Uso de eDNA para bioanálise da qualidade do solo e gestão de ecossistemas canavieiros paulista

Abstract

Defining and monitoring soil quality parameters are essential for the sustainable production of sugarcane used in bio-based industrial processes. This study evaluated the use of environmental DNA (eDNA) to biomonitor the quality of sugarcane soils in São Paulo, Brazil, managed with vinasse (V), filter cake (C), and mineral fertilizer (MF). Composite soil samples were collected using a systematic arrangement: 2 soil classes (Ferralsol and Acrisol), 2 textures (clayey and sandy), 3 management systems (vinasse, vinasse combined with filter cake, and mineral fertilization), 3 plots, and 2 seasonal periods (rainy and dry), totaling 72 samples. Analysis of organic matter (OM), soil organic carbon (SOC), and macro- and micronutrients differentiated the Ferralsol and Acrisol samples into distinct groups based on agricultural management (Global R = 0.554) and showed some overlap based on soil texture (Global R = 0.369). The quantity of nirK, nirS, and nosZ gene copies, determined by Real-Time Quantitative PCR (qPCR) from genomic DNA isolated from the 72 samples, was higher in the rainy season compared to the dry season (P>0.05). None of the genes evaluated revealed a consistent response to different sugarcane soil managements, showing a response pattern for each soil class and texture. The activity of β-glucosidase and arylsulfatase enzymes was consistent with the agricultural management of the sugarcane soil, consistently increasing in the following order: vinasse < mineral fertilizer < vinasse + filter cake, except for sandy Acrisol. This increase was more pronounced in Ferralsol than in Acrisol, where the average for vinasse + filter cake and mineral fertilizer presented 1.8 (sandy soil) and 3.9 (clayey soil) times more activity than in the soil managed with vinasse. Statistical analyses revealed negative correlations (P<0.05) between the number of copies of the nirK and nosZ genes and the activity of the β glucosidase and arylsulfatase enzymes in the soil in both seasonal periods analyzed. The number of copies of these two microbial genes was also negatively correlated with the soil OM content in the rainy season. Thus, the indications of healthy sugarcane soil based on enzymatic analyses and OM were reinforced by the lower abundance of genes associated with denitrification, indirectly allowing the activity of the β glucosidase and arylsulfatase enzymes to also reveal the potential for nitrous oxide production in the sugarcane soils analyzed. The results of this research reinforce the sensitivity of enzymatic bioanalysis for soil quality and expand the potential for its interpretation of environmental quality in sugarcane soils in São Paulo.