Wednesday, September 8, 2010
Why not grow miracle mulch?
What fixes nitrogen in your garden soil, recycles nutrients and adds organic matter, reduces compaction and erosion, and turns into thick mulch, which in turn helps suppress weeds, reduces water evaporation, acts as a slow-release fertilizer, and suppresses some pathogens and pests?
Barbara Billek of Columbia, who gardens at Westside Community Garden of Columbia Gardeners, Inc., says the answer is hairy vetch. No, hairy vetch isn’t a guy you met at the local barber shop. It’s an annual winter legume that serves both as a cover crop and mulch.
“I was searching online for a cover crop that would protect my garden soil over winter,” Barbara explained. “I ended up on the U.S. Department of Agriculture’s website and an Agricultural Research Service brochure entitled ‘Sustainable Production of Fresh-Market Tomatoes and Other Vegetables with Cover Crop Mulches,’ which is now called Farmers’ Bulletin 2280.”
Barbara read the bulletin and, convinced hairy vetch was the ground cover she wanted to use in her garden, began growing it two winters ago. She follows the recommendations in the brochure.
“You can’t buy hairy vetch seed just anywhere,” Barbara pointed out. “I found it at the Southern States store in Ellicott City. They asked how much I wanted, and off the top of my head I said, ‘One pound,’” she laughed. “They went into the back of the store somewhere with a scoop and returned with a bag of hairy vetch seed. One ounce would have been more than enough for my small garden.”
Barbara said the optimum time for sowing hairy vetch in Maryland is mid-September, when many garden vegetables have already stopped producing. “The first year you have to use a special inoculent with the seed. The inoculent consists of rhizobium microorganisms that improve growth of the hairy vetch and remain active in the soil to benefit future crops,” she explained. “Last year I sowed it late—October 9 in one bed and October 22 in another. I lucked out because we had a warm autumn and the vetch still grew well.”
“Seedlings emerge about a week after I sow the seed,” Barbara said. “By winter they form a 5- to 6-inch mat that protects the soil from erosion. During the coldest part of winter, the plants seem to die, but they start growing again when temperatures rise in spring. By early May, the individual plants are up to 3-feet long and create quite a heap of prostrate, green growth.”
“Just before the vetch blooms in mid-May and when it has added most nitrogen to my garden soil,” she continued, “I take my shears and cut it all off at ground level and just let it lie there. It slowly decomposes and turns into the best imaginable mulch. I just pull it to the sides of my raised bed and plant my tomatoes. Then I pull the mulch back around the tomato plants and am pretty much done weeding for the summer.”
Barbara pointed out a bulletin chart indicating hairy vetch adds micronutrients to the soil in addition to the important nutrients nitrogen, phosphorus, and potassium. Per acre the vetch adds about 125 pounds of nitrogen, 18 pounds of phosphorus, and 132 pounds of potassium.
“My tomato bed is only about 60 square feet,” she explained. “I’ve never taken the time to figure out how much of those elements the vetch adds to my garden each year.”
If you plant a ground cover, please post a Comment describing its pluses and minutes—how it works for you.
To access Farmers’ Bulletin 2280, CLICK HERE.