Influence of Microrelief, Aggregate Size, and Precipitation on Soil Crust Properties

The USDA-ARS is currently developing a new wind erosion prediction system (WEPS) to estimate wind-induced soil erosion on a daily basis. This new system will estimate several soil crust-related properties not used in previous wind erosion prediction methods. This study was conducted to determine the effects of selected temporally varying surface soil properties and cumulative rainfall on soil crust-related properties used in WEPS. Specifically, crust-related properties including percent aggregate cover, crust cover, loose erodible soil material cover (LEMC), loose erodible soil material mass (LEMM), and plant residue percent cover were measured on fallow, cotton and sorghum fields and related to random roughness, dry aggregate size, and cumulative precipitation. Measurements were made during 1989 and 1990 for replicated plots in fields on three different sandy soils. Mean aggregate cover over the duration of the study ranged from 32 to 33%, crust cover ranged from 56 to 63%, LEMC ranged from 19 to 40%, and LEMM ranged from 1.2 to 1.9 tonne/ha. Although sorghum fields had significantly greater residue than fallow or cotton fields in two out of three soils, management treatments generally did not produce significant differences (P = 0.05) in aggregate cover, crust cover, loose erodible material cover, and loose erodible material mass. Significant differences (P = 0.05) were found among sampling dates for all crust-related properties, indicating a dependence on factors that vary through time. Differences among sampling dates were attributed to the effects of microrelief, cumulative precipitation, and aggregate size. Analysis of variance and regression were used to investigate these effects. Aggregate cover percentage was positively related to random roughness and negatively related to cumulative precipitation. Aggregate cover was not significantly (P = 0.05) related to dry aggregate size. Crust cover percentage was negatively related to random roughness and positively related to cumulative precipitation. Crust cover was not significantly (P = 0.05) related to dry aggregate size. Loose erodible material cover percentage was positively related to dry aggregate size and cumulative precipitation. Loose erodible material mass was positively related for one soil and negatively related for another soil to dry aggregate size, and negatively related to cumulative precipitation. Neither loose erodible material cover nor mass was related to random roughness.