Agriculture of Irrigated Regions
The main areas of irrigated land are concentrated in the CIS, for example, in southern Ukraine, the North Caucasus, the steppe part of the Trans-Volga region, Transcaucasia, Central Asia, and southern Kazakhstan.
In the Non-Chernozem zone, three regions with different needs for hydromelioration are distinguished:
The region of unstable moisture is represented by leached chernozems, gray forest, and podzolized soils. Here rainfed farming is developed for most crops, combined with irrigated farming for vegetable, fodder, and other moisture-loving crops. Fertilizer efficiency under irrigation increases substantially here. Thus, on average over 18 years, according to data from VNIIUA, the increase in green mass of maize from fertilizers under irrigation increased by 15.6 t/ha, fodder beet — by 20.0 t/ha, grain of buckwheat — by 0.35 t/ha.
The region of sufficient moisture is represented by sod-podzolic soils, on which, especially those with low water-holding capacity, irrigation in combination with fertilizers for vegetable and fodder crops is promising.
The region of excessive moisture is represented by sod-podzolic soils and peatlands, on which drainage is required to increase fertilizer efficiency, and irrigation of vegetable and fodder crops is used only in certain periods. On drained peat and mineral soils, potassium, copper, phosphorus, and nitrogen fertilizers are effective. The soil drainage system in this region should function when necessary in dry years or periods of short-term droughts, just like an irrigation system.
Natural and Climatic Conditions
Climate
The climate is continental, with dry and hot summers, mild and warm winters. Mean annual precipitation is from 100 to 250 mm in the foothill plains and up to 400–500 mm in mountain areas. The growing season lasts from 170 to 240 days; the sum of active temperatures is 3400–5400 °C.
Soil Cover
In the countries of Central Asia and Kazakhstan, sierozems and sierozem-meadow soils predominate; in Transcaucasia, chestnut and brown soils; in southern Ukraine and the North Caucasus, chernozems.
Objectives of the Farming System in Irrigated Regions
The main crops cultivated on irrigated lands in the countries of Central Asia, southern Kazakhstan, and Transcaucasia are cotton, rice, sugar beet, alfalfa, maize, melons and gourds; fruit growing and viticulture are developed. In southern Ukraine and the North Caucasus — winter wheat, rice, maize, sugar beet, sunflower, fodder crops, tobacco. Part of the irrigated lands is occupied by orchards, vineyards, pastures, and hayfields. In the steppe areas of the Trans-Volga region, spring wheat predominates; considerable areas are allocated to fodder crops, and in the south of the zone — rice.
The limiting factor for agriculture in irrigated regions is moisture. Under such conditions, the farming system must ensure efficient use of moisture, reduce unproductive evaporation, and comply with irrigation technology.
Components of the farming system:
- rational structure of sown areas, including the most valuable crops and intensive-type varieties;
- crop rotations with a high proportion of leading crops, including catch crops and crops that improve soil fertility;
- rational soil tillage system aimed at improving agrophysical properties and promoting efficient use of irrigation water and atmospheric precipitation;
- fertilizer system that ensures an optimal nutrient regime and increases the utilization coefficient of irrigation water;
- seed production system providing for sowings of intensive-type varieties resistant to lodging, salinity, diseases, and pests, capable of using life factors and producing maximum yield of the best quality;
- integrated plant protection system;
- system of erosion-control measures and protection of soils from salinization and waterlogging;
- rational organization of crop rotations, taking into account the size and shape of fields and the layout and operation of the reclamation network;
- placement of field-protective forest shelterbelts.
Crop Rotation System
In irrigated regions, depending on natural and economic conditions, row-crop, fruit-changing, and grain-row-crop crop rotation systems are used.
Fertilizer System for Crop Rotations under Irrigation
The fertilizer system for crop rotations under irrigation is built taking into account specialization, soil texture, nutrient availability, groundwater level, and moisture regime. At the same time, application methods and timing are used that increase the nutrient utilization coefficient and prevent loss to the environment.
Under irrigation, plants on all soil types need nitrogen most. Application of nitrogen fertilizer against a background of phosphorus or phosphorus and potassium increases the grain yield of winter and spring wheat and the green mass of maize by 1.5–2 times. Efficiency of phosphorus fertilizers is lower than that of nitrogen fertilizers and is mainly manifested when they are applied together. The yield increase of grain and fodder crops from phosphorus fertilizers on irrigated lands is usually 20–30%, depending on soil phosphorus availability. Potassium fertilizers on irrigated lands are of little effectiveness when applied to wheat, maize, and alfalfa. In recent years, an increase in the effectiveness of potassium fertilizers has been noted.
The nitrogen problem is solved in an integrated manner: through a combination of mineral and organic fertilizers and expansion of alfalfa sowings on irrigated lands. Phosphorus deficiency is covered by mineral phosphorus fertilizers. Per hectare of irrigated arable land, mineral fertilizers are applied according to full requirement. At a high level of agronomic practice, the greatest return on fertilizers is observed.
Under irrigation, timing of fertilizer application is important. Phosphorus and potassium fertilizers for all crops are applied in autumn for primary tillage. Nitrogen fertilizers on loamy and clayey soils with deep groundwater are applied in autumn for plowing or in spring for cultivation. On sandy and sandy loam well-drained soils, nitrogen fertilizers are applied in spring before sowing. It is important to select the right forms of nitrogen fertilizers. The best under irrigation are urea, ammonium sulfate, and carbophoska. Nitrate forms are undesirable because they migrate considerably through the soil profile.
During plant vegetation, winter wheat crops are top-dressed with nitrogen fertilizers (late autumn or early spring by broadcast), maize (at the 4–5-leaf stage with cultivator-fertilizer applicators), and alfalfa is top-dressed with phosphorus fertilizers (broadcast in early spring). To improve the grain quality of spring and winter wheat, top-dressing with urea or ammonium nitrate during heading to the end of flowering is effective.
References
1. Niklyaev V. S. (2000). Fundamentals of Agricultural Production Technology. Farming and Crop Production. Moscow: Bylina.
2. Mineev V. G., Sychev V. G., Gamzikov G. P. et al. (2017). Agrochemistry. Textbook. Ed. by Mineev V. G. Moscow: Publishing House of VNIIA named after D. N. Pryanishnikov.
