Improved Plant Response to Potash Fertilization through Control of Seedling Diseases


28 Feb 2013

2012 Annual Interpretive Summary

Several studies have indicated that the commonly used potash fertilizer, muriate of potash, can increase losses of soybean and snap bean to seedling diseases. Supplementary studies suggest that this may be due to a loss in root Ca in very young seedlings that occurs with the application of a chloride (Cl-) salt. This project seeks to determine whether control of soybean and snap bean seedling diseases may be improved with an increase in seedling root Ca levels in the presence of potash fertilizer. Laboratory, greenhouse and field studies were conducted in west Tennessee in 2012 to determine the effects of seed-treated Ca supplements on the Ca content of seedling roots, seedling disease incidence, root rot, plant growth, and yield in treatments with and without K fertilizer.

Supplementing a standard soybean seed treatment (thiamethoxam + mefenoxam + fludioxonil) with Ca-lactate or Ca-formate increased the rate of radical growth of germinating seed and increased the growth of soybean seedlings grown in solarized field soil (pathogen-free). A greenhouse test using solarized field soil and in-furrow applications of granular Ca nitrate at rates equivalent to 4 and 8 lbs N/A indicated that these two rates were very injurious to seed germination. None of the seed treatment Ca supplements increased seedling emergence, seedling growth, plant height, or soybean yield in a field test (both with and without K fertilization) in soil naturally infested with Rhizoctonia solani, Macrophomina phaseolina, Pythium spp. and Fusarium spp. Treated seed were grown in solarized field soil to determine the effect of seed treatment Ca supplements on the Ca level in the roots of 10- to 13-day old seedlings. Analysis of soybean taproots using energy-dispersive analysis of x-rays found no increase in Ca levels with any of the Ca supplements evaluated. Supplementing a standard snap bean seed treatment (thiamethoxam + mefenoxam + fludioxonil) with Ca salicylate decreased snap bean root rot when plants were grown in a greenhouse test in pathogen-infested field soil. Additional growing seasons are needed to determine conclusively if an interaction between Ca-supplements, K fertilization, and seedling disease exists. TN-21