ISSUE 12    July 26, 2007


This is the season for questions regarding foliar application of fertilizer on soybeans. Recent studies on this topic suggest that soybeans generally do not respond to this practice. A large study in Iowa several years ago saw a couple yield increases out of about thirty sites, and there was no clear reason why the couple of sites responded. Soybeans in this region are not responsive to most micronutrients. Sometimes a positive response is seen in chlorotic soybeans to foliar application in greenness, but seldom in yield. Under irrigation, where there is a greater chance of higher yield, a foliar fertilizer response from a low rate N-P-K fertilizer is more likely.



There is no reason to delay soil sampling following small grain harvest. Due to the low N content of the residue, the chances of large N releases either from the residue or the soil following harvest is low. Early sampling increases the accuracy and consistency of the 0-6 inch soil core. It allows the grower to have time to plan an N rate if fall N application is planned. However, delaying soil sampling after other crops, including canola and field peas is recommended until the soil cools, usually late September. This is recommended because some soil organic matter/residue mineralization may take place between harvest and sampling.

Dr. Dave Franzen
NDSU Extension Soil Specialist

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