Qualitative and Quantitative Land Suitability Evaluation for Rice Production in Central Areas of Guilan Province

Land suitability evaluation is determining the fitness of a given tract of land based on its potential for a defined use. With regard to information in references and land suitability evaluation methods, square root parametric method for qualitative suitability evaluation and yield per unit area for quantitative suitability evaluation were selected. Potential yield was calculated about 8.5 t/ha using the method proposed by FAO (AEZ). The quantitative land suitability evaluation and its classes were defined according to incorporating potential, actual and marginal yields with the qualitative suitability evaluation results. The predicted yield varied from 5.3 to 7.9 t/ha in different land units and high correlation between the observed and predicted yields indicated the appropriate selection of the factors and evaluation methods. Obtained results showed that important limiting characteristics were climatic characteristics, especially relative humidity percentage after milky stage, harvest stage and mean temperature of the developing stage. Light soil texture in coastal lands, high groundwater table, and severe limitation of drainage in some land units caused suitability reduction. In the studied area the climatic class was determined low suitability for rice, while, results of quantitative evaluation showed that the most of the land units had high suitability for rice cultivation. With regard to low area of rice cultivation for each person, basic consumption of produced rice by farmers and their low pure income, using of secondary cultivation was proposed subsequent to rice harvest.