Physico-Chemical Characteristics and Carbon Balances in a Fluvic Entisol after Six Years of Fertilization with Manure and Gliricidia

Abstract

Soils in the semi-arid region of northeastern Brazil have low natural fertility and therefore, plant growth and productivity can be adversely affected. The application of mineral fertilizers is economically unfeasible by farmers in this region. The use of organic inputs found in farms, such as animal manure and the biomass of gliricidia leaves and branches (Gliricidia sepium Jacq. Walp), is a viable and low-cost option. Thus, the objective of this study was to evaluate influence of organic fertilizations over six years on the physical and chemical characteristics of a Fluvic Entisol cultivated with beans, cotton, corn and sunflower was evaluated. Fertilizations, of 20 Mg ha-1 year-1, were: GI - soil-incorporated gliricidia; GS - surface gliricidia; EI + GI - manure and incorporated gliricidia; EI + GS - soil - incorporated manure and surface gliricidia, EI - soil - incorporated manure; and control - without addition of organic fertilizer. In the combined applications, half the fertilizer came from each source. All fertilization systems decreased bulk density, compared to the control treatment, and in the EI + GS system, there was an increase in total soil porosity. The GS system resulted in the largest SOM stocks and C / N ratio. The EI + GI system increased the total phosphorus stock. The use and application of gliricidia biomass as a green fertilizer over time improves the soil physical and chemical conditions, promotes good agricultural productivity without the need of mineral fertilizers, being an alternative of high relevance in the reduction of costs in agricultural practices.