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Objective and technical fields:
Definition of possibility of crops root zone optimal moisture support under changing climatic and economic conditions on the base of agricultural crops water requirements and disposal forecast.
Objectives: to improve water use, to use water resources rationally, to take into account outflow and water disposal from irrigated lands in order to evaluate its secondary use.
Scientific and technical approach:
Development of optimal irrigation rates of agricultural crops under changing climatic conditions; analysis of water use state and water resources use efficiency on the base of stream-flow depletion study in-situ, main goal of experiment is approaches development to allocated water resources rational use; determination of indices of total and irrigation outflow (ranoff) from irrigated lands; definition of irrigation and drainage water quality; recommendations development on improvement of reclamation state of the Chu valley soils.
Environment characteristics:
Region climate is extremely continental. Average annual air temperature is 9-10oC, minimum temperature is in January – 3,4-8,3oC, maximum temperature is in July 21-24oC; annual precipitation is 380-460 mm, mainly precipitation occured in spring (April – May) (42-47 % of annual). In summer there is about 20-23 % precipitation. Relative air humidity 39 % in summer and evaporation during April-September is 1000 mm. Sum of positive temperatures is 3000-3800oC, duration of non-freezing period is 180 days.
Region territory is divided in plain (attitude is 500-600 m), premountain zone (700-1200 m) and mountains. There are Alamedin and Ata Archa rivers which flow is diverted for irrigation in upper reaches by semi-engineering systems and in lower reaches by large irrigation canals.
Groundwater is described for upper part of modern quaternary depositions. Groundwater salinity does not exceed 1 g/l. Chemical composition is hydrocarboheous-calcium, magnesium. Aquifer has free surface and is fed by irrigation water percolation, precipitation and overflow from underlaing aquifers. Aquifer water releases in a plain part through the places of low elevation and drainage network. Pilot plot is located on loess-loam soils. Groundwater level depth is 1,5-3,0 m within the growing period and 0,5-2,5 m in June. Slope is directed from south to north and equals to 0,0054. Soils are mostly grey-meadow and light-meadow. Mechanical composition shows middle loam, seldom heavy loam. Soils are non-salinizated except central part where they are middle salinizated. Type of salinity is sulphate in anions and sodium-calcium in cations.
Parameters of Pilot Projects and Technical Solutions:
Pilot plot is situated in state farm “Prigorodny” whose area is 1.643 ha; Occupation vegetables growing, cattle breeding and dairy farming. The main source of irrigation is Chu river. Distributing canals are not lined, their efficiency is 0,6; Irrigation water salinity is low (0,23 – 0,265 g/l).
There is close drainage network – 63,22 km, open network – 9,756 km, drainage density is 44,4 m/ha. 17,94 km close network is damaged by colmatation. Drainage effluent salinity is 0,6-0,82 g/l and it could be used for irrigation. There are 48 observation wells within the pilot plot.
Methodology:
Field observations for moisture and salts movement and stream-flow depletion measurements in unsaturated zone, groundwater and irrigation regime. Pilot plot was equipped by means of measurement of water and salts changes.
Field data were processed by means of multicriterial analysis on the comparative base of actual and planned water supply.
Results:
Soil salinization is as follow: non-salinizated 248 ha, strongly-salinizated –118 ha, middle-salinizated – 95 ha, slightly- salinizated – 1182 ha, total – 1643 ha. At the same time soil sodification is observed from slight to strong, absorbed sodium worsens soil water-physical properties. In order to improve these soil properties gipsum and deep ploughing are needed.
Slightly-salinizated soils (1182 ha) prevail over the pilot plot. Salinization type is soda and it is mostly from surface to 30 cm depth. These soils need organic and physical acid fertilizer, simple superphosphat and gipsum in amount of 0,1-0,2 t/ha before cultivation at the time of sowing.
Removed water salinity is 0,6-0,82 g/l. Carbonate – ions are not available, water pH is alcalic and it may be secondary used for irrigation.
Groundwater salinity strongly varies annually from 0,17 to 2,7 g/l.
Water removal coefficient was determined which is ratio of removed water to duty of water and equals 0,42. This coefficient definition is possible due to annual accounting of all components of stream-flow depletion, actual water stock, groundwater level and drainage outflow.
Negative water-salt balance has been formed under optimal moisture conditions.
Salt removal exceeded its input on 0,5 t/ha.
There were 7-8 sprinkler irrigations during the growing period for vegetables growing. Irrigation norm was 700 cu.m/ha, precipitation and groundwater inflow were 2500 cu.m/ha. Perennial grass was irrigated by furrows 3 times on background of groundwater inflow.
Leaching regime of irrigation was kept during the period 1986-1989.
Analysis of calculated and actual irrigation norms (rate) for perennial grass, corn for grain and silage shows that optimal moistening regime was not kept in spite of groundwater inflow share. New relations were proposed by KirgNIIR between yield corn and duty of water. Their advantage is that they use relative and consequently comparative values.
These relations can be used in any conditions on the base of maximum yield (Y max), appropriate duty of water (Wopt.) and duty water (Wo), which provides crop survival but not real cost-effective yield.
Analysis of water use in Alamedin district during the period of 1982-1989 was carried out which showed that water surplus does not lead to yield increase – duty of water should be annually regulated depending on climatic conditions of concrete years taking into account determined values of crop water consumption, which allow to define crop water consumption in relation with planned yield, water resources deficit and other factors:
- integrated curves equations of water consumption with average values of their parameters which should be differentiated on crops. With help of these equations is possible to determine water consumption value for any period of vegetation;
- technological schemes of long-term water consumption forecast (for all growing period) and short-term (for decade) that allows to foresee irrigation regimes for next growing period, to correct long-term plans of water use and control foreseen irrigation regime.
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