Sewage sludge-based fertilizer and its effects on soil micronutrients availability and carbon quantity and quality in a no-tillage system in the Cerrado region

Abstract

The use of composted sewage sludge (CSS) in agriculture may reduce reliance on mineral fertilizers and mitigate possible environmental problems. Composted sewage sludge (CSS) has considerable amounts of organic matter (OM) and plant nutrients, making it an organic fertilizer option. When CSS is used in association with no-tillage (NT), it can contribute to improving soil health, especially in highly cultivated and naturally infertile areas such as the Brazilian Cerrado. Successive applications of CSS can facilitate nutrient cycling while increasing crop productivity and carbon stocks. However, the increase in concentrations of metals such as copper (Cu), manganese (Mn), and zinc (Zn) - even essential to plants - must be monitored to avoid plant toxicity. There is a lack of information regarding the impact of successive CSS applications and their effects on carbon quality and micronutrient dynamics in soils in the Cerrado region cultivated under NT. The objective of this research is to evaluate the effect of three CSS application doses in a crop rotation by monitoring changes in carbon, Cu, Mn and Zn availability in the soil, and the agronomic performance of soybean, wheat, and marandu grass. The field study was initiated in Selvíria/MS, Brazil. The experimental design was a randomized complete block design with four replications. The research proposed here will add to that existing study. In Study I: five CSS rates were tested (0.0; 5.0; 7.5; 10.0, and 12.5 Mg ha-1, wet basis), applied in three crop years, in addition to a treatment without CSS application and with conventional mineral fertilization (CMF) only. Over three years, the concentration and total fractions available (water soluble, exchangeable, bound to organic fraction, bound to Mn oxide, weakly bound to amorphous Fe oxides, bound to crystalline and residual Fe oxides) of Cu, Mn, and Zn in the soil (0-0.2 m) will be measured. In Study II: the treatments will correspond to: 1) native forest soil, 2) CMF, 3) 0.0 rate of CSS/control - absence of CMF, and CSS, 4) rate of 22.5 Mg ha-1 of CSS (wet basis), and 5) rate of 37.5 Mg ha-1 of CSS (wet basis). In soil samples collected in the 6th year, and in a native forest, depths of 0-0.05, 0.05-0.1, 0.1-0.2, 0.2-0.3, and 0.3-0.4 m will be collected to evaluate: OM fractionation, C stock, C saturation level, microbial respiration C-CO2, C from microbial biomass, and enzymes activity ²-glucosidases and arylsulfatase. Additionally, biomass of marandu grass and the productivity of soybean and wheat will be determined. This study will provide important information on efficient use of CSS to ensure soil quality and increase crop productivity. This project adheres to the priority technological areas for sustainable development and for the quality of life of the MCTIC in 1122/2020 and 1329/2020 and with the main goal of the PNF for reducing the Brazilian foreign dependency on fertilizers and is also in line with the "2030 Agenda" of the United Nations to promote the "Sustainable Development Goals". (AU)