Adapting agriculture to climate change - An evaluation of yield potential of maize, sorghum, common bean and pigeon pea varieties in a very cool-wet region of Nayandarua County

Soil and water conservation, use of more adaptive crop genotypes and crop diversification are widely accepted as some of the management practices that can help reduce agriculture vulnerability to impacts of climate change. A study was conducted to evaluate the yield potential of maize, sorghum, common bean and pigeon pea varieties under different water management, plant densities and fertility levels in Nyahururu, Central Kenya. The study involved three experiments. The first experiment evaluated the growth and performance of three varieties (early maturing, medium maturing and late maturing) of maize, sorghum, pigeon pea and common bean. The experimental design was a completely randomized block design (RCBD) replicated three times. The second experiment evaluated maize and sorghum yield response to water conservation and three fertiliser rates (0, 20 and 40 kg N/ha). The third experiment assessed the effect of water conservation measures on crop yields of common bean and pigeon pea grown under three plant densities (low, medium and high). Tied ridge tillage was used as the water conservation measure and disc plough as the control in the second and third experiments. Results showed that water conservation in general did not have a significant effect on crop yield though they were improved. The medium density pigeon pea gave the highest grain (719 kg/ha) followed by low (688 kg/ha) and high plant density (687 kg/ha), though not significant at 0.95 confidence level. Similar trends were observed with common bean grain and dry matter yield. Tied ridges tended to lower maize yield compared to flat tillage while it increased sorghum yields but the difference was insignificant. When average across the tillage systems, the highest maize grain (5553 kg/ha) and dry matter (14298 kg/ha) yield was obtained in plots without N fertilizer. Sorghum dry matter was highest (11333 kg/ha) in plots with 40 kg N/ha and lowest (7903 kg/ha) in plots with 20 kg/ha N. In the variety experiment, the EM pigeon pea variety (ICPL 84091) yielded the greatest grain (881 kg/ha) while the late maturing variety (ICEAP 00040) gave the least (565 kg/ha). The LM maize variety (DK8031) yielded the highest grain (5701 kg/ha) and dry matter (18843 kg/ha). The LM sorghum variety (Macia) had 47% and 49% dry matter yield advantage over MM (Kari Mtama 1) and EM (Gadam) varieties, respectively. The yields for common bean varieties tended to vary with seasons. So what are the conclusions?