Effect of Land Use On Soil Productivity in the Pampas.

The Argentine Pampas covers an area of ca. 60 Mha and because of its yield potential it is considered as one of the main cropping regions of the World. Assessing for its regional soil productivity and in particular de effect of cropping is important concerning sustainable management options. The objective of this work was to evaluate regional soil productivity and compare two contrasting land uses: cropped fields and un-cropped controls. We estimated soil productivity using a locally developed model based on a polynomial regression for wheat. Productivity was assessed in terms of soil available water holding capacity (SAWHC) and soil organic carbon (SOC) content. Productivity indices were normalized to one. Eighty two farms widespread over the region were sampled during 2007-2008. At each farm paired treatments were sampled representing cropped soils and un-cropped controls. Soil productivity for wheat was not affected by cropping as no significant differences were observed between estimated productivity indices of cropped and control sites. The average difference was of 2 %. Sites corresponding to the Humid Pampa had greater productivity as these soils correspond to deeper soils with finer textures. Soils of the Semiarid Pampa with coarser textures determined lower SAWHC and lower productivity. Locally developed models should be generated for other crops in order to make more detailed analysis possible.