Growing Knowledge

Read the latest insights from our experts as they cover agronomy issues that matter most to you and your operation.

Nutrient Management With Cover Crops

Mark Glady
Regional Agronomist
Depending on your geography, planting a cover crop for nutrient and erosion benefits can make a lot of sense. Nutrient management can be tricky, however. Here are some factors to consider to determine if growing a cover crop is practical for you.
 
1.  You have some acres in sugar beets or small grains.
If you have harvested your sugar beets or wheat, barley, durum or another small-grain crop and have open soil in September and October, a cover crop can keep soil from blowing around and soak up residual soil nutrients. That cover crop can also sequester nitrate from nitrogen that’s left in the soil, using that nitrate to increase the cover crop’s biomass and keeping it from leaching into tile lines, drainage ditches, lakes, streams and rivers. When that cover crop disintegrates the following growing season, it releases nutrients for that year’s crop.
 
2. You want to seed your cash and cover crops in the same field (just not at the same time).
In one of our Answer Plot® test plots this year, we planted corn and then seeded a cover crop over top of it on the same day the corn was planted. In the plot next to that, we planted corn without a cover crop. The corn grown along with a cover crop was extremely nitrogen deficient when we soil sampled on August 2 (about 25 pounds of N in the soil) compared to the plot without the cover crop (about 90 pounds of N in the soil). The cover crop was obviously in competition with the cash crop grown for grain.
 
It’s important to know that cover crops do not magically take nitrogen out of the air and give it to the cash crop. It’s not until that cover crop disintegrates and decomposes — what we call mineralization — that it releases nutrients to the crop that follows it. So you won’t get a fertilizer credit from a cover crop until the following year. If you want to plant corn and a cover crop on the same acres, a better plan is to wait until later in the season to do so.
 
3. You want to minimize soil erosion.
In my state of Minnesota, the ground is very bare and black following sugar beet harvest, as opposed to corn harvest, which leaves residue on the soil. Planting a grass species with a fibrous root system (such as ryegrass) as opposed to a broadleaf with a taproot (such as tillage radish) as a cover crop is a better management decision. Fibrous root systems are much better at holding soil in place. Particularly on highly erodible ground on steep slopes and on flat stretches where wind erosion is likely, planting a grass species as a cover crop can be a good environmental, as well as economic, decision.
 
Talk with your agronomist and attend an Answer Plot® event this fall to find out more about cover crops and if they might be a good addition to your management strategy. 

Coping With Dry Conditions

Al Bertelsen
WinField agronomist

Despite our best efforts in field preparation, pest control, crop nutrient management and other key management steps, without the right amount of moisture at key growth stages, crops cannot reach their full yield potential. This season, some areas of the Midwest have been blessed with timely rains, while other areas, such as western South Dakota and parts of Montana, have been excessively dry.
 
To determine the overall effects of drought on crop production, we need to examine the crop’s growth stage when faced with water stress.

  • In corn, while water is most critical during pollination, a lack of sufficient moisture during any growth stage will affect yield to some extent. For example, during R4 (dough stage), a lack of moisture can reduce kernel dry weight and also cause premature black layer formation. 
  • If your corn or soybean fields are among those struggling with drought stress, it’s extremely important to be out in your fields checking crop conditions. It’s especially vital to watch for insect activity, since pests such as grasshoppers tend to thrive when it’s dry and can cause severe crop damage. When insects are detected, each field should be evaluated to determine if pest levels meet your area’s recommended economic threshold for treatment. Weighing treatment options, along with the weather outlook for the coming weeks, will help you determine if an insecticide treatment is a wise course of action. When selecting an insecticide for use later in the season, be sure to check product labels for preharvest treatment intervals.
  • Corn silage growers facing dry conditions also should check crops for nitrate levels as harvest approaches. Before cutting the crop, check a few sample stalks throughout the field and have a nitrate test run. If nitrate levels are elevated, one course of action to lower nitrates in the silage is to cut silage higher than normal at 12 inches, since nitrates are concentrated in the bottom of the stalk. Ensiling will reduce nitrate levels, but samples should be taken after ensiling to determine what is a safe amount to feed in a ration.
Contact your WinField retailer for more drought management strategies.

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