Effects of Intercrop Population Density and Row Orientation on Growth and Yields of Sorghum - Cowpea Cropping Systems in Semi Arid Rongai, Kenya

Sorghum - cowpea intercropping is an important farming system for small scale farmers in Arid and Semi Arid Lands of sub-Sahara African. Information on the cowpea intercrop population and row orientation effects on growth and yields of sorghum-cowpea cropping systems is however scanty or unavailable for tropical Africa and East African region in particular.With this in mind, a factorial designed experiments was carried out at a farmer’s field at Kampi ya Moto, Rongi, Kenya in two seasons i.e. December 2011 - April 2012 Season I (SI) and May-August 2012 Season II (SII). The treatments comprised of sorghum planted at a constant population of 55 555 plants/ha and intercropped with cowpea at varying populations of 55 555, 111 111, and 166 666 plants/hectare and rows oriented in East-West (E-W) and North-South (N-S) directions, respectively replicated three times. Results showed that increase of cowpea (intercrop) population from 55 555 to 166 666 plants/ha significantly (P ? 0.05) influenced crops growth, grain and yields attributes of both crops. However, there was no significant effect on harvest indices. Intercrop population (cowpea) of 111 111 plants/ha produced the highest cowpea grain yields of 214 and 632 kg/ha in season I and season II, respectively. The highest sorghum grain yields of 2 729 kg/ha and 3 011 kg/ha) were recorded in sole sorghum. The lowest sorghum and cowpea grain yields of 1 994.3 and 147.8 kg/ha were produced by the highest intercrop cropping system population of 166 666 cowpea plants/ha. The E-W row oriented cropping systems produced significantly higher cowpea grain yields ranging from 408 to 973 kg/ha compared to 333 to 838 kg/ha recorded under N-S row orientation. The N-S row orientation however, produced significantly higher sorghum grain yields of 1 874 and 2 123kg/ha from the sole sorghum cropping system in seasons I & II, respectively. It is recommended that farmers in semi-arid Rongai should intercrop sorghum at 55 555 plants/ha with cowpea at 55 555 during the short rainy season of SI (Oct - Dec) and at 111 111 plants/ha during the long rainy SII (May - Aug), season, with rows oriented in the E-W direction, in order to realize over 400 kg/ha cowpea and 2 000 kg/ha sorghum grains yields. The higher cowpea intercrop population of 111 111 plants/ha should be used in wetter seasons of semi arid climates.