Vetch cover crop beginning to flower. (Mary Lowther photo)

Vetch cover crop beginning to flower. (Mary Lowther photo)

Mary Lowther column: Vetch and crimson clover to the rescue of soil fertility

I add dry organic fertilizer as plants use up what is in the soil.

By Mary Lowther

We live in what geographers used to call a “temperate rain forest” supported by our west coast marine climate. Given that most of the old growth has been harvested and replaced by scotch broom, modern science will no doubt eventually develop more accurate descriptive terminology but we can hopefully assume it will still involve rain. It is less reasonable to assume that the combination of torrential rainfall and huge forests indicate fertile soil, for the opposite is true.

Did our forests grow here because of the abundance of rain or is this climate wet because trees catch, absorb and attract clouds and rain? Whatever the reason, we have winter rains that wash vital nutrients downstream. In 1958 Dr. William Albrecht, Chairman of the Soils Department at the University of Missouri, wrote about the correlation between rainfall and health. Dr. Albrecht’s research established that food grown in a climate with more rainfall is less nutritious. Therefore, rain forest gardeners gain the maximum return on their labour by revitalising their soil.

Sea or fresh water weeds often contain abundant minerals along with easily composted nutrients. The Municipality of Osoyoos regularly harvests milfoil from its lake and provides this mineral rich resource free of charge to lucky local agriculturalists. Unless the regional district develops a similar program, we Cowichan gardeners don’t enjoy this benefit, but we can buy fish and kelp fertilizer and manure from animals that were fed nutritious diets or make our own complete fertilizers.

Unless we know what the animal has been fed, it’s best to assume that local manure contains very little in the way of nutrients but is nevertheless valuable for its enzymes and bulk. I use manure in my compost heap, along with vegetation scraps, clay, soil and soft rock phosphate.

When planting and in the weeks thereafter, I add dry organic fertilizer as plants use up what is in the soil. I am careful not to overwater my garden so nutrients are not washed out during our dry summers.

My sandy soil loses a lot over the winter though, so I constantly feed it during the growing season with fertilizer and compost tea, which serendipitously also prevents plant disease.

The use of cover crop whenever soil isn’t growing vegetables also fertilizes the soil and prevents nutrient loss as the roots retain what would otherwise be washed away. Cover crop is any plant we allow to grow without harvesting, so it holds moisture and nutrients in place and contributes its own mass to the soil.

One local farmer allows weeds to grow and calls that his cover crop. It’s better than nothing, but I prefer crops like vetch and crimson clover that kill off the more invasive plants, eliminate the need for intensive weeding and clean the soil of many diseases.

Nitpickers might argue that we can make up for the deficiencies of our soil by eating more fish and seaweed. This is true, but growing your own kelp in Lake Cowichan might get a bit complicated. If a reader cares to make the attempt I would be delighted to learn the results.

Any readers interested in this subject should google Dr. William Albrecht of the University of Missouri, the definitive expert who literally wrote the book on Soil Fertility and Animal Health. I would be delighted to lend you my personal copy as soon as whoever borrowed it last returns it.

Please contact mary_lowther@yahoo.ca with questions and suggestions since I need all the help I can get.

ColumnistLake Cowichan