CONTRIBUTION OF LEGUMINOUS CROPS TO NUTRIENT AVAILABILITY AND PRODUCTIVITY OF YAM BASED SYSTEMS

A trial was conducted at Umudike, Nigeria in 2000/2001 and 2001/2002 to determine the contribution of leguminous cover crops Voandzea subterranea (bambara nut), Arachis hypogea (groundnut) and Cajanus cajan (pigeon pea) to the conservation of soil resource base and productivity of yam minisett based systems. The systems studied were sole yam minisett, yam minisett/bambara nut, yam minisett/groundnut, and yam minisett/pigeon pea. Intercropping yam minisett with either ground nut or bambara nut decreased seed yam yield relative to sole yam minisett. Highest seed yam yields of 4.70 t/ha and 4.67 t/ha were obtained with yam minisett/pigeon pea and sole yam minisett respectively and these were significantly higher (P < 0.05) than 3.41 t/ha and 3.84 t/ha obtained with yam minisett/bambara nut and yam minisett/groundnut respectively. Highest benefit cost ratio of 5.76 was obtained with yam minisett/pigeon pea followed by yam minisett/bambara nut with 2.55, sole yam minisett with 2.11 and lastly by yam minisett/groundnut with 1.78. Intercropping yam minisett with the legumes improved soil organic matter content of the soil resource base and also ensured that large quantities of biomass was left on the soil after crop harvest in form of legume haulms. Largest amount of legume haulm of 4.57 t/ha was obtained with yam minisett/pigeon pea followed by yam minisett/groundnut with 3.94t/ha and yam minisett/bambara nut with 0.54 t/ha. Quantities of nutrients (N,P,K,Ca,Mg) in legume haulms which could be released to a subsequent crop if these haulms are incorporated into the soil were determined. For nitrogen the value was 89.52 kg N/ha in yam minisett/pigeon pea system and 8.66kg N/ha in yam minisett/groundnut system. [Niger Agric. J. 34 (2003): 44-48

The effects of four agrobotanical extracts and three types of bags on the control of insect pests and moulds of stored yam chips

A study was conducted to evaluate the effects of four agrobotanical extracts and three types of storage bags as alternative options to the use of agrochemical insecticides for yam chip storage. Dried yam chips were obtained from Shaki area of Oyo State, Nigeria and treated with extracts from Azadiractha indica (neem) leaf, Xylopia aethiopica(uda) pod, Occimum graticimum (nche anwu) leaf and Zingiber officinale (ginger) stem tuber. The storage bags were 0.05mm gauge polythene bags, 0.05mm gauge polythene-lined-jute bags and jute bags. After 3 or 6 months of storage, chip weight loss was always low at 1-5% with Azadiractha indica, Occimum graticimum, Zingiber officinale compared with the weight loss of 13 to 24% obtained where no agrobotanical was applied. At either 3 or 6 months of storage, insect damage through boring of holes was evident but was significantly higher with no agrobotanical treatment or with X. aethiopica than with the other agrobotanical treatments especially at 6 months of storage. There was little or no mould growth at 3 months of storage while at 6 months, mould growth was rather enhanced by X. aethiopica, Z. officinale and O. gratissimum and b

Response of yam (Dioscorea rotundata Poir.) to various periods of weed interference in an intercropping with maize (Zea mays L.), okra (Abelmoschus esculentus L. Moench), and sweet potato (Ipomoea batatas L. Lam)

Yam was intercropped with maize, okra, and sweet potato and subjected to various periods of weed interference and weed-free regimes. The field trials were conducted for two cropping seasons at the research farm of the National Root Crops Institute, Umudike, Nigeria, 5° 29' N latitude and 7° 32' E on an altitude of 122 m above sea level to determine the critical period of weed interference in yam/maize/okra/sweet potato intercrop; assess the crop yield losses due to uncontrolled associated weeds; and assess the wrong timing of the removal of weeds and the ability of sweet potato to suppress weeds as a planofile in the mixture. The critical period of weed interference in the intercrop was between 3 and 16 weeks after planting (WAP). Weed interference in the mixture reduced yam tuber yield by 35%; maize by 60%; okra, 79%, and sweet potato roots by 80%. Although yam started early to suffer significant weed competition in the mixture 3 WAP; weeds continued to depress yields of yam up to 16 WAP as in sole cropping. There was no significant yield advantage in keeping the mixture weed-free throughout the growing season. Timing appeared to be more crucial in weed removal than the frequency of weeding the mixture. Yam tuber yield was positively and significantly correlated to increased ground coverage by the canopy formed by sweet potato (the planofile). The ability of sweet potato to suppress weeds in the intercrop increased with increase in ground coverage. The early significant weed interference observed in the mixture shortened the period of weed tolerance of the yam component. This suggests that yam is more vulnerable to early weed competition in intercropping than in sole cropping

Projet valorisation de l'igname pour les marchés urbains. Projet financé par le Ministère de la Coopération, référence : 9502111 00 230 75 01. Marché de clientèle n.9200114. Rapport final

L'igname est un aliment très apprécié en Afrique de l'Ouest mais sa consommation sous forme de tubercules frais présente, pour les consommateurs urbains, de fortes contraintes. Celles-ci sont liées aux caractères saisonnier et périssable du produit qui rendent irrégulière sa disponibilité sur les marchés urbains. Avec l'urbanisation, on observe dans certains pays, le développement d'une filière originale de cossettes d'igname. Il s'agit d'un produit stabilisé obtenu à partir de petits tubercules épluchés, précuits et séchés au soleil. Pour mieux estimer l'importance et comprendre le fonctionnement de cette filière encore mal connue, une enquête de consommation sur les produits à base d'igname a été menée en milieu urbain dans trois pays : Bénin, Nigeria, Togo. Les consommateurs expliquent leur consommation de produits dérivés des cossettes par leur qualité gustative, leur constante disponibilité, leur facilité de préparation et leur prix accessibl