Microchannels Affect Runoff and Sediment Yield From a Shortgrass Prairie

Runoff and sediment yield from rangelands are extremely important variables that affect productivity, but are difficult to quantify. Studies have been conducted to assess erosion on rangelands, but very little has been done to determine if microchannels (rills) affect runoff and sediment yield. Rainfall simulations were used to quantify the effects of microchannels on runoff and sediment loss on a shortgrass prairie with two types of range conditions (good and fair). Natural flow paths within plots in the two range conditions were defined and then enhanced with an ellipse-shaped hoe to create microchannels. Soil from plots was removed at two rates (11.2 t· ha⁻¹ and 22.4 t· ha⁻¹) to create three soil surface configurations. Soil was removed by vacuuming to create either a single microchannel or multiple microchannels down the plot, and the third treatment was uniform soil removal over the entire plot (sheet). Results showed significantly greater total runoff from both single and multiple microchannel treatments compared with sheet soil removal. The microchannels resulted in significantly less sediment yield per unit of runoff compared with the sheet soil removal treatment. Both runoff and sediment yield were affected by range condition. Plots that were in fair range condition, dominated by buffalo grass (Buchloe dactyloides [Nutt.] Engleman), had a greater amount of total runoff (double) but less sediment yield (75%) than plots in good range condition that were dominated by blue grama (Bouteloua gracilis [H.B.K.] Lag. ex Stued.). The dense buffalo grass sod protected the soil surface from erosion, but water flowed freely across the sod. This study has provided a greater understanding of how microchannels affect runoff and sediment yield under different rangeland conditions, and has illustrated how plant species composition and soil surface features relate to several hydrologic functions.