Landform, soil, and plant relationships to nitrate accumulation, Central Nevada

Authors

W.D. Nettleton, USDA, NRCS, NSSCFollow
F.F. Peterson, University of Nevada - Reno

Date of this Version

2011

Citation

Geoderma 160 (2011) 265–270; doi:10.1016/j.geoderma.2010.08.005

Abstract

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.