Soil fertility, nutrition and agronomic performance in a wheat and soybean rotation amended with composted sewage sludge and inoculated with Azospirillum brasilense and Bradyrhizobium sp.

Abstract

Food security and agricultural sustainability depend on responsible fertilizer management, especially in soils of the Cerrado region, which naturally have low nutrient availability. Considering the high costs of acquiring mineral fertilizers, it has become essential to increase the efficiency of their use, while also seeking alternative fertilizer sources. Composted sewage sludge (CSS) contains large amounts of organic matter and plant nutrients and can be supplied as an organic fertilizer. Some genera of plant growth-promoting bacteria (PGPBs) such as Azospirillum and Bradyrhizobium sp. are also being widely used in agriculture. These are both new technologies that aim to optimize food production without harmful environmental impacts. Additionally, there is a lack of information regarding the use of CSS combined with PGPBs on crop performance in the Cerrado region. The objective of this study is to evaluate the effects of CSS application rates and Azospirillum brasilense inoculation on soil fertility, and maize and soybean nutrition, morphology, yield, and quality under no-till in the Cerrado region. A field experiment will be conducted in Selvíria, MS using a randomized complete block design and a 6 x 2 factorial scheme, with four replications. The factors are as follows: fertilizer amendment (15.0; 22.5; 30.0, and 37.5 Mg ha-1 of CSS on a wet basis, conventional fertilizer, and a control with no fertilizer amendment) and (co)inoculation of Azospirillum brasilense (inoculation vs. no inoculation). In the agricultural years 2021/2022 and 2022/2023, the following parameters will be evaluated: crop nutritional status, morphological and production components, ICF, productivity and quality of wheat and soybean grain. In soybean, the nodulation potential of the crop will be evaluated. In soil samples collected in the 0.0-0,2 and 0.2-0.4 m depth layers, soil fertility will be monitored (OM, pH, CEC, H+Al, Al, SB, BS, P, K, Ca, Mg, S, B, Cu, Fe, Mn, and Zn). Based on the results, we hope to understand the most efficient way to use CSS associated with PGPBs to optimize soil quality and increase crop productivity. This project is in line with the United Nations "Agenda 2030" to promote the "Sustainable Development Goals".