Changes of chemical properties in an Oxisol after clearing of native Cerrado vegetation for agricultural use in Vilhena‚ Rondonia State‚ Brazil

Author(s)

Carvalho‚ JLN ; Cerri‚ CEP ; Cerri‚ CC ; Feigl‚ BJ ; Píccolo‚ MC ; Godinho‚ VP ; Herpin‚ U.

• Document type: Journal article
• Source: SOIL & TILLAGE RESEARCH; v. 96, n. 1, p. 95-102, 2007.

Abstract

Native vegetation clearing in the Amazon Cerrado region for agricultural purposes may be modifying soil chemical characteristics. The extent of change depends on the management practices used. We evaluated changes in chemical properties of a clayey oxisol (dystrophic red yellow latosol) under no-tillage (NT) and conventional tillage (CT). Soil samples were taken randomly (n = 5) in July 2004 at 0–5 cm, 5–10 cm, 10–20 cm and 20–30 cm depths at six treatments: Cerrado with native vegetation, CT cultivated with rice for 1 year (1CT) and 2 years (2CT), and NT cultivated with soybean for 1 year (1NT), 2 years (2NT) and 3 years (3NT) in each case after a 2-year period of rice under CT. Soil pH (CaCl2, KCl and water), ΔpH, total acidity (H+ + Al3+), total organic carbon (TOC), available P, exchangeable K, Ca, Mg, potential cation exchange capacity (CEC) and base saturation (V) were determined. The highest pH values were determined in topsoil layers at the older NT adoption. Under Cerrado pH was lower than under cultivation at all depths due to absence of lime application. Generally, negative values of ΔpH were observed at all sites in all layers indicating predominant presence of negative charges in the soil. Although not statistically significant it seems that the amount of negative charges was higher in deeper layers. Total acidity displayed the highest values throughout the soil profile under Cerrado and low pH and low concentrations of exchangeable bases. Cultivated systems with fertilizer generated considerable increases of P, K, Ca, and Mg compared to Cerrado. Soil macronutrient content and base saturation under NT gradually increased throughout the profile with time. Highest CEC values were calculated for the 0–5 cm and 5–10 cm layers under Cerrado and NT systems. For the 0–5 cm layer CEC was lower at the CT system compared to the Cerrado and the oldest year under NT system. (AU)

• FAPESP's process: 04/01230-0 - Conversion of the Cerrado for agricultural purposes in Amazonia and its impact on climate changes
• Grantee: Carlos Clemente Cerri
• Support Opportunities: Regular Research Grants