Enhancing crop productivity requires climate-smart agroforestry systems to reduce adverse weather conditions and to enhance soil nutrient fertility in the semi-arid regions. This research was carried out at the Melkassa long-term experimental site between July 2018 and February 2019. The main objective of this research was to investigate tree water use, gas exchange, and nutrient content of A. nilotica and C. africana litter to evaluate the impact on the accompanying crops. Three trees were selected from each tree species. There was a temporal variation in carbon dioxide assimilation rate between C. africana and A. nilotica. A strong correlation coefficient was observed between WUE and the carbon dioxide assimilation rate of both trees compared to other physiological measurements. Leaf water potential and sap volume of both trees declined during the dry periods. Both leaf nitrogen and phosphorous contents recorded in A. nilotica were higher compared to C. africana . However, the SPAD value measured in C. africana was significantly higher during the onset of the main rainy seasons compared to A. nilotica. The differences in WUE and carbon flux of trees are mainly dependent on environmental factors. A. nilotica demonstrated higher nitrogen contribution and more stable WUE under drought conditions, suggesting its suitability for semi-arid intercropping systems. Thus, integration of trees known for high water use efficiency and quality nutrient deposition has paramount importance to enhance crop productivity in semi-arid environments where soil fertility is slow and intermittent rainfall is most prevalent.
Assefa et al. (Thu,) studied this question.