermediate crops are an important measure in controlling wind and water erosion. Stubble and winter intermediate crops allow to protect fields from erosion in the fall and spring periods.
Influence on the balance of organic matter in the soil
Intermediate crops are a source of organic matter for sod-podzolic and low fertility soils. Due to them the soil receives up to 4-5 t/ha of plant and root residues, which has a complex positive impact on soil fertility.
In intensive farming it is more economically feasible to use stubble green manure crops instead of independent, that is, the application of green fertilizer at the expense of intermediate green manure crops, rather than separately cultivated for this purpose. White mustard, winter rape, oil radish are effective as stubby green manure for sod-podzolic soils in the Non-Black Soil Zone; for sandy and sandy loam soils – annual lupine (stubby) and underplanting of perennial lupine, bird’s-foot, sainfoins.
Plowing green mass increases the biological activity of the soil, increases the total number and diversity of soil microorganisms. The number of actinomycetes and other groups of active soil microflora increases. Thanks to green fertilizers, available forms of nitrogen for plants are accumulated in the soil.For example, when 16.7 tons of green mass of white mustard per 1 ha were plowed into the sod-podzolic soils of the Nonchernozem zone, the nitrate content in the arable layer amounted to 46 mg per 1 kg of dry soil against 18 mg against the control (no fertilizer). The value of crop green manure as a fertilizer is not inferior and sometimes surpasses the usual doses of organic fertilizers. On light soils plowing green mass of stubble lupine led to an increase in potato yield by 4-7 t/ha. Yield increase of potatoes in combination of manure and crop siderats reaches 10 t/ha.
Influence on the weediness of fields
Thanks to additional tillage in the intermediate crops in the crop rotation, weeds are eliminated. Weed emergence under the cover of fast-growing and thickened crops is suppressed and eliminated before the seeds mature when the intermediate crop is harvested for green fodder or plowed for green fertilizer. In some cases, root excretions and products of green mass decomposition have a depressing effect on the seeds of individual weeds.
For example, after stubble planting of corn in Kuban, the weed infestation of sugar beet decreased by 50% compared with the control (planting of sugar beet on fallow land).
According to the Moscow Agricultural Academy named after K.A. Timiryazev, the weed infestation of subsequent crops after stubble crops is reduced by 35-50% with a simultaneous reduction in the number of vegetative mass of the surviving weeds. Saturation of the cereal-grass-row rotation with intermediate crops up to 50% leads to a 2-3 times reduction of weed infestation of winter wheat crops.
Sources
Farming. Textbook for universities / G.I. Bazdyrev, V.G. Loshakov, A.I. Puponin et al. – Moscow: Publishing House “Kolos”, 2000. – 551 с.
Fundamentals of agricultural production technology. Farming and crop production. Edited by V.S. Niklyaev. – Moscow: Bylina, 2000. – 555 с.
Fundamentals of Agronomy: Tutorial/Y.V. Evtefeev, G.M. Kazantsev. – M.: FORUM, 2013. – 368 p.: ill.