Hideomi Minoshima, Howard Ferris, Louise Jackson, Steve Temple

The soil food web is the community of organisms in the soil that are interdependent for sources of C and energy. The soil food web provides crucial functions for the formation of recalcitrant molecules that are resistant to degradation because it regulates the biological transformations of C in the soil. The activity of organisms at higher trophic levels, and their role in decomposition and incorporation of organic matter can make soil C more stable chemically and structurally, and as a result, C sequestration may be greater, than that of organisms at the entry levels. Agricultural management intensity affects the development of the soil food web. Thus, it is expected that continuous cropping, mulches, reduced tillage, and avoidance of severe water stress are practices that can facilitate continuous feeding of soil organisms, increased structural diversity of the soil food web, and possibly its role in determining C dynamics.

The specific goal of this project is to evaluate the functional impact of soil food web structure, including microbes, nematodes, and earthworms on soil C dynamics (CO2  emission, respiration, and soil organic matter fractions). In particular, we will look at:

• Continuous cropping systems (year-round crop biomass production) vs. fallow (systems that are subject to periodic cropped and non-cropped periods), and
• Conservation tillage (low levels of disturbance) vs. standard tillage (high levels of disturbance)

This research is being conducted at the Long Term Research in Agricultural Systems( LTRAS ) site at the University of California, Davis, where several cropping systems are maintained in a completely randomized design. Field experiments are conducted as well as lab experiments. Our work aims to answer the following question: Do year-round crop rotations with CT (gradual, reliable C inputs from plants, reduced disruption of soil microbial communities by tillage), have more complex food webs and stabilized soil C fractions than fallow rotations with ST? It is expected that the results of this research may provide farmers with information about alternative cropping systems which enhance sustainable farming practice.