A Cook's Garden

A Cook's Garden: Alfalfa, an Ideal Nutrient for Soil

Grow alfalfa as a cover crop for areas not in use, or add it to your compost pile.
Grow alfalfa as a cover crop for areas not in use, or add it to your compost pile. (Bigstockphoto)
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By Barbara Damrosch
Special to The Washington Post
Thursday, June 25, 2009

Like most words beginning with "al," alfalfa derives from an Arabic word, the name given to a legume of ancient Persia. It translates roughly as the "best fodder," and now, thousands of years later, it still is. Grown for livestock, the plant is a prime source of protein as well as calcium, boron and other essential elements.

It's also highly nutritious for a garden's soil. Like peas, beans and clovers, alfalfa roots grow in association with certain bacteria, forming nodules that enable the plant to collect nitrogen from the air. A plot where alfalfa has grown, leaving behind decomposing roots and nodules, gives a boost to the next crop planted there. In addition, these roots are mighty foragers, heading straight down 12 feet or more to mine nutrients from the subsoil. The old roots then feed both the plant and the soil in which they grew.

Alfalfa makes a good drought-resistant perennial cover crop for areas not in use and for parts of the garden that are vacant between early and late plantings. Tilled as a green manure, alfalfa adds fertility, stimulates microbial activity and aerates the soil. There are even "summer" varieties that die over the winter and can be overplanted without tilling.

An even simpler approach is to mow off alfalfa repeatedly and add the residue to your compost pile. Wait until purple flowers appear, then cut them with a mower, a weed whacker or scythe. Grown in fertile, well-drained soil with a neutral pH, it should give you four cuts per season, chock-full of trace elements, with an ideal carbon-nitrogen ratio to help your compost heat up.

Simpler still, but more expensive, is to apply bagged, dehydrated alfalfa meal directly to the soil. At our farm it adds a boost of nitrogen, well-balanced with potassium and phosphorous, when we rip out one crop and plant another. For every 25 square feet of garden, we sprinkle on an amount that fills a one-quart yogurt container, raking it in thoroughly but shallowly. If garden supply stores near you don't carry alfalfa meal, you can order it from Peaceful Valley Farm Supply (http://www.groworganic.com).

Alfalfa also comes dried in pellet form, as feed for such animals as rabbits and llamas. It's even used as bedding for reptiles such as land tortoises, bearded dragons and iguanas. For garden use, look in feed stores for pelleted alfalfa in its pure form.

Rose growers revere alfalfa, scattering pellets or meal around the bushes or brewing either into a tea to spray as a foliar feed. My Kansas gardening friend Lynn Byczynski swears by pellets as a nutritious garden mulch. She likes the way they form a weed-deterring crust.

Personally, I like the idea of turning a corner of the yard into a mow-and-grow alfalfa patch, providing a steady supply of alfalfa hay for mulching, tilling-in or compost-pile-building. Maybe the rabbits would even prefer it to my peas.

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