Utilising GIS-based spatial land resource analysis for subsidised fertiliser allocation in Jombang Regency, Indonesia

A subsidised fertiliser policy is a clear option to increase rice production and maintain farmer benefits. It has proven to be costly and hence needs to be effectively calculated. This research proposes the use of advanced multi- disciplinary techniques to precisely estimate annual fertiliser demands for food production, based on the local field conditions and crop characteristics. Time-series satellite imageries (Landsat 8 Surface Reflectance of Operational Land Imager) were analysed to identify the annual cropping patterns, delineate agricultural field boundaries, and estimate land area. Monitoring and data collection on cropping patterns were conducted using normalised difference vegetation index (NDVI) data. The corrected rice field maps and cropping patterns were validated through field inspections. Subsequently, soil sampling and analysis were performed to determine precise fertiliser doses for each crop during each planting season. Finally, a fertiliser demand allocation map was created to inspect the results visually. A case study conducted in Jombang Regency, East Java Province, Indonesia, highlighted a gap of approximately 5.91 Mg urea and 1.02 Mg NPK in fertiliser demand measured using this study method as compared to the current subsidised fertiliser allocation. This gap could lead to an ineffective use of the fertiliser subsidy budget, which could jeopardise achieving the national food production target. Therefore, this study urges government stakeholders to implement the proposed method to maintain national food security in the country.