Influence of nitrogen fertilization on mycotoxin contamination of maize kernels

Two experiments were set up from 2000 to 2004 in North West Italy to determine the effects of the type (urea and a slow-release fertilizer) and the application rate of nitrogen (N) fertilizer (0, 100, 200, 300 or 400 kg ha−1) on the susceptibility of maize hybrids to ear rot and to mycotoxin contamination in natural infection conditions. The ears were rated for the incidence and severity of disease symptoms at harvest and the harvested kernels were analysed for mycotoxin fumonisin B1, zearalenone, deoxynivalenol, aflatoxin B1 and ochratoxin A. The use of urea instead of a slow-release fertilizer may reduce the contamination of some mycotoxins. There were no significant differences between the two types of N fertilizer in any of the years for zearalenone, fumonisin B1 or ochratoxin A. Fungal ear rot incidence and severity was generally higher in ears from plants fertilized with insufficient N. High N fertilizer application (>300 kg N ha−1) significantly increased the zearalenone content, while for fumonisins the highest contaminations were related to N deficiencies (+80%).Deoxynivalenol and ochratoxin A, when found, did not show a clear relationship to N fertilization rate. A negative correlation was found between the N rate and aflatoxin B1 contamination, when the climatic conditions during ripening favoured this mycotoxin. A balanced N fertilizer application (200 kg ha−1) generally seems to ensure lower mycotoxin contamination and is usually the best solution for low mycotoxin contamination. This study is the first to report on the effects of N fertilizer application on mycotoxin contamination in non-inoculated conditions.