Investigating the possibility of using saline waters for ber (Ziziphus nummularia) irrigation with determination of water salinity- dry matter yield production function in vegetative growth period

The ber is a fruit tree tolerant to drought and salinity conditions. This research was carried out in a randomized complete block design with four treatments and three replications on Ziziphus nummularia seedlings. The treatments were water salinity (ECw) of 0.3, 3, 6 and 9 dS/m. The saline irrigation waters were prepared from drain water of agricultural lands. Net irrigation depth was calculated based on soil moisture deficiency. Salinity of soil saturated extract, fresh and dry matter of root, fresh and dry matter of shoot, shoot/root ratio and shoot relative water content were measured. The production functions of water salinity or relationship between plant shoot dry matter and electrical conductivity of irrigation water were estimated in various equations including linear, quadratic, cubic, logarithmic and exponential. The results showed that irrigation water salinity had significant effect on soil salinity and root and shoot characteristics at 1% level of probability. There were no significant difference in shoot fresh and dry matter and shoot relative water content between waters of 3 and 6 dSm-1. The comparison of treatments mean showed that shoot fresh and dry matter and relative water content decreased 15.7, 15.2 and 1.8 percent, respectively, with increasing irrigation water salinity from 3 to 6 dS/m. But, total root and shoot characteristics of plant decreased significantly with rising irrigation water salinity from 6 to 9 dS/m. The root fresh and dry matter decreased 23.2 and 44.6 percent, respectively. Also, shoot fresh and dry matter and relative water content decreased 31.2, 20.7 and 24.0 percent, respectively. The cubic equation had the best accuracy for Ziziphus nummularia seedlings. All equations estimated shoot dry matter less than actual data.