Yield Response of Rice to Added Phosphorous and Potassium Fertilizer in the Dry Zone of Sri Lanka

Abstract

Purpose: Continuous application of Phosphorous (P) and Potassium (K) fertilizer over a long period in rice (Oryza sativa L) cultivation may lead to their accumulation in the soils. So, further addition of such fertilizers may be a waste in rice cultivation and also lead to environmental pollution. Thus, field experiments were carried out to study the yield response of rice to added P and K fertilizer under irrigated conditions in Low Humic Gley soils in the Dry Zone of Sri Lanka. Research Method: For the P response study, an experiment was conducted over three consecutive seasons in a rice field where P fertilizer had not been applied for 10 years before the initiation of the experiment, and for the K response study, an experiment was conducted over two consecutive seasons in a rice field where recommended K fertilizer had been continuously applied before the initiation of the experiment. Data on grain yield and yield components, milling quality, important soil properties, and soil and plant P and K contents were recorded and analyzed statistically. Findings: Grain yield, yield components and milling quality of rice did not respond to added P fertilizer over three consecutive seasons in a rice field where P fertilizer had not been applied 10 years before the initiation of the experiment. Soil P analysis indicated that enough soil P was available to maintain an adequate plant P level so that application of P fertilizer in rice cultivation can be avoided at least for about 11½ years (10 years + three seasons) without affecting grain yield and milling quality in Low Humic Gley soils in the Dry Zone of Sri Lanka while saving the cost for P fertilizer. The short-term response of grain yield in rice to added K fertilizer appeared dependent on the grain yield level obtained. No yield response of rice to added K was observed up to the yield level of about 4 t/ha. Thus, the application of K fertilizer can be avoided over two consecutive seasons without affecting grain yield in rice in Low Humic Gley soils in the Dry Zone of Sri Lanka if the yield level is 4t/ha or lower. Research Limitation: Further studies at different locations in farmers’ fields are needed to confirm the applicability of the findings of the present study in farmers’ fields in the Dry Zone of Sri Lanka. Originality/ Value: Long term (over 11½ years) P response study in rice. Such a long-term P response study in rice has not been reported to date. The short-term K response in rice is dependent on the grain yield level achieved.