Effect of zinc application timing on yield formation by two types of maize cultivars

The yield forming response of maize cultivar to zinc (Zn) application depends on its timing. This hypothesis was validated in 2007, 2008, 2009 and 2010 growing seasons. The zinc treatments as the first factor were: NPK; NPK + Zn applied before sowing; NPK + Zn applied to maize at the stage of 4th leaf. The second factor was the maize type: stay-green (modern cultivars) - Paroli, Veritis, Anamur; classical (old cultivars) - Inagua, Kirola. The grain yield of modern cultivars responded the best to zinc applied before sowing, whereas the old ones, when applied to foliage. The yield of the stay-green maize depended upon the number of kernels per row, whereas the classical one on all yield structural components. The zinc management in the modern cultivars should be oriented towards maximization of the number of kernels per row, whereas in the old one on its optimization with the simultaneous kernel weight increase. The positive impact of zinc application before sowing on dry matter translocation from vegetative tissues to growing kernels underlines its practical usefulness, especially in areas with frequent water shortage during maize growth.