Classification of Soil Quality Index in Irrigated Paddy Fields: Study in Jember, East Java, Indonesia

Abstract


 
 
 Irrigated paddy fields occupy an area of 1,071.47 km2, about one third of the whole administrative region of Jember. Rice is the principal food consumed by the Indone- sian people. Paddy fields play a vital role in rice food chain production. However, intensive paddy rice cultivation tends to use more input (including fertilizer and pesticides). It is widely accepted that these intensive agricultural practices degrade the soil quality and decrease the farmer’s income. Therefore, soil quality should be prioritized in land resources management. This study aims to assess the soil quality index (SQI) of irrigated paddy fields’ in Jember Regency, East Java, Indonesia. The research procedure consists of (1) determination of land unit, (2) soil sampling, (3) laboratory analysis, (4) principal component analysis (PCA), (5) assessment of soil quality index (SQI), and (6) interpolation. In this case, the PCA selects the most representative leading indicators. The PCA results in the form of a minimum data set (MDS) will reduce the indicator load in the SQI calculation model and avoid data redundancy. Moreover, the Inverse Distance Weighted (IDW) methodinterpolates the data points and forms a classified SQI map. This method predicts the value by considering the distance between the data point and the predicted location. Three main components, i.e., total P, silt fraction, and clay fraction, are the most determinant factors of soil quality in this study. The results showed that about 68,887.65 ha (61.32 %) of irrigated paddy fields was of very low quality, and 39,948.22 ha (35.56 %) was low quality. Meanwhile, only 3,513.83 ha (0.03 %) is in the medium category. Therefore, an effort to maintain the soil quality in paddy fields should be prioritized to guarantee the sustainability of agricultural practices. Soil quality improvement should focus on increasing soil fertility and phosphorus availability.