Monday, November 11, 2013

Update on Organic Research at the University of Missouri Bradford Research Center

The Bradford Research Center employs two research specialists in organic production. Kerry Clark ( works with row crops and Leslie Touzeau ( works with vegetable crops.  Two organizations fund this research, the Ceres Trust and the USDA National Institute of Food and Agriculture. USDA funded research is examining the role of tillage and cover crops in the generation of greenhouse gases in organic systems.  Carbon dioxide is released when soil is tilled and nitrous oxide is released during the breakdown of organic matter. The USDA funds projects that are exploring whether greenhouse gas emissions are affected by organic practices to determine if greenhouse gas sequestration payments might eventually be earned by organic growers. Because we have had two years of drought and nitrous oxide is only released when there is enough soil moisture to support microbial activity, we have so far learned little about nitrous oxide release under organic practices. Carbon dioxide has been found to be released in larger quantities where soil is tilled compared to no-till.

For the greenhouse gas project we are utilizing organic no-till, a practice that was pioneered by the Rodale Institute. After two years of growing corn and soybeans using organic no-till we have determined that it is a system that requires a very high level of management. A grower must be amenable to switching to a tillage system if they do not get adequate cover crop growth in any given year. In 2012 we had good cover crop growth and were able to hold back weeds fairly well using the cover crop mat produced in this system. In 2013 we did not get good cover crop seed germination and did not end up with stands adequate for weed control. We also have not been able to get season-long weed control from a rolled/crimped cover crop mat. We believe that for organic no-till to become widely adopted, researchers need to develop methods and equipment to deal with mid to late season weeds that emerge through the cover crop mat.

After two years of research we have determined that when using organic no-till, improved seed-soil contact may be achieved by planting into the cover crop while it is still standing, then rolling/crimping it after. When planting into the cover crop after it has been rolled/crimped, we discovered that we got better seed-soil contact and improved germination when we removed the front cutting coulters from our no-till planter. For organic no-till, we use a mix of winter annual cover crop species. These include cereal rye, hairy vetch, crimson clover and Austrian winter pea. Cereal rye and hairy vetch have a potential to become weeds in an organic system so care should be taken to prevent them from going to seed.

We have also been looking at summer cover crops that can be grown after wheat instead of double crop beans. The advantage of this is improved weed control and improved soil health and soil carbon levels. We have found that the best summer cover crops at providing weed control are sorghum-sudangrass, sunn hemp and cowpea. The latter two are legumes, so they fix their own nitrogen. Currently we are growing sorghum-sudangrass between our vegetable rows and mowing it on a regular basis. This has done an excellent job of keeping down weeds and adding soil organic matter. The following year we rotate the area of the crop row with the cover crop area and get added nutrient availability from planting into an area with increased organic matter. When sorghum-sudangrass is mowed, it puts on extra root mass to aid in its regrowth. This below-ground organic matter is very important for improving soil health. In crops that vine, we use cowpea or buckwheat between the crop rows because it does not need to be mowed, which would destroy the vining crops.

In our projects funded by the Ceres Trust we are looking at ways to transition from conventional to organic production while reducing weeds and improving soil health. We have also just begun a project that examines soil health in vegetable plots when different weed barriers are used such as fabric, plastic, straw, and crimped cover crops. As we began the switch from conventional to organic in corn, soybean and wheat we found that we had a very high weed flush in year one.

In ground that had been recently in pasture and would be comparable to transitioning CRP to organic, we discovered that perennial weeds rapidly became a problem. In transitioning crop ground, annual weeds are dominant. In plots that are planted to sorghum-sudangrass during the three years of the transition, weed levels are decreasing while all other treatments have increased weed levels. From this experience, we believe that during the three year transition it might be best to plant forage crops or something that benefits from mowing to prevent initial increases in weed pressure when herbicide usage is stopped.

On August 1, 2013 we held the first ever University of Missouri organic field day, which was attended by about 150 growers. We will have a second field day in August 2014 and welcome suggestions for topics and speakers.


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