Case Study 2: Deep Zone-Tillage (DZT)

Case Study II: Deep Zone-Tillage (DZT) at Scott’s Yankee Farmer, East Lyme, CT

By Jude Boucher, Extension Educator

Farmers: Tom & Karen Scott, and daughter, Allison

Farm size: 125 acres (half owned, half rented)

Crops: Tree fruit, small fruit, sweet corn and mixed vegetables

Climate: Located in New London County about 3 miles from Niantic Bay on Long Island Sound, the farm enjoys some on-shore breezes (winds!) during the summer months and a slightly warmer fall than most of the state.

Farm History & Markets

Tom’s father purchased the farm in the early 1940s and originally ran it as a dairy. As the years went by the Scott family transitioned to tree fruit and, in the mid-70s, began retailing through pick-your-own operations and their own farm stand. Tom farmed all his life, and he and his wife Karen began to manage the farm in 1980. In 2008, they added a CSA program to their stand operation.

Soils and identified soil health issues:

Scott Road – Agawam, Canton & Charlton sandy-loams.

Behind Stand – Paxton & Montauk sandy-loams (very stony).

Kowalski’s (rented) – Haven & Enfield sandy-loams (stony).

Bert’s (rented) – Merrimac sandy-loams.

John’s (rented) – Paxton & Montauk sandy-loams (stony).

Prior to adopting reduced-tillage, Soil Health Tests identified consistent problems in most fields with low total organic matter, active carbon, potentially mineralizable nitrogen and excess subsurface hardness (plow pans). Other fields were rated mediocre or below optimum in available water capacity, surface hardness/crusting, root health and/or had low levels of potassium. Plow pans ranged in depth from 9 to 12 inches.

Crop mix

Apples, peaches, plums, strawberries, blueberries, raspberries, sweet corn, corn maze, tomatoes (greenhouse and field), peppers, eggplant, pumpkins, summer and winter squash, cucumbers, cabbage, broccoli, cauliflower, spinach, Swiss chard, snap beans, lettuce & greens, peas, herbs, flowers, cider and donuts. They raise all their own transplants and flowers in 4 greenhouses.

Rational for Adopting Deep Zone-tillage

Immediately upon hearing about DZT in 2007, Tom expressed interest in switching to this reduce-till method. He was mainly interested in the new system’s ability to increase soil organic matter, improve soil structure, break up plow pans and improve soil drainage. He purchased a 4-row Unverferth Zone Builder in the winter of 2008 and started zone tilling in April that same year.

Early Experiences

Tom was not tentative about DZT and immediately set about using the new system on every crop on his farm, including his perennial crops, such as for strawberries and when replanting apple orchards. He figured that if it made sense to loosen the compacted soil under his annual plants, it made twice as much sense to loosen it under his perennial crops, since he would only have one chance at improving root growth. He even used the machine between the rows of strawberries during renovation to eliminate compaction causes by foot traffic during harvest.

Since the 4-row machine was as wide as a single road lane, Tom moved the machine across town to his rented fields during the middle of the night when there was less traffic. He later added hydraulic lifts on the depth wheels so he could tow the machine on the road instead of lifting it with the tractor hitch.

Because he had both early and late fields across town, but wanted to prepare them both for planting at the same time to minimize transporting the machine, he came up with a unique post-emergence herbicide program for his sweet corn. By the time he got around to planting the later field, weeds would have emerged. So, he used a combination of Callisto (3 oz.), Dual (1.5 pt), Atrazine (0.5 pt), Impact (0.6 oz), nitrogen and methylated seed oil, to provide both pre- and post-emergence control of weeds with a single post-emergence application. Upon learning that he wasn’t suppose to apply two herbicides from the same family (Callisto and Impact) during one season; he later gave up all but the Impact, oil and ammonium sulfate treatments. This single herbicide, nitrogen and oil treatment is capable of controlling both broadleaf and grass weeds if applied to the right size weeds. However, because the weeds emerged sooner in the seedbed (zone tilled strip) than from under the cover crop mulch between the rows, there was no way to make a single application before the grass in the crop row was too large to kill. He eventually settled on two applications on his sweet corn: Dual applied pre-plant/pre-emergence, and if necessary, Impact, nitrogen and oil applied post-emergence, after the weeds came up from under the mulch between the rows.

Tom’s Procedure and Techniques using DZT

A Soil Health Test was conducted on each of Tom’s vegetable fields to provide preliminary data on chemical, physical and biological attributes. He will re-test them in 5 years to see if DZT has helped improve his soil health and removed the plow pan.

