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Cultivating Questions Ridge-Till Retrospective

Cultivating Questions Ridge-Till Retrospective

Cultivating Questions: Ridge-till Retrospective

by Anne and Eric Nordell of Trout Run, PA

Bryan O’Hara’s article about his amazing no-till vegetable system in The Natural Farmer’s “Building Soil Carbon” Supplement (Summer 2014) prompted us to visit Bryan and Anita’s Tobacco Road Farm on our way to a speaking engagement in Connecticut. Not only was this the first organic farm we had seen that had successfully implemented continuous no-till for a rapid succession of intensively-planted vegetables, but the majority of their six-figure income is generated from just three acres: half permanent no-till beds, the other half infrastructure, homestead, etc…

We know of two other small-scale produce enterprises which use a similar approach to permanent no-till, Jay and Polly Armours’ Four Winds Farm in Gardiner, NY and Paul and Elizabeth Kaiser’s Singing Frogs Farm in Sebastopol, CA. The key to continuous production without tillage on all of these farms is using a permanent mulch of compost. The undisturbed 2-3” layer of compost preserves soil integrity and moisture while preventing annual weed seeds from germinating. Although dealing with crop residues and replenishing the mulch of compost requires extra work, the O’Haras’ crew prefers this no-till method over the tillage culture formerly used because it eliminates most of the time spent on hand weeding.

The permanent mulch of compost at Tobacco Road Farm makes an ideal seedbed for soil warming and direct seeding. By contrast, the more common practice on organic farms of no-tilling into a mowed, rolled or winter-killed cover crop often keeps the soil too cold in the spring for good germination, limits no-till to a few cover crop windows, and rarely provides full season weed suppression.

The reality on our farm and many others is only a few vegetables are suitable for no-tilling into a cover crop and that tillage is used before planting the cover crop and after harvest of the no-till crop. Consequently, the improvements in soil quality and plant health from no-tilling are temporary at best.

We requested permission to reprint Bryan’s article in the Small Farmer’s Journal because it points the way to a new level of soil management and provides such an instructive contrast to our land-extensive, tillage-and-cover crop dependent system. Although the intensive no-till and extensive cover crop methods may not seem compatible, there are situations where the two systems could benefit from working in tandem. For instance, Bryan emphasizes that perennial weeds can be a real challenge for permanent organic no-till. Taking land out of production to set back quack-grass, field bindweed, or Canada thistle with cover crops and tillage could make the transition to a permanent mulch of compost much smoother.

Corresponding with Bryan after our visit, we learned that he is a Small Farmer’s Journal subscriber, big fan of Lynn Miller’s, and longtime follower of the “Cultivating Questions” column. At the conclusion of a recent letter, Bryan asked, “How is the ridge-till going? Any changes?” The following is a brief overview of how ridge-tillage has evolved on our farm into a hybrid, low-till system for alliums and greens.

We began experimenting with ridge-till vegetables in 1997 thinking that this row crop system would allow us to plant spring produce into a winter-killed cover crop with a minimum of soil disturbance. Originally developed in the Midwest as an alternative to chemical no-till which aided soil warming and mechanical weed control, we adapted ridge-tillage to horsedrawn market garden production by attaching the rough equivalent of a ridge-till sweep to the middle of the riding cultivator. We initially used a cast-off roto-tiller middle buster found on the farm, then upgraded to a heavier duty customized 12” sweep, and finally settled on a 10” furrower purchased from Agri-Supply. Although all of these variations on a ridge-till sweep performed well, the latter did the best job of skimming the cover crop residue off the top of the ridge, opening up a narrow band of clean soil for direct seeding or transplanting.

Pleased with our mechanical success, we relied exclusively on ridge-till for planting our earliest crops. Over time we encountered several drawbacks to this system. Maintaining uniform depth of the ridge-till sweep could be challenging. Often the ridge-tilled seedbed was too firm for planting with our walk behind seeder unless we lightly tilled the band of exposed soil. If we were not careful, this extra step would dry out the seedbed too much for fast, uniform germination without irrigation.

Ironically, the soil tilth in the pathways where the cover crop residues were concentrated looked better than in the ridge-tilled planting zone. We eventually came to the conclusion that ridge-tillage was counterproductive precisely because it moved the fresh organic matter away from the crop row.

