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University College Dublin (1994)

Studies on maize-bean mixtures in a semi arid area of eastern Kenya

Kimani, K.S

Titre : Studies on maize-bean mixtures in a semi arid area of eastern Kenya

Auteur : Kimani, K.S

Université de soutenance : University College Dublin

Grade : Doctor of Philosophy (PhD) 1994

Résumé

Studies were conducted from 1990 to 1992 in a semi-arid region of East Africa on maize (Zea mays L.) and bean (Phaseolus vulgaris L.) grown both in monocultures and in mixtures. The grain yields realised ranged from 0.7 to 2 t ha-1 in maize and from 0.4 to 1.4 t ha-1 in beans. These yields were less than 30% of the potential yield of plants grown in semi-humid regions. Intercropping reduced grain yield by 35% and 50% in maize and beans respectively. The Land Equivalent Ratios (LER’s) were in all cases greater than 1 but showed statistical significance only under increased water supply, suggesting the lack of any benefit in growing the two crops as polycultures under rainfed conditions in dry areas. Plants in monocultures had similar nitrogen contents with those in mixtures, indicating that the mixtures removed greater amounts of soil nitrogen than monocultures. Maize had significantly greater (p 0.05) photosynthetic rates than the bean, and this was correlated with greater leaf areas and higher biomass and grain yield. Water use efficiency and nitrogen use efficiency was always higher in maize than in bean. Both the increased water supply and intercropping had no effect on soil moisture contents as measured by a neutron probe. Bean nodulation was poor and variable, under field conditions, and there was no response to inoculation with recommended Rhizobium. The poor nodulation was neither a property of the soil nor the high soil temperatures but more a response to the low soil moisture content

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