EFFECT OF INORGANIC FERTILIZERS (N, P, K) ON RICE YIELD IN ALLUVIAL SOILS OF THE MEKONG RIVER DELTA

Abstract

This study was conducted to evaluate the agronomic effectiveness of different inorganic fertilizer forms (N, P, K) on commercial rice production in alluvial soils of the Mekong River Delta (MRD), providing a basis for adjusting fertilizer rates to enhance yield and economic efficiency. Field trials were carried out in Dong Thap province over two years (2023 - 2024) using a randomized complete block design with replications. Treatments included coated urea fertilizers such as yellow urea (coated with N-(n-butyl) thiophosphoric triamide), green urea (coated with N-KEEP to reduce hydrolysis), black urea (coated with humic acid) and P-Avail (polymer-coated DAP), compared with traditional urea and DAP. Results showed that improved urea types (especially yellow and green urea) and customized NPK fertilizers increased rice yield by 7.4 - 12.8% compared with the control using conventional fertilizers, with mixing NPK customized formulas achieving the highest and most stable yields across all growing seasons. Nutrient use efficiency was highest in the customized mixing NPK treatment (42.6 kg grain/kg N+P₂O₅+K₂O), followed by yellow and green urea (~42 kg/kg), both exceeding the control by 12 - 13%. P-Avail did not show clear advantages under acidic alluvial soil conditions. In terms of economic returns, yellow urea generated the highest profit (+12.5%), followed by green urea and customized mixing NPK, while P-Avail offered only a slight increase (+2.4%). These findings confirm the potential of advanced fertilizer forms, particularly stabilized urea products, in improving rice yield and nutrient use efficiency in alluvial soils of the MRD. This study aimed to assess the agronomic effectiveness of N, P₂O₅ and K₂O fertilizers on commercial rice cultivated on alluvial soils in the Mekong River Delta (MRD).