Factors affecting precipitation use efficiency of dryland wheat and barley genotypes

Abstract Available water and its efficient use are the main determinants of yield in dryland agricultural systems. In this study, the results from two-year experiments in dryland condition of Mashhad, used to evaluate of rainfall use efficiency of wheat and barley. The results showed that under the same environmental conditions, the precipitation use efficiency (efficiency) of wheat and barley genotypes had a significant difference, and the highest and lowest efficiency in wheat genotypes belonged to Karim and Line 14 with the rate of 9.6 and 4.3 kg of grain for each mm of rainfall, respectively. The highest and lowest efficiency in barley genotypes was recorded for Mahoor and Ansar cultivars at 17.7 and 7.9 kg of grains per mm of rainfall, respectively. The difference between the two crops, in terms of efficiency, was considerable and the highest efficiency of barley genotypes compared to the wheat cultivar of Karim (the highest efficiency for wheat cultivars) was greater than 84.3%. Based on results, temperature is one of the most influential factors in improving efficiency, and on average, for 1 ˚C decrease in mean air temperature, the efficiency of wheat and barley genotypes increases by 0.83 and 1.06 kg/ha per millimeter of rainfall, respectively. The Karim wheat cultivar and Mahoor barley cultivar started spring growth faster. The biomass growth rate of wheat genotypes was in the range of 84–106 kg/ha per day, and the biomass growth rate of barley genotypes was in the range of 136–166 kg/ha per day. The highest growth rate of wheat and barley grain genotypes belonged to the Aftab wheat cultivar and Khorram barley cultivar at 78.6 and 122 kg/ha per day, respectively. The time of pollination and the harvest index also played an important role in improving the efficiency of wheat and barley genotypes. So that, every day of delay in pollination, according to the average rate of grain production in wheat and barley genotypes, means a reduction of 52.9 and 90.8 kg of grain per hectare, respectively. Despite the effective role of each trait, advantage in one trait did not play a significant role in reaching high efficiency, and the Mahoor cultivar with the highest efficiency had a favorable status in terms of all characteristics. It seems that by improving the effective traits, the efficiency of spring and winter wheat cultivars, as well as winter and spring barley, can be enhanced, according to a pattern similar to the Mahoor cultivar and even more than it. This situation only for wheat will mean an increase in grain yield potential by about 61.5% compared to the current status of the best wheat cultivar in this dryland conditions.