Abstract
A common agricultural practice of combining organic fertilizer vinasse (a liquid residue from sugarcane ethanol production) with mineral nitrogen (N) fertilizer promotes N losses such as greenhouse gas emissions due to the effects of physicochemical changes in soil on the microbiota inhabiting this environment. In this study, we applied microarray GeoChip v.5.0M technology to obtain a better insight into the prokaryotic communities and identify and quantify the N functional gene families associated with the N processes in sugarcane soils without N fertilizer (N0), with urea at 60 kg ha−1 (N60), and with vinasse combined with urea (NV). Soil samples were collected at 7 (T7) and 150 (T150) days after N application, corresponding to maximum and minimum nitrous oxide (N2O) emissions, respectively, for molecular and physicochemical analysis. Additionally, the metagenomes of these DNA samples, previously deposited in the MG-RAST server, were accessed to investigate the functions and taxonomic groups associated with selected gene families. The results revealed that 87% of the select gene families were significantly responsive to the fertilizer combined treatment (NV) in the 7 days after the application. The most responsive genes and processes were nitrification [with the amoA gene from ammonia-oxidizing Bacteria (AOB) and Archaea (AOA) and hao from Bacteria], ammonification (with gdh and ureC genes from Bacteria and Archaea), and denitrification (with p450nor from Eukarya). The AOA, Nitrosopumilus, and AOB, Nitrosomonas, were the groups with the greatest functions associated with nitrification, as well as a pathogenic Mycobacterium, with denitrification. The results also revealed that under N fertilizers and decreased O2 in soil, the increases in K and P nutrients can promote the growth of the halophile Archaea Natronomonas and the Bacteria Anaeromyxobacter, which can reduce N2O. In conclusion, this typical agricultural fertilization management may favor functional genes and archaeal and bacterial groups associated with N processes that have the potential to reduce environmental damage in tropical sugarcane soils.
Highlights
Vinasse is a byproduct of ethanol from the sugarcane industry, generated during the distillation process [1, 2], with a production rate of 10–18 L while preparing each liter of ethanol [3]
The results revealed that under N fertilizers and decreased O2 in soil, the increases in K and P nutrients can promote the growth of the halophile Archaea Natronomonas and the Bacteria Anaeromyxobacter, which can reduce N2O
C and N showed significant increases in both sample collection periods, though only in the treatment that received vinasse (15 and 5%, respectively, concerning treatment N0). These soil factors showed no significant differences between the two periods (Table 1)
Summary
Vinasse is a byproduct of ethanol from the sugarcane industry, generated during the distillation process [1, 2], with a production rate of 10–18 L while preparing each liter of ethanol [3]. Sugarcane vinasse is composed of water (93%) and organic solids and minerals (7%), such as potassium (K), calcium (Ca), and magnesium (Mg) [4, 5]. This residue from ethanol production has high levels of organic matter and low C:N ratio [6] and low contents of nitrogen (N) (0.97–4.75 g L−1) and phosphorus (P) (1–190 mg L−1). The main non-aqueous components in vinasse are organic matter, such as glycerol, organic acids, and yeasts [5], and the volatile solids are present at high levels [6]. When applied to the soil, the amount of organic material, nitrate (Ca+2),
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