Transforming Agriculture, Perennially

Soil and Intercrop Ecology

We are developing an agriculture which, like natural systems, features perennality and diversity. This program investigates how bringing critical soil functions of natural systems into agriculture, such as nutrient retention, carbon sequestration, and soil regeneration, impact diverse perennial agroecosystems.

Land Institute researchers also work to combine complimentary perennial species in intercrops for their ecological benefits. For example, we are currently experimenting with Kernza® and alfalfa bicultures to determine whether nitrogen fixed by the legume alfalfa can eliminate the need for external nitrogen inputs to grow Kernza.

Why Soil Ecology?

  • Perennial crops require far less soil disturbance than annual crops.
  • Perennials invest much more carbon belowground, in the form of roots and root exudates.  When well-fed and left undisturbed, soils become far more functional—they form aggregates which allow water to infiltrate and carbon to be stored.
  • They provide much deeper and richer habitats for soil microbes, and they provide more resources for plant growth.  Each gram of healthy soil contains on the order of a billion microbes, and may of these help crops to defend against disease or obtain nutrients like nitrogen and phosphorus.
  • Perennial roots are very efficient at taking up and using water and nutrients from large soil volumes.
  • Annual plants rarely contribute very much to the productivity of natural ecosystems except following extreme disturbances such as catastrophic fires, floods or landslides. Even in these cases, annuals primarily reduce soil loss following disturbances until perennials can re-establish and begin to re-build soil.

Why Intercrop Ecology?

  • Diversity and perennality are defining features of Earth’s natural ecosystems, from grasslands and forests to deserts and tundra.
  • The growth of some plants is actually facilitated by the presence of others, such as when a grass benefits from the nitrogen fixed by a nearby legume.
  • While they go deep, Kernza’s relatively fine roots take up the majority of water from the topsoil, whereas alfalfa maintains deep, thick taproots that can access moisture deep in the subsoil.  This “partitioning” of the water resource helps these species co-exist.
  • Legumes such as alfalfa host bacteria in their roots that tap atmospheric nitrogen.  When intercropped with a grain like Kernza, the legumes can contribute substantially to the grain’s nitrogen needs.

    Land Institute research technician Madeline DuBois and University of Minnesota graduate student James Bowden take soil samples from a mixed Kernza field. The samples will be studied to determine how much nitrogen has been mineralized in the field, a key to learning how to grow Kernza organically. 

Program Goals

To reduce the non-renewable resources required to produce perennial grains by maximizing ecological intensification. This approach involves:

  • Designing compatible intercrops that rely on different crop rooting strategies to access water and nutrients in different areas of the soil profile.
  • Recognizing and encouraging key groups of microbes to help solve several challenges, such as supplying nitrogen and phosphorus to crops.
  • Reducing reliance on fossil fuels by eliminating jobs that tractors typically perform numerous times a year such as seeding and cultivating fields.

To document and build a nuanced understanding of how diverse perennial grains provide valuable ecosystem services:

  • What factors determine the rates of soil carbon sequestration when annual croplands are converted to diverse perennial crops.
  • The extent to which nutrient runoff and leaching as well as soil erosion are reduced in perennial grain cropping systems.

Program History

In 2012, Tim Crews joined the staff as Director of Research and as a soil ecologist. He conducts research on the soil benefits that occur when annual croplands are converted to perennial grains. His team specifically focuses on biological nitrogen fixation in legume-Kernza intercrops, soil organic matter accumulation under perennial grains, and changes in other indices of soil health.  Crews was instrumental in The Land Institute hosting the “New Roots for Ecological Intensification” meeting in Estes Park, Colorado in 2014, and co-hosting the “Is the Future of Agriculture Perennial” meeting in Lund Sweden in 2019.

Research Collaborators


  • University of Copenhagen, Denmark
  • ISARA University, France
  • The Swedish University of Agricultural Sciences
  • Yunnan University, China


  • Colorado State University
  • The Ohio State University
  • University of Minnesota
  • University of Wisconsin
  • Cornell University, New York
  • University of Michigan
  • Chicago Botanic Garden
  • University of Kansas

Join us by supporting this work with a donation to The Land Institute!


Program Team

Tim Crews
Chief Scientist; Director of Ecological Intensification; Lead Scientist, Soil Ecology Program

Madeline DuBois
Research Technician, Ecology

Eric Cassetta
FFAR Phenomics Selection Technician

Related Content

Why is Soil So Important? A thin layer made up of minerals, organic matter, roots,…

Read More about Case Study 2020: Soil

What got you into this field of work? I became interested in agriculture and horticulture…

Read More about Interview with Tim Crews

Related Scientific Publications

Abstract Cover crop mixtures can provide multiple ecosystem services but provisioning of these services is contingent upon the expression of component species in the mixture. From the same seed mixture,…

Read More

The classic domestication scenario for grains and fruits has been portrayed as the lucky fixation of major-effect “domestication genes.” Characterization of these genes plus recent improvements in generating novel alleles…

Read More
Share On: Share on Facebook Share on Twitter Select other ways to share