The Effect of Biochar-Silica and N, P, K Fertilization on Soil pH, Silica Content, Phosphorus Uptake, and Rice Yield in Inceptisols

Rice is a major commodity in Indonesia, but its production in 2023 decreased by 645.09 thousand tons compared to the previous year, partly due to intensive land use leading to soil degradation. Biochar is a soil amendment that can improve soil properties and enhance nutrient retention. Silica plays a crucial role in rice cultivation, particularly in addressing issues related to acidic soil pH. This study aimed to evaluate the effects of a biochar-silica combination derived from rice husk waste and N, P, K fertilizers on soil pH, silica content, phosphorus uptake, and to determine the optimal dosage for achieving the highest rice yield in Inceptisols. The experiment was conducted from October 2024 to January 2025 at the KTNT experimental field using a Randomized Block Design (RBD) with 10 treatments and 3 replications, totaling 30 experimental plots. The combination of biochar-silica and N, P, K fertilizers significantly increased available phosphorus content, soil silica levels, and rice yield components, including panicle length, number of panicles, grains per panicle, straw weight per plot, 1,000-grain weight, harvested dry grain, and milled dry grain. However, it had no significant effect on soil pH or phosphorus uptake by plants. The optimal treatment—biochar (2.5 t ha⁻¹), silica (320 kg ha⁻¹), and N, P, K fertilizers (175 kg ha⁻¹ urea, 25 kg ha⁻¹ SP-36, and 25 kg ha⁻¹ KCl)—resulted in the highest harvested dry grain yield of 3.37 kg per plot.