Backyard Box Farm

The downside of starting garden beds from scratch is that we end up with a relatively neutral growing medium, lacking certain nutrients.

Rather than buy a commercially available fertilizer, we decided to mix our own to assure that all the ingredients are organic and save a few bucks by buying bulk. We found a good organic fertilizer recipe in a Mother Earth News magazine that goes like this:

4 parts soybean meal

1/2 part agricultural lime

1/2 part dolomite lime

1 part bone meal

1 part kelp meal

Seed meals provide an N-P-K (Nitrogen-Phosphorus-Potassium) content of about 6-4-2. All are essential in varying quantities for vegetative growth. 

Lime adds Calcium to the soil; another essential element for growth, and an important one that is passed on to us when we consume the vegetables. Agricultural lime contains mainly calcium carbonate, while dolomatic lime also contains magnesium carbonate. A mixture of the two provide a more balanced source of nutrients. A third type of lime, Gypsum Lime, contains calcium sulfate; also important. When we can source it we would like to add this to our fertilizer. 

Bone meal raises phosphorus levels in the soil.

Kelp meal is expensive, but worth every penny. It is rich in many trace minerals, growth regulators and natural hormones which greatly improve plant growth and nutritive value. 

The recipe suggests 4 quarts fertilizer per 100 square feet for low-demand vegetables, such as beans, beets, carrots, herbs, kale, peas and chard, mixed with 1/4 inch manure or finished compost. For medium-demand vegetables, such as basil, cabbage, corn, cucumbers, eggplant, garlic, lettuce, peppers, potatoes, radishes , spinach, squash, tomatoes, watermelon and zucchini, use 4-6 quarts per 100 square feet, with 1/4 inch manure or finished compost. For high-demand vegetables like broccoli, brussels sprouts, cauliflower, leeks and onions, apply 4-6 quarts per 100 square feet, along with 1/2 inch manure or finished compost.

I'm currently reading a book called Growing Vegetables West of the Cascades: The Complete Guide to Organic Gardening by Steve Solomon. It's a very regionally specific guide, full of some great information on our soil type and what it boasts and lacks. Because the Pacific Northwest gets SO MUCH rain, lots of essential nutrients are washed and leached from the soil. Solomon writes that our soils here are especially high in potassium, and lacking in calcium, magnesium and phosphorous. I'd plan to take these regional soil characteristics into consideration when mixing my next batch of fertilizer, perhaps adding more lime or other organic ingredient to boost calcium and magnesium quantities. Extra bone meal would increase phosphorous.

For now, I'm applying the prescribed fertilizer at a rate suitable for medium-demand plants. I'm incorporating this into the top 6 inches of our raised beds, which already contain plenty of beautiful aged compost, probably in excess of the recommended amount. But hey, We're trying to build humus here, a little extra might help us out. We'll see... Following this initial fertilizing, I'll side-dress later as necessary.