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Objective and technical fields:
Development of rational regime of cotton and alfalfa irrigation. Objectives: definition of comparative water requirements of these crops under conditions of medow and typical grey soils providing high yield of cotton and alfalfa and water saving.
Scientific and technical approach:
Development of rational irrigation regime and irrigated lands productivity increase on the base’s of: optimal regime of soil moisture, total water consumption and its distribution over phases of plant germination, irrigation norms. Meaning: development of the set of recommendations on irrigated lands productivity increase, water saving and farm income raise.
Environment characteristics:
Climate is sharply continental. Average annual temperature is 10.5 -13.7 oC. Frost -free period duration is 170 -190 days. Sum of positive temperatures is 4000 -4400 oC. Annual precipitation is 350 -500 mm, evaporativity is 1170 -1300 mm. Relative air humidity is 54 -80 %, in summer 32 -35 %. Relief is slightly corrugated with low slope. Area is located within premountain zone. Investigations were carried out within two experimental sites with different soils:
I - medow -grey soils; sediments -loess loam and gravel with clay filling. Loess loam thickness is 0.7 -12.5 m, permeability coefficient is 0.15 -0.29 m/day; gravel (0.8 -5.3 m) permeability is 6 -7.2 m/day. Loam is middle and heavy. Groundwater level within vegetation period was 1.8 -2.3 m.
II - typical grey soils; loess loam (10 -15 m), permeability is 0.2 -0.29 m/day. Loam is middle and light. Groundwater level is 3 m and more, salinity is less than 1 g/l. Drainability is satisfactory.
Parameters of Pilot Projects and Technical Solutions:
Irrigated area is 5250 ha (gross), 4200 ha (net). Land use efficiency is 0.8. Main crop is cotton. Water supply is performed from earthen canals which extent is 80 km. Head water intake is 5 -5.5 cu.m/sec. Canals efficiency is 0.90, for system it is 0.7 -0.75. Area of experimental sites is 100 -150 ha.
Methodology:
Field investigations and observation of water movement, water balance elements and groundwater in connection with irrigation regime. Sites were equipped by means of water accounting and piezometric network. Multicriterial analysis was used for data processing.
Results:
I site.
1. For cotton yield 3.3 -3.7 t/ha achievement on medow -grey soils under groundwater depth 1.8 -2.3 m (growing season) 5 waterings were performed (2 -2 -1) by depth 650 -850 cu.m/ha. Moisture before irrigation was kept as 70 -70 -60 % of normal moisture. Yield increased an average on 0.6 t/ha. Cotton field water requirement was 7700 cu.m/ha, including irrigation water -3950, groundwater -2450, soil water -1150 and rainfall -150 cu.m/ha.
2. For alfalfa yield 16.0 -20.0 t/ha achievement- within first year 10 waterings were carried out (1 (0) -2 -2 -3 -2) by depth of 600 -700 and irrigation norm 5800 -6600 cu.m/ha. Moisture before irrigation was kept as 80 % of normal moisture. Yield increased on 2.2 t/ha. Alfalfa field water requirement was 11600 cu.m/ha, including irrigation water 6650, groundwater -3700, soil water -1100 and rainfall -150 cu.m/ha.
- within the second year 9 vegetation waterings were performed (0 -2 -2 -3 -2) by depth 600 -650 and irrigation norm 5500 cu.m/ha. Moisture before irrigation was 80 %. Yield growth was 2.6 t/ha. Water consumption was 10750 cu.m/ha, including irrigation water -5500, groundwater -3900, soil water -1050 and rainfall -300 cu.m/ha.
3. Bioclimatic coefficient for cotton was 0.67, for alfalfa -0.81 (1-st year); 0.78 (2-nd year); 0.79 (3-rd year).
II site.
1. For cotton yield of 3.5 -3.7 t/ha achievement on typical grey middle loam soils under groundwater lower than 3.0 m 6 waterings were performed (2 -3 -1) by depth 900 -1000 cu.m/ha and irrigation norm 5600 -5750 cu.m/ha. Moisture before irrigation was 70 -70 -60 %. Yield growth was 0.8 -0.1 t/ha. Cotton field water requirement was 6750 cu.m/ha, including irrigation water -5700, soil water -900, precipitation -150 cu.m/ha.
2. For alfalfa yield of 2.0 -2.2 t/ha achievement under given conditions:
- within the first year 9 waterings (3 -3 -3) were carried out by depth 750 -800 cu.m/ha, irrigation norm 6850 -7050 cu.m/ha. Moisture before irrigation was 75 %. Yield growth was 1.2 t/ha. Water requirement was 8300 cu.m/ha, including irrigation water 7050, soil water -1100 and precipitation -150 cu.m/ha;
- within the second year 9 waterings (1 -2 -2 -2 -2) were carried out by depth 750 -800 cu.m/ha, irrigation norm was 7000 -7150 cu.m/ha. Moisture before irrigation was 75 %. Yield growth was 2.1 t/ha. Water consumption was 8400 cu.m/ha, including irrigation water -7150, soil water -900 and precipitation -350 cu.m/ha;
- within the 3-rd year 9 waterings (1 -2 -2 -2 -2) were performed by depth 750 -800 cu.m/ha, irrigation norm was 7100 cu.m/ha. Moisture before irrigation was 75 %. Yield growth was 3.1 t/ha. Water requirement was 8200 cu.m/ha, including irrigation water -7100, soil water -800 and precipitation -300 cu.m/ha.
3. Bioclimatical coefficient was for cotton 0.87; for alfalfa -0.82 (first year); 0.84 (second year); 0.81 (3-rd year).
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