Date of this Version
Geoderma 160 (2011) 265–270; doi:10.1016/j.geoderma.2010.08.005
Nitrate (NO3 −1) accumulates in Haplocambids and Torrifluvents in inset fan and fan skirt positions in central Nevada. The soils store as much as 17,600 kg of NO3 −1 N ha−1 within the upper 208 cm. This paper provides an explanation. These Holocene soils receive NO3 −1 N from mineralization of organic matter and other NO3 −1 N sources including snowmelt. The NO3 −1 is delivered to soils in the first part of snowmelt in run-off from the higher surfaces. The last part of the melt and the run-off, when sufficient, serve to move the NO3 −1 out of the root zone. Winter fat (Krascheninnikovia lanata), the most valuable winter grazing plant in the Great Basin, is the common plant on NO3 −1 N rich soils. The soils are loamy or sandy and lack horizons restricting water penetration or biological denitrification zones. Hence, some NO3 −1 is free to leach deeply past plant roots. Playas, wet floodplains, deeply gullied inset fans and well-developed soils accumulate little NO3 −1 except where the latter soils are capped by desert pavements and rarely, if ever become saturated with water. Soils with argillic or petrocalcic horizons or duripans on summits of alluvial fan remnants loose NO3 −1 through denitrification, or incorporate it in plants, commonly accumulating less than 50 kg of NO3 −1 N ha−1. These soils however do accumulate salt as shown by their shadscale saltbush Atriplex confertifolia, bud sagebrush Picrothamnus desertorum, and four-wing saltbush Atriplex conescens shrub cover.