Farm Horizons, February 2012

Continuous corn recommendations

By Dave Schwartz
Certified crop advisor,Gold Country Seed

Corn and soybean growers have gradually shifted to more corn acres on their farms for economic reasons. In recent years, corn acres are normally more profitable.

The common corn/soybean rotation has shifted in recent years to more corn/corn/soybeans. As is the case for most crops, corn yields are lower when planted in back to back years rather than in a corn/soybean rotation.

The reasons for this yield loss are not well understood but one of the main culprits may be alleopathy. Alleopathy refers to suppressed growth of plants that is caused by toxic substances released from crop residue. Alfalfa and rye are two crops best known for their alleopathic effect. Researchers typically see a 10 percent yield response for corn and soybeans due to crop rotation, so let’s discuss what can be done to lessen stress in these fields of continuous corn.

The most important point, in my mind, is to use the best ground available on a farm for corn on corn. Marginal ground with clay knolls or sandy loam soils will not tolerate stress as well, it is not good a candidate for continuous corn. I have heard of yield losses of 30 percent or more on this type of soil, so this ground should never be planted into continuous corn. Select ground that has high organic matter that will provide more soil moisture during July and August.

Researchers normally see a nice response to starter fertilizer in these fields because of more crop residue left on the surface, creating a more damp and cool seedbed. Starter fertilizer appears to be making a comeback as we see more continuous corn. This leads me to my next recommendation to use row cleaners. Row cleaners clear off residue above the seed, so soil temperatures are warmer, creating a better environment for germination.

I encourage growers to plant their first corn on soybean ground and wait a few days with their continuous corn. One other item I would consider in continuous corn is to use foliar fungicides at tasselling to help control foliar diseases. You can bet these fields will have more disease pressure, so this is where growers will get the best bang for the buck with foliar fungicides. The last item growers should consider is to use a corn hybrid that has a good root and disease package.

So, the bottom line is to baby these fields as much as possible. Whatever can be done to reduce stress on these fields will soften the yield hit we normally see in continuous corn situations.

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