Degree Type


Date of Award


Degree Name

Doctor of Philosophy




Yield increases of soybeans sprayed with foliar fertilizers containing N, P, K and S during the seed-filling period have been inconsistent. It was hypothesized that the pH of the foliar fertilizer solution may effect the absorption and/or translocation of N, P, K and S. Field experiments were conducted in 1977 and 1978 to determine if the pH or N rate of the foliar solution would affect soybean yields. The pH of the solutions ranged from 2.7 to 7.2 and the N rate varied from 45 to 135 kg/ha/year. Phosphorus, potassium and sulfur were applied at the rate of 9, 27 and 4.5 kg/ha/year;The foliar fertilizer applications did not affect the dry weights of the plant parts--leaves, stems, petioles, pods and beans. However, the nutrient concentrations of the plant parts were increased by the foliar fertilizer applications. At maturity about 75-80% of the N and P in the plants and 55% of the K in the plants were found in the beans;Soybean plant heights averaged about 122-125 cm and were not affected by the applications of foliar fertilizers. The foliar fertilized plants produced approximately six more pods per plant than did the nonfertilized plants. The number of beans per pod, ranging from 2.1 to 2.4 beans per pod, was not influenced by the application of the foliar fertilizers. The foliar fertilizers reduced the bean size in 1977, but had no effect on the size of beans in 1978. Yields of soybeans at maturity were not affected by the foliar fertilizers in either year. The yields ranged from 3577 to 3904 kg/ha in 1977 and ranged from 4091 to 4534 in 1978.



Digital Repository @ Iowa State University,

Copyright Owner

Terry L. Smith



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150 pages