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Column: why use cover crop cocktails?

Columnist David Zirnhelt on some the research into using a variety of cover crops
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Imagine a “cocktail” drink with lots of ingredients, or the complicated early “cocktail” of drugs used to treat HIV patients. This word implies several or many ingredients, each designed to achieve certain outcomes of flavour or medical impacts.

There is much research into trends in agriculture which seek a simple and sustainable way to enhance soil health.

As spring approaches, it is time to plan soil and forage management. Many farmers, ranchers and gardeners will want to improve their production.

It used to be that farmers would be counselled to plant fall rye if they just wanted the ground covered and you would farm the land again with a planting, which would be the desired end crop for hay or grain or maybe a vegetable.

Farming the ground twice should get rid of the old unwanted sods and incorporate some green manure into the ground. Or, if you knew or thought that the land was short of nitrogen, you could plant a legume, which would fix nitrogen in the root zone.

Some of these legumes were clover, alfalfa, or sweet clover. Some of the recommendations were from regional agriculture staff, or the professionals working for the soil labs ( if you tested your soil) fertilizer and seed companies.

If you were a gardener, then you might have heard of planting buckwheat, sweet clover or annual ryegrass if you wanted cover on the soil and you wanted to improve the organic matter.

There has been a lot of research, trials and developments in other areas of Canada and the U.S. In British Columbia, most of the work has been done in the Peace River. A local producers’ group has been spearheading the work there.

Government in B.C. has been very reserved about their efforts. As a result, it is very difficult to find information on recent developments as they might apply to various regions of B.C. — other than the Peace and perhaps the lower mainland.

I am hopeful that we in the Cariboo and Prince George area have turned this around by developments around climate adaptation work initially sponsored by the B.C. Government, producer groups and the Cariboo Regional District.

One of the outcomes of several years of work in the region was a regional organization designed to focus on our own information needs.

On Feb. 14, 55 people came together representing various stakeholders to launch the Cariboo Agriculture (applied) Research (and extension) Alliance (CARA).

So if there is additional work on the topic of cover crop cocktails, this will be the group to lead it.

There will soon be one place to get the latest and best information and a regionally led (universities, colleges and producer groups) organization will have a research and demonstration plan.

Recent developments suggest that one needs to know what the soil requires to support the growth of the soil health (good soil microbiology) and subsequently the crops (annual or perennial) that are desired.

The cocktail has to be designed to meet certain objectives. Agricultural scientists recommend soil testing to see what should be planted to overcome the deficiencies (or surpluses) in the nutrient makeup of the soil.

The most common ingredients seem to be grains like barley, field peas, annual ryegrasses and clovers. Now it is not uncommon to plant eight to 20 varieties.

Some of the newer ingredients in cover crop cocktails are brassicas, such as forage radishes or more exotic legumes. Now, brassicas accumulate sulphur. Feed or grazing for livestock should have 0.4 per cent sulphur, but after planning brassicas the amount can easily go to 0.6 to 0.8 per cent.

This is twice what it should be, so agronomists recommend testing the feed before grazing animals on it. Electric fencing to allow limited grazing each day can help, but animals need to have access to roughage to balance the rich cover crop plants.

Similarly, there can be a problem of too many nitrates, which can sicken or even kill the animals. This can be complicated, so know what you are doing.

One of the main purposes of cover cropping is to replenish, or make available in the soil nutrients lost to harvesting (or grazing) or to change the makeup of the pasture or field.

Your plan needs to reflect the situation (soil test) and you need to measure the outcome (forage analysis).

David Zirnhelt is a rancher in the Cariboo and member of the Cariboo Cattlemen’s Association. He is also chair of the Advisory Committee for the Applied Sustainable Ranching Program at Thompson Rivers University Williams Lake Campus.