Building Great Soil (cont)
By: Warren Schultz
Plant a Cover Crop
Compost is fine, says Richard Merrill, but he maintains that the most effective way to add organic matter to the soil is through green manures and cover crops. They get the job done without expending all the energy it takes to make and spread compost. And many types of cover crops offer a secondary benefit. "Not only are you adding organic matter," he says, "but cover crops such as buckwheat attract beneficial insects to the garden as well."
However, there is a tradeoff. Though cover crops may save energy, they use up space in the garden. "And, of course, gardeners don't like to waste space," says Merrill. But he suggests that the space is well spent and can be managed easily. "You can use a rotation plan to plant cover crops in strips or beds or boxes," he says. And a fast-growing crop like buckwheat can be in and out in eight weeks, allowing you to sow other crops soon afterward.
"We've developed our own rotation here," he says. "In summer we use buckwheat (Polygonum fagopyrum), Sudan grass (Sorghum sudanense), and sunn hemp (Crotalaria juncea). Then in fall we plant vetch (Vicia), sweet clover (Melilotus alba), and bell beans (Vicia faba)." He suggests that home gardeners start with a single crop of a warm-weather green manure, preferably buckwheat. "You can easily use it in your regular rotation. For example, if you have four boxes, plant vegetables in three and buckwheat in one, and rotate them." This works for any part of the country because buckwheat is a good warm-weather cover crop.
Buckwheat is easy to grow and easy to turn in, and it doesn't develop tough tissue as vetch does. The only difficulty that gardeners may have is deciding when and how to turn in the cover crop. Merrill believes that most gardeners wait too long, and consequently the cover crops contain too much carbon. He suggests turning buckwheat under early, when about 10 percent of it is in flower. And you don't have to do it all at once; just begin digging in strips when it reaches that point.
With buckwheat, the harvesting is easy. Just chop it off at ground level and lay it on the ground to serve as a mulch. "Sure, some of the nutrients will volatilize," Merrill says. "But we don't worry too much about that." Or, you can cut it off at ground level rake it up, and compost it. The most efficient way to use all of the nutrients is to cut the top growth and dig it into the soil along with the roots. But you'll need a tiller if you're doing more than about 2,000 square feet. Once it's all turned in, you can immediately replant with a crop.