Effect of Fertilizers and Rates of Application on Incidence of Soybean Diseases in Northern Alabama

Abstract

Field incidence of soybean stem canker (SSC), Phytophthora root rot (PRR), bacterial blight of soybean (BBS), soybean mosaic virus (SMV), and soybean cyst nematode (SCN) females on soybean cultivar Bragg were compared under complete (20-20-20), ammonium nitrate (34-0-0), superphosphate (0-46-0), and muriate of potash (0-0-60) fertilizers, and rate regimes with unfertilized controls on Decatur silty clay loam (Rhodic paleudult) in northern Alabama. Plants fertilized with muriate of potash had higher incidence of PRR and SMV. Plants fertilized with complete fertilizer had the lowest incidence of PRR and SMV, and the highest yield. Both complete and superphosphate fertilizers lowered the incidence of SMV at application rates from 0 to 100 kg/ha, then increased up to 200 kg/ha. Ammonium nitrate fertilizer had no effect on incidence of SMV. The incidence of BBS and the number of SCN females were not affected by either type of fertilizers or rate of application. Application rates of any of the four fertilizers reduced incidence of SSC. It is recommended to use only complete fertilizer to increase yield and reduce field incidence of PRR, SMV, and SSC.