Nitrogen uptake and remobilization in maize hybrids differing in leaf senescence

Maize (Zea mays L.) is an important cereal crop with multiple uses in the world. Stay-green hybrids have been developed because of their higher productivity. Few studies have been conducted to evaluate the influence of nitrogen (N) levels on N uptake, remobilization, grain yield and N concentration in stay-green hybrids compared to senescent ones. Field studies were undertaken in P.R. China on an Ustochrepts soil to determine the effects of N levels and hybrids differing in leaf senescence on grain yield and N concentration, N uptake, remobilization, and residual in vegetative tissues in 1996 and 1997. The stay-green hybrid ND 108 had greater yields than TK5 (intermediate senescing) and ZD 120 (fast senescing) under both high (225kgNha(-1)) and low N (0 in -1997 or 45kgNha(-1) in 1996, respectively) supply. ND108 took up more N than the two other hybrids. Grain N concentration of ND108 did not decrease by low N significantly, excepting the experiment sown in the summer of 1996, when post-silking N uptake was reduced greatly by the shortened grain filling duration. Nitrogen remobilization efficiency in vegetative tissue was higher in senescent hybrids ZD120 than ND108. Nitrogen retained in the stover at harvest was higher in ND 108, which can lead to a deficit of soil N for the next crop if the stover is not returned into soil. It was suggested that, though stay-green hybrids have been developed for high N conditions, they have advantages over senescent hybrids also under N limited conditions.