Research was carried out in the field on the effect of intercropping common bean and maize crops in a semi-arid zone of south-east Kenya over two rainy seasons in 1997. The experimental design was a randomised complete block design with eight treatments replicated four times. Significant differences were observed in total plant dry weight by the different treatments in pure stands, 21 days after emergence with higher values under mixed cropping system in common beans. However, at 42 days after emergence, plant dry weights in uninoculated common bean pure stands with N application were significantly higher than under other treatments. Common bean yields were significantly reduced by the maize intercrop. The inoculated common bean and N application treatment recorded the largest seed dry weights and subsequently yields per hectare. These findings suggest that intercropping common beans and maize considerably suppresses the yield of the former under the semi-arid conditions of south-east Kenya. Inoculation of common bean with the commercially available Rhizobium strain 446 on the other hand was effective and improved yields. Soil analysis of the experimental plots before and after one cropping season indicated that common beans increased N slightly or maintained it at the pre-planting levels. This was unlike the pure maize plots where there was a marked decline in soil N. There was however, a marked increase in soil phosphorus in all treatment plots.

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Tissue culturing has become a routine method for propagating plants in high technology laboratories. The cost of production using conventional tissue culture is, however, high for most of the countries in the sub-Saharan Africa. In this study, we evaluated a micropropagating protocol for local banana (Musa spp.) (Muunju landrace) in Kenya as an alternative to reduce the unit cost of tissue culture micropropagation. Matrices were satisfactory and comparable to the gelling agents. Glass beads were, however, the best matrix in shoot multiplication. Use of support matrices, locally available macronutrients, micronutrients, sugar, equipment and facility reduced the cost of consumable material for banana tissue culturing by about 94%. Putting into account energy, labour and capital investments, the cost dropped from approximately US $ 1.5 to 1.0 per plantlet. Contamination was not observed when the media and equipment were sterilised using a pressure cooker instead of an autoclave. Use of plastic syringes instead of glass cylinders and micropipettes, to measure volumes reduced the cost of the equipment by 96%. The risk of damage and loss due to breakage was eliminated compared to the use of glassware equipment. Shoots were rooted when they were transferred to Murashige and Skoog (MS) medium supplemented with 1 mg l -1 napthaleneacetic acid (NAA) or 1 mg l -1 Anatone. Acclimatised plants were successfully transplanted and established in the field. There is potential for use of locally available low cost resources as alternatives to the conventional costly laboratory resources.

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High soil temperatures influence seedling emergence as well as the performance of plant organs and yields. Temperatures of above 403C were recorded in the topsoil of the Ferralsols of the semi-arid areas of SE Kenya during the rainy season. Experiments were conducted in the climatological laboratory of the University of Trier, Germany, on two legumes (green grams and common beans var. kathika), grown by smallholder farmers in the study area under varying soil temperature conditions. The main objective was to examine the effect of soil temperature on various parameters: seedling emergence, crop water requirements, leaf area index and phenology of the two legumes. The simulated climatological laboratory conditions were similar to those at Kiboko, SE Kenya. This study confirmed that under high soil temperature conditions, green grams are well adapted to semi-arid and hot tropical lowlands as well as lower midlands due to low water requirements, high seedling emergence rates and good yield performance. However, kathika beans were very susceptible to the simulated extreme climatic environment. By means of crop simulation modelling, a temporal differentiation for potential growth of green grams is presented for the long and short rains according to different rainfall conditions (ENSO, antiENSO, normal) over a period of 31 years. Academic Press