Correlation experiments for P and K were conducted from 1968-1973 at a research farm in Qulin, Missouri to better define the relationships between soil tests, crop yields, and fertilizer treatments. Three crop rotations each were conducted for P and K trials (ranges C, D, E, F, G, and H), and included corn, soybean, wheat, cotton, and sorghum.
Comparison of four extractants used in soil phosphorus and potassium testing for two soils in a corn-wheat-soybean rotation in Tennessee receiving various amounts of P and K fertilizer
These soil samples are from field experiments initiated in 2009. There were two separate fertilizer rate trials at each location, one for P and one for K, and each was implemented in a corn-winter wheat-soybean rotation. The soils used in this study are from University of Tennessee (UT)’s Research and Education Center at Milan (35.9, -88.73333) and UT’s Highland Rim Research and Education Center at Springfield (36.466667, -86.816667).