Improved Plant Response to Potash Fertilization through Control of Seedling Diseases

Several studies indicate 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 calcium in young seedlings that occurs with the application of a chloride salt.


Justification

Several studies indicate 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 calcium in young seedlings that occurs with the application of a chloride salt. This project seeks to determine whether control of soybean and snap bean seedling diseases may be improved with an increase in root calcium. Sources of supplementary calcium will be added to soil naturally infested with several soil-borne pathogens to determine their effects on the incidence and severity of seedling diseases and their effect on seedling root calcium levels. Treatments found to decrease seedling diseases will be evaluated for their effects on plant stand and yield in field tests.


Methodology

Laboratory and Greenhouse Protocol: Sources of supplementary calcium will be added to soil naturally infested with several soil-borne plant pathogens and to pasteurized soil (pathogen-free) to determine treatment effects on the incidence and severity of soybean and snap bean seedling diseases and on plant growth in the presence and absence of disease. Effects on disease incidence will be determined by comparing seedling losses in treated soil to those observed in untreated soil and in the pasteurized soil. Disease severity will be determined by comparing seedling growth (height, vigor, and root growth or pruning) in treated soil to that observed in untreated soil and in treated pasteurized soil. Differences in root calcium between treated and untreated roots will be determined. Treatments found to decrease seedling diseases will be evaluated for their effects on soybean stand and yield in field tests.

Root Calcium Protocol: The effects of treatments on the concentration of calcium in the outer cell layers of soybean and snap bean roots will be analyzed with a Scanning Electron Microscope (SEM) and energy-dispersive X-ray analysis (EDX). The results from the field tests, supplemented with the greenhouse and laboratory experiments, will be used to validate whether or not improving the calcium nutrition of soybean and snap bean seedlings can reduce the incidence or severity of seedling diseases. Treatments found to increase calcium levels in seedlings and to reduce the incidence or severity of seedling diseases will again be evaluated for their effects on crop yield.

Field Research Protocol: Field tests will be conducted at the University of Tennessee’s WTREC at Jackson, TN. The test area has been planted annually to soybean or snap bean since 2002 with moderate to severe seedling disease losses and is naturally infested with several soil-borne plant pathogens (Rhizoctonia solani, Macrophomina phaseolina, Pythium spp., and Fusarium spp.). The site can be irrigated as needed to created conditions favorable for seedling disease development. Soybean and snap bean fungicide seed treatments, with and without calcium supplements (e.g. calcium formate, calcium lactate, and calcium salicylate) and in-furrow applications of calcium nitrate at different rates will be evaluated in a series of laboratory and greenhouse experiments for their effects on seedling emergence, seedling vigor, and disease incidence of both snap bean and soybean in 2012. Field tests of the effect of treatments on plant stand, plant growth, and yield will be limited to soybean in 2012 due to a lack of suitable field space for both crops, but will include both snap bean and soybean in 2013. The pathogen(s) infecting diseased seedlings will be identified.