Distribution of soil fertility under various management systems of paddy fields of organic, semi-organic, and inorganic using clay content as a modified indicator

The amount of chemical inputs influences long-term soil nutrient balance. Therefore, different management practices will determine the sustainability of land use. This study aimed to determine the effects of paddy field management systems on the Soil Fertility Index (SFI), identify the characteristics of clay content and its effects on SFI, and identify the determinants of SFI. The originality of this research lies in identifying the determinants of soil fertility based on soil characteristics, enabling more focused, effective, and efficient land management recommendations. Soil sampling was carried out at 24 points, comprising 8 LMUs, across 3 types of rice field management and slope gradients (8-15%) in Purwantoro District, Wonogiri Regency. Parameters observed included pH, organic carbon (organic C), Total Nitrogen (N), available Phosphorus (P), available Potassium (K), base saturation, cation exchange capacity (CEC), Aluminium (Al) saturation, and clay content. The SFI class was generated by matching data with classification, while the influence of rice field management type on SFI was analyzed using ANOVA and the determining factors of SFI were analyzed using correlation test. The study found that the soil fertility index ranged from 0.33 (low) to 0.50 (moderate). The soil fertility of each type of rice field management varied, with organic rice fields having the highest soil fertility (0.48c), semi-organic rice fields (0.42c), and conventional rice fields (0.36a). Soil fertility was also related to the proportion of clay (r2=0.2112). The strongest factors determining soil fertility were Organic Carbon (0.905) and CEC (0.805).