Submitted to: Brazilian Soil Sciences
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/15/2000
Publication Date: N/A
Citation: Interpretive Summary: Soil loss by water occurs by sheet flow and in small streams called rills in agricultural fields. Both can cause serious onsite and offsite effects. Models are used to predict the relative soil loss hazards and to administer farm programs for US Agriculture. These models use various parameters for a given site to estimate the hazard. The problem is there is not a standard method to estimate these parameters for the Water Erosion Prediction (WEPP) project model. We conducted a field experiment to compare two different shapes of the cultivated land of on sandy agricultural soil. We used a rainfall simulator to collect data on rectangular or triangular shapes. We found that for this soil that sheet erosion was greater for triangular shaped slopes. The erosion in small streams did not change with the different shapes so shape did not matter. Caution should be used when collecting values for sheet erosion and the shape of the plot should be considered. The impact of this research is that more accurate data can be collected for soil loss models and therefore they can be used more effectively in administering the billions of dollars each year in farm program monies related to soil conservation.
Technical Abstract: The interrill and rill erodibility is normally determined in the field on a bare soil after conventional tillage. However, as there is not uniformity in the soil surface condition, flat or triangular, the results are difficult to compare. The objective of this paper was to evaluate the effect of the surface condition on the results of water and soil losses and interrill and rill critical shear stress in erosion plots with two different cross section shapes of the soil surface: rectangular (RCS) and triangular (TCS). The experiment was carried out in 1998 on a sandy dystrophic red argisol with conventional tillage. The interrill plot dimensions were 0.50 m by 0.75 m; for the rills with RCS were 0.20 by 5.90 m; and for the TCS were 0.50 m by 5.90 m. A rainfall simulator was used in the interrill experiment at a constant rate equal to 65 mm h*-1 for 90 minutes. In the rill experiment, after prewetting, five different flow rates were applied increasing from 0.0002 m*3 s*-1 until 0.0010 m*3 s*-1. Interrill soil detachment, Di was 2.09 x 10-4 kg m*-2 s*-1 for RCS and 3.35 x 10-4 kg m*-2 s*-1 for TCS, the interrill erodibility Ki was 1.77 x 106 kg s m*-4 for RCS and 2.00 x 106 kg s m*-4 for TCS. Rill erodibility, Kr was 0.0110 kg N*-1 s*-1 for RCS and 0.0074 kg N*-1 s*-1 for TCS, and the critical shear stress, Tau?c, was 2.61 N m*-2 for RCS and 2.00 N m*-2 for TCS, but were not statistically different for the two cross sections studied and can be determined using both plot shapes in soils with sandy surface texture.