The Optimization of Cropping Pattern Based on Land Water Balance Analysis and Its Spatial Distribution in Rambipuji District, Jember

Abstract

Optimizing cropping patterns under monsoon climates requires accurate information on soil water availability and its spatial variability. This study aimed to optimize cropping patterns and determine the optimal planting onset based on land-water balance analysis using the Thornthwaite-Mather water balance method and its spatial distribution in Rambipuji District, Jember Regency, Indonesia. Monthly land water balance was analyzed using the Thornthwaite–Mather method based on ten-year climatological data (2015–2024), including rainfall and reference evapotranspiration, and soil water holding capacity measurements across five land mapping units (LUMs) differentiated by slope, soil subgroup, and land use. Planting onset was determined using scientific criteria where soil moisture reached water holding capacity, and the effective rainfall to crop evapotranspiration was ≥ 0.75. The results showed a distinct monsoonal pattern, with water surpluses occurring from November to April and pronounced deficits from May to October. Soil texture significantly influenced water holding capacity, resulting in variations in the duration and intensity of water deficits among LUMs. Based on these conditions, LUM 1, 2, and 5 were recommended for planting in December, while LUM 3 and 4 were more suitable for January for the paddy crop. The optimal cropping pattern consisted of paddy cultivation in the first planting season followed by secondary crops in the second and third seasons, reflecting adaptive water-use strategies under declining rainfall. These findings demonstrate that integrating land-water balance analysis with spatial land characteristics provides a reliable basis for precision-oriented cropping calendar planning, supporting sustainable agricultural management.