Alfalfa provides 'green manure' after growing season

Scripps Howard News ServiceDecember 28, 2012 

Alfalfa pellets for horses are large, highly compressed bullets of fertility and organic matter that are exceptional for winter soil-building.


“Fallow ground” is the term that farmers use when a field needs a vacation. “Fallow” simply means “uncultivated for the growing season,” and when ground is so deemed, the land is freed to its own ends. A fallow field will give life to all sorts of weeds, volunteer veggies and native species that are allowed to flourish. Underground, the microbial activity increases due to the diversity of plant roots compared with the monoculture that was there in previous seasons.

Farmers also learned how to reinvigorate their fields when fallow with another technique known as “green manure.” Instead of letting the field go entirely fallow, it is sown with legumes, a group of plants that absorb atmospheric nitrogen and transfer it through the roots into the soil. After a legume plant dies, its body is rich with stored nitrogen that farmers till back into the soil for a boost of both fertility and organic matter.

If you have a backyard food garden, particularly in raised beds where food is grown densely, do all you can to build up the soil to maintain fertility. It worked hard all summer producing food, and now you must replenish what was lost. Sowing legumes is not effective for smaller applications, but there’s a way to get the same results for about $20.

Alfalfa, a common livestock feed, is rich in nitrogen because it is a legume. Alfalfa pellets for horses are large, highly compressed bullets of fertility and organic matter that are exceptional for winter soil-building. With each pellet about the size of a large vitamin, you can pour a whole bag of them over your garden soil and work it in right now. They’re particularly well-adapted to raised beds where you need finely textured organic matter. Once the pellets are in the soil, they’ll absorb moisture and swell up, then disintegrate. This releases all the residual nitrogen to become part of your living organic garden soil.

In larger gardens where rototillers are used, alfalfa hay makes a great winter mulch that protects your fertile soil from leaching and freeze-thaw. Over winter, the hay packs down, and nutrients leach into the soil. Come spring, the alfalfa can be tilled in for boosting organic matter and nitrogen. You can also mulch with alfalfa during the growing season to get similar benefits.

The beauty of this way to green-manure your garden is that it’s so affordable. Twenty dollars will get you either a 50-pound bag of alfalfa pellets or an entire bale. You can find pellets for the lowest price at feed stores that cater to horses or cattle, the primary consumers of alfalfa. Alternative sources in a smaller bag size can be found at pet stores as feed for pygmy goats and rabbits. Green manure is an age-old way of building soil naturally. Thanks to the livestock industry, we can obtain our legumes conveniently pelleted and bagged. So don’t let your garden lie fallow this winter.


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