Effects of Sewage Sludge Stabilization Processes on Soil Fertility, Mineral Composition, and Grain Yield of Maize in Successive Cropping

The final disposal of sewage sludge (SS) in agricultural areas is considered economically and environmentally viable, but few studies on the effects of sludge stabilization processes on SS fertilizing potential are available. The present study evaluated two forms of SS stabilization on the shoot biomass, yield, and concentration of nutrients in the soil and plants in three successive maize croppings. The raw sludge was chemically stabilized (CSS) and composted (TSS) through the addition of calcium oxide and co-composting with plant residues, respectively. Five rates of each type of SS (0, 10, 20, 30, and 40 t ha(-1) dry weight) were applied to the soil in a family farm of NE Brazil. A mineral fertilization treatment was used to assess the SS fertilizer potential. Changes in soil chemical characteristics (pH, organic matter, and nutrient available contents), plant mineral composition, and maize biomass and yield were assessed at each crop cultivation. Applying sewage sludge to the soil elevated the soil organic matter and the availability of N, P, Fe, Mn, Zn, and Cu, reflecting in higher accumulation of these nutrients by plants. The CSS was more efficient in increasing soil pH than SS composting. In the first harvest, maize yield in CSS was 34% higher than that obtained with mineral fertilization. The two types of sludges had different effects on soil characteristics, plant mineral composition, and maize yield. The CSS residual effect on soil pH can dismiss soil liming. Composted sludge maintained higher soil organic matter levels in the soil with the successive croppings and promoted higher soil N concentrations in the first two croppings. Both sludges increased and maintained adequate available P concentrations in the soil throughout the successive crops. The results support SS's efficiency in providing nutrients to plants, improving soil properties, and boosting crop productivity in low-input agriculture systems.

Automated summary

The study found that chemically stabilized sludge was more efficient in increasing soil pH, while composted sludge had higher soil organic matter levels. The addition of sludge improved the availability of nutrients in the soil, aiding in plant nutrient uptake and increasing maize yield.