Severidade do míldio da cebola em plantio direto fertirrigado sob parcelamento de nutrientes e densidades populacionais

Abstract

The study analyzed the relationship between nutrient splitting (N and K) and population density on the severity of onion downy mildew under no-tillage cultivation within the conditions of Alto Vale do Itajaí (Brazil). For this purpose, field trials were conducted in the years 2017, 2018 and 2019, in Ituporanga (Brazil). The treatments corresponded to four plant densities (300, 400, 500 and 600 thousand plants ha-1) submitted to applications of nitrogen (150 kg N ha-1) and potassium (127.5 kg K2O ha-1). The doses of nutrients were distributed along the vegetative cycle of the culture via fertigation on a weekly, biweekly and monthly, based on the absorption curve of nutrients for the cultivar Empasc 352 - Bola Precoce. In fertigated no-tillage systems, the distribution of nutrients (N and K) does not influence the severity of downy mildew. Mildew severity increases linearly with increasing population density especially from 500 thousand plants per ha-1.