THE DETERIORATION OF TALL WHEATGRASS PASTURES ON SALINE-SODIC SOILS

The deterioration of sown tall wheatgrass (Elytrigia elongata) growing on 3 sodic saline soils was investigated in the Laprida basin, in the center of the Buenos Aires province of Argentina. These soils are kno wn to have poor drainage and high saline levels and support different species associations. On each soil type the native grassland was compa red to sown wheatgrass, in terms of plant density and cover and soil p hysical and chemical characteristics. The 3 soil types reacted differe ntly to tillage. Tillage had little impact on soil type A (typic Natra quoll), a poorly drained soil with a loamy A horizon (14 cm) overlying a silty clay loam. Soil type B (typic Natraquaf), a wet texture contr ast soil with bleached horizons has characteristics that are likely to severely limit plant growth. The sowing of wheatgrass increased groun d cover by live vegetation on this soil type. This contrasted with soi l type C (typic Natralboll), a saline soil with an organic matter-rich but thin (8 cm) A horizon. In this soil, the plant density declined a nd other components such as pasture cover also declined with time. Thi s pasture deterioration was attributed to several soil factors includi ng decreased organic matter content and increased soil bulk density. I t was concluded that the varied performance of wheatgrass sown pasture s was a function of the different inherent characteristics of the soil s.