Resumo

SANDOVAL-ESTRADA, Marco et al. No-tillage organic carbon contribution and effects on an andisol structure from the Chilean Andean Foothills. Agrociencia [online]. 2008, vol.42, n.2, pp.139-149. ISSN 2521-9766.

The intensive use of soils derived from volcanic ash, due to an increase in livestock and agricultural activities, has generated losses from increasing water erosion in the soils, which are reflected in lower production and an increase in the demand for agricultural inputs. Therefore, this study was conducted to evaluate, after three years, the structural state of a soil (Typic Haploxerand) subjected to four techniques for managing crop residues under zero tillage in wheat-oat rotation: 1) burned residues (T); 2) residues in rows (RH); 3) standing residues (RP); and 4) chopped residues (RPC). The evaluated variables were soil organic carbon (SOC), aggregates stability measured by mean weight diameter (MWD), distribution of water stable aggregates, saturated water conductivity (K_s), bulk density (D_a), and resistance to penetration (Rp). The experimental design was complete random blocks and means were compared with the Tukey test (p<0.05). The results showed a low MWD (0.20 to 0.28 mm) and a dominance of water stable fractions smaller than 0.25 mm that was above 66% in all of the treatments. This suggests that the structural system is susceptible to physical degradation; RP and RPC had better structural stability and a higher proportion (p<0.05) of macroaggregates (> 0.25 mm), as well as a significant increase in SOC (p<0.05). The treatment RPC had significantly lower values of K_s (0.76 cm h^-1), D_a and Rp, which is favorable for sustainability of the soil structural system.

Palavras-chave : Conservation tillage; organic matter; aggregate stability; soil.

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