SALINITY, NITRATE, AND WATER IN RANGELAND AND TERRACED WHEATLAND ABOVE SALINE SEEPS

Saline seeps have emerged over the past 20 yr in some Southern Plains soils cropped annually to winter wheat (Triticum aestivum L.). Saline seep development is a cumulative process associated with percolation of small increments of water over many years through saline strata in recharge areas to build up water tables over less-permeable strata in lower slope positions. In this study soluble salt, nitrate, and water content were determined in Woodward soils (coarse silty, mixed, thermic Typic Ustochrepts) to a depth of 3 m in terraced farmland and in adjacent native rangeland upslope from saline seeps. Significantly (P < 0.05) more soluble salt was present in the surface 3 m of rangeland than in adjacent farmland. No difference (P > 0.05) was found in soluble salt content in farmland between terraces as compared to soluble salt in terrace channels. Greater amounts (P < 0.05) of nitrate and water were in the 3-m profiles under farmland than under native range. The soluble salt profiles indicate more water has percolated through the farmland than the rangeland. The implication is cultivated land, both in terrace channels and between terraces, is contributing salt and water to saline seep. An alternative explanation is terrace channels are the major recharge areas and lateral flow of this water leaches salt from farmland between the terraces.