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By Tom Woods
Intensive food gardening is almost certain to strip nutrients from the soil, nutrients you will need to put back in order to grow vegetables year after year.
I admit I am no expert in soil science or in the practice of permaculture, which seeks to create near-closed loop systems for food production with minimal outside input; that is, without bringing in large amounts of fertilizer from the world outside your yard. But I read a lot.
To make such systems work, you usually need to create a mixed-use farm setting in which nutrients cycle from the soil as ground crops to livestock and back to the soil as manure and compost.
You can approximate such a system in the backyard setting by ensuring that your grass clippings, the leaves from your trees, your garden waste and your kitchen trimmings all end up in the compost to be used in the garden the following growing season. By doing so, you will greatly enhance levels of organic material in your soil and the health of the microbial community therein.
But the nitrogen, phosphorus and potassium content (the so-called NPK value) of the best and most expertly made compost is no better than 1-1-1, or 1 percent of each nutrient. That’s a far cry from the typical commercial vegetable fertilizer at 6-8-6, or 8-20-20 for tomato food.
For several years, gardeners have been tinkering with a fertilizer formula from Pacific Northwest gardening guru and author Steve Solomon. Much of what I have to tell you about this fertilizer you can learn from his book, “Growing Vegetables West of the Cascades.”
10 parts canola or cottonseed meal
1 part steamed bone meal
1 part kelp meal
1 part dolomite lime
1/4 part blood meal (for dark greens only)
The bulk of this fertilizer mix is seed meal, which is just the sort of material you would be adding to your soil through composting, except that seed meal has 4-10 times the nitrogen of compost. It is also dirt cheap.
As the seed meal decays with the help of bacteria, fungi and other wee beasties, the nitrogen will become available to your growing plants. When your garden seeds first sprout, they need few nutrients. But as the soil warms and plant growth accelerates, so too does the microbial activity, breaking down the seed meal just when your plants need it.
Bone meal brings phosphorus to the party, and usually brings its friend calcium as well. Phosphorus is what you need to grow roots and produce fruits. You can increase the proportion of bone meal for your tomatoes.
Solomon considers kelp meal an add-on for winter vegetables. In southeastern North Carolina with our heavy annual rainfall and leached-out soils, kelp meal is a must. It contains about 100 micronutrients, elements, amino acids and vitamins that are washed out of our poor local soils. Our soil is sandy and needs all the help it can get.
Those same rains that wash away nutrients also ensure that most local soils are acidic. Lime raises the PH of your soil and helps make nutrients available to growing plants. If testing has verified your soil is acidic, adding a little each time you fertilize should help.
Blood meal is like a steroid shot of nitrogen. You should not put blood meal into your main fertilizer bin, but you can add it when you prepare beds for kale, spinach, broccoli and other dark greens. Too much nitrogen can inhibit fruiting, so use it with care.
Most of the ingredients for this mix can be purchased at the garden center. The seed meal is usually found at farm supply stores.
You’ll want a good-sized bin with a lid to store your fertilizer. I use a plastic garbage bin.
You can apply the fertilizer generously, working it into the soil under each plant. It won’t burn and it releases slowly. Use about one cup for each large plant, perhaps half that for a head of lettuce. Use about one gallon per 100 square feet to prepare an entire bed. Sprinkle this mix lightly on each layer as you build your compost heap to supercharge decay. It will help break down tough material and create very fine compost.
Send your gardening questions or comments to: Brunswick County Master Gardener Column, P.O. Box 109, Bolivia, NC 28422, or call (910) 253-2610. Enclose a self-addressed stamped envelope if requesting information or a reply. Answers may be printed in this column.