The influence of timing the application of nitrogen fertilizer on early blight (Alternaria solani).

Abstract

Field experiments were carried out in 2016 and 2017 to study the influence of timing the application of nitrogen fertilizer (N-fertilizer) on the susceptibility of potatoes to early blight. We hypothesized that potatoes that receive N-fertilizer as split applications or a one-time application at emergence will have a higher N content and be less susceptible to early blight than those that receive N-fertilizer as a one-time application before planting. N-fertilizer was applied either as a one-time application before planting or at emergence and as split applications. Potatoes that did not receive N-fertilizer were more susceptible to early blight [high area under the disease progress curve (AUDPC)] than those that did receive N-fertilizer (low AUDPC). The timing of N-fertilizer application had a significant effect on the susceptibility of potatoes to early blight. Potatoes that received the entire quantity of N-fertilizer at emergence or as split applications had higher N contents and were less susceptible to early blight than those that received the entire quantity of N-fertilizer before planting. Potatoes that did not receive N-fertilizer had a markedly lower starch yield than potatoes that received N-fertilizer. Potatoes that received the entire quantity of N-fertilizer before planting had a lower starch yield than potatoes that received the entire quantity of N-fertilizer at emergence or as split applications. N-fertilizer applied as a one-time application at emergence or as a split application was the best treatment to ensure both high N content and lower attack of early blight, which confirms our hypothesis. © 2018 Society of Chemical Industry.