Resumo

ABRIL, Adriana et al. Long term effect of no-tillage on some soil properties in the central semiarid region of Argentina. Cienc. suelo [online]. 2005, vol.23, n.2, pp.179-188. ISSN 1850-2067.

Evaluation of the effect of crop residues accumulation on soil under no-tillage cultivation is difficult in Argentina because the relative recent adoption of no-tillage practices in the country. Moreover, most of the available research on no-tillage in Argentina refers to the humid Pampas region. In contrast, information on the semi-arid region is very scarce, despite the fact that an increased cover stubble is particularly useful in water-limited soils. In this paper we report a long-term evaluation (5 and 10 years periods) of no-tillage practices on a) chemical (SOM, total N and NO₃-N) and biological (microbial biomass and activity) soil characteristics, and b) quantity, identifiable fractions, and chemical quality of stubble material in soybean monoculture and soybean-corn rotation. Research was conducted at Manfredi INTA Experimental Station in semi-arid, central Argentina (31°49' S and 63°46' W). Soils under no-tillage system had higher SOM and total N content compared with control (conservation tillage with chisel plow) in both, soybean monoculture and soybean-corn rotations. The observed difference increased with time (10 and 20% at 5 and 10 years, respectively). Nitrate content, and microbial activity and biomass showed high variability in the measurement periods, depending on climatic condition at the sampling date. Stubble cover was greater in the corn-soybean rotation with corn as preceding crop (2473.9 g m^-2) than in soybean monoculture (1035.7 g m^-2). The stubble non-identifiable fraction was very significant in all treatments (ranging between 2-10 t ha^-1), which would favor new surface soil formation. The soybean-corn rotation with soybean as preceding crop showed the lowest values in all chemical parameters, particularly in soluble compounds (nitrate, ammonium and soluble carbon). Contrarily with what is usually assumed, our results suggest that nutrient release from long-term stubble may become a significant nutrient source for the crops. Therefore, this nutrient source should be considered when evaluating crop fertilization requirements.

Palavras-chave : Stubble; Crop residues; corn; Soybean; Nutrients; Fertilization.

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