Abstract
Waste application from the sugar-alcohol industry in the soil is a viable alternative from the point of view of the disposal of these residues, in addition to fertilizing the soil with nutrients. The aim of this study was to evaluate the physical fractions of soil organic matter (SOM), carbon management indexes (CMI) and the aggregation of a Red Latosol of clayey texture in areas of sugarcane cultivation managed differently regarding harvest and waste application. Five sugarcane cultivated areas were evaluated, differing in the management of harvest (raw and burned) and application or not of vinasse and/or filter cake, in addition to a reference area of native forest (NF) of Cerrado vegetation. Disturbed soil samples were collected in the layers 0-0.05; 0.05-0.1 and 0.1-0.2 m, and undisturbed samples were collected in the layer 0-0.1. In the disturbed samples, total carbon (TC), physical-granulometric fractionation of SOM were determined with subsequent CMI calculations. Aggregation analysis was performed in the undisturbed samples, and the weighted mean diameter (WMD), geometric mean diameter (GMD) and percentage of aggregates retained in the different sieve classes were determined, in addition to determining the TC contents of each aggregate class. The NF presented the highest levels of TC, particulate carbon (C-POM) and mineral (C-MOM). Among the managed areas, the area that received filter cake and vinasse application stood out with higher levels of TC, C-POM and C-MOM in the most subsurface layer. All areas cultivated with sugarcane presented CMI lower than the area of NF. The worst aggregation indexes were observed in the area with management with burning in the pre-harvest and application of only filter cake, and the best aggregation indexes were in the NF. There was a significant correlation between the aggregation indexes and soil TC contents. The area with the practice of burning, but with joint application of filter cake and vinasse for 16 consecutive years provided greater aggregation of soil and better CMI among the areas cultivated with sugarcane.
Highlights
The conversion of native areas into agricultural areas in the most diverse regions of Brazil added to the most different types of soil, climate, and cultivation technology, can cause significant changes in physical (Sales et al, 2018; Ozório et al, 2019), chemical (Souza et al, 2017; Souza et al, 2018; Assunção et al, 2019) and biological attributes of the soil (Barbosa et al, 2018) over the years of cultivation.Given the need for alternative energy sources, Brazil is privileged, as it is the largest producer of sugarcane globally (Camargo et al, 2019) and a pioneer in ethanol production
From the fraction retained in the 4.00 mm sieve, 50 g of aggregates were separated, an amount that was moistened with water by capillarity, on filter paper for 10 minutes
These results demonstrate that the form of soil use since the conversion of native areas, through intense soil management in sugarcane cultivation over the years of cultivation, influenced the loss of total carbon (TC) in the most superficial layers
Summary
The conversion of native areas into agricultural areas in the most diverse regions of Brazil added to the most different types of soil, climate, and cultivation technology, can cause significant changes in physical (Sales et al, 2018; Ozório et al, 2019), chemical (Souza et al, 2017; Souza et al, 2018; Assunção et al, 2019) and biological attributes of the soil (Barbosa et al, 2018) over the years of cultivation.Given the need for alternative energy sources, Brazil is privileged, as it is the largest producer of sugarcane globally (Camargo et al, 2019) and a pioneer in ethanol production. With the increase in the area cultivated with sugarcane, there is an increase in the production of waste from the sugar-alcohol industry, such as vinasse and filter cake. These wastes can be used in agriculture as sources of nutrients, reducing environmental contamination and fertilization costs (Fravet et al, 2010), with benefits to soil chemical (Rosset et al, 2014) and physical attributes, favoring the growth of the root system (Bilgili et al, 2019), which contributes to the stabilization of soil aggregates. The understanding of the processes of structure formation of the soil involves the knowledge of the interaction of the physical, chemical, biological, and geological aspects of the edaphic environment (Falcão et al, 2020)
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