Nitrogen Uptake and Utilization in Contrasting Drought- and Striga-Tolerant Tropical Maize Cultivars.

Maize is an important food crop in the Guinea savannas of Nigeria. Despite the high production potential, drought, Striga hermothnica parasitsim, and poor soil fertility particularly nitrogen deficiency limit maize production in these savannas. Breeders at IITA have developed a number of drought and Striga-tolerant cultivars for release and dissemination in the region. Information on the resposne of these cultivars to N fertilization is however not available. This study evalauted grain yield, N uptake, N utilization and NUE of 6 maize cultivars and companred these with widely used variety TZB-SR in two locations in the Guinea savannas of northern Nigeria. Maize grain yield increased with N application. Averaged cross cultivars, grain yield was 76% higher at 30, 156% higher at 60, and 203% higher at 120 kg N ha^-1 than when no N was applied. This suggests that N is a limiting nutrient in the Nigerian savannas. Five drought-tolerant varieties produced consistently higher yields when N was added at all levels. These cultivars had either high N-uptake efficiency or N-utilization efficiency confirming earlier reports that high N-uptake or N-utilization efficiency improves maize grain yield. The study also confirms earlier reports that maize cultivars that are selected for tolerance to drought are also efficient in the uptake and use of N fertilizer. This means that these cultivars can be grown with little application of N fertilizer thereby reducing investment on fertilizers and reduction in environmental pollution.