Cover Crops: Species Selection

 

 

 

 

Interest in cover crops is increasing. Farmers are growing cover crops as a monoculture or blend/s to improve soil quality and supplement forage needs. The frequently grown cover crops species in this region could belong to a broad group of plants such as warm or cool season grass, cool season broadleaf, brassica species, or legumes. One advantage of growing a blend over monoculture is it helps partition available resources to different plant species at different times rather than all plants requiring the same resource at the same time. Selecting cover crop species both as a monoculture or blend depends on the time of the year. Growers can select a blend with more warm-season grasses if growing after early wheat/oat harvest (early to mid-July). On the contrary, if the small grains harvest is delayed until late July to early August same blend can be used but with more proportion of cool-season species. Growing degree days (GDD) generally decreases as season progresses. An August day will have up to three times GDD than an October day. Therefore, we can expect less biomass production when cover crops are planted later in the season.

 

 

Another important aspect to consider while selecting cover crop species is the crop rotation. A wheat grower may not want to grow winter rye as a cover crop due to potential of becoming a weed and possibility of outcrossing. On the other hand, for corn-soy rotation winter rye could be a preferable choice due to its excellent cold hardiness and rapid spring growth. Winter rye grown after corn and before soybean can be chemically terminated in the spring or hayed as a forage crop.

 

For fall grazing, there is a trend of growing cover crops following small grains. Depending upon the time of the year, warm season grasses (millet, sorghum sudangrass) may produce greater biomass but will have lower nutritional value whereas, brassicas (radish, turnip, rape). Cool season grasses (oat, barley) on the other hand produces less biomass but have high nutritional value. A cool season mix stays green longer in the fall. Nutritionally, brassicas have shown great promise but due to high water content and bloat concerns in ruminants, it is suggested not to have more than 60 to 70% brassicas in the blend.