November 18, 2012

Should I Consider Cover Crops Next Year?

The practice of planting cover crops.is growing in popularity. There are a variety of reasons to plant cover crops. Cover crops can help:

  • Reduce erosion to protect precious.top soil.
  • Improve soil health by adding organic matter, improving soil structure, and breaking up compaction.
  • Capture unused nitrogen (N) in the fall and make some of the N available to the crop next year.
  • Add available N to the following cash crop as legume cover crops break down.

There are several cover crop choices and it can be overwhelming to know what to plant. In my opinion, you have to prioritize what is imp​ortant. Also, one must decide if frost is expected to kill the cover crop or if it will be killed by herbicides or tillage next spring. In early spring, it is very important to kill cover crops that overwinter, especially during dry years, as they can use a lot of the available water.

Cover crops that can utilize residual N are grasses such as rye and oats. This is shown in Figure 1 as this spring’s anhydrous application can be seen​ in the plant growth. Cover crops that provide an N credit are legumes such as alfalfa, red clover, sweet clover and vetch. The N credit for fall-planted legumes is about 40 lbs N/acre.

cover crops

Radish is a cover crop that can aid in the reduction of soil compaction through its elongated tap root. Radish roots can break through the compaction and crop roots can access water and nutrients through the created channel after they decompose.

green manure nitrogen credits

In addition to timing and planting methods, a few things to consider are: 1) chopping corn silage opens the door for planting cover crops using a drill or planter; and 2) aerial application is the only option if your intention is to have cover crops planted before harvest. It is important to research cover crop options to develop a plan that meets your needs. In the future, cover crops may start to look more attractive, especially if N costs continue to increase. For more information on cover crop options, visit your local USDA-NRCS and Extension offices.

a: Use the upper end of the range for spring seeding green manures that are plowed under the following spring. Use the lower end for fall seeding.

b: If top growth is more than 12 inches before tillage, credit 110-160 lb N/a.

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Sources: Ruark, M., et al. Considerations for cover crops in 2012. Integrated Pest and Crop Management. University of Wisconsin. Laboski, C., J. Peters and L. Bundy. 2006. Nutrient application guidelines for field, vegetable, and fruit crops in Wisconsin. A2809. University of Wisconsin. Green manure nitrogen credits for commonly used legumes in Wisconsin. (Table 9.5 in A2809). http://ipcm.wisc.edu/blog/2012/08/ considerations-for-cover-crops-in-2012/tablegreen- manure-nitrogen-credits-2/

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