Due to drought, population growth and the demand for fresh water resources and low irrigation water use efficiency in agriculture, water scarcity crisis is not unexpected. Chaharmahal va Bakhtiari province with cold and cool weather, have a good potential in potato and maize production. But decreasing of precipitation, significant reduction in the water table elevation and increasing of demand for these productions, will be cased to supply it be difficult in the future. Therefore the present study was conducted to investigate the effect of different irrigation levels on the yield, irrigation water use efficiency and quantitative and qualitative characteristics of potato (cv. Burrne) and the Forage Maize (cv, NS) and also determine the optimal amount of applied water at the Agricultural Research Center Shahrekord in 2014. The investage of randomized complete block design with seven treatments of different irrigation levels under furrow irrigation and three replications were performed. Different irrigation levels include: 40, 55, 70, 85, 100, 115 and 130% of the soil moisture deficit. The results of potato showed that different irrigation levels had significant effect on yield percentage of starch, soluble sugar, dry matter, irrigation water use efficiency and weight of marketable tubers. So that with increasing irrigation water level, yield, soluble sugar were increased and the number of marketable tubers and tuber dry matter and starch precent were decreased. The minimum and maximum potato yield were related to 40 and 130% treatments and their yields were 13.19 and 45.21 tons per hectare respectively. These values for irrigation water use efficiency were 6.96 and 4.84 Kg per cubic meter related to 85% and 40% treatments respectively. The results showed that the optimal depth of water was 533 mm that is equal to 82% full irrigation treatment. The results of maize showed that different irrigation levels had significant effect o yield, irrigation water use efficiency, plant height, stem diameter median, corn diameter, corn length, corn weight, fiber percentage, dry
