Co-Application of Bokashi and Biochar Alleviates Water Stress, Improves Soil Fertility and Enhances Wheat Production Under Water-Deficit Conditions

Water stress and nutrient stress are major limiting factors affecting crop productivity. Biochar-based organic fertilizers improve soil nutrient availability, water use efficiency (WUE), and crop yields under these adverse conditions. This study investigated the mechanistic effects of biochar–bokashi mixtures under a controlled glasshouse pot experiment on soil fertility, available nutrients, soil moisture, plant water use efficiency (PWUE), and wheat yield parameters under three moisture levels. Four treatments were included, (1) a control, (2) bokashi only, (3) 1% biochar + bokashi, and (4) 2% biochar + bokashi, under 30% (IR30), 50% (IR50), and 60% (IR60) field capacity, totaling twelve treatments in a completely randomized design with three replications. The combined bokashi–biochar application significantly (p < 0.05) improved growth parameters and yields, including plant height, number of fertile tillers (NFT), number of spikes (NS), spike length (SL), 1000-grain weight, biological yield (BY), root biomass, and grain yield (GY), compared to the control and bokashi-only treatments. Bokashi with 1% biochar exhibited superior agronomic performance over the other treatments, including 2% biochar. Biochar addition enhanced soil moisture and PWUE across irrigation levels. Bokashi–biochar treatments under IR30 outperformed the control and bokashi-only treatments under IR60, highlighting biochar’s effectiveness in alleviating water stress and increasing yields. Moreover, co-application significantly increased soil pH while enhancing the organic carbon, total nitrogen, available phosphorous and exchangeable potassium nutrient levels, which positively correlated with yield. Bokashi–biochar mixtures have been proven to be an effective strategy to enhance soil fertility, increase soil moisture to alleviate water stress and support sustainable wheat production under water- and nutrient-limited conditions.