Nitrogen fertilizer response and use efficiency for three cereal crops in Niger

Nitrogen (N) is one of the most limiting nutrients for cereal production in many areas of west Africa such as Niger. One of the strategies to improve yields is to choose crops with high N use efficiency (NUE) that can produce economic yield under limited water supply. Little information is available on comparative performance of pearl millet [Pennisetum glaucum (L.) R. Br.], sorghum [Sorghum bicolor (L.) Moench], and maize (Zea mays L.) for their NUE. A field experiment was conducted to evaluate several components of NUE for the three crop species on a Psammentic Paleustalf sand at two locations in 1997 and three locations in the 1998 rainy seasons in Niger. Nitrogen use efficiency components were calculated as incremental increases in yield per applied N or per plant N. Leaf area index and leaf chlorophyll were determined as concomitant data. Among the three cereals, sorghum and millet had greater responses to N (kg grain kg(-1) N) than maize. Nitrogen use efficiency differed widely among species. Partial factor productivity (kg grain kg(-1) N applied) was higher in sorghum and pearl millet than maize over three sites in two years and declined with increasing N levels. Agronomic NUE (delta grain weight kg(-1) N applied) was also higher in sorghum compared to pearl millet and maize over all N rates. Nitrogen recovery efficiency (delta grain weight kg(-1) N applied) was higher in sorghum followed by millet and lowest in maize. Marginally lower NUE for biomass production in pearl millet was associated with higher biomass yield in non-fertilized treatments. The ability of pearl millet to extract N from nutrient degraded sandy soils and its better drought tolerance is the primary reason for its adaptation to the Sahel where it produces a moderate although reliable grain yield. Although pearl millet tended to have better performance where frequent drought was prevalent, sorghum had higher yields than pearl millet under improved N management and thus can significantly contribute to enhancing food production in areas where good management is practiced. This study also indicated that N deficiency could be detected using a SPAD chlorophyll meter early enough to apply additional N for achieving target yield levels.