Effects of bean planting density and planting time on growth and yields of maize and beans in an . intercropping system
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Intercropping is a farming practice that has recently received attention from agronomists as a means of improving land use efficiency. This study was conducted to determine whether manipulating bean density and planting time could have any effects on the growth and final yield of intercropped maize and beans. The effects of bean density and planting time on bean nodulation, soil nitrogen levels, growth and final yields of maize and beans under intercropping system was investigated at the University of Nairobi, Kabete campus field station, on reddish brown nitosol clay. Increasing bean density increased bean height but lowered bean biomass significantly during both seasons. Increasing bean density to three or more plants per hill significantly reduced bean nodulation. Planting beans two weeks after maize increased nodulation significantly. There was high nitrogen levels in the soil at flowering time in treatments where beans were planted two weeks before maize as compared to where beans were planted two or four weeks after maize. Increasing bean density increased bean yields. There was an increase of 116% and 126% in bean yields in treatments having four bean plants per hill compared xiv to those treatments having one bean plant per hill, during the 1993/94 and 1994/95 seasons respectively. The treatments having four bean plants per hill also had the highest land equivalent ratio (LER) of 1.3 in season one and 1.6 in season two. High LER of 1.3 in season one and 1.7 in season two were also obtained in treatments where beans were planted two weeks before maize. Results during the 1993/94 and 1994/95 seasons showed that bean planting density and time significantly affected the general development of both maize and beans. However, the two factors did not significantly affect the final yields of maize, though that of bean was significantly affected. During the 1993/94 season, beans planted two weeks before maize had the highest yield (1134.4 kgs/ha), compared to treatments where beans were planted at the same time with maize (784.4 kg/ha), two weeks after maize (723.3 kg/ha) and four weeks after maize (402.9 kg/ha) respectively. Beans planted four weeks after maize had the lowest yields. The trend was similar during the 1994/95 season. From the results it shows that it is more advantageous to plant beans before maize in order to obtain higher bean yields. Upto four bean plants per maize plant can be planted to achieve higher bean yields without affecting maize yield.