Dryland Soil Carbon and Nitrogen Influenced by Sheep Grazing in the Wheat–Fallow System

摘要: Sheep (Ovis aries) grazing during fallow for weed control in wheat (Triticum aestivum L.)-fallow systems may influence soil C and N levels grain yields by returning part of consumed crop residue to the through feces urine. We evaluated effects management (sheep [grazing], herbicide application [chemical], tillage [mechanical]) water conservation cropping sequence (continuous spring [CSW], wheat-fallow [SW-F], winter [WW-F]) on organic carbon (SOC), inorganic (SIC), total nitrogen (STN), NH 4 -N, NO 3 -N at 0- 120-cm depth yield. The experiment was conducted a Blackmore silt loam (fine-silty, mixed, superactive, frigid Typic Argiustolls) from 2004 2008 southwestern Montana. Annualized biomass were greater CSW than SW-F WW-F other years. From 2007, SOC concentration 15-cm declined 2.99 g kg -1 yr . In 2008, content 10 120 cm mechanical or chemical treatment SW-F. STN 0 5 but 30 60 CSW. 2006, 90 treatment. SIC contents largely not influenced treatments. Continuous tillage, followed reduced amount returned 2007 probably storage. contrast, ofN removed due continuous For sustaining maintaining levels, with less intensive sheep that increase could be adopted.