Amado, Telmo (Univ.of Santa Maria, Soil Departament, Federal University of Santa Maria, Santa Maria, RS, 97105-900, Brazil, Phone: (55)2208916; Fax: (55)2208256; Email: tamado@smail.ufsm.br)

Carbon Sequestration in No-Tillage Systems with Intensive Use of Cover Crops in Southern Brazil

T.J.C. Amado*

Brazil has more than 20 millions hectares on no-tillage system. Although this system has recognized potential of carbon sequestration, it is necessary to obtain regional data considering the soil and weather conditions. With the main objective to evaluate the potential of no-tillage, with intensive use of cover crops, in promoting carbon sequestration this research was carried out. Two long term soil management experiments in Paleudulf’s Southern Brazil were selected to achieve this subject. In the first experiment, carried out for ten years, five treatments were selected composed of three crop systems (winter fallow/corn, rye/corn and mucuna/corn); the other two treatments were bare soil and native vegetation. In this experiment the soil texture is sandy (15 g kg^-1 clay). In the second, carried out for 15 years the following treatments were selected: black oat/corn under conventional tillage without N fertilization, and three other treatments composed of soil tillage systems (conventional, reduced and no-tillage) with black oat/corn. Also included were black oat+common vetch/corn+cowpea and pigeon pea/corn under no-tillage; all five of the last treatments with the use of N fertilization applied to corn. In this experiment native vegetation (non-disturbed) was used as reference treatments. The soil texture in this experiment is clay-loam (22 g kg^-1 clay). The main objective of this research was to evaluate the potential of cover crops used in corn production systems in increasing total organic carbon (TOC) and total nitrogen (TN) content in comparison with traditional farm system (fallow/corn) and a native grass field. Although the clay-loam soil had approximately the double of TOC compared to that of the sandy soil, the annual rate of carbon sequestration in no-till with cover crops was similar in both the soils. The use of conservation cropping systems in substitution to traditional fallow/corn system was an efficient tool to increase agriculture carbon sequestration and, therefore, mitigate the greenhouse effect.