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. 

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