Exploitation of sensitivity to N-supply of maize (Zea mays L.) genotyp
es is of both economical and environmental importance. Therefore, the
objectives of this study were to identify the N-sensitivity of differe
nt maize genotypes, and to find the possible explanations for this sen
sitivity: Two-model hybrids were investigated in a 2-yr lysimeter tria
l, where low, moderate, and high N-supplies (50:50% ammonium and nitra
te) were provided. This resulted in extra low, low, medium, and high y
ield levels in the two years investigated. Supply of water was control
led. One hybrid was considered as N-sensitive, whereas the other was c
onsidered as N-tolerant according to their performance in earlier eval
uations. In the present study, N-sensitivity was determined regarding
the N-response of whole plant, grain, and N yields of the two hybrids.
The N-sensitive genotype proved to be sensitive at either low or high
N-supply showing yield increases, and decreases, respectively, compar
ed with the N-tolerant hybrid, while the latter produced higher yields
at the medium N-treatment. The higher N-sensitivity might be due to t
he lower N-uptake, within which a higher NH4+-N ratio could result in
less energy requirement for N-assimilation; or lower N-storage capacit
y; or better N-efficiency. However, the N-tolerant took up more NO3--N
from the soil, therefore it was effective to decrease NO3--N leaching
. Regarding to the differences between the two genotypes in storage ca
pacity and efficiency, the N-sensitive genotype seems to be more suita
ble for grain production, while the tolerant one for forage use. Furth
er research should focus on morphological and biochemical reasons of h
ybrid differences in N-uptake, N-efficiency, and storage capacity.