According to the time of management implementation, the amount of crop residues added to the soil surface can increase in no-tillage systems (NTS) and promote changes in the chemical and physical soil properties. The objective of this study was to quantify the deposition of plant residues on the soil surface (RSS) and variations in the light organic matter (LOM), in C and N stocks, remaining phosphorus (Prem), the soil physical characteristics (particle density (PD), bulk density (BD) and total pore volume (TPV)), and to evaluate the origin of C by isotopic techniques (13C). For this purpose, areas under no-tillage (NTS) after different periods of implementation were selected in Montividiu (GO) as follow: NTS after 3 years (NTS3), NTS after 15 years (NTS15) and NTS after 20 years of implementation (NTS20). These areas were compared with an area of native cerrado "stricto sensu" (CE) and with a planted pasture of Brachiaria decumbens (PA). In each of these areas, soil samples were collected (layers 0-5, 5-10 and 10-20 cm). The soil of the study areas was classified as Rhodic Hapludox. The experiment was evaluated in a completely randomized design. Increased levels of RSS, LOM, PTV, Prem, C, and N were observed as a function of time of NTS implementation. The NTS20 area showed higher C and N values than the CE area and similar values of BD and LOM. The 13C analysis showed that legumes contribute significantly to the organic matter content in the NTS areas, where increases in the carbon and nitrogen stocks as function of the time of implementation were also observed in all layers analyzed. In the surface layer of the areas NTS15 and NTS20 these values were similar and, or, higher than under CE. The analyzed properties had poorest values in the PA area, indicating an advanced stage of degradation.
No-tillage; pasture; soil organic matter
