Rapid Evaluation of Foliar Fertilizer-induced Damage: N, P, K, S on Corn
1979
Neumann, Peter M.
Foliar spraying of crops with fertilizer solutions often causes leaf bum, which reduces the photosynthetic area of the leaves and can reduce yields. Damage can be avoided sometimes by careful control of factors such as spray droplet size, wetting agents, ambient temperature, pH, and concentration of solutes. However, information concerning the mechanism inducing burn damage or the comparative merits of different fertilizer sources of the same mineral is limited. The objects of this work were: 1 to use a rapid laboratory assay to compare the damaging effects of various fertilizer sources of N, P, K, and S on leaf cell membranes, 2 to identify the mechanism of membrane damage by fertilizer solutions, and 3) to make a preliminary evaluation of any correlation between solute-induced membrane damage and leaf bum in the field. The laboratory assay consisted of a 4-min vacuum infiltration of 0.3-cm leaf segments with test solution followed by assay of UV-absorbing materials leaked subsequently into a distilled water rinse. Threshold concentrations of fertilizers causing membrane damage symptoms were determined for nine fertilizer sources. Damaging concentrations of N ranged from 3.5 to 31 g/liter depending on the fertilizer assayed. Damaging concentrations of various P, K, and S sources ranged from 3.8 to 11 g/liter for P, 12.2 to 22 g/liter for K, and 6.4 to 8.2 g/liter for S. No evidence was found for the existence of a causal relationship between either pH, molarity, conductivity, or osmotic potentials of test solutions and the onset of membrane damage. Preliminary field trials showed that the assay could predict damage trends for urea and urea phosphate sprays.
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