Diverse feedstock's biochars as supplementary K fertilizer improves maize productivity, soil organic C and KUE under semiarid climate

The contemporary exhaustive agriculture has led to drastic reductions in soil potassium (K) status because of constant soil K mining by crops without sufficient recharge through external K inputs. Therefore, substituting and/or supplementing K through alternative sources has great prospects in developing countries like Pakistan, where imported K fertilizers are comparatively expensive. This two-year field study reports the effects of alternative sources of K as farmyard manure (FYM), sugarcane bagasse and woodchip, and their biochars (B) i.e. FYM-B, bagasse-B and woodchip-B on soil fertility, K availability, K use efficiency (KUE), soil organic carbon (SOC) and maize productivity in calcareous soil of the semiarid northern region of Pakistan. Alternative sources of K and their biochars were applied along mineral K fertilizer as muriate of potash (KCl) at 60 kg ha-1 rate in a randomized complete block design. Results showed that FYM-B significantly increased plant height, grains per cob and 1000-grain weight. The FYM-B increased grain yield by 6.5, 37.2, and 87.0% when compared with woodchip-B, chemical fertilizer and control treatments, respectively. Similarly, FYM-B and woodchip-B significantly increased SOC and soil available K contents as compared with the rest of the treatments. Grain K contents and KUE were generally higher in biochar than their feedstock treatments during both years. However, FYM-B resulted in significantly higher KUE compared to the other K sources and their biochars during both years. The biological and grain yields showed significant positive correlations with soil K and SOC contents. Our study concluded that FYM and FYM-B can be applied as alternative and/or supplementary K sources along woodchip-B and bagasse-B to improve maize productivity, KUE and SOC contents in nutrient poor soil. However, economic feasibility of such practices is required to be priorly investigated on long-term basis.