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Building a crop rotation

Placement of crops and fallows in the rotation is subject to certain laws, taking into account the impact of preceding crops on growth, development and yield of subsequent crops, as well as the impact on the physical, biological and chemical indicators of soil fertility.

For this purpose, despite the diversity of biological properties and cultivation technologies, it is customary to combine crops into groups according to their similar qualities as predecessors and similar impact on fertility indicators.

Crop and fallow grouping in crop rotations

The modern grouping consists of the following groups:

  • bare fallows,
  • seeded fallows,
  • perennial grasses,
  • leguminous crops,
  • row crops,
  • technical non-row crops,
  • winter cereal crops,
  • spring cereal crops,
  • intermediate crops.

The groups are arranged in descending order of the quality of predecessors. That is, the best qualities are bare and seeded fallows. Cereal crops are the worst predecessors.

To assess the crops as precursors the following criteria are taken into account:

  • influence on agrophysical, biological and agrochemical indicators of soil fertility and water regime;
  • the effect of the predecessor on the growth, development, yield and its quality of subsequent crops;
  • soil-protective and ecological function of the predecessor;
  • impact on phytosanitary condition of soil;
  • influence on the overall productivity of the crop rotation.

The generalizing evaluation criterion is the effect of the predecessor on the yield of subsequent crops and the productivity of the rotation as a whole.

The main principle of crop placement in the rotation is to rotate crops so that each successive crop corresponds to the best predecessor. The most demanding crops should be placed after the best predecessor and at the same time be a good predecessor for the following ones.

Section of a crop rotation is a part of a crop rotation consisting of 2-3 heterogeneous crops, including fallow. For example: 1 – bare fallow, 2-3 – winter wheat; 1 – potatoes, 2 – spring wheat; 1 – first-year clover, 2 – second-year clover, 3 – flax; 3 – barley or oats; 1 – grain legumes, 2 – winter wheat, 3 – spring wheat; 1 – sideral fallow, 2 – winter rye; 1 – corn for silage, 2 – winter wheat.

Crop rotation is composed of separate sections, and it may be shifted in the direction of predominance of grain or row crops.

Any section starts with the best preceding crop: fallow, grain legumes, row crops, or grasses. As a rule, the rotation does not start with grain crops, flax, rice.

When constructing crop rotations it is necessary to avoid repeated sowing of cereals for more than 2 years. An exception is grain crop rotations on fertile non-weeded fields after a bare fallow. In this case, 3-year repeated sowing of cereals, preferably of different species, is allowed.

Sunflowers should not be sown after perennial grasses, sugar beets and Sudan grass, nor vice versa, because of the strong drying of deep soil layers, where the root system of these crops is located.

It is inexpedient to use repeated sowing of legumes, because the nitrogen accumulated in the first year is not used in the second year, while cereals, on the contrary, have a great need for nitrogen. Legumes and row crops are good precursors for almost all crops, so do not place bare and seeded fallows after them, and vice versa, including the fact that after row crops the soil in a bare fallow is strongly dispersed. In areas threatened by wind and water erosion, for the same reason, the repeated sowing of row crops is not used.

Perennial grasses, as a rule, are placed under the cover of winter, spring grain crops or annual grasses. This is due to the fact that perennial grasses develop slowly in the first period of their life and do not give satisfactory yields. If they are sown in the same field as the cover crop, they form a root system, and after harvesting cereals in the next year provide a good yield.

Perennial grasses in the year of sowing show high sensitivity to weeds, due to which they are placed in the best sections. For example: 1 – sugar beet, 2 – barley with underplanting of perennial grasses; 1 – bare fallow, 2 – winter wheat with underplanting of perennial grasses; 1 – seeded potato fallow, 2 – winter rye with underplanting of perennial grasses; 1 – bare fallow, 2 – spring or winter wheat, 3 – spring wheat with underplanting of perennial grasses.

As a rule, fields with the worst predecessors, such as oats, are assigned for bare fallow.

When building crop rotations it is necessary to take into account not only the effect of the predecessor on the first crop, but also its effect on subsequent crops.

