Controls on carbon and nitrogen cycling in various cropping systems

Our research focuses on elucidating linkages between soil microorganisms, soil organic carbon (SOC) dynamics and nitrogen (N) cycling. Soil store the largest fraction of terrestrial organic C and act as a nutrient reservoir. A healthy soil has many facets but can be broadly defined as a soil that supports plant and animal health and productivity, while promoting air and water quality. Soil health is a very generic phrase encompassing a wide variety of valuable soil services provided by microorganisms as mediated by soil physical and chemical properties. We focus specifically on one aspect of a healthy soil, efficient N cycling. A healthy soil, which contains a diverse and active microbial community, will promote internal N cycling and provisioning through the reduction of N losses via nitrate leaching and gas efflux. Nitrogen balances in agricultural systems are generally positive, with more N going into the system than is removed via harvest. This means there is excess N, with potentially considerable N losses to the environment as well as financial losses to farmers in N amendment costs. Importantly, the status of SOC stocks and organic matter inputs coupled with N fertilizer additions can determine N transformations and losses.

Whether applied in organic or inorganic form and regardless of when the N amendment is applied, ultimately, the availability of N to plants is controlled by soil microorganisms that mediate transformations of that N into plant usable forms or forms easily lost (NO3 and N2O or N2) from the system . While this coupling of above- and below- ground biological N-cycling processes is well known, the direct impacts of microbial N transformations on plant productivity are poorly understood.

We want to better understand how SOC and N cycling dynamics are coupled in row crop systems. We are particularly interested in soil health building management practices such as increasing cropping system diversity through the addition of rotational crops, cover crops or intercrops. These avenues of research are critical in the context of soil sustainability and productivity in support of food crop production in Michigan, the U.S. and the world.