The current low prices of grain crops are adding to planting decision challenges in 2016. Reduced prices for corn, wheat, and soybeans, the three crops most commonly grown in South Dakota, will make it more important than ever for producers to use best management techniques to reduce risk and production costs. One tactic that can provide numerous benefits is to have diversity in the crop rotation. Using rotations with both warm and cool season, grass and broadleaf crop types will increase diversity.
Benefits of Rotational Diversity
Many producers in South Dakota have reduced rotational diversity over the last few decades due to market and policy forces. The availability of technologically advanced inputs, such as round-up ready crops, has mitigated the increased pest pressure that resulted from this approach. Low commodity prices coupled with the development of pest biotypes resistant to many of the frequently used products makes staying the low-diversity course less attractive. Especially troublesome are crop production practices that include only two species with the same life cycle such as both warm-season crops or both cool-season crops. One year away from a crop is often not enough of a break to reduce pest issues. Research done in South Dakota and Colorado by Dr. Randy Anderson, USDA Weed Ecologist, has shown that if producers can rotate out of a crop or crop type (i.e. warm season vs. cool season) for periods of two or more growing seasons, pests that are inherent to those crops are significantly reduced as compared to fields where there is only one year between similar crops.
For instance summer weeds that tend to germinate in late June and July are often more of a problem in crops like corn and soybeans. Growing small grains would extend the interval between corn crops and soybean crops. This could be seen as an integrated pest management tactic. Small grains would be much more competitive with summer weeds because by the time warm-season weed types germinate the small grain crop would be tall and leafy with an extended root system. This would enable it to outcompete the summer weeds for nutrients, water and light, often without the need for an herbicide treatment. Those summer weeds that do survive could be controlled as well with a wide variety of herbicide choices after the small grains harvest. Dr. Anderson concluded that utilizing diverse crop rotations, can substantially and naturally decrease problem weeds.
Similar benefits can be expected from rotations when considering other pests. In fact some researchers attribute the synergism seen from crop rotation to be, in part, attributed to reduced levels of root diseases or other pests specific to a host crop. For instance fields growing corn on corn could have high levels of root and foliar pathogens specific to corn. A three or four year rotation out of corn would reduce those pathogens and other corn specific pests in that field to much lower levels.
Why Include Small Grains?
Including a small grain in a rotation with corn and soybeans can provide producers with a window to grow a cover crop. Cover crops have been shown to benefit agricultural soils by increasing soil biology, improving nutrient cycling, organic matter and water efficiency. Cover crops can also provide livestock producers with additional forage.
Another benefit of small grains is their high carbon content. Including another high carbon crop (in addition to corn) to a crop rotation will make the ratio of high carbon crops to low carbon crops 2/3’s to 3/4’s. This can also improve water efficiency, soil structure and quality, and increase water holding capacity.
The addition of small grains in a crop rotation can also help producers by allowing them to spread equipment and labor over more acres.
Trading good agronomic practices for short-term profit will only increase risk. Enjoy the short and long-term benefits of keeping diversity in your crop rotation.
Source: Ruth Beck, South Dakota State University
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