single irrigation and sowing date for rainfed barley in maragheh region and estimation of production functions

this study investigated the effect of sowing date and limited water allocation management for single irrigation on the grain yield of rainfed barley. the experiment was a split-split plot arranged in a randomized complete block design with three replications from 2004 to 2006 at the main station of the dryland agricultural research institute at maragheh. the treatments comprised three sowing dates (early, normal, late) and yesevi-93 (abidar), and dayton (urb79-7) barley varieties. the single irrigation allocations tested were rainfed, planting time irrigation (50 mm and 100 mm), and spring irrigation (50% and 100% depletion of available water). grain, straw and biomass yields were measured. barley production function was estimated for total water used (sum of precipitation and irrigation water). generally, there was a linear function between water use and yield and the effectiveness of the amount and time water allocation was evident. results showed that single irrigation at planting time and limited single irrigation (50% depletion of available water at root zone) at spring time (during heading to flowering stage) had significant effects on yield and water use efficiency. the average grain yield for single irrigation at planting time (3794 kg.ha-1) was about 300% more than the average for rainfed (1170 kg.ha-1). single irrigation at planting time caused early crop establishment for autumn and relatively early maturity, which reduced the growing period. the grain yield for spring single irrigation was about 1000 kg.ha-1 more than the average rainfed condition. spring single irrigation improved soil water content and increased yield and yield components (especially thousand kernel wt.). thus, wheat production can be substantially and consistently increased under cooperative management of limited single irrigation and agronomic management.