Phosphorus Use Efficiency on Yield and Economic Returns of HomWarin Rice Variety Grown in Low Fertility Sandy Soil

Phosphorus (P) is a critical nutrient for rice (Oryza sativa L.) growth and productivity. This study investigated the effects of varying P fertilizer rates on grain yield, yield components, phosphorus use efficiency (PUE), and economic returns for the HomWarin rice variety cultivated in low-fertility sandy soil. A field experiment was conducted using a randomized complete block design (RCBD) with three replications and five P application rates: 0, 4, 8, 12, and 16 kg P2O5 per rai. All treatments received uniform applications of nitrogen (18 kg N/rai) and potassium (15 kg K2O/rai) in three split doses at establishment, tillering, and panicle initiation stages. Results revealed significant differences (p≤0.05) in grain yield and yield components among P rates, while plant height, tiller number per hill, panicle number per hill, panicle length, 1,000-grain weight, and straw yield were unaffected. The highest grain yield (635.25 kg/rai) and spikelet number per panicle (131.01) were achieved with 16 kg P2O5/rai, but these results were statistically similar to the yield at 12 kg P2O5/rai (618.36 kg/rai). Phosphorus use efficiency declined with increasing P application rates, with the highest efficiency (8.97 kg grain/kg P) observed at 4 kg P2O5/rai, followed by 12 kg P2O5/rai (8.02 kg grain/kg P). The marginal rate of return was maximized (217.83%) at 12 kg P2O5/rai, which also provided the optimal balance between high yield, phosphorus use efficiency, and economic returns. These findings suggest that applying P fertilizer at 12 kg P2O5/rai is the most effective rate for maximizing grain yield phosphorus use efficiency and economic benefits in HomWarin rice grown under low-fertility sandy soil conditions.