Fusarium head blight and deoxynivalenol contamination in wheat as affected by nitrogen fertilization

Many studies have evaluated the effects of nitrogen-fertilizer rates on Fusarium head blight (FHB) and mycotoxin contamination of wheat (Triticum aestivum) in both conventional and organic systems. Results are often conflicting while underlying mechanisms remain illusive. This study aimed to provide insights into these conflicting results. Spring wheat was grown at two sites in the Netherlands in 2006 and 2007 using compost-, slurry-, or farmyard manure-based organic fertilizing systems, each with five total-nitrogen rates. In 2006, overall Fusarium infection levels and deoxynivalenol (DON) contents of the grain were low, and the data suggested a positive, multivariate relation between DON content and grain-nitrogen content. Higher DON contents were also accompanied by more vegetative growth (straw biomass). In 2007, plant density of the crop was relatively low while overall FHB infection levels and DON contents were relatively high. In this year, no clear correlations between straw dry matter production or grain-nitrogen content and DON content were found, while weed infestation increased with higher nitrogen levels. Practical implications of the multivariate relations between N-rates, N-contents, DON, microclimate and the presence of weeds are discussed.