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Cover Crops for Watermelons

Hello everyone my name is Kurt Vollmer. I’m a
weed scientist with the University of Delaware and today I’m going to be
showing you some of our watermelon trials for the Northeast IPM Center. In
particular, this trial is looking at how we can utilize cover crops in between
the rows of plastic to suppress weeds and improve soil health. Weed control between
the rows of plastic mulch can be challenging.
Weeds are primarily controlled by herbicides, cultivation, mowing or hand
weeding. However, due to wider row spacing, herbicide treatments may lose efficacy
before vines effectively cover the soil and additional management tactics may be
required. Grass cover crops such as cereal rye, have been shown to provide weed
suppression in agronomic crops such as soybean. However, cover crops are often
planted in the fall giving them plenty of time to grow before summer annual
weeds start to emerge. In this study, we are evaluating whether or not spring
seeded grass cover crops can be integrated with other tactics for weed
management between rows of plastic. Plastic was laid four weeks prior to
transplant and five different cover crops species were hand seeded and raked
in within 24 hours of laying the plastic. In addition, Dual Magnum was
applied two weeks prior to transplant in order to reduce competition with early
emerging weeds. To prevent cover crop interference with watermelon vine growth,
cover crops were terminated with Select Max four or six weeks after transplant.
Annual rye was seeded at 31 pounds per acre and accumulated between 400 and 700
pounds of biomass per acre prior to termination. Cereal rye was seeded at
120 pounds per acre and accumulated 300 to 600 pounds of biomass per acre. Spring barley was seated at 125 pounds
per acre and accumulated 1500 to 1600 pounds of biomass per acre. Spring oats were seated at 138 pounds
per acre and accumulated 2,000 to 3,500 pounds of biomass per acre. Sorghum sudangrass was seeded at 49 pounds per acre and accumulated 200 to 300 pounds of
biomass per acre. By incorporating cover crops with a
pre-plant Dual application all species except sorghum sudangrass reduced early
season weed biomass 90 to 97 percent. However, this tactic alone did not provide
full season control. Weeds that were present at cover crop termination were
able to grow up to harvest. While spring seeded cover crops provided
early season weed management in row middles, further research is being
conducted on how this approach may be incorporated with other weed management
tactics for full season control.

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