Short-term changes in nitrogen availability, gas fluxes (CO 2, NO, N 2O) and microbial biomass after tillage during pasture re-establishment in Rondônia, Brazil

• Published in: Soil & tillage research 2007-10, Vol.96 (1), p.250-259
• Main Authors: Carmo, Janaina Braga do, Piccolo, Marisa de Cássia, Andrade, Cristiano Alberto de, Cerri, Carlos Eduardo Pellegrino, Feigl, Brigitte Josefine, Neto, Eráclito Sousa, Cerri, Carlos Clemente
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Amazon; Biochemistry and biology; Biological and medical sciences; Brazil; Chemical, physicochemical, biochemical and biological properties; Cropping systems. Cultivation. Soil tillage; Fundamental and applied biological sciences. Psychology; Gas fluxes; General agronomy. Plant production; Microbial biomass; Microbiology; Nitrogen; Pasture re-establishment; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Soil science; Soil tillage; Tillage; Tillage. Tending. Growth control
• ISSN: 0167-1987; 1879-3444
• DOI: 10.1016/j.still.2007.06.002

Anthropogenic conversion of primary forest to pasture for cattle production is still frequent in the Amazon Basin. Practices adopted by ranchers to restore productivity to degraded pasture have the potential to alter soil N availability and N gas losses from soils. We examined short-term (∼35 days) effects of tillage prior to pasture re-establishment on soil N availability, CO 2, NO and N 2O fluxes and microbial biomass C and N under degraded pasture at Nova Vida ranch, Rondônia, Brazilian Amazon. We collected soil samples and measured gas fluxes in tilled and control (non tilled pasture) 12 times at equally spaced intervals during October 2001 to quantify the effect of tillage. Maximum soil NH 4 + and NO 3 − pools were 13.2 and 6.3 kg N ha −1 respectively after tillage compared to 0.24 and 6.3 kg N ha −1 in the control. Carbon dioxide flux ranged from 118 to 181 mg C–CO 2 m 2 h −1 in the control (non-tilled) and from 110 to 235 mg C–CO 2 m 2 h −1 when tilled. Microbial biomass C varied from 365 to 461 μg g −1 in the control and from 248 to 535 μg g −1 when tilled. The values for N 2O fluxes ranged from 1.22 to 96.9 μg N m −2 h −1 in the tilled plots with a maximum 3 days after the second tilling. Variability in NO flux in the control and when tilled was consistent with previous measures of NO emissions from pasture at Nova Vida. When tilled, the NO/N 2O ratio remained