Effects Of No-Till and Reduced Tillage On Soil Physical and Biochemical Properties In The Semiarid Pampean Region, Argentina.

Research on the effect of agricultural conservacion practices on Petrocalcic Paleustolls typical of the semiarid pampas of Argentina is scant and show inconsistent results. Our objective was to evaluate soil physical and biochemical properties in production plots from each of six combinations found in the region and defined by conservation practice (reduced till, RT; no-till, NT), years since implementation (10 or 15), rotation (continuous wheat, WWW; wheat-sunflower-wheat, WSW; and wheat-fallow-wheat, WFW) and with soil textural classes (loamy sand, 1; and clay loam, 2) characteristic of the region. Combinations are hereby refered as RT15WSW1, NT10WSW1, NT15WSW1, NT15WWW1, NT15WFW1, and NT15WSW2. We took composite soil samples from 4 to 6 production plots of ~50ha each for each combination and at three successive depths (0-5, 5-10, and 10-18cm). We used a CRD design with repeated measures approach for the statistical analysis of the soil variables. NT15WSW2 showed the highest content of particulate organic carbon and more favorable physical properties than the other combinations. NT10WSW1, NT15WSW1, NT15WFW1, and NT15WWW1 showed higher values of bulk density and relative compaction related to lower total porosity and water aggregate stability when compared to RT15WSW1. Results from this study showed that on loamy sand soils of this semiarid region, the long term use of no-till practices are detrimental to the dynamic soil properties of the surface soil in particular when sunflower is part of the crop rotation.