The excessive tillage that occurs on most vegetable farms (e.g., plowing, harrowing, cultipacking, bed formation, cultivating) has many unintended consequences for soils and the environment. Some of the problems associated with excessive tillage include loss of organic matter and beneficial soil organisms; increased soil erosion and pesticide runoff; reduced soil fertility; loss of soil structure and porosity; compaction; surface crusting; formation of plow pans; reduced root growth; poor drainage; and reduced water-holding capacity. Results from a survey of 55 vegetable farms in Connecticut found that almost 90% of conventionally tilled vegetable farms had plow pans, compared with 33% of reduced-till operations, and the latter group had almost twice as much organic matter in their soils.
Tillage is also expensive and consumes a lot of energy. Reduced-tillage systems can reduce fuel usage and reduce field preparation time by over 66% when compared with conventional tillage systems. In addition to the these benefits, reduced-tillage systems can provide equal or better yields than conventional tillage for some crops.
Reducing the amount of tillage can help reverse the problems created by excess tillage and begin to restore the health of a soil. It can include making fewer tillage passes per year and/or reducing the intensity of tillage. Practices can be implemented individually or as a group and include switching from moldboard plows, disk-harrows, and rototillers to less impactful implements like chisel plows, s-tine cultivators, and spaders. Other examples of ways to reduce tillage include:
- Using chisel plow shanks, subsoilers, or zone-tillers to loosen soil before preparing raised-beds instead of a plow and harrow;
- Planting summer cover crops, such as buckwheat, after an early cash crop as a substitute for repeated harrowing to control weeds;
- Using tarps to kill weeds on smaller acreage.
- Mowing crop residues instead of disking;
- Planting tillage radishes or other deep-rooted cover crops to help prevent plow pans from developing;
- Using a no-till drill to plant cover crops and assure good seed-to-soil contact, instead of a harrow.
Minimum- and no-till systems rely on cover crops and their residues to protect the soil surface, prevent weed growth, and improve soil health. In these systems, a cover crop is planted and grown to a certain stage, then killed but not removed from the soil surface. Cash crops are planted into the field while some amount of the cover crop residues remain. Cover crops in these systems are most often terminated using herbicides, but can also be terminated using a roller-crimper or, on smaller acreage, crimping hand tools or tarps. Reduced tillage systems include no-till, deep-zone-till, strip-till, ridge-till, and permanent bed systems, each detailed below.
No-till systems involve planting directly into a thick cover crop residue. This system can be used for late-planted vegetables in New England, such as pumpkins, winter squash, and summer plantings of sweet corn or other large-seeded or transplanted vegetables. The thick layer of cover crop residue insulates the soil and keeps it cool longer into the spring than bare soil, making no-till unfeasible for early-season crops. No-till planters have double-disk openers and closing wheels to create and close the seed furrow in unworked soil, through a thick cover crop residue. These planters rely on down-pressure springs and/or extra weight to assure that the seed furrow can be created, especially in dry or compacted soil. If the accumulated crop residue is too thick or unevenly distributed, the planters may also have residue managers to move some of the debris before planting. When transitioning from conventional to no-till, yields have been known to decline slightly for a few years before recovering as the soil characteristics improve.
Deep zone-tillage, also known as vertical-tillage, involves tilling a 5”- to 12”-wide strip into cover crop residue with several implements, including a deep shank to break up the plowpan. The cash crop is planted into the tilled strip, and the soil surface between crop rows retains the heavy cover crop residue. The tilled strip warms faster than the residue-covered soil, which allows for the successful production of early-season crops. The inclusion of the subsoiling shanks means that soil drainage can be improved immediately. Implements used for deep zone-tillage usually consist of a lead coulter to cut through the dead cover crop residue, followed by the deep shank or subsoiler, and finally a pair of fluted coulters and a rolling basket to prepare a narrow seedbed and help break up soil clods. The deep shanks are mounted onto a hinged frame, which allows the shanks to rise out of the ground when they encounter large rocks or ledge. Additional coulters or finger-like residue managers may be mounted on the planter in front of the planting shoes to remove excess cover crop residue and stones to provide finished seedbeds. Planting and fertilizing can often be done in the same pass, further reducing fuel usage, machine hours, labor costs, and soil compaction.
There are challenges to successful zone-tillage management. Killing cover crops and controlling weeds can be difficult, especially on farms with heavy weed pressure. Plant establishment can also be negatively affected by the presence of cover crop residues. Growers will need to be innovative to overcome these challenges.
