Cereals in the crop rotation – a group of crops in the crop rotation, relating to cereals and occupying in the structure of cultivated areas, as a rule, half or most of the arable land.
Main article: Cereal crops
Repeated sowings of cereal crops
Cereal crops in most cases react to repeated sowing with a sharp decrease in yields. Winter wheat is especially sensitive, the others are less sensitive.
In the chernozem steppe of the Middle Volga region, repeated and permanent sowing of spring wheat reduces yields due to high weed infestation and root rot. Thus, at repeated sowing due to root rot the grain yield of spring wheat decreased by 31.1%.
Table. Influence of preceding crops, repeated and permanent crops on weediness and yield of spring wheat (Korchagin, Neyasov, 1996)[1]Farming. Textbook for universities / G.I. Bazdyrev, V.G. Loshakov, A.I. Puponin et al. - M.: Publishing house "Kolos", 2000. - 551 p.
| Winter rye on bare fallow | |||
| Corn | |||
| Spring wheat repeatedly | |||
| Spring wheat is permanent | |||
However, the effect of repeated sowing on grain yield depends strongly on climatic conditions and preceding crops. In the Non-Black Soil zone, winter wheat re-cropped after perennial grasses reduces grain yield, while in the Black Earth steppe zone of the North Caucasus and Southeast the effect of repeated crops after bare fallow is much less.
The share of sown areas occupied by winter wheat in the forest-steppe zone, South-East, Kuban of Russia can reach 30-40% of arable land, so it can be grown in repeated crops after bare fallow. In these regions, it also gives high yields after alfalfa 2-3 years of use, as well as after leguminous crops and corn for silage.
A similar effect is shown for spring wheat: under conditions of sufficient moisture in the European part of Russia, repeated crops sharply reduce yields, while in the arid steppes of Altai, Western Siberia and other eastern regions after bare fallow to a much lesser extent affect yields.
In crop rotations in which spring wheat accounts for large areas, it is sown in succession for two years.
Repeated sowing of oats and barley in all regions of Russia leads to a decrease in yields by 15-20% and to severe weed infestation. In areas where grass sowing is applied, these crops are cultivated with underplanting of perennial grasses.
Rice under special agrotechnics – a complex system of plant protection, irrigation by checks and high doses of fertilizers, withstands the 2-3-year repeated sowing without a marked decrease in productivity, for example, in the crop rotations of rice-growing enterprises of Kuban. In case of permanent rice crops, salinization and swamping of soils, accumulation of hydrogen sulfide and ferrous oxide forms, weed infestation of crops by specialized weed plants: rice weed, bulrush (Bolboschoenus), arrowroot (Sagittaria), sedge (Carex) and others negatively affects the yield. Therefore, repeated sowing of rice alternates with the best preceding crops for it – alfalfa, leguminous plants, corn, winter wheat with intercrops.
Predecessors of cereal crops
The place of cereals in the crop rotation is determined by their food value, so they try to place on the best predecessors – bare and seeded fallows, after perennial grasses or leguminous crops.
Winter cereals
The best predecessor of winter cereal crops is bare fallow, but it is not economically profitable everywhere. The greatest effect of bare fallow is observed in arid zones and areas with insufficient moisture. In areas with sufficient moisture it is more expedient to sow winter crops after seeded fallows, which give the same results as bare fallows.
In the Non-Black Earth zone of the European part of Russia, winter rye and winter wheat are placed after perennial grasses, such as clover-timothy mixture of 2-3 years of use, after clover, vetch-oat or sideral fallow, after peas, early potatoes (in the central regions of the zone) or corn for green fodder. In the northeast of the zone can be placed after bare fallow.
In this zone grain and fodder yields from 1 ha of arable land in crop rotations with seeded fallows are higher than with bare fallows. It should be taken into account that the seeded fallows are effective on condition of high level of agrotechnics, sufficient amount of organic and mineral fertilizers, timely harvesting of fallow crops and preparation of the field for sowing winter crops. When the fields are heavily infested with vicious weeds, it is advisable to include bare fallow in the crop rotation. Clean couples are justified in the farms of the Volga-Vyatka economic region: the cultivation of winter crops, with their large share in the structure of sowing areas, without bare fallow is difficult.
