Integrated coffee husk biochar and NPSB fertilizer improve bread wheat productivity in acidic soils

Abstract The integrated use of organic and inorganic fertilizers improves soil physicochemical properties and wheat productivity, whereas sole reliance on inorganic fertilizers leads to declining soil fertility. In the Bita District of Southwestern Ethiopia, the limited use of lime and coffee husk biochar constrains soil fertility improvement and wheat yields. To address this challenge, a field experiment was conducted during the 2023 main cropping season to evaluate the effects of integrating coffee husk biochar and blended NPSB fertilizer under limed and unlimed conditions on the yield and yield components of bread wheat. The experiment consisted of three levels of coffee husk biochar (2.5, 5, and 7.5 t ha -1 ) combined with three rates of NPSB fertilizer (50, 100, and 150 kg ha -1 ), along with two positive controls (5 t ha -1 biochar and 100 kg ha -1 NPSB) and one negative control (no fertilizer). Treatments were arranged in a randomized complete block design with three replications in a factorial arrangement. The results indicated that the interaction between coffee husk biochar and NPSB fertilizer significantly increased grain yield. The highest grain yield (3.59 t ha -1 ) was obtained from the application of 5 t ha -1 coffee husk biochar combined with 100 kg ha -1 NPSB fertilizer under limed conditions. This treatment also provided the greatest economic return, with a net benefit of 276,280 Birr ha -1 and a marginal rate of return (MRR) of 22,076%. Under unlimed conditions, the same combination yielded the highest net benefit (197,080 Birr ha -1 ). Additionally, applying 7.5 t ha -1 coffee husk biochar with 100 kg ha -1 NPSB under limed conditions resulted in a net benefit of 221,440 Birr ha -1 and an MRR of 13,292%. In conclusion, the application of 5 t ha -1 coffee husk biochar combined with 100 kg ha -1 NPSB fertilizer, particularly when applied with lime, significantly enhances both the grain yield and economic profitability of bread wheat production in the Bita district.