All of Tom’s vegetable fields are planted to winter rye for a cover crop. Tom kills the cover crop when it is 4 to12-inches tall using Roundup and oil, at least 3 weeks prior to zone building and planting. He tried using paraquat and oil on one early corn field when the temperatures were low to see if he could get a faster kill, but ended up re-spraying with Roundup to get a complete kill. He usually mows off the previous season’s crop and spins on his cover crop in the fall. However, in the field(s) where he planned to make raised-beds the next season, he used to harrow in the cover crop seed in the fall to improve seed-to-soil contact and germination, but also to loosen the soil so that he can make the beds in an unplowed (zone-tilled) field in the spring. Tom found that the ground was too hard to make beds with just zone tillage in the spring if the cover crop was mowed off in the fall.

Tom has been transplanting all his small-seeded crops, such as beets and Swiss chard, for years to improve emergence and plant stands. He used to use his zone builder to subsoil under the planting row before preparing and covering his beds with plastic. In order to gather up enough soil to make a raised-bed in the untilled, rye-mulch-covered ground, he added extra-large, aggressive, 22-inch disks to his bedmaker. For single row crops, like tomatoes, he would leave a strip of untilled mulched soil between the beds. However, with double-row crops, like peppers, he used to run his zone builder up and back to subsoil under both rows in each bed. On his return trip, he passed close to the first pass to loosen the soil under both crop rows in each bed, but because he has a 4-row machine, he ended up zone-tilling 4 beds at once, and there was no rye-mulched-ground left between the beds. Since all the ground ended up being tilled by either the zone tiller or the bedder, this seemed to run counter to the philosophy behind reduced till. However, Tom felt that he still eliminated the plowing and harrowing prior to bed-making and that it was just as important to loosen the soil under his bedded crops as under his non-bedded crops. He pointed out that on other farms where they only zone-till their large seeded crops (i.e. sweet corn and pumpkins), and rotate their land, they end up skipping reduced till all together the year they bed the ground for solonaceous or cucurbit crops. He noted that when he bedded a piece of land, he at least reduced the number of passes with tillage equipment and continued to loosen the soil and break up the plow pan under the row.

In 2010, Tom discontinued using his Unverferth Zone Builder to prepare beds and built a homemade “zone tiller” to loosen soil under the crop row before making beds. Originally, this consisted of 2 chisel plows, followed by coulters to help loosen the soil for the bedmaker. However, his latest model consists of only 4 chisel plows, spaced about 11-inches apart to loosen the soil under the bed. The chisel plows facilitate the bedding process and leaves rye-mulched-ground undisturbed between the beds.

He uses a 4-row John Deer 7000 planter for large-seeded crops, with 36-inch row spacing, so his Zone Builder is set up to match. The subsoiling shank on the zone builder is usually set to a depth of 15 inches to break up the plow pan. Dawn (brand) residue managers, attached immediately in front of each shoe on his planter, help clear away any remaining cover crop residue or stones that the Zone Builder fails to re-move from the seedbed. The Dawn residue managers have a knob to easily make fine adjustments in height, so that only debris and not soil is removed from the planting row. Common pre-emergence herbicides are used on most crops at planting or post-emergence herbicides are used between beds.

In 2009, Tom designed and built a fifth-wheeler-style, goose-necked hitch that allows him to pull his planter behind his Zone Builder. This hitch allows Tom to prepare the field and plant it in a single-pass, thus further reducing soil compaction and fuel consumption. He pulls his machines with a 110-hp John Deer 4240 tractor and has added a quick-attach forklift weight to the front end to compensate for the weight of the Zone Builder. Because he has rocky soils he usually drives at about 3 mph, which is slower than is usually recommended for a zone tiller. Growers with rock-free ground sometimes zone till at 7-8 mph.

Fields are spread with lime in the fall. Potassium, phosphorus and nitrogen are banded at planting and ammonium nitrate and/or urea is side-dressed when the corn is 8 to 20 inches tall.

Notable Changes in the Field Preparation Process

The biggest changes in preparing Tom’s fields include an additional herbicide application to kill the cover crop, and the speed at which he can now prepare a field. He doesn’t miss the plowing, harrowing and many passes with a cultivator or the dust associated with conventional tillage. He notes that he still uses his in-row Reggie cultivator for crops like pumpkins, winter squash and strawberries. Tom has also eliminated the backbreaking chore of picking rocks on his stony ground. Now, he simply removes the occasional large stone which the zone tiller pulls to the surface with the front bucket on his tractor. He has also switched to mowing off crop residue before spinning on cover crop seed for all of his acreage rather than harrowing in the crop residue and seed.

Originally, Tom planned to buy a second one-row zone builder for his pumpkins, so he wouldn’t have to take tools off to increase row spacing. However, since he usually grows pumpkins on plastic mulch, he now uses his homemade chisel plow to loosen the soil for his pumpkin beds as well.

Tom’s DZT Equipment and Modifications

Unverferth 4-row Zone Builder, equipped with a 22-inch wavy front coulter, re-set springs for the sub-soiling shanks, two 13-inch coulters, and rolling baskets. He used shims to reduce the spring reset tension from 8,000 to 6,000 psi so that the shanks would trip faster in his rocky ground.

