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,
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