Plant density and nitrogen responses of maize hybrids in diverse agroecologies of west and central Africa

Abstract

Maize (Zea mays L.) breeders in the West and Central Africa have developed and commercialized extra-early and early-maturing maize hybrids, which combine high yield potentials with tolerance/resistance to drought, low soil-N and Striga infestation. Hybrids of both maturity groups have not been investigated for tolerance to high plant density and N application and are new to the farmers; thus, the urgent need to recommend appropriate agronomic practices for these hybrids. We investigated the responses of four hybrids, belonging to the extra-early and early-maturity groups, to three plant densities and three N rates in five locations of different agroecologies. The early-maturing hybrids consistently out-yielded the extra-early maturing hybrids in all the five agroecologies. The hybrids showed no response to N-fertilizer application above 90 kg ha−1. All interactions involving N had no significant effect on grain yield and other measured agronomic traits except in few cases. The extra-early and early-maturing hybrids had similar response to plant density; their grain yield decreased as density increased. Contrarily, flowering was delayed and expression of some other agronomic traits such as plant and ear aspects were negatively impacted by increased density. Optimal yield for hybrids of both maturity groups was obtained at approximately 90 kg N ha−1 and 66,666 plants ha−1. Most of the measured traits indicated high repeatability estimates across the N levels, densities and environments. Evidently, the hybrids were intolerant of elevated density. It therefore, becomes necessary to improve maize germplasms for high plant density tolerance in the region.