He also built a goose-necked hitch to tow his planter and added hydraulic lifts on the depth wheels of his Zone Builder so he could tow instead of carry his machine on the road.

4 Dawn (brand) Residue Managers for planter.

4 plastic seed firmers (for uniform seed depth and emergence)

2 22-inch aggressive disks for his homemade bed-maker.

Homemade 4-shank chisel plow to help prepare raised or flat plastic-mulched beds.

Brushhog rotary mower (to prepare field for seeding cover crop)

DZT Benefits and Drawbacks

Tom measured out 2 square acres of field and used conventional tillage (plow and harrow) to prepare one acre for planting and deep zone tillage to prepare the other. He measured both the time it took him to prepare the planting site with each technique and the amount of fuel used to do so. He found that it took him 1.5 hours to prepare the field with conventional tillage and just 0.5 hours with DZT: a 66% reduction in preparation time. He also found that he reduced his fuel consumption from 4.5 gallons/acre to just 1.25 gallons/acre using the new reduced tillage method: a 72% reduction in fuel consumption. This was done before Tom built the hitch for his planter.

He then estimated that if he had included planting time, he would have reduced his time to prepare and plant the field by 80-83%, because he could pull the planter behind the zone builder and accomplish both tasks at the same time (0.5 hours), while it would have involved another trip across the field after conventional tillage. Planting may have added another gallon of fuel to the conventional method, resulting in a total fuel savings of 77% using DZT. His calculations did not include cost reductions for machine-hours, reduced cultivation time and less time spent picking rocks. Tom has experienced both increased water drainage in his fields after storms and the preservation of soil water during drought conditions due to DZT. He has watched 3 to 5-inch rainfalls absorb into the ground within hours where it used to stand for days in low wet holes. He even has a set of pictures of himself in another grower’s field (only 100 yards from one of his fields) knee-deep in water after a storm and again 3 days later. The standing water soaked into Tom’s DZT field within three hours the same day. During the wet 2009 season, Tom estimated that he increased his yields by 12% because he was able to plant on time despite the rain and plant some areas he would not have normally been able to in a wet season.

It is common for the East Lyme area to go six or more weeks without rain during mid-summer because of on-shore winds that seem to blow the clouds inland. Tom has some rented sweet corn fields without water and has experienced better plant stands with much less wilting or drought-related crop damage since switching to DZT. In fact, with the extreme dry conditions in 2010, he didn’t feel the need to hook up his irrigation for his pumpkins and the crop did well.

The main drawbacks that Tom has observed with DZT, are the additional herbicide applications and “just getting acclimated to a different system.” He continues to explore ways of getting good weed control with a single application and another to kill the cover crop. He also continues to build and modify his equipment to perfect zone tillage.

Art of DZT (What has Tom learned)

Tom has learned that you can’t skip the pre-emergence herbicide application for corn because weeds emerge in the row and between the rows at two different times. This is a particular problem if you prepare a field way ahead of time with the zone tiller and plant much later (6 weeks). You also lose the benefit of retaining soil moisture for quick crop seed emergence if you delay between DZT and planting.

He also learned the hard way, by popping a wheelie, that you need extra weight on the front of the tractor to counterweight the Zone Builder. He had originally purchased a hitch from the dealer to pull his planter behind the Zone Builder. However, the hitch was designed to stick straight off the back of the machine and weighed 200 pounds. After his wheelie experience, he decided that a goose-neck hitch that brought the weight of the planter up near the tractor would be much safer. He returned the original hitch to the dealer and built his own. His hitch has worked well.

He learned that ground that isn’t at least lightly harrowed in the fall is hard and tough to bed in the spring if you are just zone tilling prior to bedding. He has not experienced this same problem when he pre-conditions the ground with chisel plows immediately before making raised-beds.

He also confirmed that, although he loves DZT, he doesn’t like standing up in front of a crowd talking about it (public speaking). He would rather talk to farmers interested in DZT one-on-one.

Tom’s Advice to Farmers Interested in DZT

DZT is a much faster, cheaper and easier way to prepare your fields and you improve them at the same time.

“There is no turning back!”

DZT works much better if the cover crop is completely dead. Spray Roundup 3 weeks before you DZT and plant.

What’s next?

Tom will be adjusting all his equipment from a 36- to a 30-inch row spacing for next season. He hopes to continue to help other growers transition to DZT. He invites you to give him a call and/or come for a visit to see his equipment.

Tom Scott Scott’s Yankee Farmer 291 N. Bride Brook Road East Lyme, CT 06333 860-739-0247

T. Jude Boucher, Agricultural Educator-Commercial Vegetable Crops, UConn Cooperative Extension, Vernon, CT. November 2010. Reprinted from Croptalk v.6.2

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