Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School


First Advisor

Paul L. Carson


The soybean (Glycine max (L.) Merrill) is a very important world crop. The seed is rich in both protein and oil, making it a valuable human food resource. Many scientists believe that there are physiological barriers preventing increased soybean yields. Any agronomic discovery that would consistently increase soybean yields would be important to world food production. One possible yield barrier in soybeans concerns the mineral nutrition of the plant during the seed-filling stages of growth. During this period of growth, translocation of N, P, K, and S from the plant foliage to the developing seed occurs, accompanied by a virtual cessation of uptake of these elements. The possibility of a yield increase from the foliar application of these elements during this period of growth has been suggested. Soybean yield increases of over 1500 kg/ha (23 bu/ac) have been recorded in Iowa from the application of N, 'P, K, and S in the form of foliar fertilizers. Preliminary research with foliar fertilizers in South Dakota showed no yield response and considerable leaf necrosis. Little is known about the effect of foliar fertilizer-induced leaf necrosis on soybean yields. A better understanding is also needed of what weather conditions minimize this leaf necrosis. The purpose of this study was threefold: (1) to determine if foliar fertilization can increase soybean yields under South Dakota growing conditions, (2) to determine the effect of foliar fertilizer-induced leaf necrosis on soybean yield, and (3) to quantify the relationship between foliar fertilizer-induced leaf necrosis and the weather conditions at the time of fertilizer application.

Library of Congress Subject Headings

Foliar feeding




South Dakota State University