In order to evaluate the predecessors, the following should be taken into account:

  • irrigability of the fields;
  • previous weed infestation of fields;
  • Infestation of soil and plant residues by pests and pathogens;
  • technology of cultivation of the preceding crop;
  • impact of the preceding crop on agrophysical, agrochemical and biological indicators of soil fertility;
  • previous erosion state of the fields and influence of preceding crops and crop rotation as a whole on it.

Types of fallows

Different types of fallows are considered the most valuable predecessors in terms of their effect on yields for all subsequent crops in the crop rotation.

Fallows are divided into two types and subtypes:

  1. bare:
    • black;
    • early;
    • late;
  2. seeded:
    • row crop;
    • continuous;
    • sideral.

Black and early fallow can have a variation, the coulis fallow.

Semi-fallow fields are distinguished separately.

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

Principles of building crop rotations

Principle of adaptability

The principle of adaptability implies the use of crops in the rotation, adapted to local soil and climatic conditions and the planned structure of the sown areas of a particular farm.

The principle of biological and economic feasibility

The principle of biological and economic feasibility determines the use in the rotation of bare or seeded fallow, winter or spring forms of cereals, single or mixed crops of perennial or annual grasses, no cover or under cover crops, sowing of intercrops and green manure, withdrawal fields, etc.

The principle of alternation of crops

The principle of alternation of crops provides for an annual change of crops belonging to different economic and biological groups and differing in biology and cultivation technology. The most striking classic example of crop rotation is the Norfolk rotation: cereals – 50%, row crops – 25%, legumes – 25%.

The principle of periodicity

The principle of periodicity implies the need to observe the period of return of the same crop to its former place of cultivation. For most of them this period is 2-3 years, for some – 5-7 years or more.

Crop
Period of return to the previous place of cultivation, years
Cereals (wheat, rye, barley, oats)
1-2
Millet, buckwheat
2-3
Corn
1
Legumes (peas, vetch, china)
3
Lupine
4-5
Potatoes
1-2
Sugar beet
3-4
Flax fiber
5-6
Sunflower
6-7
Perennial grasses
3
Forage, root crops
2-3
Tobacco
2-3
Rapeseed
3-4

The principle of compatibility and self-compatibility

The principle of compatibility and self-compatibility provides for the possibility of using as the main crops the predecessors of the same economic and biological group or their re-seeding.

For example, sowing winter cereals after spring cereals, oats after spring wheat or after barley, etc., as well as the repeated sowing of spring or winter wheat after bare fallow, repeated sowing of potatoes, corn, rice under special conditions of agricultural engineering. According to this principle it is not allowed to place plants of the same family after each other.

The principle of compacted use of arable land

The principle of compacted use of arable land defines the inclusion of intermediate crops in the rotation in order to increase the efficiency of arable land use.

It is implemented in conditions of intensive farming to organize the conveyor belt of green forage production, as well as sideration. In the conditions of southern areas, intermediate crops allow getting two crops of grain, tuber crops or other products.

Principle of specialization

The principle of specialization determines the possibility of scientifically justified maximum saturation of crop rotation with one crop or one economic and biological group. It is realized in the conditions of intensive farming in the construction of specialized crop rotations.

Building crop rotations

All principles of building crop rotations are interrelated with each other. The scheme of alternation should meet the requirements of the tasks of a particular farm for the production of agricultural products, taking into account the reproduction of soil fertility and maximize profitability of production.

When building any crop rotations, an important place is the knowledge of the best predecessors for the main crops, the possibility of their use in specific soil and climate conditions and the provision of the company with means of production: machinery, fertilizers, seeds, plant protection, labor resources, etc.

Table. Predecessors of major crops (generalized).

