Cultivating Questions Concerning the Bioextensive Market Garden
by Anne and Eric Nordell of Trout Run, PA
I bought your video several years ago at a Washington Tilth conference; and I’ve changed my farming for the better because of it. Thank you. While I hope to transition to horses in the future, I currently farm using a Farmall Super A tractor. My hope is that I’m approximating horsedrawn tillage with this small tractor – it’s something like a motorized (and very heavy) riding cultivator. Alas, I can’t keep it from producing all that noise and noxious gas. Its single bottom plow even allows me to skim plow (albeit a little sloppily).
As Anne well knows, our mild climate makes it too easy to overwinter cover crops. Then the typically wet springs (and, on our farm, wet soils) let the cover put on loads of topgrowth before getting on the soil (the Super A is no help here). Buckwheat is the only crop that I can be certain will winterkill. Field peas, oats, annual rye and crimson clover have all overwintered here. Any suggestions?
My wife and I have just purchased a farm (I use the word “purchase” lightly as it is not paid for – Western Washington farmland is fast going the way of estates and golf courses and is priced accordingly). We’ll be working out rotational cover cropping for these new soils – silt loam and peat muck. At times they’re good and wet, and the weed pressures will be new to us also. It seems that a three mile move has us learning from the beginning again.
Best wishes for the coming year, and thank you for your fine work. Your articles are among my important resources.
Winterkilled Cover Crops For A Mild Climate
We feel a little bit more prepared to answer Jeff’s question about selecting winterkilled cover crops for a mild climate now that we have been in touch with several growers located in the coastal Northwest and the warmer parts of the central Midwest. All of these growers rely on cover crops that die back overwinter.
Each one agreed that buckwheat is the most dependable winterkilled cover for their area because it is so susceptible to a light frost. However, they warned, the timing for planting this frost-sensitive green manure can be tricky. Establishing buckwheat early enough to maximize biomass runs the risk of this quick-maturing cover setting viable seed before the first killing frost. These farmers also noted that the succulent buckwheat residues breakdown very quickly in the spring: a real advantage for early planting, but a drawback if a lot of winterkilled mulch is desired to hold in soil moisture and suppress weed germination.
Another favorite of these mild climate market gardeners is sorghum-sudangrass. They claimed this warm season grass is almost as frost-sensitive as buckwheat but produces a lot more coarse biomass. For this reason, we have trailed sorghum-sudangrass mixed with forage soybeans the last two years, comparing it with our usual winterkilled mix of oats and Canadian field peas.
We were pleased that the sorghum-sudangrass (“sudex” for short) could be planted a month earlier than the oats and peas without any danger of it going to seed before it died with the first fall frost. The sudex also produced significantly more topgrowth. However, the slow-to-decompose bamboo like stalks did not blanket the ground as completely as the mat of winterkilled oat-and-pea residues the next spring, allowing weeds to germinate in the patches of exposed soil which were also susceptible to the drying effects of the sun and wind. Several participants at our small group tours last year mentioned that they prefer Japanese Millet because its finer, leafier stalks produce a denser stand than the coarse sudex, resulting in much better weed suppression and moisture preservation.
If the seeds for these warm season annual grasses are not available in your area, both the sudex and Japanese Millet can be ordered from the Albert Lea Seed House in Albert Lea, Minnesota (1-800- 352-5247). Also, Seedway of Hall, New York (1-800-836-3710) offers several lines of sorghum-sudangrass as well as a new forage soybean. (Make sure to specify you want untreated seeds if your farm is certified organic. Also, be forewarned that shipping charges may double the costs of these reasonably priced cover crops.)
Seedway’s Donegal forage soybean variety grew 3-4’ tall in our trials and is supposed to get even taller where the summers are hot. Mixed with the sudex, or planted alone, this warm season legume should add some nitrogen to the soil system before it dies back with the first hard frost of the fall. It might also serve as a more manageable alternative to buckwheat or sudex where the winters are mild.
In addition to selecting cover crops with the appropriate degree of frost sensitivity for the area, the maturity of the plants at the onset of winter can make a big difference in their winter hardiness. Even in our relatively cold climate, we have noticed that the short and succulent topgrowth of late planted oats does not start dying back until the soil is frozen deeply and then thaws again. On the other hand, oats planted early enough to begin making seedheads before the first hard frosts will begin yellowing as soon as the ground starts to freeze. This principle may also hold true for more frost-sensitive covers, like sudex and soybeans, in milder climates.