We tried no-tilling directly into the cover cropped ridges to keep the residues in place and maintain soil integrity. No-tilling the ridges was definitely a boon to soil quality, but leaving the blanket of winter-killed biomass intact limited crop selection to vegetables that were fairly slug resistant and appreciated cool, moist soil. At the other extreme, the spring drought of 2005 taught us that the cover crop mulch was not adequate for preserving the moisture unless we added straw to the valleys and lightly tilled the ridge-tops at the very start of the growing season.

To get away from buying in straw to beef up the mulch in the valleys we began experimenting with growing additional cover crop mulch next to the ridge-planted crops. Noting that the cover crop stubble was well suited to minimum-tillage led to a hybrid, low-till system which works for a wide range of vegetables. We use the cover cropped ridges exclusively for onions and garlic because they seem to benefit the most from the heavy cover crop mulch and undisturbed soil. The short cover crop stubble remaining after mulching the alliums facilitates minimum-depth tillage and soil warming while virtually eliminating slugs, a nice combination for planting spring and fall greens.

Due to the difference in planting windows and cultural requirements between garlic and onions, we use two slightly different cover crop / stubble tillage systems:

– No-till garlic on early planted oat ridges mulched with adjacent cover crop oat straw, with spring lettuce, spinach, salad mix ingredients, beets and peas planted in the shallow-tilled oat stubble.

– Minimum-till onions on late planted oat ridges mulched with adjacent cover crop rye straw, with fall lettuce, spinach, salad mix ingredients and brassicas planted in the shallow-tilled rye stubble.

The photo essay in the Fall 2013 Cultivating Questions illustrates the no-till garlic / oat stubble sequence. This column includes images from this past year of the minimum-till onion / rye stubble combination. A big difference between the onion and garlic sequences is we have found it beneficial to delay planting the oats for the onions a month later, the first week of September. The later planted oats decomposes more quickly in the spring, facilitating seedbed preparation, planting and cultivation. The first week of September is also an optimal planting period for the adjacent strips of rye to maximize biomass production for mulching the onions.

Our rationale for lightly tilling the ridge-tops is to prevent the soil from crusting and drying out before planting the onions. Our primary objective for cultivating the onions is similar: to maintain an earth mulch to hold in moisture while the soil in the ridges has a chance to warm up and the onions take off. Cultivation also deters blown-in dandelions from getting established before mulching the ridges.

Due to the three-dimensional topography of this ridge planting system, we break cultivation down into several steps, first focusing on the level ridge-top using a sweep on each side of the row, then turning our attention to the sloped sides of the ridges and the pathways using a couple of quack-digger shovels (one forward, one at the back) on each gang. Although the sweeps are set flat and shallow, they shed soil off the shoulders of the ridge. The action of the shovels throws soil back on the ridge. It often requires two passes with the straight shovels at different depths and positions to thoroughly loosen the firm valleys and re-berm the shoulders. Yes, this ridge cultivation program requires several passes, but it simplifies cultivator adjustments and eliminates problems with oat residue plugging.

The timing of cultivation really depends on soil condition, moisture and weeds. In 2015, the ridge-tops remained loose and moist during the dry month of May which also delayed germination of the dandelion seed. We planted the Walla-Walla, Expression and Candy onions between May 4 and May 9 and cultivated the ridges on June 12.

Meanwhile, we mowed the rye growing on either side of the onions on May 29 when it was 4-1/2 – 5-1/2‘ tall and dropping pollen. We raked the dry straw into windrows on June 17 and immediately moved the windrows into the freshly cultivated pathways by hand.

Mulching the onions mid-June reduces thrip activity and preserves moisture before the crop begins bulbing up after the Solstice. Despite the heavy mulch, the ridges provide excellent drainage and good air circulation would the weather turn wet. In 2015, we experienced an unusually high number of rainy days from the beginning of June through the middle of July when the weather turned abruptly dry.

Harvesting ridge-planted onions promptly is important since the necks tend to grow thick, slowing dry-down of the tops and making the crop more susceptible to bacterial center rot. According to research at Penn State, planting onions close together in multiple-row beds keeps the necks thin and can minimize the impact of this disease by speeding up curing. So does harvesting the crop early although this strategy can reduce bulb size. We pulled the storage onions on August 7 when most of the bulbs weighed over a pound, topped them 10 days later and cured them in a well-ventilated hoop-house with no evidence of center rot.

