Biological activity and organic carbon resources in managed and native soils of the Brazilian Cerrado

V. Steven Green, Purdue University

Abstract

The Brazilian Cerrado is undergoing a rapid transition from native savannah vegetation to intensive agricultural management. Some of the tributaries of the Amazon basins and Paraná River originate in the Cerrado region; it is imperative that agricultural management is implemented to protect environmental quality and promote agricultural sustainability. Base-line data of the current biological status of this area is needed in order to monitor the soils of this region through time. A study was conducted to determine base-line biological properties and processes as well as organic C resources in major soils of the native Cerrado region of Brazil. Additionally, the effects of tillage on biological properties and processes as well as organic C resources in a managed agricultural system was determined. Soil biochemical properties were used to predict C- and N-mineralization as well as aggregate stability. The Humic Rhodic Acrustox had very high biological activity and organic resources while the Ustoxic Quartzipsamments had low biological activity. Soil biological activity was generally greater in no-till soils than in tilled soils, but the native soils still maintained higher biological activity, even though they were nutrient limited. Carbon- and N-mineralization can be predicted using soil enzyme activities in native soils (R2 = 0.92 and 0.90 respectively), but not in managed soils. Aggregate stability can be predicted using soil enzyme activities in managed soils (R2 = 0.98), but not native soils. Total N, acid phosphatase, arylamidase, C-mineralization, and N-mineralization were the most responsive to changes in tillage management. The fluorescein diacetate (FDA) hydrolysis procedure was optimized for soils; it is a simple, quick, and precise method for the measurement of biological activity. Kinetic parameters for FDA hydrolysis reaction in soils were determined. The results from this research will aid land managers in developing sustainable agricultural practices for Oxisols and will allow monitoring of soil biological activity of the Cerrado region. A clearer understanding of the biochemical attributes of Oxisols will aid in developing agricultural management practices that utilize natural nutrient cycling processes.

Degree

Ph.D.

Advisors

Stott, Purdue University.

Subject Area

Soil sciences|Ecology

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