An investigation of Rainfall and Supplementary Irrigation Productivity in some Wheat Cultivars

In water scarcity areas, improving water productivity is one of the most effective options to increase production. This is achieved by improving both crop and irrigation management. An experiment was laid out in strip plots with a randomized block design consisting of six rotations, six cultivars of wheat and two irrigation regimes (rain-fed and supplementary irrigation) treatments with three replications during the four years (2007-2011). Results show that varieties, climate conditions and irrigation has affected on wheat production. In contrast, different rotations of wheat have no significant effect on wheat yield. In the years that a significant portion of the total crop water requirement was provided by rainfall about 75 percent, yield potential of irrigated wheat was low and also there was no significant difference between wheat yields in irrigated and rainfed conditions. So that, irrigated wheat yield from 2007 to 2011 was obtained about 69, 6, 21 and 88 percent higher than the rainfed wheat, respectively. Rainfall use efficiency of wheat in four consecutive years was obtained 1.67, 1.79, 1.31 and 1.1 and irrigation water use efficiency was obtained 0.75, 0.36, 0.81 and 2.2 Kg/m3, respectively. Highest wheat yield and also highest rainfall/irrigation use efficiency is related to the cultivars N-80-19 and N-81-18. Since supplemental irrigation in most cases has not led to increased water productivity, in the Golestan province condition, wheat irrigation should be done in the critical period of wheat growth and saved water could be allocated to water scarcity areas or for the summer crops.