Supplemental irrigation in the humid Pampean region: Effects on soil salinity, physical properties, nutrients and organic carbon

The use of supplemental irrigation could stabilise crop yields in the Pampean region in the face of climate variability. However, inadequate management of this practice could compromise soil quality. The effect supplemental irrigation on soil salinity and sodicity, nutrients, organic carbon and some physical properties was studied on a farm, with production of grains and oilseeds, in the Pampean region of Argentina. Although the groundwater used for irrigation is classified as sodium bicarbonate type, it has no risk of soil salinity and sodicity. This work was carried out on 7 plots with different conditions of soil type, soil cover and recovery time after last irrigation. Significant increases in salinity, sodicity and alkalinity due to supplemental irrigation were observed. Phosphates content (PO4) and organic carbon (OC) slightly decreased, while nitrate content (NO3) did not change significantly. It is assumed that PO4 may have decreased due to increased leaching and/or consumption by the irrigated crop, while the change in OC may be related to an increased rate of organic decomposition. Changes in physical properties were less important. Slight increases in aggregate stability (AS), bulk density (BD) and loss of clay content were observed. It may be hypothesised that the observed joint increase in salinity and sodicity may stabilise the flocculation-dispersion processes that give structure and aggregation to the soil, thus neutralising the effects of irrigation on physical properties.