Likewise, if the winter freezes are not strong enough to kill even the least winterhardy cover crops, then mowing the plants just before they reach maturity may do the job. We often use this mowkilled method for cover crops that we expect to overwinter in our area. For example, the old sicklebar mower is very effective at killing rye once this winterhardy cover has formed seedheads. We are guessing that oats and peas planted early enough to initiate seedheads by late winter in the Pacific Northwest could be successfully mowkilled before spring planted cash crops.
If none of these cover crop options prove dependable, then possibly the techniques we have developed for shallowly tilling winterhardy covers in northern Pennsylvania could be adapted to overwintering cover crops where the off-season is milder. The following photo essay documents two of the cover crop-tillage combinations we now use before LATE planted cash crops in the bio-extensive market garden. Maybe they would also work for earlier planted cash crops in coastal Washington. Mechanically speaking, we feel pretty certain that the horsedrawn tools shown in the photos would make a good match for the old Super A tractor.
We must end with one warning. The combination of winter cover crops and minimum tillage creates a wonderful habitat for slugs. Mulch-tilled cover crop residues provide both shelter and sustenance for these slimy critters, especially during the long periods of wet, cool conditions so common to the west side of the Cascades.
If slugs are already a problem, we suggest starting out with the most slug-resistant crops – such as garlic, potatoes, dill, cilantro, and transplanted tomatoes – for your first experiments with mulch-tilled cover crops. In the next column we plan on highlighting a couple of the makeshift ways we have tried to keep the slugs at bay, hoping this will encourage others to send us by snail mail their strategies for outsmarting these slow moving bugs for us to share in these pages.
Cover Crop-Tillage Combinations – 2002 Field Notes
Field 1 – Oats surface tilled before late May, zukes, cukes, lettuce, peas and spinach interseeded with buckwheat followed by a cover crop of rye late September; peppers and carrots on north side interseeded with string beans (for slug control), the pathways mulched with old hay after picking the beans
Field 2 – Rye surface tilled before summer cover of buckwheat and sudex followed by oats planted on ridges second week of September
Field 3 – Rye on ridges in middle of field surface tilled before late June and July, zukes, cukes, lettuce, peas and beans interseeded with buckwheat followed by cover crop of rye and spelt late October; surface tilled sudex, forage soybeans and field peas before May, spinach and peas interseeded with buckwheat followed by rye mid-September on north side of field; surface tilled sudex, beans and peas before April planting of strawberries interseeded with vetch on south side of field, berries mulched with wheat straw in December
Field 4 – Rye surface tilled/chicken tilled late June followed by cover crop of sudex and field peas seeded late July on south side of field and sudex, peas and oats mid-August in middle of field; rye on north side surface tilled before July broccoli, kale, pak choy, carrots and beets interseeded with rye
Field 5 – No-till garlic, onions, strawberries, leeks and radicchio early April on oat and pea ridges, surface tilled/chicken tilled late August followed by rye late September; ridge-tilled oats on north half of field seeded to April carrots, spinach, larkspur, beets and peas interseeded with buckwheat or hairy vetch, followed by rye mid-September
Field 6 – Rye surface tilled before June cover crop of oats and peas surface tilled before planting oats and peas on ridges late August
Field 7 – Rye and vetch surface tilled in June before July and August plantings of carrots, broccoli, kale, collards, lettuce, spinach beets and salad turnips interseeded with rye
Field 8 – Rye surface tilled late June replanted to rye and vetch early August; strawberries on south side surface tilled/chicken tilled after harvest before planting rye on ridges early September
XP (Experimental Patch) – Surface tilled sudex, peas and beans before planting alternating rows of tomatoes, onions and cut flowers interseeded with vetch followed by rye and spelt late October
Field 9 – Surface tilled oats and peas before May plantings of onions, leeks, winter squash, lettuce and peas; north half interseeded with vetch; south half interseeded buckwheat followed by rye and spelt mid-October
Field 10 – Rye and Italian ryegrass cover crop clipped repeatedly all summer, providing chicken pasture in October
Field 11 – Skim plowed Italian ryegrass clover mix before May planted potatoes interseeded with rye and vetch and followed by rye cover crop mid-September
Field 12 – Rye plowed early June replanted to vetch and clover mix early July
CS (Contour Strip) – Deep plowed bare ground on north side before April, carrots, beets, spinach and lettuce followed by rye late September; surface tilled oats and peas before early potatoes followed by oats and peas late August