The effect of different Maize/Sorghum mixtures on grain yield in three plant population densities in Western Kenya

Abstract

The effect of maize/sorghum mixtures and their pure stands on grain yields were examined at three population levels and two locations, at Mbita Point Field Station and Homabay FTTC in Western Kenya in 1981 and 1982. The mixtures studied were 30:70, 40:60, 50:50, 60:40 and 70:30 of maize, sorghum proportions, respectively. The optimum plant population densities (OPD) were 44,444 plant/ha for maize and 111,111 plants/ha for sorghum. The high and the low population densities were 25% above and 25% below the optimum plant populations in each crop respectively. The component crops in the mixtures were planted in alternate rows of 90 cm between the rows of each species and within row spacings were varied according to the difference plant populations densities. There were significant differences between intercrop treatments and their sole crops. However, there was no significant differences between the trhee population levels. The highest maize sole yields were obtained at the high plant population densities (HPD) and the lowest yields at the lowest plant populations densities (LPD). In the case of sole sorghum, the lowest yields were obtained at the LPD but the highest were obtained at the LPD. The difference between these two extreme yields in sorghum was very little. It is suggested that LPD’s were able to compensate by the greater number of productive tillers due to wider spacing within the rows. With regard to intercrops; maize yields increased with increase in the maize proportion in the intercrop mixture. However, sorghum showed very small changes in yield as its proportion in the mixture was varied. This can again be attributed to its greater tillering and longer panical lengths at the low sorghum proportion levels in the intercrop-mixtures. The total grain yield production from both crops increased as the maize proportion in the mixture was increased significantly. Therefore, the best intercrop combination was found to be 70 maize: 30 sorghum ratio. Mixed cropping gave significantly higher gross returns than sole cropping. Like maize yields, these cross returns were found to increase with increase in maize proportion in the intercrop mixture. This is attributed to higher maize yields and higher market prices. The highest returns were also obtained at the high plant population densities. The 70 maize: 30 sorghum intercrop combination gave the highest gross returns. When land equivalent ratios were calculated it was found that intercropping had significantly yield advantage of up to 82%. However, 1982, long rains experiment at Mbita Point Field station gave no yield advantages except in only one treatment. There were more sorghum shootfly infestation in sorghum sole crops than in the intercrops. However, there were no differences in stem borer infestation in both species. It can be concluded, therefore, that plant population levels grain yields of both crops whether grown sole or mixed. Intercropping gives yield advantages and high gross returns than sole cropping