African Green Revolution interventions and the functional diversity of soil microbial communities

Background/Question/Methods

Soil microbial communities are known to dominate most biogeochemical processes. These processes—and thus the diversity and composition of the microbial communities that drive them—are essential for the functioning of ecosystems, both in natural and managed, agricultural settings. Efforts to feed growing human populations have led to the extension of mineral fertilizers and hybrid seed varieties in previously unused quantities. Little is known about the impacts of these efforts to increase food production on ecosystems. Particularly little is known about their impacts on soil microbial communities, which dominate most biogeochemical processes; even less is known about their impacts in the tropics, where most smallholder farmers reside. We collected soil from experimental plots and actively managed farms in western Kenya to assess the impact of agricultural intensification on soil microbial communities in sub-Saharan Africa. 

Results/Conclusions

We find that the functional diversity of soil microbial communities follows a hump-shaped relationship with fertilizer applications in experimental plots. On actively managed smallholder farms, microbial diversity is not significantly different between high- and low-fertilizer farms; however, farms that annually plant fast growing leguminous species during the short rains have significantly higher functional diversity than the other farms. Our results suggest that although nitrogen- and phosphorous-based fertilizer addition impact microbial functional diversity, the presence of plant taxa with particular functional traits can play an important role in determining the functional diversity of belowground communities. These results further imply that efforts to increase crop yields for smallholder farmers can enhance microbial diversity in the presence of land-sharing strategies, such as agroforestry.