How to Use Season Extension Effectively for Winter Market Sales: Investigating Planting Date, Types of Cover, and Fertility

Project Overview

Project Type: Partnership
Funds awarded in 2010: $12,417.00
Projected End Date: 12/31/2011
Region: Northeast
State: New York
Project Leader:
Robert Hadad
Cornell Cooperative Extension

Annual Reports


  • Vegetables: broccoli, greens (leafy)


  • Crop Production: organic fertilizers
  • Education and Training: on-farm/ranch research, participatory research
  • Production Systems: general crop production

    Proposal abstract:

    As the local foods movement expands, the focus on late season production becomes greater. “Eating in season” opens new market demands for supplies that haven’t yet been matched. Winter CSAs (Community Supported Agriculture) enterprises have begun and in a couple locations, actual winter farmers markets have started up. One such market in Rochester, NY began in Dec. 2008. The Long Season Market attracted so many customers that all the farmers who had leafy greens, root crops, brassicas, and storage squash sold out before the market hours were over. After several years of promoting this new market potential with growers, questions from the field keep adding up. There is increased interest in using low tunnels (the practice of using metal hoops or PVC or metal pipes arched over a row of vegetables covered with fabric row cover and/or clear plastic). The cost of building high tunnels (hoop houses) can be considerable (prices range from $1500 for a small set-up to over $7500 for the typical 30ftx96ft models with roll up sides) so adopting the use of low tunnels(estimated cost for plastic and piping for a 4ftx100ft section is less than $250) is becoming an attractive option. Several of the popular seed companies have now started advertising supplies for making low tunnels. Before growers start making investments in expanding their season extension, there are questions that have been brought up: What is the environment like under the low tunnels (ambient air temperature and soil temperature)? What vegetable varieties work best grown under low tunnels? How far into the late fall can leafy vegetables be grown using different covers? As the temperature drops, what type of organic fertility produces the best crops? As the temperature drops and light levels diminish, does nitrate toxicity in leafy green vegetables become a food safety issue? Answering these questions through our research will ultimately help reduce the “trial and error” costs often associated with untested grassroots technologies. By working out the big questions and getting the information out to the farming community, this will provide farmers across the Northeast with the tools to increase their profitability potential with the new winter marketplace thus furthering their agricultural sustainability.

    Project objectives from proposal:

    We will use the type of low tunnels now called quick tunnels. These are inexpensive alternatives to the more expensive high tunnels (unheated semi-permanent greenhouse type structures). The quick tunnels are set up in the field right over rows or beds of vegetables using metal conduit. Many growers use a similar system for early season production where day length is increasing and warmer days are beginning. These low tunnels are made by using shorter lengths of 9-10 gauge wire hoops covered with clear plastic over a row/bed of black plastic with trickle irrigation. The crops grown under these tunnels typically are tomato, pepper, eggplant, and melons (NCAT 2005).

    The winter markets officially get started in November. The trial will begin in August. We will setup quick tunnels on 4 farms in western NY. There will be 4 tunnels set up on two farms and two farms with one tunnel. Each tunnel will be 50-60 ft long (x4ft wide). The farms with one tunnel are interested in the variety trial part while the other two farms will do all aspects of the project.

    The farmers have picked an assortment of greens to trial. These are spinach (36 days), arugula(40days), pak choi (40d), cilantro (55d), broccoli raab (rapi) (35d), radicchio (65d), an assortment of Asian brassicas (45-55d) and mustards (35d), fennel (80d), and sprouting broccoli(90d). These selections are based on farmer/customer communications for late season sales. Our farmers who are looking to expand their operations to include winter markets are looking for information on what varieties will work. This is their list. These will be trialed to see if a crop of market quality can be produced using the low tunnels at the time needed to supply the many weeks of a winter market. Will they grow big enough? Will they hold up to cold and lower light conditions? Are there pest issues?

