Nitrogen Level and Irrigation Interval on Mitigating Stemphylium Blight and Downy Mildew in Onion

Abstract

Field trial was conducted on horticultural farm of Lamjung Agriculture Campus, Lamjung, Nepal between December-April 2016/17 on onion (Allium cepa), following two factorial Randomized Block Design with three replications and fifteen treatments to assess disease severity of Stemphylium blight (Stemphylium vesicarium) and Downy mildew (Peronospora destructor). The onion cultivar Red Creole, widely grown in this locality and susceptible to these diseases was used for trial. The disease intensity for Stemphylium leaf blight and Downy mildew was rated on weekly basis. Disease severity of both the disease significantly varied with nitrogen level and irrigation interval during initial and middle growth stage of onion, but in contrary, was found non-significant during later days as the plant approached harvesting stage. Area under Disease Progress Curve (AUDPC) also significantly varied in both treatments for both disease. Yield parameters recorded viz. bulb diameter and bulb yield significantly varied with nitrogen level and irrigation interval. The interaction effect of both the treatment was found non-significant for disease severity, AUDPC level and yield parameters during entire growth stage of onion. The results indicated that 7 days irrigation interval and government recommended dose of nitrogen i.e. 235 kg/ha were significantly better over other level of treatments in reducing Stemphylium blight and Downy mildew disease severity and also increasing yield parameters.

Onion downy mildew severity in no-tillage irrigation under nutrient budgeting and population densities

“…The epidemics of downy mildew can be favored by excessive fertilization with soluble mineral fertilizers, especially nitrogen [8] . Studies conducted by Acharya & Shrestha [17] , revealed that nitrogen doses above 140% of the recommended ones can promote increased severity of downy mildew in onion plants. However, Gonçalves; Souza & Silva; Boff [9] observed no effect of mineral fertilization on downy mildew infestation for doses of N and K between the normal and up to three times the recommended.…”

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We analyzed the relationship between nutrient (N and K) parceling and population density on the severity of onion downy mildew under no-tillage fertigation cultivation in the conditions of Alto Vale do Itajaí (Barzil). For this purpose, field trials were conducted in the years , 2018 and 2019. The treatments corresponded to four population densities (300, 400, 500 and 600 mil plants ha -1 ) subjected to applications of nitrogen (150 kg N ha -1 ) and potassium (127.5 kg K 2 O ha -1 ) distributed throughout the vegetative cycle of the crop via fertigation on a weekly, biweekly and monthly basis, based on the absorption curve of these nutrients for the cultivar Empasc 352-Bola Precoce.

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

“…As epidemias do míldio podem ser favorecidas pela adubação excessiva com fertilizantes minerais solúveis, em especial, do nitrogênio (WORDELL FILHO;BOFF, 2006). Estudos realizados por Acharya & Shrestha (2018), revelaram que doses de nitrogênio acima de 140% das recomendadas podem promover o aumento da severidade do míldio em plantas de cebola. No entanto, Gonçalves; Souza e Silva; Boff (2004) não observaram efeito da adubação mineral sobre a infestação de míldio para doses de N e K entre a normal e até três vezes a recomendada.…”

“…Dessa forma, a ausência de relação entre o parcelamento de nutrientes e a AACPD pode estar relacionada tanto à dose fornecida dos nutrientes, considerada baixa em relação as doses citadas por Acharya & Shrestha (2018) que podem promover o aumento da severidade do míldio, quanto, no caso do nitrogênio, à fonte utilizada (nitrato de amônio). Isso indica que a metodologia adotada permitiu que os nutrientes fossem fornecidos de forma a não interferir no processo doença.…”

“…Severidad del mildiú velloso de la cebolla en el sistema de fertirrigación con labranza cero bajo abono parcelado de nutrientes y densidades de plantas Resumen Se analizó la relación entre la entrega de nutrientes (N y K) y la densidad poblacional sobre la severidad del mildiú velloso de cebolla bajo labranza cero en las condiciones de Alto Vale do Itajaí (Brasil). Para ello, se realizaron ensayos de campo en los años 2017, 2018y 2019. Los tratamientos correspondieron a cuatro densidades poblacionales (300, 400, 500 y 600 mil plantas ha -1 ) sometidas a aplicaciones de nitrógeno (150 kg N ha -1 ) y potasio (127,5 kg K2O ha -1 ) distribuidas a lo largo del ciclo vegetativo del cultivo vía fertirrigación en forma semanal, quincenal y mensual, en base a la curva de absorción de dichos nutrientes para el cultivar Empasc 352 -Bola Precoce.…”