The effect of applied micronutrients on yield and plant uptake of soybeans

Experiments were conducted at Milan and Martin, Tennessee, in1966, on Memphis and Grenada soils, respectively. The purpose of these experiments was to determine the yield and plant uptake response of soybeans to applications of the micronutrients boron, copper, manganese, and zinc at two rates, and 4-16-16 fertilizer at two rates. Leaf samples were collected when the soybeans were 12 inches high, in bloom, and when the pods were filling. Tissue analysis for manganese, zinc, and copper were determined on an atomic absorption spectrophotometer. Boron content was determined by the curcumin colorimetric method and phosphorus by the 1,2,4 aminonapthosulfonic acid reduced molybdophosphoric blue color method. Applications of zinc, boron, copper, and manganese singly and in combination gave no increased or decreased yield of soybean seeds. Application of boron increased the boron content of the soybean leaves. Manganese content in the leaves was increased by applications of manganese to the soil. Zinc application did not result in any significant increases in zinc content of leaves. Copper content of leaves remained relatively the same throughout the experiment.