Laboratory and greenhouse experiments were conducted to study the availability of fertilizer P in 20 samples of different soils representing 10 of the principal soil associations in Iowa.
Ryegrass plants recovered an average of approximately 50 percent of the added fertilizer P during a 385-day cropping period in the greenhouse. It appeared that continued cropping would have resulted in very little additional recovery of the added P. Differences in recovery of the added P from the different soils were relatively small, despite differences in rate of fertilizer addition or differences in soil pH, CaCO3 content, level of available soil P, soil organic matter content, and soil texture.
Koswara, Oetit and Hanway, John J.
"Plant availability of added phosphorus in different Iowa soils,"
Research Bulletin (Iowa Agriculture and Home Economics Experiment Station): Vol. 36
, Article 1.
Available at: https://lib.dr.iastate.edu/researchbulletin/vol36/iss570/1