On-farm Rain Water Productivity Improvement in Producing Rainfed Wheat by Advanced Scenarios at Semi-Cold Region of Upper Karkheh River Basin (KRB)

In order to investigate the effects of limited irrigation (LI) scenarios on bread rainfed wheat (Triticum aestivum L.) on-farm experiments were conducted during the 2005-08 cropping seasons at multiple farms across benchmark watershed of Honam (Lorestan Province) in the upper KRB. The treatments included two main management (Traditional and advanced management) and four levels of limited irrigation (Rainfed، single irrigation of 50 mm at spring time، single irrigation of 75 mm at planting time and 125 mm irrigations at planting and spring times). The results of this study showed that under rainfed conditions، wheat grain yield of (2269 kg ha-1) increased by 33% as compared to TM (1726 kg ha-1). The optimal program was a combination of advanced agronomic management with LI options (single irrigation at planting time / or spring time). At this preferred program، maximum water productivity and net benefit were obtained. At rainfed conditions RWP of traditional management (0. 35 kg m-3) increased by 28. 6% as compared to advanced management (0. 45 kg m-3). The results showed that a single irrigation application at sowing or spring time (during heading to flowering stage) increased total water productivity (TWP) of wheat to an average range of 0. 57 to 0. 63 kg m-3 over the three growing seasons. The average irrigation water productivity (IWP) of wheat reached a range of 2. 15-3. 26 kg m-3 by using single irrigation at sowing or spring time. Supplemental irrigation at critical stages (planting time / or spring time)، deep root expansion، incrassating green canopy cover and its influence on evaporation control، were main reasons on effectiveness of limited irrigation. Low RWP (and yield) in farmers’ practices were mainly due to suboptimal agronomic management practices. These preliminary results confirm the potential of single irrigation and early/normal planting as an effective scheme to enhance productivity.