Agro-economic Evaluation of Fertilizer Management for Wet Season Rice in Southern Cambodia

Abstract

On-farm experiments were conducted to determine the economic efficiency of fertilizer management and the optimal rate of fertilizer application for rainfed lowland rice (Oryza sativa L.) cultivation on Prateah Lang (sandy) soil in southern Cambodia. Five trials were conducted at different locations in 2013 and 2014. Each trial had six treatments of different nitrogen (N)-phosphorus (P₂O₅)-potassium (K₂O) rates with three replicates in 2013 and four replicates in 2014. The amounts of P₂O₅ and K₂O applied differed between the trials, although P₂O₅ and K₂O application rates were the same between the treatments in each trial. The results demonstrated that the application of 60 kg ha^-1 of N, 30 kg ha^-1 of P₂O₅, and 15 kg ha^-1 of K₂O, whose cost was the second lowest (97.8 US$ ha^-1) among those for 25 different N-P₂O₅-K₂O rates, was the most profitable, suggesting that the N-P₂O₅-K₂O rate of 60-30-15 is the best application rate at the experimental sites. While the grain yield increased with a higher fertilizer rate, the optimum rate to maximize income was achieved at a rather low fertilizer rate; hence, the fertilizer cost should be considered before determining the best fertilizer management strategy.