Mineralization and Leaching of Phosphorus from Soil Incubated with Surface-Applied and Incorporated Crop Residue
- A. N. Sharpley * and
- S. J. Smith
With the increasing use of conservation tillage, consideration of crop residue as a potential source of plant-available P and mobility of this P in soil will be important from both agronomic and environmental standpoints. The effect of placement (surface or incorporation) of residue of six crop types (alfalfa, Medicago sativa L.; corn, Zea mays L.; oat, Avena sativa L.; peanut, Arachis hypogaea L.; soybean, Glycine max (L) Merr.; wheat, Triticum aestivum L.) on the mineralization and leaching of P from eight soils was investigated. Significantly greater (1.0% level) amounts of inorganic P were leached from surface-applied compared to incorporated residues during the 84-d incubation at 35°C, with the maximum amount leached after 28 d. The opposite was true for organic P, with greater amounts leached from incorporated residue than from surface-applied residue. These amounts steadily decreased during the 84-d incubation. Apparently, mineralization of residue P and movement within the soil was greater for surface-applied compared to incorporated residue and was a positive linear function of available soil P content (r2 = 0.69–0.81). Any increase in soil P solubility caused by residue leachate would be expected to occur to a greater extent with an increase in available soil P. Leaching of mineralized P may be an important source of available P during initial crop growth.
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