Iowa State University - Marsden Research Farm - Cropping Systems Experiment with Dr. Matt Liebman - Tuesday, May 20th, 2014

Dr. Matt Liebman discusses the cropping systems trial at the Marsden Research Farm.

Today, we visited the Iowa State University Marsden Research Farm to meet with Dr. Matt Liebman. Dr. Liebman is ISU's Henry A. Wallace Endowed Chair for Sustainable Agriculture.

We visited a set of long-term experimental plots where diversified and conventional crop rotation systems are being compared in terms of yield, profitability, soil function and environmental quality. Much of Dr. Liebman's research pertains to weed ecology and management in agricultural system, but the long-term plots have been evaluated from numerous perspectives and are ripe with potential for future research.

Three different rotations are being compared:

• corn - soybean (conventional; 2 year)
• corn - soybean - spring oat/red clover (3 year)
• corn - soybean - spring oat/red clover - alfalfa (4 year)

The corn-bean rotation is a typical rotation found on Iowa's farms. In the three year rotation, the oats are harvested for their grain and the clover residue is incorporated by tillage. Clover, like soybeans, is a legume which means it can form an association with soil bacteria that fix atmospheric nitrogen into plant available forms. Incorporation of the clover residue increases the amount of nitrogen in the soil that can later be released to support the corn crop. Alfalfa, a perennial legume, is added to the 4 year rotation and it is an excellent livestock feed. It is cut once in the first year after it is seeded. In subsequent years, it can be cut four to five times to produce a nutritious, high value feed.

Second year alfalfa in foreground and soon-to-be soybeans in the background.

Dr. Guillard discusses the oat-clover portion of the rotation with Joe while
Dr. Liebman speaks with Dr. Morris and Andrew.

Close-up view of spring oats and red clover phase of rotation.

-Andrew