Growing the onions on mulched ridges increases the odds of getting good crop without irrigation. Removing the rye straw for mulching the onions also simplifies minimum-depth tillage of the rye cover crop. In 2015, we skim-plowed the rye stubble on one side of the onions to create a clean seedbed for direct seeded fall greens. The rye stubble on the other side we worked up with a single 3’ section of spring-tooth harrow equipped with 7 widely-spaced teeth followed by sweeps on the riding cultivator. Working the stubble into the surface of the soil held enough moisture for transplanted lettuce and brassicas to take off without missing a beat, quite a contrast to the slow start of the same crops in a field of plowed clover.

Removing the cover crop straw makes it possible to grow a mature cover crop with an extensive, soil building root system and take advantage of the moisture preserving benefits of shallow tillage without contending with a lot of troublesome trash. The downside to this low-till system is that growing a mature cover crop and removing the biomass depletes soil nitrogen. Applying a light coat of compost to the rye four months before the first harvest of fall greens meets food safety guidelines and supplies just enough nitrogen for the lighter feeders like lettuce and salad mix. This past year we also spread peanut meal before stubble tillage which made all the difference in the growth of the brassicas, spinach and other heavy feeders.

At this point in our ridge-till adventure, growing our own mulch for the alliums seems like a tradeoff between buying in nitrogen instead of buying in straw. We have been experimenting with sweet clover as a nitrogen-fixing alternative to rye. The fall greens planted in the shallow-tilled sweet clover stubble look like they are getting enough nitrogen, but the flowering legume is challenging to mow, makes a stemmy mulch, and covers half as much area as the mulch produced by a rye cover crop. We may need to try growing a legume in the understory of the rye or significantly increasing the compost rate. One way or another, the next step in this hybrid, low-till system is figuring out how to grow a cover crop mulch and a cash crop, too, without buying in nitrogen.

Ridge Building

Cultivating Questions Ridge-Till Retrospective

The ridge building process has not changed much over the years. First, we shallowly till a spring cover crop and application of compost, then broadcast oat seed before forming the ridges with the riding cultivator. Two sets of disc-hillers on the cultivator form a broad ridge, roughly 5” high, while incorporating the cover crop seed. A straight shovel at the back of each gang marks a guidance furrow for the next pass and for seeding a single row of oats in the valleys with the walk behind seeder.

Cultivating Questions Ridge-Till Retrospective

Rolling the field with a cultipacker insures good seed-to-soil contact and flattens the ridge-tops. A firm, level ridge-top makes planting the low-till alliums easier.

Cultivating Questions Ridge-Till Retrospective

This photo shows the oats growing a month after ridge building and seeding a single row of oats in the valleys. Our goal is complete soil cover as quickly as possible because the hilled field is more prone to erosion than flat land.

Cultivating Questions Ridge-Till Retrospective

Using the customized 12” sweep to skim the top off the ridges opens up a band of clean soil for direct seeding or trans-planting. Ridge-tilling also enhances soil warming for the earliest spring vegetables, but it moves the most improved soil and fresh organic matter out of the planting zone.

Cultivating Questions Ridge-Till Retrospective

The combination of live roots, compost, fresh cover crop residues and well-aerated soil creates a beautiful crumb structure in the ridges. Reduced tillage systems seem to perform best when soil tilth and structure are improved well ahead of planting.

Lightly Tilling the Ridges

Cultivating Questions Ridge-Till Retrospective

Chopping the winter-killed oat residue with the custom-made residue cutter on May 1, 2015. A second pass with the coulters offset slices the residue into smaller pieces.

Cultivating Questions Ridge-Till Retrospective

Rotary hoeing the ridges the same morning. Although we have not tried it, a disc with the blades set straight might make a readily available substitute for the less common residue cutter and rotary hoe. Either way, lightly tilling the ridge-tops makes…

Cultivating Questions Ridge-Till Retrospective

…a nice seedbed and preserves moisture for transplanting the onions without irrigation.

Cultivating Questions Ridge-Till Retrospective

Onions well established on the ridges despite the unusually dry, hot conditions in May. Rye growing on either side of the onions to be used for mulching the valleys, then planting fall greens in the shallowly tilled stubble.

Cultivating Questions Ridge-Till Retrospective

Andrew mowing sweet clover, June 15, for mulching fall lettuce and brassicas to be planted in the adjacent tilled soil. This tap-rooted legume leaves more nitrogen in the soil than the rye, but can be more challenging to mow and does not produce as much mulch material.