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Water application (watering)

Water application (watering) is one-time artificial soil moistening under agricultural crops and plants or for other land reclamation and economic purposes. In an arid zone, one should surely use a land reclamation method by employing which an optimum water regime is created.

From the soil-conservation and organizational-economic points of view, the following water application types can be distinguished:

- presowing watering is carried out with the view of soil moistening and obtaining good and fully emerging crops, acceleration and rapid growth and development of crops in the initial, per se decisive, period of plant life. Presowing watering is generally performed at small rates: 600...800 m3/ha applied for soil layer moistening of 0.6...0.8 m. Water application is carried out by furrows, border irrigation, and even multitower sprinkling machines.

- presowing charge watering is also executed before sowing and for the purpose of not only obtaining good and fully emerging crops, but also creating the deposit of moisture in deeper (1.5...2.0 m) soil layers. Presowing charge watering is carried out at heavy water application rates, 800...1500 m3/ha, usually by deep furrows or border irrigation.

- charge (off-season) watering is carried out in the autumn or late autumn period. In order to create moisture deposit in a layer of 1.5...2.0 m for winter and spring cereal crops, sugar beet, horticultural crops, and grape, charge watering is executed, as a rule, by deep furrows or border irrigation or basin flooding at a rate of 800...1200 m3/ha.

- provocative watering is performed with the view of calling forth sprouting of weeds that are eliminated by presowing cultivation. Provocative watering is of considerable importance for weeded lands in steppe areas where weed seeds are accumulated because of soil dryness and do not sprout under natural conditions. Water application is generally in autumn after harvesting. At first, pre-plowing watering is carried out by using the existing irrigation network, and then cultivation is performed after weeds sprout. This operation is repeated several times by plowing for different depths. Weeds are eliminated in not only top but also in deeper soil layers. For provocative water application, sprinkling with soil penetration is expedient to be applied to 0.250.3 m. In Central Asia areas, such water application is executed as well in early spring, before sowing.

- feeding watering is as a matter of fact regarded as provocative watering but in respect to weeds and such cultivated plants as cereals, cotton, sugar beet, etc., when unexpectedly long (for 2-3 weeks) dry weather becomes settled after sowing, and seeds do not sprout. If water application is not carried out on time, sprouted seeds will perish. Before carrying out feeding watering, these fields are sown by fast-growing so-called marker crops, according to the shoots of which they determine the direction for cutting furrows and perform water application by those. Feeding watering is convenient to be carried out by means of sprinkling machines. Sprinkling irrigation is used for the purpose of attaining good and even sprouts of tilled and cucurbitaceous crops, rice, etc.

- egetative watering is the main type of water application to crops. Execution of it requires knowing not only biology of crops and time of the most important phases and periods of crop growth and development, but also moisture availability in the soil as well as how hydrometerological, i.e. weather, conditions develop during the growing season. In many areas of the European territory of Russia, water application during the growing season can be considered as supplement to precipitation. Vegetative watering is essential from the agrotechnical point of view. It in many respects determines the efficiency of fertilizers. Vegetative watering is carried out by different methods: by furrows; by border irrigation; by flooding; and by sprinkling irrigation. Water application rate fluctuates from 400...600 to 1000...1200 m3/ha.

According to its physiological significance, water application can be of moistening purpose aiming at keeping a certain moisture content (70...80% of field capacity) in soils active layer and refreshing purpose when water is delivered at a small rate 50...100 m3/ha mainly during sprinkling irrigation for rising the moisture content in the surface-layer soil, cooling leaves as well as preventing them from contamination (removal of dust, fertilizer remainder from leaves surfaces, etc.), and hence improving plant assimilation and photosynthesis.

Refreshing watering at a rate of 50100 m3/ha is particularly effective for the majority of crops (vegetables, tea, potato, beet, etc.) during atmospheric drought, when assimilation process goes slow because leaves are overheated.

Leaching watering is performed, as a rule, in autumn or autumn-winter seasons in order to remove excess of water-soluble salts.

Leaching watering is carried out at high rates, 46 ths m3/ha and over, with the view of thorough soil leaching or relatively low rates for preventive or exploitative purposes. Thorough soil leaching is executed usually 1...2 times during crop rotation cycle; preventive watering, every 1...2 years. It is usually carried out in autumn in the form of charge watering at a higher rate of 2.2...5 ths m3/ha by border irrigation or check irrigation.