Do you have a patch of cover crop that has gotten away from you? Dreading pulling out the brush hog to wrestle with your overgrown rye? You might consider rolling it down flat, then planting a veggie crop directly through the resulting "mulch".
Over the 2002-2003 growing season, our farm enacted a no-till vegetable research project funded by the USDA Sustainable Agriculture Research and Education program (SARE). In the fall of 2002, we planted two pairs of fields to cover crops: one half of each pair was planted to a rye/vetch combo, and the other half was planted to rye only. All fields were equally fertilized with compost and amendments, and the rye/vetch fields were deep chisel plowed before seeding in the fall. In the spring of 2003, the rye fields were mowed and tilled, then vegetables were planted into the bare soil. In the rye/vetch fields, the cover crops were allowed to grow to near maturity, when we rolled them down with a crimping roller to kill them. We then planted the exact same mix of vegetables through the dead cover crops and into the untilled soil below. Our research compared how much time we spent weeding each field, how weeds grew in unweeded test plots, yields and crop quality between fields, and also water usage.
To kill the rye/vetch cover crop, we waited until the vetch was in flower, and the rye had headed out but not yet ripened. Our neighbor Glen Jamison had a crimping roller that we borrowed for the afternoon. It was made of several small sections of 9" diameter steel pipe, with flat 4" fins welded onto them parallel to a common axle. The effect was great! As we pulled the roller over the standing cover crops, it knocked them down flat and crimped them in several places in just one quick pass. This effectively killed the rye/vetch, leaving behind a nice thick mulch on the surface. (We tried this out in 2002 with a flat roller… while it knocked things down nicely, we had to make several passes before we were convinced that the cover crops were dead, inevitably compacting the soil. The crimping action of those fins really makes a difference).
To plant into the mulch, we measured out the field, then stretched drip tape to mark straight rows. We used a bulb planter to poke holes in the soil for transplants of winter squash, melons, and tomatoes. This got old after a while on the larger fields, as those bulb planters really wear out your wrists as the untilled ground can be pretty firm. (Our neighbor Glen has used a waterwheel transplanter with good results.) We then watered things in with the drip tape. Meanwhile, in the tilled fields right next to our experimental patches, we were transplanting the same mix of squash, melons, and tomatoes into bare soil.
Our results were surprising and not what we would have expected in some cases. The first thing we learned is that you CAN raise a decent crop of vegetables in a rolled down cover crop without spring tillage. Most crops grew fine, though the winter squash had a difficult time establishing in the untilled ground due to poor root / soil contact in our bulb planter holes. The roll-down plots were also attractive in the exceedingly wet spring of 2003, when finding dry days for tillage operations was really difficult. While we had to push the line with compaction issues in the tilled plots, it was easy to find an afternoon dry enough to pull the roller over the spongy cover crops.
Where things got iffy was when the weeds started to grow. We actually spent more time weeding in the rolled-down mulch: since we couldn't cultivate or hoe out the weeds, we had to pull them all by hand. The mulch did do a decent job of reducing pressure from annuals like pigweed and lambsquarter throughout the season. However, perennials like bindweed and Canada thistle really took hold in the absence of tillage and gave us some problems. It seemed that vinegar or one of the other organic weed sprays might be a nice addition to this system.
Yields were also not what we had expected. Tomatoes produced equally well in the experimental and tilled plots, but crop quality was badly impacted by slugs during our wet growing season. The slugs were much worse in the mulch, bringing our marketable yield down to 67% as compared to 80% in the tilled tomatoes. Winter squash was weaker in the mulch early in the season, and ended up yielding 23% less, with a lower percentage of quality fruit as well. Melons however did perform better in the dead cover crops, presumably because of better water balance or else less annual weed pressure during a critical period.
Despite these results, we still feel that no-tilling veggies is worth pursuing in an organic system. The experimental tomatoes required about 2/3 the water of the conventional patch, and the soil was in much better shape at the end of the year, with 10 times as many worms and much less compaction. With prior-season planning for weed and slug control (or a drier year), those factors might present less of a problem. While we don't recommend you bet the whole farm on roll-down cover crops just yet, it is certainly worth a try if you are seeking a more soil-friendly production system.
We found the SARE program to be very friendly to work with, and we are grateful for the opportunity to test out this project on our farm. You can apply to the SARE farmer grants program at www.sare.org. Just never underestimate the challenge of running a production vegetable farm and a research grant in the same season! For more info on no-till vegetables, see Steve Groff's website at www.cedarmeadowfarm.com or see great pictures at http://www.sedlab.olemiss.edu/uep_unit/projects/cover_crops/.