GROW YOUR OWN NITROGEN

Enlarge Image Image Gallery [1] Peas will enrich the soil for a subsequent corn crop. [2] Bean vines ? dug into the earth ? will release nitrogen. [3] Mature sweet clover seedpods. [4] Red clover (Trifolium pratense) and a passerby. [5] Corn grows vigorously with a legume companion. [6] Harvest the brown heads of red clover for seed. [7] White clover (Trifolium repense). [8] A stand of hardy yellow sweet clover (Melilotus officinalis). [9] Wild white sweet clover (Melilotus alva). Photos by the Author

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By simply planting some legumes in your garden, you can . . .

By Edward Null

Nitrogen makes up about three-fourths of the air we breathe. Since this colorless, odorless gas is the basic building block for protein, its availability is extremely important to the plants (and animals) that feed us. Technology has developed a wide variety of nitrogen sources for agricultural use. However, there's no need to pay for such substances (many of which are the results of energy- and pollution-intensive manufacturing processes) . . . because it's easy to grow your own nitrogen!

As you may know, members of the legume family have the ability to grab free nitrogen from the air for their own use and — with the help of certain bacteria — to "fix" it in the soil, where the substance can benefit other plants. Beans, peas, clovers, and the like all possess this useful trait. So, by thinking ahead a season or two, you'll be able to put such fertility "factories" to work supplying your vegetables with this nutrient.

SHORT-TERM TRICKS

You can give this fall's cole plants (cabbage, broccoli, cauliflower, etc.) most of the nitrogen they'll need by putting in a spring crop of snap beans. I try to dig the bean vines into the soil while they're still green and leafy, just as production tapers off. In that way, I get beans and fertility . . . that's really double-cropping!

This year, in addition to my regular legume patch, I sowed a few extra plants in the open spaces in my corn plot. The beans are doing well, and even seem to have suffered less insect damage than did the main patch. The corn is more vigorous than in previous years, too, as a result of both the nitrogen boost and the extra soil cover.

As you can imagine, there are dozens of ways to rotate or interplant legumes with other crops . . . in order to reap both soil enrichment and food from the same ground. Many legumes make champion green manure crops as well . . . as they're among the best soil conditioners around.

Soybeans or cowpeas, if sown thickly in late summer and then dug in at frost-time, will provide rich earth for next year's early greens and such. It's really not hard to turn under the lush herbage, either: The secret is not to be finicky. Just upend a spadeful of soil at a time, covering as much greenery as you can without wearing yourself out. (The leaves that remain above the dirt will wilt and provide some extra winter soil cover.)

Canada or Alaska peas make good early "fertilizer crops" for summertime greedy-feeders. Plant them as soon as possible in the spring, and turn the vines under a few weeks before sowing the following crop. (As with all green manures, a short delay is necessary to give the succulent green matter a chance to break down and release its treasure for the vegetable to follow.)

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