Loss of Phosphorus by Erosion
1952
Ensminger, L. E.
A study was made of the phosphorus status of soils which had received phosphate applications over a period of years to determine the loss of phosphorus by erosion. Phosphorus that could not be accounted for by analysis of the surface 16 inches of soil and by crop removal was assumed to be loss by erosion. Where corn and cotton was used as the rotation, an average of 63% of the phosphorus applied during a 16-year period to a Hartsells fine sandy loam soil had been lost by erosion as compared to 40% for a corn, cotton, and winter legume rotation. The results show that most of the accumulated phosphorus could be extracted by a HCl-NH₄F solution. Three plots in the corn, cotton, and winter legume rotation contained 7 to 8% of < 2 µ material in the surface 0 to 8 inches originally, but after 16 years of cropping the < 2 µ material had been reduced to 5 to 6%. The clay fraction contained 25 to 30% of the total phosphorus. These results indicate that only a small part of the phosphorus was lost along with the clay fraction. A study of 22 fields in Baldwin County that had been in potatoes from 5 to 30 years shows that the surface soil accumulated an average of 103 pounds P₂O₅ per acre per year in potatoes, although an estimated 200 pounds of P₂O₅ was added each year potatoes were grown. An inventory of the phosphorus status of soils in cement bins after 12 years of phosphate applications shows that 80% or more of the applied phosphorus could be accounted for on the basis of soil analysis and crop removal. The plots were enclosed by cement walls which prevented run-off except during very heavy rains.
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