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 glaucun (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 NU E for the three crop species on a Psammentic Paleustalf sand at two locatio ns in 1997 and three locations in the 1998 rainy seasons in Niger. Nitrogen use efficiency components were calculated as incremental increases in yiel d per applied N or per plant N. Leaf area index and leaf chlorophyll were d etermined as concomitant data. Among the three cereals, sorghum and millet had greater responses to N (kg grain kg(-1) N) than maize. Nitrogen use eff iciency differed widely among species. Partial factor productivity (kg grai n 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 compar ed 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 mi llet and lowest in maize. Marginally lower NUE for biomass production in pe arl millet was associated with higher biomass yield in non-fertilized treat ments. The ability of pearl millet to extract N from nutrient degraded sand y soils and its better drought tolerance is the primary reason for its adap tation to the Sahel where it produces a moderate although reliable grain yi eld. Although pearl millet tended to have better performance where frequent drought was prevalent, sorghum had higher yields than pearl millet under i mproved N management and thus can significantly contribute to enhancing foo d production in areas where good management is practiced. This study also i ndicated that N deficiency could be detected using a SPAD chlorophyll meter early enough to apply additional N for achieving target yield levels.