Effects of integrated use of coffee husk and maize straw biochar‐based fertilizers on maize yields, nutrient uptake and soil properties in southern Ethiopia

Abstract

In Ethiopia, the use of fertilizer is low due to high cost and limited availability, leading to low yields. Using organic amendment, such as biochar together with mineral fertilizers could be a more effective solution. A field experiment was conducted in clay‐textured soil with a slightly acidic pH of 5.82, located in southern Ethiopia to determine the effects of two different types of biochar, including coffee ( Coffea Arabica ) husk and maize ( Zea mays L) straw biochars, at three application rates (0, 2.5, and 5 t per hectare) with and without mineral fertilizer on maize yields, nutrient uptake, and soil properties. The experimental design used was a randomized complete block design with 10 treatments and three replications. Three‐way analysis of variance was conducted to quantify the effects of biochar type, rate, and mineral fertilizer combinations on maize yields, nutrient uptake, and selected soil properties. Biochar application, alone or with fertilizer, improved maize yields, nutrient uptake (N and P), and soil properties (organic carbon, bulk density, and soil moisture content) significantly. Coffee husk biochar outperformed maize straw biochar by 44% in enhancing maize yield. Coffee husk biochar was also better in improving soil properties (4%, 5%, and 13% enhancement of organic carbon, soil moisture content, and soil bulk density, respectively, compared to maize straw biochar). Increasing the biochar application rate from 2.5 to 5 t ha ^{− 1} resulted in maize grain yield increase of 45.1%, irrespective of the biochar type. Combining coffee husk biochar at 5 t ha ^{− 1} with mineral fertilizer showed the best results in terms of nutrient uptake, maize yield, and soil improvement. This study suggests that using biochar from coffee husk and maize straw can boost maize productivity in similar environments by enhancing soil moisture and nutrient availability.