Impact of foliar diseases in organically grown barley: Influence of fertilization, nutrient content in leaves, varietal disease resistance characteristics and yield potential

Abstract

Significant increase in severity of powdery mildew,leaf rust and net blotch with increasing N-content in plant leaves 30 days after germination (all years where the relevant diseases were present at a substantial level). This may explain: · Most of the environmental main effects (field) on disease. · Effect of treatments, i.e., treament 4 resulted in reduced N/increased K content in leaves, which coincided with reduced levels of disease. We observed no clear effect of P, Ca, S, and Zn content in leaves on disease. Micronutrients as Cu, Mo and Mn showed significant effects on powdery mildew in one year but not the other; further interpretation may not be possible due to inter-correlation among the effect of micro-nutrients. The diseases had a significant yield reducing effect, in particular powdery mildew and net blotch, which occurred at highest severities. In addition, net blotch affected root development, resulting in significant shorter roots, whereas powdery mildew did not. The effect of disease on root length was of the same order of magnitude as the factor 'variety', but larger than effects of 'year'