EFFECT OF FERTILIZERS AND RATES OF APPLICATION ON INCIDENCE OF SOYBEAN DISEASES IN NORTHERN ALABAMA

Field incidence of soybean stem canker (SSC), Phytophthora root rot (P RR), bacterial blight of soybean (BBS), soybean mosaic virus (SMV), an d soybean cyst nematode (SCN) females on soybean cultivar Bragg were c ompared under complete (20-20-20), ammonium nitrate (34-0-0), superpho sphate (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 pota sh had higher incidence of PRR and SMV. Plants fertilized with complet e fertilizer had the lowest incidence of PRR and SMV, and the highest yield. Both complete and superphosphate fertilizers lowered the incide nce 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 af fected by either type of fertilizers or rate of application. Applicati on rates of any of the four fertilizers reduced incidence of SSC. It i s recommended to use only complete fertilizer to increase yield and re duce field incidence of PRR, SMV, and SSC.