THE EFFECT OF SOIL AMENDMENTS AND N, P, K FERTILIZERS ON POTENTIAL K, EXCHANGEABLE K, K-UPTAKE, AND YIELD OF LOWLAND RICE ON INCEPTISOL SOILS

Abstract

The decline in soil quality caused by the intensive use of inorganic fertilizers is a major obstacle in lowland rice cultivation on Inceptisol soils. These soils have low natural fertility, particularly limited potassium availability. Low potential and exchangeable potassium reduce potassium uptake by plants and rice productivity. Continuous cultivation without organic matter input accelerates potassium depletion and soil degradation. This study aimed to analyze the effect of a combination of soil amendments with N, P, and K fertilizers on potential potassium, exchangeable kalium, plant potassium uptake, and lowland rice yield on Inceptisol soils. The experiment was conducted from June to November 2025 using a randomized block design with nine treatments and three replications: control; recommended N, P, and K fertilizers; 1 soil amendment; ¼ soil amendment + 1 dose of N, P, and K fertilizers; ½ soil amendment + 1 dose of N, P, and K fertilizers; ¾ soil amendment + 1 dose of N, P, and K fertilizers; 1 soil amendment + ½ dose of N, P, and K fertilizer; 1 soil amendment + ¾ dose of N, P, and K fertilizer; and 1 soil  amendment + 1 dose of N, P, and K fertilizer. The soil amendments used consisted of water hyacinth compost, rice straw biochar, and humic acid. The experimental results showed that the H treatment (1 soil amendment + ¾ dose of N, P, and K fertilizer) significantly increased potential potassium, exchangeable potassium, plant potassium uptake, and rice yield components (number of grains per panicle, percentage of filled grains per panicle, 1,000-grain dry weight, and dry milled grain yield) on Inceptisol soil from Jatinangor.