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High tunnel tomato variety trials

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Four RI farms participated in a 13-variety tomato trial in 2013. The trials were funded through a 1-year $15,000 Northeast Sustainable Agriculture Research & Education (SARE) Partnership Grant titled “Realizing the potential of high tunnel tomato production and income in southern New England.”

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Andy Radin of URI Extension led this project and oversaw URI’s Experiment Station demonstration of intensive indoor tomato cultivation methods including pruning and an adjustable, “leaning and lowering” trellising system.

Project Summary

Season extension using high tunnels has increased the economic viability of small farms across the globe. Indoor production generally reduces disease pressure and fungicide cost. Early production means higher prices in early summer value often leading to higher profits. Smaller varieties were ready by the end of June. The extra labor required for intensive indoor growing and trellising is generally easily recovered in increased early sales (at high margins) and reduced input costs.

The primary parameters measured in the trial were yield and tissue nutrient levels. Growers used their preferred production method, either conventional or organic. Farmers grew with or without mulch, using various water and pest management plans, trellising systems and fertility inputs.

Tomatoes are well suited to intensive production under cover. RI has 66 high tunnels constructed through the NRCS-EQIP Seasonal High Tunnel Initiative with many more in nearby CT and MA.

These tomato trials benefit new and experienced high tunnel growers with tomato variety recommendations and trellis demonstrations for maximum use of covered growing space. Growers from RI, CT and MA attended a Twilight Meeting at URI’s Agronomy Research Farm, which featured tasting, comparison of tomato varieties and a demonstration of the trellising technique. The Northeast Organic Farming Association of Rhode Island (NOFA/RI) held a Collaborative Regional Alliance for Farmer Training (CRAFT) Workshop at Blue Sky Farm in Cranston, RI, one of the four tomato trial farms.

Variety Trial Results

The 13 indeterminate tomato varieties were selected because they tolerate the 10 to 20% lower light intensity of the high tunnel yet have exceptional flavor, appearance and direct-marketability. The varieties are (in order of greatest yield per plant): Clermon, Golden Rave, Rebelski, Granadero, Suzanne, Pink Beauty, Sakura, Juliet, Pozzano, Black Cherry, Golden Sweet, Red Pearl and Indigo Rose.

Planting Recommendations

Tall high tunnels are the best suited to this type of trellising system. Radin recommended a 96’ by 30’ tunnel for 330 plants, though growers use a much higher density. A typical planting might include 175 cherry tomato plants (yielding 12 pints/plant at $4 each for $8,400). The remaining 155 plants could yield 7 pounds/plant at $2.50/pound for $2,700. Total sales could reach $11,000 in a “full size” tunnel. Early greens could increase grower income until late May or early June under the young tomato plants. Radin said supplemental heating (converting a “high tunnel” into a “greenhouse”) may yield extra early production but when adding in labor costs, it does not typically pay. Numbers could vary in either direction; these are presented as “ballpark” figures.

Smaller fruits mean earlier ripening, which allows farmers to sell early tomatoes at premium prices when consumers are keen for fresh, local tomatoes.

Production Schedule, Pruning & Trellising

Start tomato seedlings indoors the first week of February. To take full advantage of spring season extension, transplant tomatoes into high tunnels in April. Protect plants on chilly nights with winter-weight row covers. Lower leaf pruning only up to the first fruit cluster began the second week of June. As lower fruit was picked, leaf pruning continued up to next fruit clusters. Radin recommended leaving some leaves above fruit to prevent sunscald. Pruning to a single stem and removal of suckers and branches was done throughout the growing season.

The URI Agronomy Farm used “leaning and lowering” trellising allowing additional vertical growing all season long. The long string was wound on trellis hangers (rectangular spools) near the high tunnel ceiling. When the vines reach the top of the string, the string was unwound and the hangers were slid along overhead tunnel-length cables or other cross bars. The leafless vines were laid along the high tunnel floor. If using string trellis without lowering, late season harvests requires a high ladder and regular pruning maintenance is likely to be neglected.

University of Rhode Island Trial

In the URI high tunnel, soils were tested and amended per New England Vegetable Management Guide recommendations in late March or early April. Amendments included: Earthcare Farm compost, hydrated lime and 7-5-7 granular organic fertilizer. A light dose of Organic Gem liquid fish emulsion was watered in at transplant time. Plants were spaced 16” within rows, 5’ between rows.

At the URI Agronomy Farm, tomato transplants were set in the ground on April 18 with soil temperature at 62 degrees F and overnight temperatures in the high 20s. Reemay row covers over hoops were used overnight through the first week of May to prevented cold damage. Nylon trellising strings were set up when covers became unnecessary. High tunnel sides were rolled up most days and closed nightly through mid-May. Water was applied for 1 hour on alternate days, increasing to 1.5 hours. Straw mulch was installed in late May when soil temperature reached 70 degrees F.

Vines were secured to trellis strings with plastic clips. Trellis and plant lowering began in late June to keep plants below hot greenhouse covers. “Leaning and lowering” allowed additional vine growth.

Season-long plant fertility was maintained using drip fertigation with organic fertility sources (fish emulsion and seaweed extract). Supplements included Ocean Organics (0-0-1), Fish emulsion Organic Gem (3-3-0.3), Stimplex from Acadian Seaplants, Epsom Salt (magnesium sulfate), Sul-Po-Mag dry granular, Bone char, FullMeasureCal (12.5% Calcium carbonate and EDTA).

This tomato trial measured yield, fruit weight, fruit number, harvest period and tissue nutrients.

Trial Leadership

Andy Radin is an URI Agricultural Extension Agent holding an M.S. in entomology from UMaine and B.S. in Horticulture from the University of Wisconsin-Madison. He has authored peer-reviewed papers, has seven years experience as a research grower and was sole proprietor of a 3-acre organic vegetable farm for nine seasons.

Dr. Rebecca Brown is an Associate Professor in URI’s Plant Sciences Department and oversees research, teaching and vegetable Extension projects including high tunnel vegetable research since 2011. Dr. Brown’s PhD in vegetable breeding is from Oregon State University.

Learn More

Trial results will be posted at the URI website.

For questions, contact Andrew Radin, URI Agricultural Extension Agent, via email at andy_radin@mail.uri.edu or call 401-874-2967 or Dr. Rebecca Brown, URI Associate Professor, via email at brownreb@uri.edu or call 401-874-2755. Andrew Radin’s office is at CE Extension Center, 3 East Alumni Ave, Kingston, RI 02881.

Contact the participating farmers:

A similar story ran in the June, 2014 Eastern edition of Country Folks Grower.

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