|Kamilov, B - UZBEKISTAN NATL. COTTON|
|Ibragimov, N - UZBEKISTAN NATL. COTTON|
|Heng, Lee - IAEA|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: August 1, 2002
Publication Date: October 13, 2002
Citation: KAMILOV, B., IBRAGIMOV, N., EVETT, S.R., HENG, L. USE OF NEUTRON PROBE FOR INVESTIGATIONS OF WINTER WHEAT IRRIGATION SCHEDULING IN AUTOMORPHIC AND SEMI-HYDROMORPHIC SOILS OF UZBEKISTAN. PROCEEDINGS OF THE INTERNATIONAL WORKSHOP ON CONSERVATION AGRICULTURE FOR SUSTAINABLE WHEAT PRODUCTON IN ROTATION WITH COTTON IN LIMITED WATER RESOURCE AREAS. 2002. P. 225-229. Technical Abstract: Today, approximately 1 million ha of irrigated winter wheat are produced in the Uzbekistan piedmont. The relatively low yields, averaging 3.5 Mg/ha, are partly due to incorrect irrigation scheduling. Investigations of water use (ET) and irrigation scheduling of winter wheat were conducted in the autumn to summer period of 2000-2001 and 2001-2002. Field experiments were carried out at the Central Experiment Station of the Cotton Growing Research Institute in Tashkent (old irrigated typical gray soil, medium loam, water table >15 m deep) and at the Syrdarya Branch Station of the Institute (meadow-gray soil, light loam, moderate saline, underground water level is 2.0 to 2.5 m). Measurements of soil profile volumetric water content were conducted twice a week and in two replicates by field-calibrated soil moisture neutron probe to 2-m soil depth in 0.20-m increments. The time of irrigation was determined for each experimental treatment in comparison with the field capacity (FC) (for instance: 70% of FC). The experiments comprised four treatments: #1) 65, 65, and 60% of FC; #2)70, 70, and 60% of FC; #3) 75, 75, and 60% of FC; and #4) 80, 80, and 70% of FC. Each treatment consisted of scheduling irrigations at the specific percentages of FC during each of the three plant growth periods, respectively. Results showed that top yields at both sites were reached for treatments 3 and 4, which were concluded as optimal and high moisture mode, respectively. Additional yield received in 2001 at the optimal mode in comparison with treatment 1 was: for Tashkent, 0.98 Mg/ha; and for Syrdarya, 0.66 Mg/ha. Water use was measured by the soil water balance method at Tashkent. In 2001, the ET ranged from 426 to 493 mm, depending on treatment. A shallow water table at Syrdarya precluded measurement of ET.