Indexes of Salt Tolerance of Cotton in Akesu River Irrigation District

【Objective】This experiment is to construct the linear subsected functions and the nonlinear S-shaped functions between the cotton relative yield and soil salt content in the salinized soil in Akesu River Irrigation District and to determine the index of cotton salt tolerance.【Method】The linear regression and the nonlinear least square approximation were used to deduce two yield response functions of cotton to soil salt content,which are respectively for the 0-20 cm soil layer and the 0-40 cm soil layer,based on experimental data from the four observation points during the three years,whose applicability were analyzed and compared and then the indexes of cotton salt tolerance were drawn up with the function with better applicability.【Result】 Both the linear subsected functions and the nonlinear S-shaped functions were founded for the 0-20 cm soil layer and the 0-40 cm soil layer.It was found that the nonlinear S-shaped function fitted better with the response relationship between the cotton relative yield and the soil salt content in the salinized soil in Akesu River Irrigation District than others.【Conclusion】The cotton critical soil salt content the cotton threshold soil salt content,the soil salt content at the fastest rate of cotton relative yield reduction,and the soil salt content at the 50% cotton relative yield reduction are respectively 0.302%,1.119%,0.558%,0.581%(0-20 cm soil layer) in Akesu River Irrigation District.