Response of soil microbiota to nine-year application of swine manure and urea

Resposta da microbiota do solo a nove anos de aplicações de dejetos suínos e ureia

ABSTRACT:

Manure fertilization is a common practice, but little is known about its impacts on soil microbial activity and organic matter. Aiming to evaluate soil microbial response to nine years of successive applications of swine manure, organic carbon (TOC), total nitrogen (TN), pH, microbial biomass carbon (MBC), basal respiration (BR), metabolic quotient (qCO₂), and enzyme (ß-glucosidase, phosphatase, arylsulphatase, and FDA) activities were measured in the 0-10cm soil layer, in a no-tillage system. Treatments were: control soil without fertilization (C), and application of two doses (104 and 209kg of N ha^-1year^-1) of urea (U₁ and U₂), pig slurry (PS₁ and PS₂) and deep litter (DL₁ and DL₂). TOC, TN, soil pH, MBC, and BR increased in soil fertilized with DL, and were lower in U treatments. Soils with U and DL application had higher qCO₂, related to different sources of stressors like nutrient imbalance. Phosphatase and ß-glucosidase activities were not affected by treatments, increased with time, and had a strong correlation with MBC. We conclude that long-term swine manure applications increase microbial activity and soil organic matter, mainly in DL form; while urea applications have negative impacts on these indicators.

Key words:
soil microbial activity; nitrogen amendments; soil quality.