Abstract
Corn producers are faced each year with the decision of how much money to invest in fertilizer for use on their crop. Differing philosophies used by those who make fertilizer recommendations often leave the grower bewildered as to what is best to do. It is not unusual for a producer to be told by his agricultural extension agent that he doesn't need any phosphate and potash on fields which test high in these nutrients while other sources may recommend fertilizer use. The philosophy behind the zero P-K recommendation made by extension agents in such cases is based on University of Kentucky College of Agriculture research which over many years has shown that corn yields are not increased by adding P and K to soils which test in the upper range of the medium level or higher. This is called the "crop sufficiency" approach to making a fertilizer recommendation and results in a fertilizer recommendation for P and K only if soil tests are below that which research has shown necessary to get top yields. Research at UK has shown this approach to be valid regardless of yield goals or actual yields obtained. In other words, a soil testing on the line between medium and high levels of P and K can supply enough P and K for a 200 bushel per acre yield just as adequately as it can a 100 bushel per acre yield. Nitrogen is a different situation. Any corn producer knows that good yields of corn require the availability of ample N. But how much N is sufficient? Again, UK research on N response by corn has shown overwhelmingly that there is little relationship between N fertilizer rates based on some yield goal and yields of corn actually obtained. If a field already contains quite a bit of potentially available N (for example an old legume sod) high yields of corn can be obtained with minimal use of fertilizer N. In addition to residual soil N, soil drainage characteristics and type of tillage (conventional or no-till) also greatly influence the amount of N necessary for top corn yields and when it should be applied. Recommendations made by UK agricultural extension agents reflect these soil conditions, and rarely exceed 150 pounds fertilizer N per acre except on heavy textured, poorly drained soils where it may require 200 pounds N to get the same yield that could be obtained on lighter, drier soils with 100 pounds N.
Publication Date
11-1988
Volume
9
Number
10
Repository Citation
Wells, Kenneth L. and Turner, Keenan, "How Much Fertilizer ls Needed For Corn?" (1988). Soil Science News and Views. 143.
https://uknowledge.uky.edu/pss_views/143
