Reduced Tillage

The excessive tillage that occurs on most vegetable farms (plowing, harrowing, cultipacking, bedding, 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 during droughts. Results from a recent survey of 55 vegetable farms in Connecticut found that almost 90% of conventionally-tilled vegetable farms had plow pans, compared with 33% for reduced-till operations, while 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 often reduce fuel usage and reduce field preparation time by over 66% when compared with conventional tillage systems. These systems usually provide equal or better yields than conventional tillage and may provide many other benefits as well.

Reducing the amount of tillage that takes place can help reverse the problems associated with excess tillage and begin to restore the health of a soil. There are many ways to reduce tillage on your farm, from simply swapping from moldboard plows and disc-harrows to using spaders, chisel plows or subsoilers which cause fewer problems, to implementing strip-till, zone-till, ridge-till, no-till or permanent-bed systems. Most reduced-till systems are used in conjunction with cover crops or organic mulches to protect the soil surface at all times, help increase organic matter over time, or to help control weeds. 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; the use of summer cover crops, such as buckwheat, after an early cash crop, as a substitute for repeated harrowing to control weeds; mowing crop residues instead of disking; planting tillage radishes or other deep-rooted cover crops to help  prevent plow pans from reforming; and using a no-till drill to plant cover crops, instead of a harrow to assure good seed-to-soil contact for emergence.

Deep zone-tillage, also known as vertical-tillage, is one of the more promising and versatile methods of reduced tillage for vegetables in our climate and can help vegetable farmers reverse the ill effects of years of excessive tillage on their soils. Deep zone-tillage is similar to no-till in that it relies on the residue of a cover crop to protect the soil surface and help improve soil health over time. Unlike no-till, which relies on a heavy blanket of plant residue in the planting row to protect the soil, and inadvertently delays crop growth in Northern climates, deep zone tillage uses a 5 to 12"-wide tilled strip to simultaneously break up plow pans, prepare a seedbeds and warm the soil. The cover crop must be dead before preparing the seedbeds. Planting and fertilizing can often be done in the same pass, further reducing fuel, machine hours, labor costs, fertilizer rates, and soil compaction. Soil drainage can be improved immediately and continues to improve each year.  The same herbicides, or some of the same cultural practices, are used to control annual weeds.

Machines used for deep zone-tillage usually consist of a lead coulter to cut through the killed-cover crop residue, followed by a deep shank or subsoiler to break up the plow-pan, 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, while spring resets push the shanks back down into position after passing over the obstacle. Crop roots grow deep through the slit made by the shank rather than just spreading out in the top few inches of soil above the plow pan. Additional coulters or (finger-like) residue managers are mounted on the planter in front of the planting shoes to remove excess cover crop residue and stones to provide a finished seed beds.

The soil surface between the crop rows retains the heavy surface residue from the dead cover crop. The 5 to 12"-wide tilled strip is slightly raised, warms faster than residue-covered soils or flat surfaces, and if installed across a slope, does not allow water to build up enough speed to erode a slope. Roots and surface residue from the cover crop in the untilled area between crop rows do not break down as fast as when the soil is tilled/aerated, so organic matter tends to increase over time. With the return of organic matter, comes the return of beneficial soil organisms, better soil structure and a healthier, more productive soil.

There are challenges to successful zone tillage management.  Killing cover crops and weed control can be problematic, especially with organic systems that do not allow herbicide use. Plant establishment can also be negatively affected by the presence of cover crop residues. Growers will need to be innovative to overcome these challenges.  Organic growers may try planting perennial rye or turf grass in the fall, and using a modified rototiller with the outside tines removed, to prepare narrow strips or seedbeds at the desired row spacing in the spring.  A subsoiler could be used to rip through the plow pan under the prepared strip to improve drainage, and a mix of soil, fertilizer and/or compost could be used to level the seedbed for planting or transplanting.  The living grass mulch between the crop rows can be controlled by mowing, while weeds within the row could be controlled by mulching, flaming or hoeing, or by planting competitive crops, such as pumpkins.  At the end of the season, simply seed the strip back to turf.  The next season, move the strips mid-way between the previously prepared rows and switch crops to complete your crop rotation.

There are other options to avoid using herbicides. Before early planted spring crops, use oats or a blend of cover crops that winter kill, such as oats, tillage radish and sun hemp before zone tilling and planting. Cultivation can then be used for weed control.  For summer vegetable plantings, use winter rye, but wait until it sheds pollen in June to roll it, or cut it and either bail it or windrow it to help suppress weeds between rows.  Organic 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.  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 Yoman Plow, which can be pulled with a 16 to 18 horsepower tractor.  

No-Till planters have double-disk openers and closing wheels to create and close the seed furrow in 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 a 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. No-till planting can be used for late-planted vegetables in New England, after the soil has warmed under the cover crop residue. It works well for pumpkins and winter squash or summer plantings of sweet corn or other vegetables. 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.

Strip-tillage, sometimes referred to as shallow zone-tillage, is similar to deep zone tillage without the subsoiling shank to break up the plow pan. The machine has two or three closely-spaced coulters and a rolling basket to prepare and smooth a narrow seedbed through the surface residue. Because the machine lacks a deep shank, this system does not have the ability to improve drainage immediately, and it may take several years for the soil health attributes and drainage to improve. However, on farms without a plow pan this system can provide most of the benefits of deep zone tillage and uses less fuel.

Strips for cash crops can vary in width and be used without herbicides.  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 just begins 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.  Plant or transplant the cash crop in the prepared beds while the cover crop continues to grow between the beds.  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 prepared bed 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.  Supplement the rye/vetch mulch with straw from a nearby field of rye.  

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 get a thicker stand late in the season.  After the cover crop winter kills, use a spader to make planting beds 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.  To initially construct ridges, start in the spring with a tilled field, and broadcast a cover crop that will winter kill, like field peas and oats.  Immediately construct the ridges, roll them to flatten the tops, and interseed the pathways between the ridges.  In the spring, use a residue cutter to slice up the dead cover crop and a rotary hoe to loosen the top inch of soil. The old crop residue and the top of the ridge is scrapped away or flattened to plant the new crop and then the ridge is restored to full height during the final cultivation. Usually two 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, lower inputs, and provide a warmer and dryer soil environment for seeds.

Permanent bed systems help limit soil compaction and maintain soil structure. Equipment and foot traffic is limited to paths or tracks between the beds. Some permanent beds are raised structures while others are not. There are many different ways to construct permanent beds. One simple method is to use a spader to till the soil and provide a rotation between cover crops and cash crops to provide organic matter, nutrients, weed suppression and a great soil environment for healthy crops.  Mulch is often used with permanent raised beds to add organic matter and suppress weeds.

For example, you can use a perennial sod cover crop for wheel tracks to avoid compaction on the beds and to increase habitat for beneficial insects.  In the beds, sow oats and field peas in the spring, and flail chop at a foot high. Incorporate it to plant summer vegetables.  For early vegetables, simply allow the oats and peas to grow all season and allow to winter kill before planting the cash crop the second spring.  If you use rye and vetch, flail mow it two or three times in the spring: first at six inches high, then very low before incorporating with a spader.  Multiple mowings help to slow the growth of the cover crops, allows the vetch to become dominant, and finally chops the residue finely for incorporation.  

Properly prepared weed-free compost can be used to fertilize and simultaneously mulch the beds for weeds.  Organic growers have even found that constructing raised-beds, and then using a thick layer of weed-free compost as a mulch, reduces weed seeds over time, and the same beds can be used for years, with straw mulch to control weeds between beds.