Description: The influence of balanced mineral fertilization on net assimilation rate during maize ontogenesis was examined.Two groups of hybrids were used throughout the experiments: hybrids with middle early ripeness (400 FAO) and late ripeness hybrids (700 FAO). A seven-year field experiment was carried out on Chromic Luvisol (WRBSR FAO,1998) at the experimental station of G.Lozen and on Calcic Chernozem (WRBSR, FAO, 1998) at the experimental station of Kovachitza. It was found that the effect of mineral fertilization on the average values of net assimilation rate was more strongly expressed in maize cultivated on Chromic Luvisol (WRBSR, FAO, 1998). The trend of dependency showed a maximum of net assimilation rate at fertilizer concentrations of 214 kg.ha-1 and 150 kg.ha-1for N and P, respectively. When maize was grown on Calcic Chernozem (WRBSR, FAO, 1998), the effect of mineral fertilization was more slightly expressed. Regression equations describing this dependency in specific soil-climatic growth conditions were worked out

Remarks: Proceedings of the XI National Conference on Plant Physiology, 18-19 november 2009, Sofia, Bulgaria