The grass is always greener: cropping and grazing

Cover crop selection requires background research and forward thinking

By Kate Ayers

Cover crops planted after a cereal crop, such as winter wheat, fit well into the growing season and provide opportunities for livestock grazing. The crop can also provide a wealth of benefits for the field, such as improving infiltration, reducing erosion and increasing soil organic matter.

Proper seed selection is important to ensure the needs of both the livestock producer and the cash crop farmer are met. The final mix depends on a variety of factors such as crop rotation, harvest timing and spray programs.

The first step in cover crop selection is determining the goals you wish to achieve, as well as the length of the growing season for the crop.

Cover crop species fit into one of three categories – grasses, legumes and non-legume broadleaves. Below, we list some cover crop options and provide a few details about each species. This list offers a few examples from each category – it is not exhaustive. The information is compiled from the Ontario Ministry of Agriculture, Food and Rural Affairs website and Midwest Cover Crops Council website.

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Grasses

Rye

• Has a fibrous root system
• More drought tolerant than wheat or oats
• Returns large volumes of plant biomass to the soil
• Provides forage in mid- to late- fall and is very palatable
• Can be used as an emergency forage if alfalfa winterkills
• Overwinters
• Can tie up nitrogen in spring which is needed by the subsequent crop

Oats

• Fast growing annual grass
• Readily winterkills, holds nitrogen over winter but then releases N as it decomposes
• Establishes a vigorous canopy to smother weeds
• Tolerates a larger pH range than wheat or barley
• Seed is easily available and relatively inexpensive

Barley

• Tillers more than oats
• Winterkills, however cold tolerance increases as the plant matures so winterkill is not always consistent in mild winters
• Grows best in cool and dry conditions; less tolerant of wet soils than oats
• Establishes a vigorous crop canopy to smother weeds
• Has a very high salt tolerance

Legumes

Red clover

• Generally, two types of red clover are grown in Ontario
  • Double-cut or “medium” red clover: flowers in seeding year
  • Single-cut or “mammoth” red clover: does not flower in seeding year, slower growing
• Best growth in moist, cool conditions
• Thick tap root that grows 60 to 90 cm (24 to 35 inches) per year
• Grows in a wide variety of soil conditions
• Overwinters

Hairy vetch

• Fixes nitrogen and provides a longer window of protection than other cover crops
• Root growth can continue while plant is dormant
• Overwinters
• If left to grow too long in the spring, it will deplete moisture in seedbed for the following crop
• A single application of glyphosate is not effective in killing hairy vetch

Field peas

• Growth is rapid under cool conditions
• Requires a supporting crop (like oats or rye) to stand
• Can withstand freezing temperatures but does not overwinter consistently
• Fixes nitrogen, adding up to 100 lbs/acre
• Adds considerable biomass to soil

Non-legume broadleaves

Buckwheat

• Fastest growing cover crop
• Fibrous root system, moderately aggressive
• Very cold sensitive and easily killed by frost
• A good stand of buckwheat can usually compete well with most weeds
• Attracts beneficial insects

Oilseed radish

• Good nitrogen scavenger – is a good fit with fall manure applications or when excess soil nitrogen is expected
• Winterkills in normal winter conditions
• Prefers cool, moist growing conditions
• Residues decompose quickly
• Returns moderate amounts of organic matter to the soil

Marigold

• Non-host for nematodes, suppresses nematode populations
• Does not require mowing
• Medium-sized root system
• Winterkills
• Seed is expensive and can be hard to source

Additional information on these crops and others can be found here.

Cover Crop Decision Tool

Grain Farmers of Ontario, the Canadian government and the Agricultural Adaption Council funded the development of a Cover Crops Decision Tool that is available at decision-tool.incovercrops.ca/. The University of Guelph led the creation of this tool, which provides some guidance for farmers when making seed selection decisions.

It may also be useful to check out the list of cover crop seed providers here. BF