Salt Tolerance Indices And Safty Assessment For Cotton Under Pre-sowing Irrigation With Saline Water

Rational development and utilization of shallow underground saline water resources in agricultureirrigation has important theoretical significance and practical value in relieving the contradictions of theshortage of water resources, as well as ensuring the stabilization of agricultural production andecological environment security in the low land plain area around Bohai Sea. A field study on cottonwas conducted at Hengshui, Hebei province during the2006-2013growing season. Border irrigationand furrow irrigation were adopted to supply pre-sowing water. The irrigation water quota was75mmfor border irrigation and37.5mm for furrow irrigation. Five salinity levels of mineralized water wereincluded in the experiment:1,2,4,6, and8g/L (denoted as B1, B2, B3, B4, and B5for borderirrigation; F1, F2, F3, F4, and F5for furrow irrigation). The response of cotton growing and soilenvironment to long-term saline water irrigation was investigated, and the evaluation method of safetyirrigation with saline water was probed in this research, and appropriate irrigation methods andirrigation water salinity index were obtained. The main results showed that:(1) The change rate of soil salt and the desalinization rate of salt input by irrigation water weredetermined to to be important evaluation indexes in cotton field salt balance analysis of saline waterirrigation and drainage. Compared to the initial soil EC1:5within0～1.0m soil layer in2006(0.25dS/m), the final soil EC1:5in2013decreased by11.8%,8.7%and10.1%for B1, F1and F2treatment,but increased by1.5%,41%,42.9%,90.8%,7.3%,24.5%and65.2%for B2, B3, B4, B5, F3, F4, and F5treatment. It can be seen that the level of soil salt accumulation were higher in border irrigationtreatments significantly. Eventually, more than86%of salt input by irrigation water was leached out ofthe1.0m soil layer for all treatments. The salt peak of B1, B2, B3, B4, B5and F1, F2, F3, F4, F5was2.3,2.1,1.9,1.7,1.5, and2.1,2.1,1.9,1.9,0.7m, respectively. The peak values of salt in the soil profileshowed a tendency to move up with the increasing salinity of the irrigation water under the sameirrigation method.(2) The response of cotton growing and soil environment to long-term saline water irrigation wasrevealed. There was a close relation between salinity of water and the cotton growth index and yield in asingle cotton growing season. Among the years, the interannual fluctuations of all cotton growingindicators and yield were mainly affected by salinity of irrigation water and the meteorological factors.the interannual fluctuations of seed cotton yield might be mainly affected by mean air tempreture atblossing and boll-forming stages.(3) By means of the definition of judging principle of cotton salt resistance appraisal index, cottonplant height, number of boll, number of branches, and pre-frost yield rate all could be used as salttolerance appraisal indices of cotton. Meanwhile, the plant height and number of boll are the mostreliable index to predict the seed cotton yield.(4) Taking yield, price, irrigation quota, and salt input by irrigation water into consideration, andensuring the higher income and the soil safety, the maximum salinity of irrigation water for border irrigation and furrow irrigation treatment was6.0and4.0g/L, respectively.(5) The suitable saline water safety irrigation principle and evaluation method were proposed forthe local. It demonstrated that after7years of saline water irrigation, the soil quality decreased with theincreasing salinity of irrigation water under the same irrigation method; the soil quality were better inborder irrigation treatments when salinity of irrigation water was lower than6.0g/L, the soil quality wasbetter in furrow irrigation treatment when salinity of irrigation water reached to8.0g/L. Considering theeconomic benefits and soil quality, short-term saline water irrigation is feasible in the low plain aroundthe Bohai Sea with the low soil salinity. Border irrigation and conventional planting for cotton aresuggested under pre-sowing irrigation with saline water and transplanting after sowing, and the suitableeigevalue for irrigation water salinity is6.0g/L.