Cattle-Urine-Enriched Biochar Enhances Soil Fertility, Nutrient Uptake, and Yield of Maize in a Low-Productive Soil

Poor soil fertility, imbalanced fertilization, and limited use of organic fertilizer by farmers are significant limitations contributing to lower crop productivity in Nepal. Biochar-based organic fertilizers have been identified as efficient soil amendments to improve soil fertility and boost crop yields. In this study, we investigated the effects of biochar-based organic fertilizers on soil properties, fertilizing efficiency, and maize yields in low-productivity Nepalese soil. A field trial was conducted using a randomized complete block design comprising four treatments with three replications: (1) control without biochar (CK), (2) biochar (BC), (3) biochar + manure (BC+M), and (4) urine-enriched biochar + manure (BU+M). Recommended NPK fertilizers were applied to all plots, including the control. Urine-enriched biochar (BU+M) significantly improved soil pH, organic carbon, and soil nutrient levels (N, P, and K) compared to the control (CK). Total N, available P, and K were significantly higher (p < 0.05) in BU+M treatments compared to the other two biochar amendments (BC and BC+M). A similar trend was observed in the NPK uptake by plants, with BU+M outperforming CK, BC, and BC+M. Moreover, BU+M increased (p < 0.05) the partial factor of productivity of N (PFPN) and P (PFPP) compared to CK. The application of urine-enriched biochar resulted in a 62% increase in maize yield compared to the CK. These findings suggest that farmers can improve soil fertility and increase grain production with the use of urine-enriched biochar, which can be easily produced by farmers themselves using locally available feedstocks and cattle urine.