Perennial grasses in the crop rotation is a a group of crops in the rotation that primarily includes forage legumes – clover, alfalfa and forage cereal grasses – timothy, fescue, ryegrass multiyear, vetch and others. Their qualities as a predecessor are determined by the ability of legumes to accumulate nitrogen in the soil, a complex positive impact on fertility and productivity of subsequent crops.
Strongly developed root system with a large mass of cereal grasses allows to accumulate humus in the soil, positively affecting the balance of organic matter. The mass of plant residues reaches 7-8 t/ha of absolutely dry matter. Often the group of perennial grasses by their influence on fertility and yields of winter cereals and other crops exceeds the seeded and bare fallow on condition of sufficient moisture because of high moisture 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 areas with sufficient moisture as well as on irrigated lands as predecessors to winter crops. Their effect is maintained on the second and third crops, determines their versatility and diversity of use as a predecessor.
Main article: Perennial grasses
Features of perennial grasses in crop rotations
In the first year, perennial grasses develop slowly and do not yield much. During this period, they form a root system, which is preserved under the cover of the main crop, after harvesting of which grasses continue to vegetate and go under the winter. In the spring of the following year, vegetation resumes. Perennial grasses allow you to make 2-3 mowing operations during the summer. The period of their use may be in field crop rotations 2-3 years, in forage and specialized – 4-5 years and more.
Perennial grasses in the crop rotation are usually sown under the cover of preceding annual grasses or cereal crops or sown simultaneously with early spring crops. Grain-grass seeders are used for this purpose.
Sowing of perennial grasses in the Nonchernozem zone is carried out in spring under the cover of spring and winter cereals. However, with a high yield of cereals up to 3.5-5 t/ha of grain, seeded perennial grasses are oppressed by the cover crop, which leads to their significant thinning. For this reason perennial grasses are sown under the cover of annual grasses, winter crops or a forage mixture.
Perennial grasses in the crop rotation are, in addition to cereals, good precursors for potatoes (in the absence of wireworms), spring cereals, millet, hemp, and cabbage. For fiber flax, clover and some other perennial grasses are particularly valuable precursors, reducing weed infestation, disease and pest incidence and yielding high yields of seeds and flax fiber.
In the eastern areas of the Nonchernozem zone perennial grasses are a good predecessor for spring wheat provided there is no wireworm.
Strong infestation of wireworms makes perennial grasses in the crop rotation unsuitable for use as a precursor for potatoes, corn and spring wheat.
Sowing of row crops – sugar beet, corn, potato, hemp, tobacco and others 1 year after perennial grasses shows good results.
Under irrigated and southern humidified conditions alfalfa 2-3 years of use is a good predecessor of winter crops and rice. In Central Asia, it interrupts the permanent crops of cotton. In these regions, it is possible to sow perennial grasses without cover, and they already give the first crop of fodder mass in the first year of sowing. In this case the year of sowing is the first year of their use.
Moisture is the main influence on the efficiency of perennial grasses. The timing and methods of cutting turf, weight and composition of root and hay crop residues, degree of contamination by diseases and pests, weediness.
Perennial grasses perform an ecological function of soil protection from erosion. Due to the strong herbage, they shelter the soil from intensive atmospheric precipitation and wind. Their powerful root system creates the upper layers of soil strengthened against the destructive effects of water and wind.
Due to accumulation of large amounts of plant and root residues, perennial grasses are an important factor in increasing soil fertility. The accumulated stocks of organic matter from the decomposition of plant residues structure and improve soil fertility indicators, increasing its moisture capacity, aeration, the proportion of available and fixed forms of nutrients, including from applied fertilizers.
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.