Application of Urea and Muriate of Potash Biochar-Absorbed Forms to Reduce Nutrient Losses

Abstract

Though potassium (K) is a cation, it is liable to leaching loss in soils because it is a monovalent one. Considerable leaching of K from applied muriate of potash (MOP) has been reported in soils. Using biochar to absorb MOP may reduce this loss. While urea-intercalated biochar (UIBC) has been studied in Sri Lanka, research on MOP-absorbed biochar is limited. This study aimed to produce potassium-enriched biochar (PEBC) from coir dust and evaluated its potential as a slow-release fertilizer in combination with UIBC, formulated in a previous study. A preliminary research optimized PEBC production under two soaking methods (capillary and direct soaking) and three MOP concentrations (30%, 60%, and 100%) in a two- factor factorial design with three replicates. Statistical analysis (two-way ANOVA, P < 0.05) confirmed that direct soaking, 100% concentration, recorded the highest potassium content 50.87% ± 0.01. A leaching column experiment was conducted using ten treatments: T1 – Control, T2 –Department recommendation, T3-100% UIBC, T4- 75% UIBC, T5- 100% PEBC, T6- 75% PEBC, T7- 100% UIBC + 100% PEBC, T8- 100% UIBC + 75% PEBC, T9- 75% UIBC + 75% PEBC, and T10- 75% UIBC + 100% PEBC, in a completely randomized design (P & lt; 0.05) with four replicates. Over four weeks, the leachate study expressed that all UIBC and PEBC combinations or single treatments significantly reduced the losses of cumulative nitrate and K compared to the department recommendation, indicating their potential as effective slow- release fertilizers.