The Effects of Potassium Fertilization and Irrigation on the Yield and Health Status of Jerusalem Artichoke (Helianthus tuberosus L.)

The objective of this study was to determine the effects of potassium fertilization (applied to soil at 150, 250, and 350 kg K2O ha−1) and irrigation on the yield (fresh matter yield and dry matter yield of above-ground biomass and tubers) and the health status of tubers and leaves of three Jerusalem artichoke—JA (Helianthus tuberosus L.) cultivars (Topstar, Violette de Rennes, Waldspindel). The Topstar cultivar was characterized by the highest total tuber yield (60.53 Mg FM ha−1) and the highest above-ground biomass yield (65.74 Mg FM ha−1). An increase in the rate of potassium fertilizer to 350 kg K2O ha−1 did not affect total tuber yields. The greatest increase in above-ground biomass yields was observed in response to the potassium fertilizer rate of 150 kg K2O ha −1 (64.40 Mg FM ha−1). Irrigation increased tuber yields by 59% and above-ground biomass yields by 42% on average. Phytopathological analyses revealed that JA leaves were most frequently colonized by fungi of the genera Alternaria, Fusarium, and Epicoccum. Alternaria and Fusarium fungi were more prevalent in non-irrigated than in irrigated plots. A higher number of fungal pathogens was isolated from the leaves of cv. Violette de Rennes grown in a non-irrigated plot fertilized with 250 kg K2O ha−1. Tubers were most heavily colonized by fungi of the genera Penicillium, Fusarium, Alternaria, Botrytis, and Rhizopus. Fungal species of the genus Fusarium were isolated from tubers in all irrigated treatments, and they were less frequently identified in non-irrigated plots. Only the tubers of cv. Topstar grown in non-irrigated plots and supplied with 150 kg K2O ha−1 were free of Fusarium fungi. The number of cultures of pathogenic species isolated from Jerusalem artichoke tubers had a minor negative impact on fresh and dry matter yield.