**4. Conclusion**

*Environmental Issues and Sustainable Development*

Change Model (GCM) used.

**3.2 Pigeonpea yields**

duration pigeonpea intercrops, respectively, by 2050. Maize yields under maize/long duration pigeonpea intercrop will declined by 16%. However, maize yields will increase by 18, 13, and 4% under maize/short duration pigeonpea, maize/medium duration pigeonpea and maize/long duration pigeonpea intercrops, respectively, in the far future (2100). Because of these conflicting results, it is difficult to generalize the impacts of climate change on maize yields from maize/pigeonpea intercrops in Katumani and similar areas in the country. Further simulations involving many GCM model X scenario combinations are therefore required to establish the correct direction of change in maize yields under these systems, whether they will increase or decrease. Meanwhile, the results corroborate observation by Herrero et al. [20] that climate change impacts on maize yields depend on the emission scenario, crop model and the Global Climate

Long-term yields of pigeonpea under variable and changing climate in Katumani are presented in **Figure 2**. Unlike maize, both CSIRO and CNRM models predicted decreased pigeonpea yields in Katumani in the near and far future. Yields from sole pigeonpea crop will decline by 10–20% and 4–9% under CSIRO and CNRM models, respectively, by 2100. Intercropping short and medium duration pigeonpea varieties with maize will reduce pigeonpea yields by 60–80% and 70–90% under the CSIRO and CNRM model, respectively. However, long duration varieties will yield highest under the two Global Climate Change Models (GCMs) irrespective of the cropping system, but the yields will be much lower than the potential yield of over 2 t ha−1 obtained from research experiments and large-scale commercial farms in the region. The decline in pigeonpea yields could be attributed to the projected 2°C and 11% increase in temperature and rainfall, respectively. Pigeonpea is a Carbon-3 (C3) plant and is highly sensitive to waterlogging; therefore, existing pigeonpea varieties may not thrive in the predicted hotter and wetter conditions [59, 60]. High temperatures reduce the rate of photosynthesis in legumes due to their C3 photosynthesis cycle leading to low yields [61, 62]. Waterlogging blocks oxygen supply to roots which hamper permeability [63], delays flowering and reduces vegetative growth, photosynthetic rate, biomass and grain yield in pigeonpea [64, 65]. Short duration

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**Figure 2.**

*Projected pigeonpea yields for Katumani in the near and far future.*

Prospects for growing maize in Katumani are high both in the near (2050) and far (2100) future. However, pigeonpea production will be negatively affected by climate change going forward due to pigeonpea's susceptibility to high temperatures and waterlogging. Therefore, farmers in the ASALs need to rethink their dependence on pigeonpea while national plant breeding programs need to start developing heat and waterlogging-tolerant varieties to help thousands of resource-poor households in ASALs to adapt to climate change and protect the huge pigeonpea export market that Kenya currently enjoys.
