dc.description.abstract | The restoration of soil health is a crucial step in maximizing productivity in the
historically-eroded Ultisols of the Southeast. The utilization of winter cover crops can
potentially improve soil health by increasing soil organic matter, improving soil structure,
and enhancing nutrient-use efficiency. Studies were established at the Tennessee Valley
Research and Extension Center (TVREC) and Wiregrass Research and Extension Center
(WREC) to examine the impact of cover crop monocultures and mixtures on dynamic
soil health indicators in cotton (Gossypium hirsutum) production systems. Eight
treatments including monocultures and combinations of cereal rye (Secale cereale),
crimson clover (Trifolium incarnatum), and Daikon radish (Raphanus sativus) were
arranged in a randomized complete block design with winter fallow controls. Cover crop
biomass was collected at termination, and soil samples were collected two weeks
following termination. Measured soil health indicators included permanganate oxidizable
carbon (POXC), total carbon (TC), water stable aggregates (WSA), and soil strength
(AUCC.I.). Stratification of TC with depth occurred at TVREC, and TC under crimson
clover, rye-clover, and rye-radish was higher than TC under the winter fallow control. In
both 2018 and 2019, POXC at TVREC was not different between treatments at the 0-5
cm and 5-10 cm depths, while POXC was higher under crimson clover compared to the
rye-crimson clover mixture at 10-15 cm. There were no differences in TC and POXC
between treatments at WREC, but POXC was higher in 2019 than in 2018. WSA values
from both locations were not different between treatments within the same depth class in
both 2018 and 2019. No differences in AUCC.I. occurred between treatments at TVREC,
while the rye monoculture was less compacted than the crimson clover monoculture and
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crimson clover/radish mixture at WREC. Additional years under these cover crop
treatments may be required to detect changes in soil health.
Winter cover crops are also a common tool for integrated weed management in
both conventional and conservation agricultural systems. Two trials were established at
E.V. Smith Research Center in Shorter, AL in November 2016 to evaluate the efficacy of
several cover crop systems as a supplemental form of weed control in cotton production
systems. The first trial consisted of twelve treatments. Cover crops included a rye
monoculture, a mixture of rye, oats (Avena sativa), wheat (Triticum aestivum), crimson
clover, and Daikon radish, and winter fallow. Each cover crop system was evaluated
under four herbicide regimes including PRE only (pendimethalin and fomesafen), POST
only (dicamba fb glyphosate), PRE+POST, and herbicide-free. Amaranthus control was
lower in all herbicide-free treatments compared to all PRE+POST, and cotton lint yield
was lower in the herbicide-free treatments compared to treatments with herbicide
applications. Lint yield was higher in PRE+POST treatments compared to herbicide-free
treatments, regardless of cover crop. Lint yield under PRE only treatments were not
different from PRE+POST while POST only treatments had lower lint yield than
PRE+POST treatments in 2018. The second trial includes rye monocultures as whole-plot
and row-middle only treatments, a clover-radish mixture in the whole plot and within the
cotton row only, and three-species mixtures as whole-plot treatments and with precision
placements; all treatments managed with a PRE+POST herbicide regime. In the cover
crop placement trial, weed control was often similar between treatments in the same year,
and cotton yield was only influenced by year. Results indicate that cover crops alone will
not eliminate the need for chemical weed control. | en_US |