September 12, 2003: Chemical-free
no-till is one of the current frontiers of organic farming. No-till
and min-till crop systems’ benefits include improved soil
moisture retention, reduced erosion, higher soil organic matter
levels and, when chemicals are not used, higher microbial diversity.
Sean Clark of Berea College in Kentucky has been carrying out experiments
on spring roll-down of winter cover crops as a substitute for herbicides
before planting spring crops. Clark cut his teeth as a primary researcher
on the rigorously designed and analyzed University of California
Davis long-term crop systems research experiments, which for me
gives this research more significance.
By rolling down the cover crop in spring instead of mowing it,
the cover crop takes longer to decompose and becomes a weed-suppressing
mulch. A common problem is cover crop regrowth which causes competition
with the main crop. Another problem is that the mulching effects
of the rolled-down cover crop may not last long enough to suppress
weeds before the main crop becomes large enough to be suppressive.
There were three treatments:
winter rye cover crop roll-down only, followed by corn;
roll-down with a glyphosate application at corn planting, and
roll-down with glyphosate at corn planting and another herbicide
application one month after planting. The cover crop was rolled
with a rolling stalk chopper when it reached the soft dough stage.
Corn seed was planted with a planter modified for high residues.
The roll-down treatment performed as well as the single herbicide
treatment and only slightly less well than the double herbicide.
Yields of corn grain and net returns per acre were only slightly
higher in the double herbicide treatment than the other two treatments.
The experimenter’s conclusion is that winter rye roll down
can be an effective method of suppressive weeds without chemicals.