Was your vegetable garden all that you'd hoped this summer, with plants healthy and vigorous? If disease made an appearance or if some plants failed to thrive, perhaps it is time to think about the health of your soil, and to take steps to improve it. With the possible exception of some herbs, most edible plants benefit from plenty of organic matter in the soil. With all soil types, the advice is to work in generous amounts of humus, in the form of manures, vegetation or finished compost. And now is the easiest time to add organic matter, as finished summer vegetable plants are removed.
Don't confuse fertilizers with organic matter. While fertilizers, either organic or otherwise, add essential nutrients, most do little for the structure and texture of the soil. They have a valid place in our gardens but they don't improve the water holding capacity, good drainage and tilth.
If you have compost piles, you can supply at least part of what your soil needs, but many gardeners find that they cannot create enough compost to cover their beds as generously as needed. Compost and composted manures can be purchased in bulk or in bags, but the cost can be a factor. (Check Organic Materials Exchange for local free or inexpensive sources of manure.) You can add fresh-from-the-barnyard manure to your compost, but the usual advice is not to use uncomposted manure directly on your soil to avoid burning your plants. My experience, however, has been that if fresh manure is spread now, while the garden is fallow, no damage occurs. (If you are fortunate enough to have access to llama manure, it is known to be safe to use on plants right after it is produced, and it has the added advantage of having very little odor.) Regardless, the manures must be collected and transported, and then spread over your garden, eventually turned in, and some gardeners will find the work a bit daunting.
So how can you easily and inexpensively add organic matter? One of the best ways is to plant a green manure, or cover crop, and now is the best time to get one started. Green manure consists of plants grown for the purpose of digging them in and allowing them to decay where they were grown. Any plant material that decays in the soil will add organic matter, but especially beneficial are legumes, because they have the ability to fix nitrogen in the soil. Clover, fava beans, bell beans and vetch are the most commonly used legumes in the Santa Cruz area. Also often used are annual rye and other grasses. They all decay quickly if turned in while still young and succulent. Most soils will be ready for planting six weeks after the green manure crop is dug in. If your green manure is planted now, and grown over the winter, your soil will be ready for spring planting by the time the rains taper off and you are ready to put in spring vegetables or flowers.
Legumes are prized because bacteria in their roots usually produces more nitrogen than is used. The nitrogen is left behind in the soil when the plants are dug in. Most legume seed sold for green manuring is already inoculated with the bacteria needed for nitrogen fixing but you can also purchase inoculant to add to seed that has not been pre-treated.
Seed house Thompson and Morgan has come out with a packaged product called "Green Manure for Organic Gardening." Contents include seed of mustard, phacelia, buckwheat and clover. Or you can buy individual seed for planting the cover crop of your choice. All will benefit your soil, and after turned in, the health of the plants in next season's garden.
-Sharon Hull
