Why are belowground responses to management and their feedbacks to crops so difficult to predict?

Background/Question/Methods

Responses of belowground processes to management in agroecosystems are highly variable, especially when the crops and soils are not being inundated with exogenous inputs to overwhelm resource limitations. Understanding how combinations of soil physical, chemical, and biological factors interact to influence crops in low-input cropping systems is even more difficult. I will explore how managing belowground processes in agroecosystems for ecosystem services such as N availability to plants for yield, N retention to minimize loss to aquatic ecosystems and the atmosphere, and soil C accumulation to mitigate climate change.

Results/Conclusions

Our ability to predict plant responses to inputs is predictable at coarse levels of resolution in simplified plant communities, but in polycultures these responses are often swamped by species composition, soils, and other management factors. If diversified agroecosystems are to flourish, we will need to understand these complex dynamics mechanistically or find ways to manage for a relatively high degree of uncertainty, especially in the face of more erratic weather patterns. This latter approach has been the focus of grazing management in arid and semi-arid rangelands for over half a century, but has not gained traction in cropping systems.