Improved Plant Response to Potash Fertilization through Control of Seedling Diseases

Research at The University of Tennessee’s West Tennessee Research and Education Center evaluated the effects of potash application, four seed treatment supplements, and in-furrow applications of liquid calcium nitrate (CAN) fertilizer on snap bean diseases, seedling emergence, plant stand, plant growth, and yield in two experiments in a field naturally infested with several soil-borne plant pathogens. In a test planted April 23, seedling emergence 15 days after planting was greatest when a standard seed treatment (thiamethoxam + mefenoxam + fludioxonil) received a calcium-containing supplement (Treatment A).

The number of healthy plants per row was highest when the standard seed treatment was supplemented with Treatment A, particularly in plots receiving KCl. Pathogens isolated from diseased seedlings during this experiment were tentatively identified as Fusarium spp. (60%), Macrophomina phaseolina (17%), Sclerotinia sclerotiorum (6%), and Rhizoctonia solani (5%). Snap bean yield was highest when the standard seed treatment was supplemented with Treatment A. The seed treatment supplements had no effects on seedling vigor, plant height, or plant flowering. In a snap bean test planted August 2, seedling emergence 5 and 7 days after planting was significantly delayed with the application of KCl at 100 lb K₂O/A. Four calcium-containing seed treatment supplements had no effect on seedling emergence. Supplementing the standard snap bean seed treatment with a high rate of another experimental treatment (Treatment E) increased the number of healthy plants per row two weeks after planting, while a lower rate increased the number of healthy plants five weeks after planting. Potash application increased the number of plants lost to seedling diseases by over 56%, decreased plant height by 5% and decreased snap bean yield by 45%. The seed treatment supplements failed to significantly affect plant height or snap bean yield. Macrophomina phaseolina was isolated from 96% of the diseased plants.

In a separate soybean field experiment, four application rates of an in-furrow calcium nitrate spray (0, 1, 2, and 3 lb N/A) were evaluated with and without KCl to examine their effects on soybean seedling diseases, plant growth, and yield of untreated soybean seed. Soybean yield was lowest in plots that received the 1 lb N/A in-furrow spray plus potash fertilization.