Relationship between Yield and a Soil Quality Index in Paddy Fields

Rice is one of the strategic agricultural crops in Iran and provides a high percentage of dietary calorie and protein of the people. With a rapidly increasing population and the consequent increase in food demands, it is necessary to know the relationship between rice yield and soil conditions. Therefore, the objective of the present study was to evaluate the relationships between yield and soil quality (SQ) in order to provide guidance regarding proper soil management practices for the sustainable development of Goldasht region paddy fields, in Mazandaran province. One hundred and twenty-eight surface soil samples were collected to measure some physical and chemical soil properties. At harvest time, grain yield was measured at 14% moisture content. Firstly, to determine the SQI, the characteristics with the highest effect on the SQI of the region were identified by the Principal Component Analysis. Fuzzy logic method was used to convert quantitative soil properties to qualitative ranking and, finally, the indices were combined using the concept of coefficient of variation. The average recorded rice grain yield of the studied area was 3498 kg ha-1 and SQI varied between 0.47 and 0.97. Contrary to expectation, there was no significant correlation between performance and SQI in the studied area (reasons are explained in discussion section). According to the results of SQI classification, available phosphorous is the most important limiting factor for soil quality in the area. Direct comparison among maps of yield and soil quality indices indicate that proper soil conditions along with proper management of the farm can be an effective solution to maximize rice yield. Thus, proper management by the farmers can remedy shortcomings and somewhat inappropriate soil conditions. However, in many cases, proper soil quality alone cannot compensate for crop management shortcomings.