Effect of preharvest desiccants on Group IVGlycine maxseed viability

Abstract

The effect of two commonly used desiccant tank mixtures on Glycine max seed production and viability when applied at G. max growth stages R5 to R8 (R5 = beginning pod fill, R6 = full green pod, R7 = beginning maturity, R8 = full maturity) was evaluated. Two mid-Group IV G. max cultivars, one conventional (‘Northrup King 4260’) and one glyphosate-tolerant (‘Asgrow 4701RR’), were evaluated. Tank mixtures containing either glyphosate + sodium chlorate or paraquat + sodium chlorate + surfactant reduced yield, seed weight, and subsequent germination, emergence, and seedling growth when applied at R5 or R6 to either G. max cultivar. Glyphosate + sodium chlorate applied at R7 reduced germination of the glyphosate-tolerant cultivar. When applied at R6 or R7, glyphosate + sodium chlorate reduced the next generation's seedling length compared to paraquat + sodium chlorate. Glyphosate + sodium chlorate increased the number of abnormal seedlings produced in the conventional cultivar compared to paraquat + sodium chlorate. These results indicate that preharvest desiccant applications should not be made prior to G. max maturity (R7).