For at least the past decade, no-till production systems have become increasingly popular with conventional vegetable growers. Now the interest in no-till is spreading to organic farms. Results are mixed so far, with perhaps as many failed crops as successful ones, but no-till advocates are undeterred. They believe that the benefits of this system are so profound that obstacles must be overcome.

In a no-till system, a cover crop is grown, then killed and left as a mulch on the ground. Crops are planted right into the mulch. In a variation called strip-tillage, a thin strip of soil is cultivated for planting the cash crop. Among the most important benefits of no-till:
•Soil erosion is prevented because the soil is held in place by the cover crop. “Soil erosion is the most detrimental aspect of agriculture,” says Steve Groff, a Pennsylvania farmer and advocate of no-till vegetables. “We can’t turn our backs on soil erosion and call ourselves sustainable!”
•The permanent cover crop mulch improves soil tilth, increases organic matter levels, enhances water infiltration, and conserves soil moisture.
•No-till often leads to increased yield, with less need for additional fertilizers because of the nutrient contribution of the cover crop.
•Some diseases, such as early blight in tomatoes, are delayed in a no-till system. Colorado Potato Beetles also appear to be deterred by the cover crop mulch.
•No-till sequesters carbon in the soil, reducing the carbon dioxide gas that is blamed for global warming. One researcher has found that carbon loss in the first five hours after moldboard plowing was almost 14 times greater than undisturbed soil. He described it as “a large burp of CO2” released by tillage.
•Cereal crops such as rye, which are usually used in a no-till cover crop, have an allelopathic effect on seeds, preventing their germination. In addition, the mulch from the killed cover crop shades the soil, also preventing weed seed germination.

So what’s the problem? If the system offers all these benefits, it stands to reason that organic growers would be eager to adopt it. But the research that has been done so far on organic no-till has proven it to be management-intensive, and not a panacea for organic farming’s problems. Asked about organic farmers’ success with no-till, Dr. John Teasdale of USDA’s Beltsville research center replied: “Success is a tricky thing. I think of success as getting consistent results on a fairly regular, predictable basis. Many have shown success on an occasional basis but it is harder to get consistency. I do not think we are there yet but getting closer.”

The biggest problem facing organic no-till is weed control. In a typical no-till situation, the farmer plants a mixture of rye and hairy vetch in fall and allows it to grow until it’s in bud or blooming in spring. Then the farmer rolls, chops or mows the cover crop to kill it, and leaves it lying on the ground. Next, the farmer cuts slits in the mulch and plants, either by hand or with a specially designed no-till transplanter. At first, the killed cover crop does a good job of keeping out weeds.

But as the season progresses, weeds inevitably make their way through the deteriorating cover. Conventional farmers spray the emerging weeds with herbicide. Organic farmers, who can’t use their usual cultivation equipment because of the mat of mulch, are stymied.

“The only way no-till has worked in conventional agriculture was with a broad array of herbicides,” said Dr. John Luna of Oregon State University, who recently conceded defeat by weeds in his organic strip-tilled fields. “It is a completely herbicide-dependent system. Realistically, expecting season-long weed control by depending on just some cover crop lying out there, you’re going to lose.”

Drew Norman, a Maryland market farmer who received a SARE grant to trial no-till organic cabbage, said that his crop got weedy in the row where the planter disturbed just enough soil to allow weed seed germination. Then perennial weeds came up through the mulch between the rows.

Don’t give up
Dr. Ronald Morse thinks the weed problem can be overcome. He has been working on no-till agriculture for more than 20 years, ever since an Extension agent sent him a photo of a mudslide coming off a cabbage field onto a highway. The photo was accompanied by a brief note saying “Help!” “It didn’t take a rocket scientist to figure out what I had to do,” Morse said. “It has taken a long time to figure out how to do it.”

Although most of his research has been on conventional farms that used herbicides, Morse became interested in an herbicide-free system after organic growers repeatedly approached him for help.
This year, he has a grant from the Organic Farming Research Foundation to study no-till organic potatoes. In his recent conventional work on no-till potatoes, he found that weed suppression made the system promising for organic farmers.

“I got good yields and I had at times amazing weed control,” he said. “This year, I decided to bite the proverbial bullet (and use no herbicides) and the field was almost weed free.” Morse says that several changes should be made to adapt no-till to organic production. Most important is the choice of cover crop. Teasdale’s USDA research had already shown that a mixture of cover crops provided better weed control than a single variety of cover crop. He recommends a mixture of a cereal grain and a legume, such as rye and hairy vetch for an overwintering cover crop, or soybeans and millet for a summer cover. The proportions of each depend on your situation. Cereal grains are better at suppressing weeds because of their allelopathic effect and because they are woodier and degrade more slowly than succulent legumes.
“If you need weed control, go to a higher level of cereal crops like rye,” he said. “If the problem is not so much weed control as fertility, go with a heavy amount of legume like hairy vetch.”

Morse said he once compared three combinations of cover crops for no-till tomatoes: all rye, with 100 pounds per acre of Nitrogen fertilizer added; all vetch, with no fertilizer; and a mixture of half vetch, half rye with 50 pounds of Nitrogen. All three yielded almost identically, he said.

A cover crop of pure vetch will disappear so quickly that you can revert to regular cultivation if you don’t want to rely on the mulch for weed control. Morse cautions that hairy vetch seed has a certain percentage of what is known as “hard seed” that won’t germinate until the next season, when it could become a weed in the next crop.

Another good combination for overwintering is barley and crimson clover, he said. Barley is shorter than rye, and crimson clover is more easily killed than vetch, but it doesn’t contribute as much nitrogen.
Another strategy against late-season weeds is to supplement the cover crop mulch by applying more mulch, such as alfalfa hay, which contributes nitrogen as well.

Which crops?
Not all vegetable crops are suitable for no-till. Planting will be several weeks later than conventional planting dates for three reasons: First, the cover crop tends to keep the soil moist and cold in spring; second, the cover crop has to get big enough to make a good mulch; third, the farther into blooming the cover crop is when mowed or rolled, the more easily it will be killed. Trying to kill a cover crop before it’s flowering increases the chance that it will regrow; in fact, some growers wait till vetch is 50% in bloom before mowing it.

“For anything where you don’t need earliness, you need to take a serious look at no-till,” Morse said. “Pumpkins are the classic example of that. No-till pumpkins is the way pumpkins are grown now in many states.” Other crops that have succeeded with no-till include cabbage, tomatoes, cucumbers, potatoes, winter squash, and fall broccoli (which Morse likes to grow on a crop of German millet and soybeans).

Equipment needed
No-till requires a drill to plant the cover crop, which should be done in September in most parts of the country. Morse recommends first making raised beds, which will warm up and dry out sooner in spring than flat fields, but planting the cover crop seed on the top and sides of the beds and in between.
In spring, the cover crop can be mowed with a flail mower – less common than a rotary mower, but preferred because a rotary mower tends to make windrows of the crop rather than leaving it uniformly in place as the flail mower does. (A flail mower has rows of flails that look like pieces of chain that rotate around a drum and thoroughly chop the cover crop as they hit it.) Some growers also use rolling stalk choppers, used to chop corn stalks, or even just rollers that crimp the cover crop and kill it.

To plant through the cover crop, small growers use a coulter with extra weight on it, then plant by hand. Larger growers might want to purchase a mechanical transplanter that Morse designed especially for no-till vegetables. It costs about $4,500 and Morse says that about half of those that have been sold have been purchased by conservation districts or Extension offices. The planter is manufactured by B&B No-Till in Laurel Fork, Virginia. Direct-seeded crops such as pumpkins and winter squash can be planted with a jab planter.