Author(s): NOGUEIRA, M. A.

Summary: Indicators of soil quality associated with N-cycling were assessed under different land-use systems (native forest ? NAT, reforestation with Araucaria angustifolia or Pinus taeda and agricultural use ? AGR) to appraise the effects on the soil potential for N supply. The soil total N ranged from 2 to 4g⁄ kg (AGR and NAT, respectively), and the microbial biomass N ranged from 80 to 250 mg⁄ kg, being higher in NAT and A. angustifolia, and lower in P. taeda and AGR sites. Activities of asparaginase (ca. 50?200 mg NH 4 + -N ⁄ kg per h), glutaminase (ca. 200?800 mg NH -N ⁄ kg per h) and urease (ca. 80?200 mg NH -N ⁄ kg ⁄ h) were also more intense in the NAT and A. angustifoliareforested soils, indicating greater capacity for N mineralization. The NAT and AGR soils showed the highest and the lowest ammonification rate, respectively (ca. 1 and 0.4 mg NH 4 + -N ⁄ kg per day), but the inverse for nitrification rate (ca. 12 and 26%), indicating a low capacity for N supply, in addition to higher risks of N losses in the AGR soil. A multivariate analysis indicated more similarity between NAT and A. angustifolia-reforested sites, whilst the AGR soil was different and associated with a higher nitrification rate. In general, reforestation with the native species A. angustifolia had less impact than reforestation with the exogenous species P. taeda, considering the soil capacity for N supply. However, AGR use caused more changes, generally decrease in indicators of N-cycling, showing a negative soil management effect on the sustainability of this agroecosystem.

Publication year: 2012

Types of publication: Journal article

Unit: Embrapa Soybean

Keywords: Ammonification, Amonificação, Nitrification, Nitrificação, Qualidade, Soil quality, Solo