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8 cover crop tips for a cool spring

A year ago, farmers around the nation were already in the field planting the 2012 corn crop. But, soil temperatures from the western Corn Belt to the northeast have yet to crack the critical 50-degree mark, so in a lot of areas, a planter wheel has yet to turn.

There's another element to this year's unique equation if cover crops are part of your crop rotation. If you're itching to get into the field to get those cover crops knocked down so you can get to planting, you might want to hold off a bit; killing those plants before they have begun to grow can nullify the benefits for which they were added to the rotation in the first place.

"Don’t get too eager to kill those cover crops this spring until they are actively growing and hopefully have contributed some benefit to soil quality and the subsequent cash crop," says Pennsylvania State University weed scientist William Curran. He recommends the following tips to handle cover crops this spring when time could potentially be tight:

  • Herbicide rate: most glyphosate labels recommend increasing the rate of product as the cereal grain and weeds mature. This is just as important under cool-cloudy conditions like we have been experiencing. With Gramoxone, use the 3 pt rate and remember that it is better on smaller cereals or after they have reached the boot stage -- during the period of rapid culm elongation it is less effective.
  • Include appropriate adjuvants in the spray tank -- include 1 to 2 qt/100 gal nonionic surfactant (unless fully loaded formulation) plus 8.5 to 17 lb/100 gal AMS or equivalent with glyphosate. The AMS helps alleviate hard water problems and also can reduce antagonism if tank-mixing with other herbicides such as 2,4-D.  Be sure to add the AMS first to the spray tank and agitate before adding the glyphosate.
  • Use a clean water source that does not contain soil or other sediment that can reduce glyphosate or Gramoxone activity.
  • Use flat fan nozzle tips that produce a uniform spray pattern and thorough coverage.
  • Spray in sufficient carrier to achieve good coverage (usually between 10 and 30 GPA).
  • Make sure the sprayer is accurately calibrated (output, pressure, pattern, speed, etc.) to deliver the appropriate rate uniformly.
  • Air temperature can influence control before, during, and after application. Cold nights (<40 F) will reduce activity, particularly for glyphosate, and especially when followed by cool (<55 F) cloudy days.
  • The more time between application and rainfall the better, especially with difficult to control perennials.
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