Some factors affecting soybean viability and emergence in the lowland tropics

Seed viability and emergence is one of the most important problems affecting soybean production in West Africa. Results from the multi-location yield trials indicated that introduced cultivars such as Bossier, Jupiter and Improved Pelican showed excellent adaptation and high yields provided seedling emergence was high and plant population was optimum. Diseases and insects are as yet not a major problem. An integrated approach on soybean emergence problem has been carried out by the IITA physiologist, agronomist and soybean breeder to identify factors affecting soybean viability and emergence, and to find a practical solution for this problem. Results obtained so far indicated that poor germination was observed in some cultivars right from the time they were harvested. After harvest, factors such as seed quality, method of threshing, temperature during drying, length and method of storage could also lower the viability of soybean seeds; their effects were more pronounced in some cultivars than in others. At planting, sowing depth I soil temperature and soil moisture were found to influence seedling emergence. Soil temperature up to 42 C during rainy season at Ibadan, Nigeria has been recorded, and 2 hours of 42C soil temperature was found to reduce hypocotyl extension by more than 70% in soybean. Seed dressing with a fungicide, sowing depth between 2.5 - 5 cm, adequate soil moisture at planting and mulching are all beneficial in improving seedling emergence. The present efforts are being concentrated on developing suitable screening methods for high seed quality and Viability, and ability to tolerate high soil temperatures during emergence

Cowpea as an intercrop under cereals

Meeting: Symposium on Intercropping for Semi-Arid Areas, 10-12 May 1976, Morogoro, TZIn IDL-196

The Effect of Mixture Proportions and Fertilizer Nitrogen on Morphology, Insect Pest Damage, Competition and Yield Advantages in a Maize/Bean Intercrop

A field experiment was conducted at Cornell University, New York, USA during 1990 and 1991 growing seasons to determine the effect of the proportions of beans and maize and of nitrogen on insect pest damage, morphology, competition and yield advantages of the two crops grown in mixtures. Inter- cropping reduced the incidence of Japanese beetles (Popillia japanica) and Mexican bean beetles (Epilachna varivestis Mulcant) compared to sole beans. Both bean beetles decreased with decrease in bean proportion in the mixtures. Sole maize tasseled and matured earlier than intercropped maize in both years. Nitrogen application resulted in earlier maize tasseling. Bean vegetative growth was greater and maturity delayed the higher the nitrogen rates. Competitiveness of either maize or beans increased with decrease in crop proportions and maize competitiveness increased with increasing N level. Land Equivalent Ratios (LERs) were greater for intercropping than for sole cropping in both years. LERs were also higher without N application suggesting better utilisation of soil nutrients by intercrops.Un champ experimental etait conduit a l'Universite de Cornell, New York aux Etats Unis au cours de 2 saisons culturales en 1990 et 1991 pour determiner l'effet des proportions de haricot et de mais et de l'azote sur l'attaque des insectes, la morphologie, la competition et les avantages en rendement de 2 cultures plantees en association. La culture mixte reduisait l'incidence de coleopteres "Japanese beetles" (Popillia japanica) et de coleopteres d'haricot "Mexican" (Epilachna varivestis Mulcant) comparee au haricot en monoculture. Les deux insectes decroissaient avec la reduction de l'haricot dans la culture mixte. Le mais plante en monoculture fleurissait et arrivait plus tot en maturite que le mays en culture mixte au cours de 2annees. L'application de l'azote entrainait une floraison precoce du mais. La croissance vegetative de haricot etait plus grande et la maturite etait retardee par les taux d'azote tres eleves. La competitivite de mais ou de l'haricot croissait ou decroissait selon les proportions culturales tandis que la competitivite de mais croissait avec le niveau d'azote. Les rapports d'utilisation de la terre ou Land Equivalent Ratios (LERs) etaient plus grands pour la culture mixte que pour la culture pure dans les 2 saisons. Les LERs etaient egalement plus grands, en absence d'application d'azote, ce qui suggere la meilleure utilisation des nutriments du sol par la culture mixte