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CROP BREEDING & GENETICS

Nitrogen Uptake and Utilization in Contrasting Nitrogen Efficient Tropical Maize Hybrids

^a Bako Agricultural Research Center, P.O. Box 03, Bako, West Shoa, Oromia, Ethiopia
^b CIMMYT-Kenya, P.O. Box 25171, Nairobi, Kenya
^c Institute of Plant Nutrition, Univ. of Hanover, Herrenhaeuser Str. 2, D 30419 Hanover, Germany
^d CIMMYT-Ethiopia, P.O. Box 5689, Addis Ababa, Ethiopia

^* Corresponding author (m.banziger{at}cgiar.org).

Maize cultivars with improved grain yields under nitrogen (N) stress are desirable for sub-Saharan African maize growing environments. This study assesses N uptake, N utilization, and the genotype x environment (G x E) interaction of 16 tropical maize (Zea mays L.) hybrids differing in grain yield under low-N conditions. Hybrids were evaluated under low-N, medium-N, and high-N at Harare, Zimbabwe, in 2003 and 2004 and at Kiboko, Kenya, in 2003. At maturity, N accumulation in the aboveground biomass ranged from 47 to 278 kg N ha^–1 in various experiments. Grain yields ranged from 1.5 to 4.3 Mg ha^–1 and 10.6 to 14.9 Mg ha^–1 for the same experiments, respectively. Significant G x E interactions were observed which became more pronounced as the difference in N stress intensity between two environments increased. High grain yield under low-N was consistently associated with higher postanthesis N uptake, increased grain production per unit N accumulated, and an improved N harvest index. Additive main effect and multiplicative interaction analysis identified hybrids with specific adaptation to either low-N or high-N environments. Several hybrids produced high yields under both low-N and high-N conditions. More detailed studies with these hybrids are required to examine the underlying physiological mechanisms contributing to the N-use efficiency.

Abbreviations: AD, anthesis date • AMMI, additive main effect and multiplicative interaction • G x E, genotype x environment • GY, grain yield • H, hybrid • IPCA1 and IPCA2, axes 1 and 2 of the interaction principal component analysis • LSD, least significant difference • N, nitrogen • NUA, nitrogen uptake at anthesis • NUAP, nitrogen uptake between anthesis and physiological maturity • NUT, N utilization • NHI, N harvest index • STONP, stover N at physiological maturity • Z03N1, Z03N2, Z03N3, K03N1, K03N2, K03N3, Z04N1, Z04N2, Z04N3 are abbreviations for experiments coded for location (K—Kenya, Z—Zimbabwe), year (2003 or 2004), and N level (N1—low-N, N2—medium-N, N3—high-N).

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