Improving fertility in reduced-tilled soil with sewage sludge and frequent irrigation enhances maize silage yield and water productivity

ABSTRACT Improving soil moisture management can result in higher crop yields and water productivity by enhancing the benefits of organic and inorganic components found in sewage sludge. The study aimed to improve soil and crop fertility by testing different irrigation strategies with varying amounts of stabilized sewage sludge (0, 30, 60, and 90 t·ha-1 in SS0, SS1, SS2, and SS3, respectively) under reduced tillage to enhance the water productivity of silage maize. Soil moisture was adjusted to field capacity when the total estimated evapotranspiration minus effective precipitation reached 25, 50, and 75 mm in irrigation strategies W1, W2, and W3, respectively. Results from two years with three replicates showed that organic matter, macronutrients, and exchangeable cations increased significantly with higher doses of sewage sludge, while pH decreased and salinity remained low. Frequent irrigation increased organic matter mineralization, enhancing plant nitrogen uptake and improving soil fertility. This resulted in improved crop nutrient contents, chlorophyll, stomatal conductance, leaf water content, and membrane damage index. The SS3-W1 treatment produced the highest fresh biomass at 130.5 mg·ha-1, a 37.5% increase over SS0-W1, mainly due to increased leaf and stem growth. SS3-W1 also showed the highest water and irrigation water productivity at 30.3 and 40.3 kg·m-3, respectively, a 37.1% improvement over SS0-W1. The study indicates that higher water productivity can be achieved in frequently irrigated silage maize by increasing sewage sludge dose.