Impact of nitrogen and potassium on coffee rust

Diseases of the coffee plant can be effectively managed via well-balanced nutrition. This study assessed the effect of nitrogen and potassium fertilizers on the intensity of coffee (Coffea arabica) rust (Hemileia vastatrix) under greenhouse conditions. The susceptible cultivar New World 376/4 was used as the test species. Treatments included five N rates (3, 7, 11, 15 and 19 mmol L-1) with five K rates (3, 5, 7, 9 and 11 mmol L-1) in a 5 x 5 factorial design, for a total of 25 treatments and three replications with each treatment involving two plants growing in a nutrient solution. The completely randomized experimental design permitted evaluation of N and K on rust incidence and disease severity. The portion below the severity progress curve (AUDPCS) was calculated. Disease severity increased 16.48% with a dose of 7 mmol N L-1 and 11 mmol K L-1. There was an interaction of N with K in the AUDPCS and dried plant mass occurred. The AUDPCS (42.00) was lower when the next dose used was a combination of 19:07 mmol L-1 of N and K. A significant negative correlation was seen with the dry mass of the coffee seedlings.