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Window to establish cover crop closes with more rain…

November 30, 2020

In the last few weeks many including myself have watched with eager anticipation as soybean and corn harvest resumed allowing for cover crop acreage to be planted.

When I first checked into the available growing degree days left in the year, getting a winter grain in the week of November 18th and even in the next 30 days  looked promising under a clear blue south Jersey skyline.

After a year of above average rainfall the delay in harvesting full season and double crop soybeans and corn for grain is well underway. Using a growing degree day (GDD) calculator base 32 degrees Fahrenheit, small grains will germinate and establish given the 60 day forecast for Salem County with an estimated 207 GDD accumulation by November 28 based on forecast; and another 180 plus GDD by December 10. The planting of these grains serves two purposes. A potential grain crop for the 2021 growing season and a cover crop to manage soil moisture, erosion and improve soil health.

The observed values according to Cornell University’s Climate Smart Farming GDD calculator show accumulation of 119 days as of November 15th conducive to germination and growth of small grains if they were planted on November 13th.

Fast forward two weeks and the region is under a tornado, flash flood and wind advisory with a significant amount of wind driven precipitation battering down unharvested crops and saturating field conditions for new crop establishment.

There may still be a window to plant small grain for the purpose of a cover crop if the precipitation stops and wind and sun surface soil moisture evaporation occurs allowing for another 180 growing degree days above 32 degrees. This is the relative amount of days needed for cover crops to germinate and reach tillering before going into vernalization by below freezing temperatures. Cover crops once established will continue to accumulate below ground and above ground biomass through spring when temperatures are above 32 degrees which will assist with drawing down excessive soil moisture and prevent wind and rain driven erosion in fields with no vegetative cover.

To watch a model of your area over time in growing degree days, plug in your location into Cornell University’s Climate Smart Farming Calculator. If the calculator will go beyond October, check the long range forecast for number of days above 32 degrees fahrenheit.