reviseduniversalsoillossequation-version2(编辑修改稿)

reviseduniversalsoillossequation-version2(编辑修改稿)内容摘要：

Buffer, filter, strip cropping, barriers  Terrace/Diversion  Impoundments  Tile drainage CoverManagement Subfactors  Canopy  Ground cover  Surface Roughness  Ridges  Below ground biomass Live roots, dead roots, buried residue  Soil consolidation  Antecedent soil moisture (NWRR only) CoverManagement Effects Raindrops intercepted by canopy cover Raindrops not intercepted by canopy cover Intercepted rainfall falling from canopy cover Canopy cover Ground cover Ridges Buried residue Dead roots Live roots Antecedent soil moisture (NWRR) Soil consolidation Random roughness Canopy  Cover above soil surface that intercepts rainfall but does not touch soil surface to affect surface flow  Main variables Percent of surface covered by canopy Effective fall height Effective Fall Height Effective fall height Canopy height Height to bottom of canopy Gradient of canopy density Material concentrated near top Ground Cover  Cover directly in contact with soil surface that intercepts raindrops, slows runoff, increases infiltration  Examples Live plant material Plant residue and litter Applied mulch Stones Ground Cover Effect 00 . 20 . 40 . 60 . 811 . 20 20 40 60 80 100 120G r o u n d C o v e r ( % )Ground Cover Effectb = 0 . 0 2 5b = 0 . 0 5Eff = exp(b x %grd cov) b greater when rill erosion more dominant than interrill erosion Ground Cover  Live cover depends on type of vegetation, production level, and stage  Residue Amount added by senescence, flattening, and falling by deposition at base Deposition • Rainfall amount • Temperature Interaction of Ground Cover and Canopy  Canopy over ground cover is considered to be noneffective  As fall height approaches zero, canopy behaves like ground cover Random Roughness  Creates depressions  Usually creates erosion resistant clods  Increases infiltration  Increases hydraulic roughness that slows runoff, reducing detachment and transport capacity Random Roughness  Standard deviation of microelevations  Roughness at tillage function of: Implement Roughness at time of disturbance and tillage intensity Soil texture Soil biomass  Decays with: Rainfall amount Interrill erosion 0 12 0 Range (in) Random Roughness (in) Ridges  Ridges up and downhill increase soil loss by increasing interrill erosion  Function of: Effect increases with ridge height Effect decreases with slope steepness above 6%  Ridge height decays with rainfall amount and interrill erosion  Effect shifts from increasing soil loss when up and downhill to decreasing soil loss when on the contour Dead Biomass Pools  Killing vegetation converts live standing to dead standing and live roots to dead roots  Operations Flatten standing residue to flat residue (ground cover) Bury flat residue Resurface buried residue Redistribute dead roots in soil Material spread on surface Material incorporated (lower one half of depth of disturbance)  Deposition at base causes standing residue to fall Deposition of Dead Biomass  Function of: Rainfall Temperature Type of material Standing residue decays much more slowly Below ground biomass  Live roots Distributed nonuniformly within soil  Dead roots  Buried residue Half of material deposed on surface is added to upper 2 inches Incorporated biomass Effect of Below Ground Biomass  Roots mechanically hold the soil  Add anic matter that improves soil quality, reduces erodibility, increases infiltration  Affect rill erosion more than interrill erosion  Effect of roots considered over upper 10 inches  Effect of buried residue over upper 3 inches, but depth decreases to 1 inch as soil consolidates (. notill) Soil Consolidation  Overall, freshly tilled soil is about twice as erodible as a fully consolidated soil  Erodibility decreases with time Seven years in the Eastern US Depends on rainfall in Western US, up to 25 years Width of Disturbance  Width of disturbance taken into account in surface cover, random roughness, and soil consolidation Antecedent Soil Moisture (NWRR)  Soil loss depends on how much moisture previous cropping systems have removed from soil Supporting Practices  Contouring/Crossslope farming  Strips/barriers Rotational strip cropping, buffer strips, filter strips, grass hedges, filter fence, straw bales, gravel bags  Terraces/diversions  Impoundments Contouring/Cross Slope Farming  Redirects runoff  Fail at long slope lengths  Effectiveness depends on ridge height (no ridge height—no contouring effect) Contouring/Cross Slope Farming (continued)  Function of: Ridge height Row grade Covermanagement Hydrologic soil group Storm severity (10 yr EI)  Varies with time Tillage that form ridges Decay of ridges Critical Slope Length  If slope length longer than critical slope length, contouring fails allowing excessive rill erosion  Function of: Storm severity, slope steepness, covermanagement, EI distribution  Critical slope length extensions below strips depend on degree that strip spreads runoff  Terraces are used if changing covermanagement or strips are not sufficient  Soil disturbance required to restore failed contouring Buffer/Filter Strips  Narrow strips of dense vegetation (usually permanent grass) on contour Effective by inducing deposition (partial credit) and spreading runoff Most of deposition is in backwater above strip  Buffer strips Multiple strips Either at bottom or not a strip at bottom。