The article presents calculation of irrigation regime of winter wheat in the Fergana Valley, which, depending on agro-meteorological conditions of the year, may vary from 3100 to 5000 m³/ha.

The studies of water consumption by winter wheat using the SANIIRI Institute’s lysimeters, as well as the results of joint research project (within the framework of INCO-Copernicus programme) implemented by SIC ICWC together with the Lisbon Technical University in the Fergana Valley showed that daily water use by irrigated field sown by winter wheat is 18-20 m³/ha during autumn period, and only by early December water use can decrease significantly due to increased humidity and decreased temperature.  

Under conditions when rainfall is virtually not available in autumn during dry year and the norm of recharge (before or after sowing) irrigation is 900-1000 m/ha, the moisture storage becomes exhausted by the end of autumn and crops will suffer from shortage of moisture.

For calculation of water requirements and irrigation regime for winter wheat, the FAO’s program for irrigation scheduling - CROPWAT - approbated in Uzbekistan was applied.

In calculations the calibrated crop coefficients for estimation of evapotranspiration ЕТо by Penman-Monteith method and crop growth stages derived by SIC ICWC and the Lisbon Technical University under the ЕU-INCO CIR-MAN ARAL Project were used.

As currently there are no data on frost period duration during dry year, crop coefficients in winter were taken for frozen soil since winter frosts maintain the status of winter dormancy or zero potential for growth of winter wheat. 

Groundwater contribution to the rooting zone of winter was determined on the basis of SANIIRI’s long-term research.

Irrigation regime of winter wheat in dry year is comprised of recharge and vegetative irrigation events both in autumn due to small amount or lack of precipitation and in spring-summer period.  

The calculation of irrigation regime of winter wheat for the Fergana Valley was made for medium-dry year.