Abstract

Field experiments were conducted to study the effect of biochar on potassium fertilizer leaching and uptake, efficiency and effectiveness of K fertilization, and economic viability of farming maize. Thirty tons ha^-1 of biochar prepared from organic waste was applied to an Inceptisol. The experiment was arranged in a randomized block design with 7 treatments, namely control (without biochar and KCl), K1 (200 kg ha^-1 KCl), BK0 (biochar, without KCl), BK1/4 (biochar + 50 kg ha^-1 KCl), BK 1/2 (biochar + 100 kg ha^-1 KCl), BK 3/4 (biochar + 150 kg ha^-1 KCl), and BK1 (biochar + 200 kg ha^-1 KCl) and three replicates for each treatment. The results suggest that biochar could replace and reduce KCl fertilizer. Biochar application increased the availability of nutrients by 69-89% for K⁺, 61-70% for Ca⁺⁺, 39-53% for N total, 179-208% for P, and 14-184% for K.The results showed that the sole application of biochar increased maize production (6.24 Mg ha^-1) by 14% compared sole application of KCl fertilizer (5.45 Mg ha^-1). In contrast, dual application of biochar and 75% lower dosage of KCl fertilizer application increased maize production by 29%. Application of biochar and KCl fertilizer at the rate of 50 kg ha^-1 resulted in the highest relative agronomic effectiveness (137%) and K fertilizer efficiency (18%). This application rate was also superior both technically and economically as assessed in terms of production (7.02 Mg ha^-1), value of sales (revenue; IDR 19,305 million ha^-1), income (IDR 8,663 million ha^-1), and economic feasibility (R/C, 1.8).

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