Determining Soil and Landscape Requirements of cotton for Using in Land Suitability Evaluation

The strategic importance of cotton in providing the fiber needed by humans, animal feed and job creation raises high attention to cotton production. This study was aimed to investigate the effect of soil characteristics on cotton yield and their rating for applying in land suitability assessment studies. Consequently, 123 farms in Qom, Khorasan Razavi, Golestan and Fars provinces were selected. In each farm, a soil profile was studied and a land use questionnaire completed.After handling the necessary physical and chemical analyzes, multivariate regression was performed by the backward method between yield (dependent variable) and different soil characteristics (independent variables). By creating simple regression relationships between effective soil characteristics on yield, the characteristics rating was determined for different land suitability classes. Results showed that the amount of variance of salinity, ESP, potassium, lime and soil texture components was high and insignificant for soil pH and organic carbon. Therefore, most of the data were very extensive. In multivariate regression, the variables of salinity, lime, organic carbon content, silt, ESP, soil pH and gypsum percentage, which had the highest correlation with yield, remained in the equation, respectively. The coefficient of determinationof the proposed relationship was about 0.9. The validation of the proposed soil requirements table was performed using data from 24 cotton fields (about 20% of the data). The value of the coefficient of determination between yield and soil index was 0.78, which indicates the reliability of land characteristics rating and the table prepared in this study.