Crop
Predecessor
Winter cereals (rye, wheat, barley)Bare fallows, perennial grasses, seeded fallow, legumes, corn for silage and green forage, winter cereals
Spring wheatBare fallows, row crops, perennial grasses, seeded fallow, legumes, winter cereals
Oats, spring barley, buckwheatRow crops, legumes, winter cereals, spring wheat, technical non-row crops
MilletRow crops, legumes, winter cereals after fallows or perennial grasses
Peas, lupine, vetch, lentils, soybeans and other legumesRow crops (except legumes), winter and spring cereals
PotatoesWinter cereals, leguminous crops, perennial grasses, row crops, spring cereals
Sugar beetWinter cereals, leguminous crops, potatoes, spring wheat
CornWinter cereals, potatoes, legumes, spring wheat, barley, oats
SunflowerWinter cereals, leguminous crops, corn, coriander
Flax fiberPerennial grasses, legumes, potatoes, corn for silage, winter crops after perennial grasses
HempPerennial grasses, legumes, row crops
RiceAlfalfa, leguminous crops, corn, winter cereals
TobaccoWinter cereals, perennial grasses, leguminous crops, corn
CottonwoodAlfalfa, corn, leguminous crops
Perennial grassesSowing under spring cereal crops, under annual grasses, under winter cereals or sowing after row crops or cereals
Annual grassesSpring cereals, row crops
Forage root cropsWinter and spring cereals, corn, potatoes
Intermediate cropsWinter and early spring cereal crops, annual forage grasses and other crops harvested early

In the above list of predecessors, the main crops are arranged in descending order of their value. However, under specific conditions, the priority of predecessors may vary. For example, in arid areas perennial grasses cannot be classified as good predecessors of wheat because of soil drying, while in conditions of sufficient moisture they are not inferior to the effectiveness of seeded fallows.

When compiling schemes of alternation tend to place the most valuable and demanding crops after the best predecessors, guided by the principles of building crop rotations.

Another example of the relativity of this order is that winter wheat following perennial grasses may be the best preceding crop for buckwheat or millet, in contrast to row crops that are not provided with a sufficient level of agrotechnics and following cereals. Also, not all row crops may be the best preceding crop for spring wheat. For example, sunflowers or sugar beets are less valuable precursors than leguminous crops or winter wheat with bare fallows because of severe soil desiccation. In addition, sunflowers strongly contaminate crops with fallen seeds, which makes them an unacceptable predecessor for cereal crops.

After determining the scheme of alternation, develop the technology of growing crops for each field. For this purpose they specify terms and methods of tillage and fertilizer application, their types and rates of application, system of plant care, measures to control pests, diseases, weeds, etc.

When planning crop rotations by area, the composition of soils and soil differences, the impact of relief elements on plants and other natural, soil-climatic, organizational and economic features are taken into account. Fields on sloping lands are located across the slope, so that plowing, cultivation, sowing and other techniques to be carried out across the slope, preventing washout and erosion of the soil.

At agricultural companies such types and species of crop rotations are introduced, which most fully meet the natural conditions, farm specialization, scientifically justified structure of sown areas, requirements for the reproduction of soil fertility and growth of crop yields.

No less important is the organizational placement of production and auxiliary areas, their remoteness from settlements and water bodies. For example, the remoteness of silage and fodder crops from storage sites and livestock farms.

It is necessary to provide the most convenient conditions for the use of tractors and machinery to reduce economic and resource costs in the performance of field works. Optimal construction of crop rotations allows to distribute the terms of field work in time than in monoculture, which reduces the burden on machinery and workers. 

The placement of crops in the crop rotation also takes into account the requirements for the timing and methods of sowing, tillage, crop care and harvesting.

Rotation

The rotational table is a guide for the placement of crops on the fields for the next rotation. It serves as a basis for the implementation of systems of tillage, fertilization, plant protection, varietal change, soil protection against erosion, irrigation and other components of cultivation technology.

When implementing the planned rotation of crop rotations, various deviations from the established order of alternation are possible. The reasons for such deviations can be numerous, they are associated with the influence of weather, organizational and economic, soil and other conditions. For example, due to unfavorable conditions of overwintering the crops of winter wheat died. In this case a decision is made to plow the field and sow spring wheat, barley, oats or others in place of winter wheat. If perennial grasses die for the same reason, annual grasses are planted in their place, corn is replaced by other silage crops, etc. Adjustments can also be made for economic reasons – lack of fuel, lack of seed, changes in market conditions, etc.

Substitution of crops within their economic and biological group does not refer to the violation of crop rotation, but indicates its flexibility if necessary within the originally laid structure of cultivated areas, which is especially important in a market economy.

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.