Effects of cattle manure application on quality of runoff water and soil properties were studied on 0.04‐ha plots cropped with millet (‘Gahi‐1’ pearl millet [Pennisetum americanum (L.) K. Schum.]) and rye (‘Abruzzi’ rye [Secale cereale L.]) and instrumented for measuring and sampling runoff water. Manure applied at the rate of 45 metric tons ha−1 year−1 (dry weight) for 3 years and incorporated into the surface 15 cm of soil did not result in runoff water biochemical oxygen demand (BOD) values exceeding those for untreated soil. Nitrate levels in runoff water were not affected by the manure application and averaged less than 2 mg/liter of NO3‐N. There was a slight accumulation of nitrate in the soil profile due to the manure applications. After 3 years, nitrate averaged 0.15 and 0.08 meq NO3/100 g greater in the manured plots than in the check plots at the 0‐ to 45‐cm and 45‐ to 90‐cm depths, respectively. Nitrate accumulated in the millet forage above the safe level for feeding cattle, but not in the rye forage. Soil pH was increased to a depth of about 60 cm by manure application. Periodic carbon analysis of the soil indicated that organic matter was being decomposed fairly rapidly, and at the end of 3 years only 38% of the applied carbon remained.

Infiltration into the soil is regulated in part by sealing of the soil surface by raindrop impact. Soil surfaces protected from such impact maintained higher rates of infiltration than exposed soil surfaces. It was hypothesized that the cover particles protected the covered portion of the soil and prevented the reaction of raindrop impact on the sot1 state. The soil under the cover particles remained in the original state in which infiltration could occur. However, since the cover particles in this study were impervious, infiltration could not occur on the covered area but would occur along the available perimeter of the cover particles. Water would then move in both vertical and lateral directions. The effective lateral distance that the water moved after entry was defined as the effective width. To evaluate the effects of soil surface cover on the infiltration rate of soils exposed to raindrop impact, simulated rainfall was applied at a constant rate to one soil type in small plots with free drainage, and square and rectangular cover particles of varying sizes and percentages were used as surface cover. THEORY AND PROCEDURE Infiltration involves three interacting phases:(1) the surface entry of water, (2) the available storage capacity of the soil, and (3) the movement of water through the soil profile. The surface entry of water controls the rate of infiltration during all periods when water can be stored in the soil or passed downward through the soil profile more rapidly than it can penetrate the soil. Generally the initial infiltration rate is high. The rate diminishes, however, during continued rainfall toward a nearly constant lower rate.The initial rate, the rate of decrease, and the final rate are affected by characteristics and conditions of the soil surface, soil profile, and rainfall.

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