Potential for developing nitrogen use efficient maize for low input agricultural systems in the moist Savannas of Africa
1997
Kling, J.G. | Oikeh, S.O. | Akintoye, H.A. | Heuberger, H.T. | Horst, W.J.
The moist savannas of Africa have considerable potential for maize production, but soils are generally low in available N. Improved N use efficiency is a key to economically and ecologically sustainable maize production. Studies have been conducted at IITA to determine the potential for breeding maize with greater N use efficiency (grain yield per unit available soil N) and to identify mechanisms of N stress tolerance. Elite populations and hybrids were found to differ in N uptake, utilization and grain yield, but genotype by N interactions (GxN) frequently were not significant. Phenological traits including grain- filling duration and anthesis-silking interval have shown GxN in some environments. GxN interactions for yield and ears plant-1 were detected among S2 families from the TZPB-SR population, indicating the potential for using population improvement methods to develop varieties with specific adaptation to N stress. Combining ability of elite inbred lines was evaluated under low and high N. Crosses involving Tzi lines 25, 34, and 35 performed well under low N. TZi 3 was the best parent under high N. Crosses with TZi 15 were susceptible to N stress. Precise selection criteria related to the mechanisms of N stress tolerance are needed to achieve more rapid progress through breeding. Studies were undertaken to investigate relationships between root morphology and N uptake efficiency and to develop screening techniques for root characteristics. The temporal movement of mineralized N through the soil profile was measured to see if rapid early root growth could increase N uptake. Results suggest that maximum rooting depth may be more critical in the savannas, because substantial quantities of N move out of the root zone around flowering time.
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