Good preceding crops for winter crops in many areas of the Non-Chernozem zone are perennial and annual grasses, leguminous crops, early silage crops, barley for early harvesting.
In the Central Black Earth zone, good winter cereal predecessors include: in the arid part of the zone – bare fallow; with insufficient moisture – bare and seeded fallow; in areas with sufficient moisture – seeded fallow, perennial and annual grasses, corn for green fodder and silage, leguminous crops.
In the North Caucasus and its subzones, the effectiveness of bare, seeded fallows, and other predecessors is different. For example, in areas with sufficient moisture in Krasnodar Krai, winter wheat can be placed after legumes, perennial grasses, corn for green fodder or grain, castor oil plant, sunflower, winter wheat, barley and seeded fallow. A good predecessor in these areas is alfalfa. After which the grain yield of winter wheat was by 0.5-0.6 t/ha higher than that of corn, sunflower and cereal grains cultivated on the type of half-fallow. When sown on sainfoin seeded fallow, it gave the same high yields as on black fallow. In addition, in 6 years of sainfoin seeded fallow, an average of 3.71 tons of high quality hay per hectare was obtained. Moisture content in the seeded sainfoin fallow was almost the same as in the black fallow.
On the background of high doses of fertilizers and timely tillage in the subzones of the North Caucasus, high yields of winter and after row crops are obtained. In Kuban, maize harvested early for green fodder or early silage is a good predecessor of winter wheat.
In arid and semi-arid areas of Stavropol Krai and Rostov Oblast, winter wheat and winter rye give very low grain yields when sown after all non-fallow predecessors, and in dry years high yields are possible only when sown after properly treated bare fallow. According to the data of the Stavropol Research Institute of Agriculture in the arid regions of the Stavropol Territory winter wheat yields in 15 years on average 2.09 t/ha of bare fallow, and only 1.26 t/ha on non-fallow preceding crops. At the same time, bare fallow showed an aftereffect on subsequent crops. In another experiment for the same zone the yield of winter wheat after bare fallow was 3.04 t/ha, while after corn – 1.99 t/ha.
Yield of winter wheat variety Bezostaya 1 in the experiments of Zernograd breeding station of Rostov region after black fallow reached 4.47 t/ha, while after corn for silage – 1.47 t/ha. These experiments confirm that in arid and semi-arid conditions it is possible to obtain high and sustainable yields of winter wheat if bare fallow is included in crop rotation.
The main preceding crops in arid areas of the Southeast are bare fallow and strip fallow. According to Krasnokutskaya and Kamyshinskaya breeding stations, the grain yield of winter rye after corn for silage decreases by 33-45% compared with bare fallow. In conditions of moisture deficit, seeded fallows and even more so, non fallow preceding crops cannot provide normal sprouting of winter crops.
Based on many years of observations of research institutions and advanced farms in the most arid regions of Russia, which include Volgograd, Saratov and other regions, it is recommended to place winter cereals only after bare or strip fallows, and in dry years, when by the time of sowing winter water reserves in fallow field will be insufficient for sprouts, it is advisable to use these fallows for sowing of spring wheat. In less arid right-bank districts of the Southeast, it is also recommended to sow winter cereals after bare and strip fallows. However, in more favorable weather conditions, winter cereals, mainly rye, can be sown after seeded fallows, corn for green fodder or early silage and early leguminous crops. For example, in the right bank of the Saratov region, winter wheat along with black fallow is sown in favorable years after harvesting early varieties of peas, pea, Hungarian sainfoin and early varieties of maize for green fodder or early silage.
In the forest-steppe regions of the Volga region, winter crops, mainly winter rye, are sown after seeded fallow, legume crops, corn for early silage or green fodder. To maintain optimum sowing conditions for winter crops, it is important to timely harvest the fallow crop and prepare the soil well.
Unlike winter wheat, winter barley is less winter-hardy, so it is widespread in the south of the North Caucasus. Fields occupied by the most valuable preceding crops are allocated for winter wheat, and winter barley is placed after non-fallow crops. High barley yields can also be obtained by planting barley after legumes, sunflowers, castor beans and corn for silage or grain.
