The Importance of Fertilizer (and How to Mix Your Own)

When I first began vegetable gardening twenty years ago, I knew that I wanted to be organic. I didn’t want to hurt the earth—or myself—with synthetic chemicals. I wanted to grow plants the way nature did: with nothing but dirt, water, and sun. I dug a little composted steer manure into my beds (a 40-lb. bag per 120 sq. ft., which was all my high school budget could afford), but that was it as far as fertilizer. In went the seeds. Up came the weeds. And the harvest was about what you should expect if you were to depend on nature’s labor alone: a few tiny fruits very sparsely distributed.

Try gathering wild foods in your local fields and forests. They’re there, once you learn how to recognize them. But you have to hunt for them. And you need a pretty big territory if you’re going to collect anything more than the occasional supplement to your diet. The natural fertility of soil varies greatly from place to place, but even where it’s at its richest, it’s not enough to grow the kinds of dense yields we expect from our farms and gardens. And of course the wild world doesn’t naturally channel all of its fertility into producing food directly consumable by humans. It has a lot of other concerns as well. Like covering bare soil with grass to prevent erosion. (Farmers and gardeners just hate this!)

Now there’s a lot to be said for a hunting and gathering way of life. Agriculture as it’s been practiced throughout most of recorded history has been destructive of soil and thus unsustainable in the long term. (For more on this, see Wes Jackson’s recent book Consulting the Genius of the Place.) And probably we should hope one day to establish a new relationship with the earth that is more like the hunting and gathering lifestyle, one that cooperates more with nature’s established processes. In the meantime, though, we have the need to grow our food more intensively. And that means we have to make the soil more intensely fertile. Fertilizer is simply not optional in the vegetable garden, as I learned the hard way.

There’s good news, though. There are organic fertilizers available, and they don’t have to cost an arm and a leg. Steve Solomon, in his book Gardening When It Counts, offers a recipe for complete organic fertilizer that you can mix from relatively low-cost ingredients available at your local farm and garden store. I’ve been using it for the last five years with great success, and so I’m going to pass the recipe on to you.

Actually, what I’m going to give you is the recipe for the specific mix I make. Solomon offers many different recipes, which you can adapt to the materials available to you most cheaply. For all the details, check out his book. It’s entirely worth the $20 to buy it.

Getting low. Time to make more!

I mix my fertilizer in a three-gallon bucket. (A five-gallon bucket would be better, but I didn’t have any empty ones when the time came to make my first batch, and I’m a creature of habit.) To measure ingredients, I use the bottom half of a half-gallon plastic milk carton, giving me a quart measurement. For a small batch, I combine:

• 4 quarts soybean meal (This is a common livestock feed. It costs me between $18 and $22 for a 50-lb. bag, depending on where I buy it. It’s a good idea to store this in a container where moisture and mice can’t get to it. Well stored, it should be good for several years.)
• ¾ quart dolomitic limestone, in pellets (This cost $5.99 for a 50-lb. bag. Store this where it won’t get wet. Another lesson learned the hard way.)
• ¼ quart gypsum, in pellets (This cost $9.99 for a 40-lb. bag. Store this where it won’t get wet.)
• 1 quart bonemeal (This was $25.99 for 24 lbs. Mice like to get into this, so store the bag inside a mouse-proof container, like a garbage can.)
• ½ quart kelp meal (This was $12.99 for 4 lbs. It’s the most expensive ingredient, but essential for its range of trace minerals and natural plant hormones.)

When I’m preparing garden beds for the new year, I spread a ¼- to a ½-inch layer of composted manure (primarily for the organic matter, not the fertilizing value) and then sprinkle about 5 quarts of fertilizer per 100 sq. ft. Throughout the growing season, I periodically sprinkle more fertilizer around my plants, which adds up to about another 5 quarts per 100 sq. ft. over the rest of the summer. But at present, my primary use for fertilizer is in my potting mix for starting seeds indoors. I add a ½ cup to 1¼ gallons of soil plus ¾ gallon compost. As the seedlings grow, I give them a liquid feed, but that’s for another post. This one’s long enough!

One more thing, though, that I can’t help mentioning: those fruits that I harvested from my first garden, unfertilized and overgrown by weeds, may have been tiny and sparse, but they were incredibly delicious. My lone cantaloupe was less than 5″ in diameter, but my grandfather, an avid and successful gardener, said it was the sweetest he’d tasted. What nature may lack in quantity, it seems to make up for in quality. Maybe “natural” gardening calls for further investigation….

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