A review of no-till systems and soil management for sustainable crop production in the subhumid and semiarid Pampas of Argentina

The western part of the Argentine Pampas is a subhumid and semiarid region consisting of extensive plain with deep sandy and sandy-loam soils. The agricultural system includes pastures in rotation with annual grain crops and grazed crops or continuous annual row cropping. The objective of this review was to present and discuss changes in soil properties due to different soil management systems, mainly no-tillage practices, in the western part of the Argentine Pampas. The effects of tillage, crop sequences under no-till, and grazing on soil properties and crop productivity have been studied since 1990 on loamy and sandy Haplic Phaeozem (Typic Hapludolls and Entic Hapludolls) and Haplic Kastanozem (Typic Haplustolls). A database developed from the yield and soil test records of growers affiliated with Regional Consortium for Agricultural Experimentation (CREA) were also utilized in the study. The results showed that soil organic C (SOC) content depends both on soil texture and soil management. SOC decreases when the length of the row crop cycle increases and also in moldboard plow and chisel-tillage systems. Pastures and no-till row crop sequences with more years of maize (Zea mays L.) and wheat (Triticum aestivum L.), than sunflower (Helianthus annus L.) or soybean (Glycine max (L.) Merrill) tended to increase the SOC content in the 0-20 cm layer. Deep tillage of no-till soils with compacted layers improved maize dry matter production but, in the same experiment, yield was increased more by nitrogen fertilization than by subsoil tillage. The grazing of crop residues increases the soil bulk density only in the 0-5 cm layer of tilled soils, but did not significantly change bulk density on soils under continuous no-till. Crop productivity was related to SOC content of the 0-20 cm layer of the soils. Due to the positive effect of SOC on crop yields, no-till soil management and pasture-annual row crop rotations are two practices that pen-nit the development of sustainable production systems in the western part of the Argentine Pampas. (C) 2002 Elsevier Science B.V. All rights reserved.