The Biochar Amendment Improves Tomato Growth and Yield under Deficit Irrigation in Sandy Loam Soil in Senegal.

Poor agricultural soil management practices and water use optimisation in irrigation are major challenges facing crop production in Senegal. To address these problems, a factorial experiment was conducted in 2021 and 2022 to investigate the effects of biochar on tomato growth and yield in sandy loam soil under different irrigation levels. Treatments included three biochar treatments (B2 = 30 t·ha^-1, B1 = 15 t·ha^-1, and B0 = 0 t·ha^-1) and three irrigation levels (full irrigation, W0 = 8 L·m^-2·day^-1; medium deficit irrigation, W1 = 6 L·m^-2·day^-1, which is 75% of W0; and deficit irrigation, W2 = 4 L·m^-2·day^-1, 50% of W0). The results showed that using biochar at 30 t·ha^-1 significantly (P < 0.05) reduced the bulk density of the soil by up to 8.3% under W1. In addition, biochar at 15 t·ha^-1 and 30 t·ha^-1 enhanced, regardless of the amount of water applied, the growth of tomato plants by at least 14% compared to that in the B0 treatment. Furthermore, the tomatoes' yields in biochar treatments B1 (12.58 t·ha^-1) and B2 (12.45 t·ha^-1) under W2 were greater than those under B0 (9.27 t·ha^-1) under full irrigation. The combinations of biochar and the lowest irrigation water level (W2 and B1 or W2 and B2) can therefore allow a water economy of up to 50% of full irrigation without compromising yield. Our study concluded that biochar could sustainably reduce agricultural water consumption while increasing yields. To further understand the influence of biochar on sandy loam soil, more research is needed on its effects on soil moisture content at permanent wilting points and field capacity.