Co-composted Poultry Litter Biochar Enhanced Soil Quality and Eggplant Productivity Under Different Irrigation Regimes

The use of biochar has mostly moderate-positive to negative yield effects. However, integrating biochar with compost considerably enhanced biochar’s positive effects on crops. This study aimed to investigate the potential effects of co-composted poultry litter biochar incorporation under deficit irrigation on eggplant’s growth and productivity grown in salt-affected soil. Summer and fall season field experiments were conducted during 2016/2017. Three levels of co-composted biochar (CB) (0, 5, and 10 t ha−1) were used as a soil amendment combined with three irrigation levels (100, 80, and 60% of ETc). CB ameliorated the negative effects of water stress on eggplants, showing increased yield and irrigation water use efficiency (IWUE). This mainly due to the positive effect of CB on soil properties (i.e., bulk density, hydraulic conductivity, electrical conductivity, pH, useful pores%, water-holding pores%, available water, fine capillary pores%, and soil biota). The results showed that CB increased stomatal conductance, relative chlorophyll content (SPAD), and the photosynthetic efficiency of water-stressed eggplant at 80% ETc and consequently improved eggplant growth (i.e., leaf area, leaf number per plant, dry matter, stem diameter) and productivity. In summer and fall seasons, the highest fruit yields were recorded under full irrigation (28.3 t ha−1) and 10 t ha−1 of CB (27.8 t ha−1). Soil supplemented with 5 or 10 t ha−1 of CB increased IWUE by 31.6 and 64.1%, respectively, compared to CB-untreated soil. Adding 10 t ha−1 of CB under irrigation with 80% ETc increased fruit yield by 37% and IWUE by 69% in relation to full irrigation and CB-untreated soil. CB may be recommended as a soil amendment for vegetable crops such as eggplant to overcome the negative effects of water stress.