Influence of foliar and soil-applied potassium fertilizer sources on rice (Oryza sativa L.) yield performance and potassium utilization under tropical monsoon conditions

Abstract:

Foliar potassium application has emerged as a complementary strategy to conventional soil-applied K fertilization for improving nutrient delivery efficiency in rice, yet direct field comparisons between foliar and soil application methods using different K sources remain limited in tropical monsoon environments. A field experiment was conducted during the main season of 2023 at the Penang Institute of Agricultural Technology, Penang, Malaysia, to evaluate the effects of foliar potassium sources (KNO₃ at 2 percent and KH₂PO₄ at 1.5 percent, applied three times at tillering, booting, and heading), soil-applied KCl (80 kg K₂O/ha), soil-applied KCl supplemented with zinc sulphate (80 kg K₂O/ha + 5 kg Zn/ha), and a combined foliar-plus-soil treatment on grain yield and potassium utilization of rice (Oryza sativa L.) variety MR297. Six treatments including an unfertilized control were arranged in a RCBD with four replications. Results showed that the combined foliar-plus-soil treatment achieved the highest grain yield of 5.72 t/ha, followed by soil KCl + Zn (5.58 t/ha) and soil KCl alone (5.45 t/ha). Foliar KNO₃ alone produced 5.18 t/ha while foliar KH₂PO₄ alone achieved 4.95 t/ha, both significantly higher than the control (3.35 t/ha). The incremental yield analysis demonstrated that each component contributed additively, with soil K providing the largest increment, followed by the micronutrient and foliar K supplements. These results indicate that an integrated approach combining soil and foliar K application optimizes rice yield in tropical monsoon conditions.