Effect of Soil, Cover, Slope, and Rainfall Factors on Soil and Phosphorus Movement Under Simulated Rainfall Conditions
1973
Munn, D. A. | McLean, E. O. | Ramirez, A. | Logan, T. J.
Three soils were treated with phosphorus at 25, 125, and 625 µg P/g soil in bare and cropped microplots and subjected to simulated rainfall. Five combinations of rainfall intensity and duration and microplot slope were used. Movement of soil and phosphorus from the microplots was measured. The quantity of runoff water, eroded solids, and P in the runoff increased with degree of slope and rainfall intensity. A high correlation (r = 0.997) was found between total P in the runoff from the bare plots and the quantity of soil eroded. Concentrations of soluble P in runoff from the plots was sufficient to eutrophy empounded water. The soil was nearly saturated with water and the system was “closed” so that runoff and leachate from a given rain were inversely related. Hence, the plant cover which was very effective in reducing runoff volume and soil erosion (as well as P losses) increased the quantity of percolating water. The increased percolation of water increased the P leached from cropped plots having uniformly mixed P. A well aggregated silty clay soil (Toledo) exhibited more infiltration than coarser textured soils with less granular structure. A modified Chang and Jackson fractionation of the sediments showed the dominant P fractions and their increases with rate of P application to be directly related to extractable Fe and Al content, pH, and percentage base saturation of the original soils. There was no significant change in the amount of P in organic form with rate of P application. While considerable caution must be used in extrapolating results of this kind to field conditions, the simulated rainfall and microplot method may prove useful in the study of nutrient movement by erosion and leaching under specified conditions.
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