Code Number: cs02004 ABSTRACT Sorghum (Sorghum bicolor (L.) Moench) is an important crop that is usually grown on the Vertisols of north eastern Nigeria during the dry season. The crop is grown on soils with residual moisture, and thus exposing it to terminal drought stress. Improvement of resource use efficiency and yields is probably possible through the use of appropriate plant densities. Field trials were therefore conducted to study the effects of four plant densities, varying from 2.0 to 12.5 plants m -2 on water and radiation use and performance of two Masakwa sorghum varieties grown on a Vertisol under residual soil moisture conditions. At higher plant densities the locally adapted Nigerian variety, Bulwalana produced higher grain yields than the selection from Cameroun, Bourgouri-28. It also had more efficient water use and better light interception. At low plant densities, Bourgouri-28 yielded higher than Bulwalana. Leaf area index and radiation interception increased with increasing plant density. Stem borer incidence decreased with increasing plant density. More stem borer holes and stem tunnelling were recorded in Bulwalana than in Bourgouri-28. Covered kernel smut [Sporisorium sorghi (Ehrenberg) Link] appeared to be a potentially serious disease of the crop. The study showed that the performance of the crop can be improved through manipulation of plant population and use of early maturing cultivars. pour étudier les effets de quatre densités des plantes, variant entre 2.0 et 12.5 plantes m -2 sur l'utilisation de l'eau, de la radiation et sur la performance de deux variétés de sorgho Masakwa cultivées sous des conditions d'humidité résiduelle. A des densités de plantes élévées, la variété Nigériane localement adaptée, Bulwalana a produit un rendement en grains plus élévé que la sélection du Cameroun, Bougouri-28. Elle avait aussi une utilisation plus efficace de l'eau et une meilleure interception de la radiation. Aux densités basses, Bougouri-28 a eu un rendement plus élévé que celui de Bulwalana. La surface foliaire et l'interception de la radiation ont augmenté avec la densité des plantes. L'incidence des foreurs des tiges a diminué avec l'augmentation des densités des plantes. Un plus grand nombre des trous des foreurs des tiges et des percements des tiges ont été enregistrés sur Bulwalana que sur Bourgouri-28. Le charbon couvert [Sporisorium sorghi (Ehrenberg) Link] apparait comme une maladie potentielle sérieuse de ce sorgho. Cette étude a montré que la performance de ce sorgho peut être améliorée en manipulant la densité des plantes et en utilisant des cultivars adaptés et précoces.

Farmers participation in the process of on-farm research does not only enrich the speed up of information gathering, but also result in large scale adoption of the product of research. A small farmer deals with a variable environment and has multiple production objectives that will affect his or her choice of crops and selection of genotypes. In areas where farmers are unfamiliar with available improved varieties, there is need of conducting effective variety evaluations with farmers. The usefulness of the participatory approach for identifying cultivars for harsh environments, which are difficult to replicate in research stations, has been recognized by the crop breeders. Participatory plant breeding/selection has shown success in identifying more number of preferred varieties by farmers in shorter time (than the conventional system), in accelerating their dissemination and increasing cultivar diversity. This paper describes how plant breeders and farmers worked together to test and selected farmers preferred pearl millet varieties; PE05684 and PE05532 from a diverse pearl millet accessions in a participatory varietal selection program conducted across some states of Northern Nigeria.

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