Many early adopters of planting cash crops into standing cover crops have succeeded with front-mounted roller-crimpers and planter-mounted roller-crimpers. However, some producers have had less than desirable results, reports Zachary Larson, Penn State Extension agronomist.

One issue involved planting corn into a standing small grain cover. The causes for not rolling may have been letting a fast-growing cover crop get too tall or overconfidence in planting “green” without knowing its limitations. That may be this spring’s scenario.

In 2017, Penn State Extension educators surveyed fields planted green to see what may have been the cause of some of these issues. Here’s a summary of some observations:

• Reduced populations. In the few locations where un-rolled areas could be compared to rolled or bare areas, corn populations were lower in the lower populations were present, which often correspond to a yield reduction. That yield loss could be from shading by emerged seedlings or inconsistent planting conditions due to the cover.

Data from a Somerset County site found that the portion of a field rolled with a cultipacker before planting had higher populations and lower plant-to-plant height differences than the unrolled portion. Plants in unrolled areas appeared more “spindly”; stands were more variable. That variability can negatively impact yield.

• Variable stands. Those plant height differences may lead to intra-plant competition, Larson adds. Smaller plants may strive to compete to the point where they may not make an ear.

• Slugs still a problem. Planting green is thought to be a means of reducing slug pressure as cereal grain cover crops provide an alternate food source for slugs rather than an emerging corn or soybean cash crop, but the results aren’t guaranteed. In 2017, slug damage was variable in planted green fields with sites in Lancaster and Cambria showing slug feeding, with one requiring replanting and having slug damage to the replanted crop.

And the recommendation is…
Larson suggests the following:

1. Plant corn into green only if you can roll. Utilizing a roller-crimper when planting green is likely the best method to guarantee success. Planter-mounted units will likely become the most common method due to ease of use and limited setup time.

However, if you’re looking to dabble in a few acres, using a cultipacker to roll cover is still an option. Just be sure to roll in the direction of planting to reduce hairpinning and wrapping of residue around the planter.

2. If you’re unable to roll cover crops, soybeans may be better when planting into unrolled covers. They can better compensate for reduced populations and inconsistent plant heights.

3. Start simple. If you’re modifying equipment for planting green, simpler is better. Smooth row cleaners are an excellent start. They reduce wrapping and open a seed furrow.

Coulters should be removed if possible to eliminate another potential wrapping point. That also places more weight on row units and rollers.

4. Smooth or shorter spiked closing wheels are a good starting point, especially if guards can be installed to keep residue away from them. Fertilizer applied behind the closing wheels is another practice that works well.

5. Be prepared for the nitrogen penalty. As small grain cover crops mature, the amount of carbon relative to nitrogen increases. That means nitrogen needs to be removed from the soil for residue to decompose. The timing of this can negatively impact the growing cash crop.

Those planting green have seen success in applying 50 pounds of N at planting to promote residue breakdown and provide available nitrogen as the corn begins to grow. Those with frequently manured systems may find that extra nitrogen isn’t necessary. The same is true with legume cover crops.

Source: Penn State Extension