OrpOMHbIM BKJIa,IJ: B JJ,eJIe nporpecca JJ,aHHoro npoeKTa. IRRIGATION SCHEDULING STUDY OF DRIP IRRIGATED COnON BY USE OF SOIL MOISTURE NEUTRON PROBE B.Komilov, Uzbekistan Scientific Production Centre of Agriculture,

Investigations of water use (evapotranspiration or ET) and irrigation scheduling of drip irrigated cotton (Gossypium hirsutum, cv. Akdarya-6) were conducted at the Central Experiment Station of the Uzbekistan Cotton Growing Research Institute (UNCG RI) on the old irrigated typical gray soil (deep silt loam) in 2000 and 2001. Water use was established using the soil water balance approach on a weekly basis. Deep measurements of the soil profile water content were accomplished using soil moisture neutron probes (SMNP), which were calibrated in polyvinyl chloride (PVC) access tubes for the soil and each soil horizon. Soil water measurements were used for determination of irrigation rates and times for drip irrigated cotton during the growing season. Cotton water use was measured by the soil water balance method. The results revealed that drip irrigation of cotton under the given circumstances improved water use efficiency and seed-cotton yield. Under drip irrigation practices and the optimal mode (70- 70-60 % of field capacity) of irrigation scheduling, 31 to 39 % of the irrigation water was saved in comparison with surface irrigated cotton grown under the same condition. The seed-cotton yield was increased by 21 to 22 % relative to the surface irrigated cotton