In addition to the size of the winter wheat grain yield, the predecessors have an impact on its quality. Grain obtained in the 2nd year of repeated sowing of winter wheat after row crops had the lowest weight of 1000 grains with low protein content. On the contrary, the grain obtained when winter wheat was grown after bare and seeded fallow or after perennial grasses and castor bean had the highest weight of 1000 grains, high bulk density of grain and protein content.
In the forest-steppe and eastern steppe regions of Russia, for example, in the Volga region, Southern Urals, Western Siberia, Altai and adjacent areas, spring wheat, occupying 50% or more of arable land with a limited number of cultivated crops, can replace bare fallow, including for reseeding, as well as barley, corn for green fodder, annual grasses.
Spring wheat is the most demanding to soil fertility and predecessors. It is widespread in Siberia, the Trans-Urals, southeastern Russia and Kazakhstan. In other parts of the country it occupies smaller areas.
The main predecessors of spring wheat in all zones of Russia are row crops: sugar beets, potatoes, corn, etc., as well as leguminous crops that enrich the soil with nitrogen – lathyrus, lentils, peas, etc.
The value of row crops as predecessors is due to the fact that during the growing season, these fields are repeatedly cultivated, reducing weeds, and a large amount of fertilizer is applied.
Perennial grasses are a good predecessor for spring wheat, as well as for other spring cereals. They increase the yield and grain quality of spring wheat, especially durum.
Often, winter wheat and rye are used as precursors of spring wheat, especially if the latter were placed after bare, seeded fallow or perennial grasses.
According to the Nizhny Novgorod Agricultural Academy, oats turned out to be the best predecessor of all cereals for spring wheat on light gray medium-cultivated soils. Sown after oats, it was 2 times less affected by root rot than after barley.
In the steppe arid regions of the Trans-Urals and Siberia, the best precursor of spring wheat is bare fallow, after which the crop can be grown repeatedly for two, sometimes three years. Leguminous crops, corn for silage, potatoes, and winter rye after bare fallow can be the predecessors for spring wheat in the Trans-Urals and Pre-Urals.
In the arid areas of the South-East (Volgograd, Orenburg, Saratov regions), winter crops cultivated after bare or seeded fallow, corn, sorghum, and broadly sown millet may be the predecessors of spring wheat; in the Central Black Earth zone – sugar beet, potato, corn, leguminous plants and winter crops.
Spring forage crops (oats and barley) are responsive to the same predecessors as spring wheat, except for bare and seeded fallows, as well as perennial grasses, which are used for more demanding crops.
The most common good predecessors of barley and oats are row crops such as corn, potatoes, castor beans, sunflowers, etc., and sugar beets in the beet-growing areas.
Oats and barley in all zones of Russia show high yields after leguminous crops: soybeans, peas, beans, lupine, as well as cereals – winter and spring wheat and winter rye. Their infestation by fungal diseases and weed infestation of fields after rye and wheat is less than in repeated crops.
Groats cereal crops
Groats cereal crops (millet, buckwheat) are preceded by winter cereals following perennial grasses, as well as row crops such as potatoes, corn, sugar beets, fodder crops, etc.
Millet is very demanding with respect to soil fertility and cleanliness of the fields.The highest yield is noted when it is placed on fertile virgin lands and fallow lands, as well as after perennial grasses. Good predecessors are leguminous crops and well-tilled row crops such as sugar beets and potatoes. It is possible to place millet after winter crops in a bare or seeded fallow.
Buckwheat is less sensitive to weeds than millet, but reacts sharply negative to repeated sowing. Potatoes, corn, sugar beets and other row crops as well as leguminous crops are good predecessors. With high farming techniques, it can be grown on winter and spring cereals.
According to the All-Russian Research Institute of Legumes and Cereals, for the Central Black Earth zone the best preceding crops for buckwheat are row crops – corn, potatoes, sugar beets, as well as winter crops, under which fertilizers were applied.
