Effect of ridging and intercropping on sorghum productivity in arid and semi-arid lands of eastern Kenya

Soil moisture deficit is a key constraint to sorghum (Sorghum bicolor) productivity in arid and semi-arid lands globally. The objective of this study was to determine the effect of ridging and sorghum-bean intercropping (additive system) on soil moisture conservation and sorghum productivity. Sorghum (gadam) was grown either as a sole crop or intercropped with two bean (Phaseolus vulgaris L.) varieties (KATx56 and KAT B1), under two types of ridging (open ridges and tied ridges), and a control without ridges for two years. The study was set up in split plot arrangement, in a randomised complete block design, at the Kenya Agricultural and Livestock Research Organization, Kiboko, in 2019 and 2020. There was no significant interaction between ridging and intercropping. Soil moisture content increased by 11-26% due to ridging; and decreased by -11 and -7% due to sorghum-KAT B1 and Sorghum-KAT X56 intercropping, respectively. Higher moisture content due to ridging was attributed to formation of basin-like structures, which increased water harvesting and infiltration compared to the no ridges where surface run-off was predominant. The highest moisture content was attained on sole bean, followed by sole sorghum and then sorghum/bean intercropping. The decrease in moisture content in intercrops of sorghum/bean relative to their specific sole crops was attributed to higher crop density, which reduced crop spacing, thus triggering competition for available soil moisture. The highest sorghum grain and equivalent yields were obtained in the ridged plots. Intercropping resulted into decrease in sorghum grain yield, but led to increase in sorghum equivalent yield (SEY) and Land Equivalent Ratio (LER). The results show that both ridging and intercropping are suitable for higher water use efficiency and land productivity in ASALs of Kenya.