The Bradford Research Center employs two research
specialists in organic production. Kerry Clark (clarkk@missouri.edu) works with
row crops and Leslie Touzeau (touzeaul@missouri.edu) 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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