There are options to avoid using herbicides. For summer vegetable plantings following winter rye, wait until it sheds pollen in late May or early June to crush it with a roller crimper. Farmers who have worked most of the weed seed bank out of the top few inches of their soil through a combination of winter/summer cover crops, mulches, summer fallow periods, and timely cultivations may find it easier to adapt to zone-tillage than those fighting high levels of weed seeds in their soils. Note that specialized cultivation equipment will be needed to manage in-row weeds. The heavy residue or living mulch between rows will make mid-season cultivation of those areas difficult. Be sure to try this practice on small areas with low weed pressure. Small farms with equipment of insufficient size to pull a zone-tiller might try lighter-weight equipment to break through a plow pan and produce a seedbed, such as a Yeomans Plow, which can be pulled with 20 horsepower per shank.
Strip tillage, sometimes referred to as shallow zone-tillage, is similar to deep zone-tillage but without the subsoiling shank to break up the plow pan. The implement used for strip tillage has 2 or 3 closely spaced coulters and a rolling basket to prepare and smooth a narrow seedbed through the surface residue. Because the implement lacks a deep shank, drainage is not improved immediately in strip tillage, but should improve gradually over many years as the soil health improves. On farms without a plowpan, strip tillage can provide most of the benefits of deep zone-tillage while also using less fuel.
Strips for cash crops vary in width. To make wider strips in winter rye and vetch for late-planted vegetables, use a spader to prepare planting strips early in the spring, when the rye is just beginning to grow, leaving equally wide strips of the cover crop to mature. A cultipacker or some other finish tool may be needed to smooth the seedbed for small-seeded crops. The cash crop will be planted into the prepared strips while the cover crop will continue to grow in between the strips. To kill the cover crop, cut it when the rye is shedding pollen or when the vetch begins to flower, and spread the straw residue over the planted strip as a mulch to help suppress weeds around the cash crop. It is best to cultivate the beds once before cutting and spreading the residue from the adjacent cover crops. The rye/vetch mulch can be supplemented with straw brought in from other fields.
For early-season vegetables, use a two-year system with spring-planted oats and field peas. During the first summer, after the cover crop forms seeds, mow it to drop the new seeds onto the soil and get a thicker stand late in the season. After the cover crop winter-kills, use a spader to make the tilled strips for vegetables and use a straw mulch between beds or cultivate. A similar process can be done with medium red clover sown between or under a cash crop the first year. When the cash crop is harvested and mowed off in late summer or fall, the clover will fill in to make a solid stand by spring. A spader can then be used to make seedbeds for the new cash crop in the clover stand.
Ridge tillage is a reduced-tillage system where the crop is grown on top of permanent ridges. This system works well for fields that are often too wet to work in the spring. To initially construct ridges, start in the fall with a tilled field, and broadcast a cover crop that will winter-kill, such as field peas and oats. Immediately construct the ridges and roll them to flatten the tops. In the spring, use a flail mower to chop the dead cover crop residue followed by wavy coulters or a rotary hoe to loosen the top inch of soil. This scrapes away the old crop residue and flattens the top of the ridge in order to plant the new crop. The ridge is then restored to full height during the final cultivation. Usually 2 cultivations are required to help control weeds, loosen the soil, and re-construct the ridges. Straw can also be used between ridges to suppress weeds. The ridges can be replanted for many seasons before they need to be reconstructed. As with many reduced-till systems, specialized equipment is required for planting, cultivating, and possibly harvesting. Ridge tillage helps conserve moisture, reduce inputs, and provide a warmer and drier soil environment for seeds.
Permanent bed systems can be established where equipment and foot traffic are limited to paths or tracks between beds. Mulch or properly prepared, weed-free compost is often used to add organic matter and suppress weeds.
Tarping can be used in reduced- or no-till systems to kill weeds and terminate cash and cover crops. This practice is most often used on relatively small acreage—tarp weight and bulk is the limiting factor. The typical tarp size ranges are 16’–50’ wide and 50’–100’ long. A 50’ x 100’ 5 mil silage tarp weighs 150 lb when clean and dry. It is possible to purchase tarps less than 4 mil thick, but they often do not last longer than a single season. While 5–6 mil tarps contain more plastic, they typically last many (8–10) seasons. Black tarps successfully control most weeds when left on fields for 3 weeks during the early or late season or for 1 week mid-summer.
To successfully use tarps for bed preparation, the tarp must: 1) terminate any living plants (cash crop, cover crop, or emerged weeds), 2) help create a planting bed that is suitable for the following crop, and 3) provide adequate weed suppression in the early period of cash crop growth, if not longer. If tarping achieves these 3 goals, this practice can provide some or all of the bed preparation services typically provided by tillage. Tarps can help fill a niche for farmers using minimal tillage by creating weed-free planting conditions for the following crop.