Based on 8 years of crop yield measurements (4 years corn
and 4 years soybean) for three tillage systems with and without
cover crops, cover crops did not affect plant populations or crop
yields. However, all three tillage systems with cover crops had
statistically similar SOC levels with the same tillage system
without a cover crop. No soil carbon sequestration (net increase)
occurred over time for any of the tillage treatments with cover
crops when compared with 2000 SOC levels for each treatment.
The NT system seems to have resulted in reduced soil erosion
and maintained more SOC than that in the MP and CP systems
with or without a cover crop. However, on an upland landscape
basis, the MP system with and without cover crops was the only
tillage system to retain more SOC on the upland landscape as a
result of more sediment rich in SOC being retained in the border
and filter strips and sod waterways. Apparently, more humus is
created in the MP system as a result of better mixing of plant
residues into the soil by tillage each year and as a result of the
more SOC-rich sediment being captured in the border and filter
strips and sod waterway. This sediment, rich in SOC, seems to be
retained for many years on the upland landscape as a result of
the conservation practices and not immediately transported to
the streams and returned as methane or carbon dioxide to the
atmosphere. The results of this study should be applicable to
similar root-restricting, sloping, and moderately eroded soils in
Illinois, Indiana, Missouri, and Kentucky