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Objective and technical fields:
Agricultural crops furrow irrigation technological process perfection in order to moisten soil equally along furrow, water saving, soil fertility improvement.
Scientific and technical approach:
Agricultural crops furrow irrigation technology perfection is based on irrigated lands smoothing without slope and twofold water supply providing optimal management by water flow. Scientific meaning: ground of measures on furrow irrigation technology perfection.
Environment characteristics:
Investigations were carried out in the lower reaches of Amudarya river. Climate is sharply continental with very hot summer and cold winter. Average annual temperature is 12oC.
Minimum temperature is -29oC in January and maximum is 40oC in July. Growing season is short, non-freezing period duration is 200 days. Sum of positive temperatures is 4200-4300oC. Precipitation is mostly dedicated to winter-spring time. They are 100 mm/year. Wind velocity is 3-5 m/sec. Air relative humidity is 70% in January and 36 % in July. Average annual air humidity deficit is 10.8 mb; 1.2 mb in January and 24.8 mb in July. Evaporativity is 1320 mm/year. Pilot plot is located within alluvial valley of Amudarya river. Surface slope is 0.0002-0.0005 and directed to south-west.
Alluvial sediments consist of fine-grained sand, sandy loam, loam and clay with total thickness 50 m. Soil of 1 m cover layer is represented by heavy loam and light clay. Its permeability coefficient is 0.6 m/day. Underlying layer - sandy loam and sand with permeability 8-10 m/day.
Soil 1 m- layer is middle salinizated: 0.31-0. 54 % in solid residue and 0.03-0.08 % in chlorine. Salinization type is chloride- sulfate. The least moisture capacity of soil 1m-layer is 23.6 5 of dry soil weight, density - is 1.44 g/cu. cm., solid phase density - 2.72 g/ cu. cm., porosity - 47 %. Groundwater level depth is 1.5-2.2 m during growing season and 3-3.5 m in winter period. Groundwater salinity is 3-5 g/l.
Parameters of Pilot Projects and Technical Solutions:
Pilot plot area is 1500 ha (gross), land use efficiency is 0.7. Main agricultural crop is cotton. Irrigation network specific extent is 28 m/ha. Its efficiency is 0.75 - 0.80. Irrigation norm is 4000-52000 cu. m/ ha, irrigation depth - 1000-1200 cu. m/ha, number of irrigation - 4. Irrigations were performed along furrows with length of 150-250 m and depth of 17-24 cm. Simultaneous irrigation area was 4.5 -5.0 ha. Leaching and water stock irrigation in autumn - winter time was 3000 cu. m/ha
Methodology:
Selected sites were distinguished into 4-5 field which were properly graded: on each site weirs were installed for irrigation depth definition and observation wells for groundwater level and salinity measurements.
At the same time similar investigations were carried out within the control fields with surface slope 0.001 - 0.002. All fields were sown by cotton.
Irrigations were carried out from two opposite sites along the furrows and for control field from one side. Soil water-physical properties, soil moisture dynamics along the furrows, irrigation technique elements, labour expenses, cotton yield were studied.
Results:
Cotton yield before experiments was 1.6-1.7 t/ha; irrigated lands were exposed to secondary salinization which led to low soil fertility. New cotton irrigation technique imbedding allowed:
- to increase water flow regulated by one operator to 70-90 l/sec;
- to cut down irrigation time for standard (4.5-5 ha) sites from 2-3 days to 20-30 hours or 2-2.5 times lower to compare with control sites;
- to reduce 1.8-2 times irrigation stream reach time at expense of 2-side irrigation;
- to raise soil moisture equally along furrow length and achieve the equality efficiency 0.90-0.96, that is to make it 10-12 % more to compare with control;
- to automatize water distribution into the furrows by its supply to additional special furrows;
- to cut down irrigation depth on 2000-2400 cu. m/ha which leads to irrigation technique efficiency increase on 8-10 % and achieving 0.80-0.88;
- to cut down water expenses for 1 ton cotton production on 50 cu. m. Total irrigation water expenses were 2100 cu. m/t;
- to reduce specific inputs for irrigation they were 3.95 ruble/ha (1984 prices), which are 2.25 ruble/ha less to compare with control;
- to raise operator’s work efficiency 1.5-2.0 times;
- to increase cotton yield and achieve 4.0 t/ha.
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