Many agronomy professionals attended the Integrated Pest Management School this year in Beresford, S.D. at the SDSU Southeast Research farm. There has been a growing interest in cover crops and the benefits of their influence on commonly grown cash crops in South Dakota. Topics presented about cover crops included fitting cover crops into rotation, grazing cover crops, how herbicides interact with cover crops and other considerations.
Fitting Cover Crops Into Rotation
Crop rotations with small grain in the sequence allow an adequate seasonal window following grain harvest to establish cover crops of various blends. Early harvest can follow with cover crop mixes that are high in warm season species whereas late harvest (into August) will favor mostly cool season species with small proportion of warm season species.
The predominant cropping system, especially in the Eastern S.D., is corn and soybean. Due to limited heat units following grain harvest of either of these crops, producers are limited with their cover crop species options. One of the cover crops that has worked in S.D. environments to fit the corn-soy rotation is winter rye. The importance of incorporating winter cereal rye into corn-soy rotation and its benefits, and constraints were highlighted among the attendees.
Cover Crops & Grazing
One of the major reasons for adopting cover crops into S.D. farming systems is supplemental forage. Results obtained from a study conducted at the SE research farm near Beresford were highlighted in this section. This section showed the participants how replacement heifers performed after allowing grazing on a six-way cover crop blend grown following winter rye grain harvest. Some of the variables shared were average initial weight, average final weight, and daily weight gain. In addition, another study focused on how grazing of cover crops species of different fiber contents influence cattle performance.
Other topics covered during this session were nutrient cycling, rate of decomposition of cover crop species, and corn performance following different cover crop blends.
Herbicides & Cover Crops
Herbicides and their interaction with cover crops are always a concern with producers. Producers often ask how growing this cover crop will affect their herbicide selection for their cropping rotation.
Herbicides with long residuals are a tool for weed control in cropping systems. Therefore, herbicides are still needed, but there is a balance between benefiting your soil, crop, and continuing proper weed control. This brings many problems with incorporating cover crops. The first question you need to ask yourself is “Will this cover crop be grazed or harvested for feed?” In all cases, the label is the law. Any rotational plant back restrictions, grazing restrictions, and/or harvesting restrictions must be followed to protect the food chain. If the cover crop will not be used for livestock grazing or feed and is not mentioned on the herbicide label, then the following would apply to choosing a species to grow. First, the producer needs to know how sensitive the species is to the herbicide used and how persistent it is in your environment starting from time of application. Then from that information a selection can be made. If herbicide longevity is not known then a field bioassay should be made before planting the cover crop.