High and stable rice yields are possible with repeated sowing alternating with perennial grasses or leguminous crops. Experiments conducted in Krasnodar Territory show that the best predecessor of rice is alfalfa, while 3-year repeated sowing leads to a decrease in soil fertility, field clogging and reduced yields. In scientifically grounded crop rotation the rice yield is 5.54 tons of grain and more per 1 hectare. Good precursors of rice are leguminous crops and seeded fallow.
Under irrigated conditions of the Lower Volga region (Astrakhan oblast) rice yield at repeated sowing was 3.1 t/ha, by alfalfa layer – 4.7 t/ha.
Cereal crops as predecessors
Cereal crops
The value of cereal crops as predecessors is determined by the level of agricultural technique and their predecessor, i.e. pre-predecessor. Winter and spring wheat and winter rye cultivated after bare fallow or perennial grasses are good predecessors for many crops due to the after action of steam and perennial grasses.
Sugar beets, corn, potatoes, sunflowers and other row crops especially effectively use this aftereffect. Therefore, in many areas of cultivation of these crops are crop rotation sections: bare fallow – winter cereals – row crops or perennial grasses – winter cereals – row crops.
Winter cereals in the crop rotation are good precursors for fiber flax, millet, spring cereals, leguminous crops, and rice. However, due to specific pests and diseases, the use of cereals as predecessors is undesirable.
Winter cereal crops, due to early harvesting dates, allow the use of fields for sowing intercrops. For example, under irrigation conditions in the southern regions of Russia, after harvesting winter barley or winter wheat, corn is sown in the stubble, which gives up to 40-50 t/ha of green mass before the onset of cold weather.
In areas of sufficient moisture in the North Caucasus with a long fallow period, repeated sowing of winter wheat is interrupted by sowing of intermediate crops, the use of which for fodder or green fertilizer allows for good yields from repeated sowing of winter wheat.
The value of spring cereals as precursors is relatively lower than that of winter cereals, although it also depends on the level of agricultural technique and the predecessor. Spring wheat can be a satisfactory predecessor for reseeding and for other crops, provided it comes after clean fallow or perennial grasses. It is of lesser value if it is cultivated after row crop predecessors. Spring wheat is considered to be an unacceptable predecessor after repeated crops or its sowing on other cereal crops.
Oats, due to the fact that they are almost not affected by root rot and other specific diseases of cereals, can be considered a good predecessor for most cereals, legumes and row crops.
Barley, cultivated after row crops, leguminous crops, is considered a satisfactory predecessor for winter rye due to the early release of the fields with, as a rule, a sufficiently high fertility. It can be a precursor to many row crops. Barley is not suitable as a predecessor for winter and spring wheat because of the susceptibility to the same root rot diseases.
Groats cereal crops
Millet, coming after perennial grasses or well fertilized row crops, is considered a good predecessor among groats cereal crops. Intercropping repeated crops of spring wheat with millet increases its yield by 15-40%.
Experiments of the Krasnodar Research Institute of Agriculture showed that millet is a good cover crop for alfalfa or sainfoin.
Buckwheat is also considered a good preceding crop for spring cereals because of its belonging to another family, its ability to reduce the weediness of fields and to assimilate hardly soluble phosphates of soil. It is followed by leguminous crops, corn, potatoes and other row crops. Because of the late harvesting period in the Non-Black Soil Zone, it cannot be used as a predecessor for winter cereals.
In the humidified regions of the Northern Caucasus and in the south of Russia, buckwheat should be cultivated after harvesting winter wheat or barley and harvested before the fall cold. In this case, it interrupts the cultivation of winter and subsequent spring grain crops, which has an important agronomic value.
The quality of cereal crops as predecessors, change depending on fertilizers, herbicides and other means of agricultural intensification. According to S.A. Vorobyov, barley yields on sod-podzolic soils of Moscow Region vary greatly depending on the predecessors on unfertilized soil (background). Application of fertilizers significantly levels the yield. According to the Krasnodar Research Institute of Agriculture, high efficiency of legume crops as predecessors of winter wheat is noted only on unfertilized background. Fertilizer application eliminates the difference in winter wheat yields after predecessors and is 63-80% higher than in permanent 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.