Effect of NPK and lime application on root-rot of erva-mate seedlings

The present work aimed to evaluate the effect of different dosages of nitrogen, potassium, and phosphorus and liming on the incidence and severity of erva-mate (Ilex paraguariensis A. St.-Hil) root-rot. The experimental design was an entirely randomized factorial (4x3x4). The factors levels consisted in the inoculation or not of Fusarium solani and Fusarium oxysporum (Factor F), in lime (Factor C) and NPK dosages (Factor A) above and below the levels recommended for the species. The seedlings were cultivated in polypropylene vases containing 2 kg of soil, under greenhouse conditions. The nutrients application was based on the soil chemical analysis, with the utilization of NH4NO2, P2O5, and KCl and dolomite lime as nutrient sources. The inoculation of Fusarium isolates was performed when the seedlings were five months old, by soil incorporation of a spores suspension. It was observed that the NPK and lime application contributed to the highest severity of the erva-mate rot-root symptoms, and the smallest symptoms were observed with the application of 50% of the NPK recommended for the species, without lime application.O presente estudo teve por objetivo avaliar o efeito de diferentes doses de nitrogênio, potássio e fósforo e da calagem do solo sobre a incidência e severidade da podridão-de-raízes da erva-mate (Ilex paraguariensis A.St.-Hil). O delineamento experimental utilizado foi o inteiramente casualizado fatorial (4x3x4). Os níveis dos fatores consistiram na inoculação ou não de Fusarium solani e Fusarium oxysporum (Fator F), em doses de calcário (Fator C) e NPK (Fator A) acima e abaixo do recomendado para a espécie. As mudas foram cultivadas em vasos de polietileno contendo 2 kg de solo, mantidas em condições de casa de vegetação. A aplicação dos nutrientes foi baseada na análise química do solo, utilizando-se NH4NO2, P2O5 e KCl e calcário dolomítico como fontes de nutrientes. A inoculação dos isolados de Fusarium ocorreu quando as mudas estavam com cinco meses, mediante a incorporação no solo de uma suspensão de esporos. Foi observado que a aplicação de NPK e calcário contribuiu para a maior severidade dos sintomas da podridão-de-raízes da Erva-mate, sendo que, a menor manifestação de sintomas ocorreu com a aplicação de 50% da recomendação de NPK para a Erva-mate, sem aplicação de calcário.Palavras-chave: Controle de doenças; Ilex paraguariensis; nutrição de plantas; proteção florestal. AbstractEffect of NPK and lime application on root-rot of erva-mate seedlings. The present work aimed to evaluate the effect of different dosages of nitrogen, potassium, and phosphorus and liming on the incidence and severity of erva-mate (Ilex paraguariensis A. St.-Hil) root-rot. The experimental design was an entirely randomized factorial (4x3x4). The factors levels consisted in the inoculation or not of Fusarium solani and Fusarium oxysporum (Factor F), in lime (Factor C) and NPK dosages (Factor A) above and below the levels recommended for the species. The seedlings were cultivated in polypropylene vases containing 2 kg of soil, under greenhouse conditions. The nutrients application was based on the soil chemical analysis, with the utilization of NH4NO2, P2O5, and KCl and dolomite lime as nutrient sources. The inoculation of Fusarium isolates was performed when the seedlings were five months old, by soil incorporation of a spores suspension. It was observed that the NPK and lime application contributed to the highest severity of the erva-mate rot-root symptoms, and the smallest symptoms were observed with the application of 50% of the NPK recommended for the species, without lime application.Keywords: Disease control; Ilex paraguariensis; plant nutrition; forest protection