Summary of research project: |
Objective and technical fields:
To study how micro-relief (grading quality) of rice checks influence the depth of ponding, irrigation norm and rice productivity. Scientific justification of optimum parameters for rice fields micro-relief for achieving high yields of rice under water consumption reduction.
Scientific and technical approach:
Studying an influence of rice checks grading on depth of irrigation, irrigation norm and rice productivity. Economic justification of the parameters of rice field relief. Determination of the optimal parameters of rice field micro-relief.
Environment characteristics:
Climate. Considered region is related to Kzylkum sub-zone of dry hot zone of deserts and semi-deserts. Total annual precipitation according long-term data is 165...200 mm, the largest amount is fixed in Spring and Autumn. Total precipitation for a warm period with air temperature of more than 10 oC accounts for 60...70 mm, the smallest amount is fixed in July (2 mm) and September (1 mm). Total positive air temperature for a period, when air temperature is more than 10oC, accounts for 4600...4800oC, duration 200..210 days. Evaporativity is 1100 - 1200 mm. Relative air humidity in winter is 70...76%, in other period is not more than 34...45%, a minimum value 18% is in July...August. Number of days with relative air humidity less than 30% is 180. Deficit of air humidity grows from 8...9 Mb in April to 32 Mb in July.
Relief. Kzylkum massif is a plate valley, lightly lowering in north-west direction with 0,0002...0,0003 slope. Height above sea level is 200...250 m. Relief is smooth, has a light bench terraced nature. There are two bottoms and modern flood plain on the scheme’s territory.
Lithology of the massif has a uniform nature. The lowest layer includes gray and yellow-gray fine-grained sands with thin interlayers of clay, sandy loam and loam, sometimes with coarse sediments (gravel, shingle, etc.). Top layers include yellow-brown loam and sandy loam with clay and sand interlayers. Thickness of loamy layer varies from 0,5 to 3 meters. Soil texture consists of top loams, thickness of which is up to 3 m, and bottom sands - up to 60 m and more. Permeability coefficient (PC) from soil surface is 0,21...0,35 m/day. PC of bottom sandy loam layers is 1,4...1,6 m/day and sands - 2,4 m/day. Level of ground waters in spring accounts for 1,6...2,5 m, in growing period - 0,6...1,8 m. Salinity of ground waters is 1,87...8,14 g/l. Type of salinity is chloride-sulphate. Permeability varies from minimum (11 mm/hour) in loamy soils to maximum (100 mm/hour) in eolic sands.
Parameters of Pilot Projects and Technical Solutions:
The irrigated area is 33 ha. Specialization of farm is rice-growing. Water supply and release are done by earthen canals. Crops rotation has a following scheme: 1. Rice, 2. Rice, 3. Alfalfa, 4. Alfalfa, 5. Rice, 6. Rice, 7. Rice, 8. Fallow lands (barley). Irrigation schedule, developed by KazNIIrice, for rice and alfalfa was common for the Kzylkum massif. Rice in the pilot plot was cultivated under shorten ponding regime. UZROS-59 sort was sowed.
Methodology:
Quality of rice checks grading was determined with leveling on squares (20x20m). Observation of water depth in check during growing period by gauges. The pilot plot was equipped with water meters and balance platform.
Results:
Effectiveness of water use in rice irrigation systems of the Syrdarya basin depends, to a considerable degree, on parameters of rice field relief. Deviations from average plane up to +5 cm, arisen during grading, were increased considerably during operation of the system due to heave, settling of soil and tillage by loosening instruments. As a result, despite of pre-sowing leveling 47,8% of check area have deviations up to +5 cm, 51,4% - up to +10 cm and 6,8% - +10 cm more. This does not allow to create even depth of water within the check area and leads to over discharge of irrigation water from 200 to 1000 m3/ha. Analysis of variance confirmed existence of a close linkage between depth of water in check and rice productivity, the maximum value of which (6,0 t/ha) is observed in checks with grading deviation of +3 cm less.
An economic assessment of rice field relief influence on rice system productivity shows, that the damage from arrears of rice yield accounts for 200 US$/ha and more under deviation of +3 cm more.
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