Soil chemical attributes, nutritional status and agronomic performance in the soy-corn succession fertilized with sewage sludge compound in the Cerrado region

Field crops in soils of the Brazilian Cerrado region are becoming increasingly deficient in some micronutrients, making supplemental fertilizer application an indispensable management practice. Sewage sludge compost (SSC) contains considerable amounts of organic matter and crop nutrients and could be used as an organic fertilizer. However, minimal research has been conducted to evaluate the potential of SSC as a nutrient source in the Cerrado region. The objective of this study was to evaluate the agronomic viability of SSC as a micronutrient source for soybean and maize crops grown successively on a typical, low fertility Cerrado soil. The experiment was conducted under field conditions in Selvíria, MS, Brazil, with soybean as a summer crop and maize as a winter crop. A randomized complete block design with four replications was implemented. The treatment structure used in the study followed a 4 × 2 + 2 factorial arrangement: 1. SSC: 10, 15, 20, and 25 Mg ha-1, on a wet basis); 2. Application method: whole area or between rows for both crops. The two additional treatments were: i) a control where neither CSS nor mineral fertilizers were applied; ii) an area treated with conventional fertilization (CF, hereafter) only. In this last case, NPK mineral fertilizers were applied along the plot directly on the sowing line; B and Zn were applied after the emergence of soybean and maize plants. At the end of each crop cycle, soil samples were collected (layer 0.0–0.2 and 0.2–0.4 m deep) to assess the soil fertility (OM, pH, CEC, H + Al, Al, SB, BS, P, K, Ca, Mg, S, B, Cu, Fe, Mn, Ni, and Zn). In both crops, agronomic parameters, including yield components, concentrations of macro- and micronutrients in plant tissues (nutritional status) and in grain, Falker chlorophyll index, the capacity of extraction and export of nutrients and grain yield were measured. The SSC improves soil chemical attributes and provides nutrients for the proper development and adequate nutritional status of crops. Maize plants showed the best results in terms of yield compared to soybean. There was no difference for SSC application in relation to the variables studied for both crops, suggesting that SSC should be applied to the whole area. The effects of SSC and mineral fertilizer application on the variables evaluated were similar. Our study showed that use of SSC as a micronutrient source for field crops is a viable option for lowering production costs while also allowing for sustainable disposal of sewage sludge. (AU)