    One tunnel will be devoted to growing all of the varieties (approx 12 types). We will first look at the influence of planting dates on timing of harvest and quality of the plants. This tunnel will be at least 60ft long and divided so that every 15 feet or so will seeded each week. There will be three rows per 12ft section made up of 4 Varieties of vegetables per row. This equals a seeding every week for 4 weeks beginning early August for items like radicchio and fennel And mid-late August for the rest.

    The farmers will be monitoring outdoor and under-tunnel air temperatures using max/min thermometers. They will decide what type of covers to use based on impending weather conditions. If it is mild, no cover would be needed; cooler weather might require a fabric row cover; colder cloudy weather might require covering with clear plastic. Very cold weather might require both a plastic and fabric cover for protection. Variations in day and night time conditions will also dictate the strategies the growers will use. These decisions, data, and activities will all be recorded by the growers and my technician to be used as part of a primer we will create for use by farmers looking to use low tunnels as part of their production scheme.

    Production of late season vegetables is dependent on several factors. There needs to be sufficient nutrients available to the plants. There needs to be sufficient warmth in the soil to allow for biological activity and root growth. There needs to be sufficient warmth for the plants under the cover. There needs to be adequate ventilation to prevent fungal diseases from establishing due to high humidity under the cover.

    The fertility issue is directly tied to soil temperature. In cold soils, biological activity slows. Under organic production practices, soil nutrients are released from organic matter through the activity of soil microorganisms. We will compare different strategies for delivering the necessary nutrients to the crops. Poultry manure compost will be used for two treatments. The first treatment will be the incorporation of the compost into the soil one month before seeding of the crops. The second treatment will be incorporated right before seeding. The third treatment will be the use of liquid fish fertilizer. The fourth treatment will be the incorporation of Chilean nitrate just before seeding. The last treatment will be a control of no added fertilizer.


    The quick tunnels offer short term protection from frost and freezing weather. The tunnels can also create a moderate growing environment that farmers can use to push production later into the season where the harvests can be sold through winter markets. There have been a number of literature references to using low tunnels, especially in conventional production but these have been mostly for early spring production using wire hoops with plastic set by mulch layers. There haven’t been very many reports investigating late season practices, using different covers and combinations to match weather conditions, seeding dates, or fertilizer usage. Using the quick tunnels made with piping was tried for getting a jump on early production (Hadad 2000) but this was using PVC piping and there were wind and ventilation problems associated with this early research. For late season production, having heavier tubing would help with any snow load (Roos & Jones 2005).

    A review of the SARE Project Reports site found that there have been a number of season extension investigations with most directly pertaining to the use of high tunnels (FNE08-632; ONE04-028 + ONE05-046 with tomatoes; ONE05-047 with peppers; ONE09-101 with sprouting broccoli). FS09-240 was a project that looked at using season extension techniques for getting an early start with various vegetables in the south. They used a high tunnel, wall-of-water, and low tunnel (thick wire hoops with fabric row cover) for their treatments. Again, the focus was getting tomatoes, peppers, and eggplants into the marketplace by late spring/early summer ahead of other growers.

    FNC99-286 looked at lettuce production with season extension by using row cover and low tunnels trying to get an early jump on the market in the early spring and run lettuce all season into the late fall and early winter. They looked at lettuce varieties that worked well. Their late- season trial failed due to weed pressure. Our project stands alone for looking at a rugged type of structure, a wider range of varieties of leafy greens, looking at soil and air temperatures over the course of the trial, issues of fertility and the possible issue of nitrate toxicity.

    The questions growers keep asking relate to timing, practices of protection against low temperatures but dealing with sunny warmer days, issues of light levels and ventilation, and what is a good nutrient program for the plants under these conditions. We will investigate timing of seeding to find appropriate dates for different varieties of leafy greens. Temperatures fluctuate with the weather. As seen with the current conditions this fall, cool wet weather followed by cold and below freezing night temperatures through October followed by mild sunny days in early November, how to manage the tunnels needs to be documented to optimize growth for the plants.
    There are a number of fabric row cover of various weights available.

    Agribon 19 is a medium weight cover good to 28o F with 85% light transmittance. Agribon 30 drops to 26°F with 70% light transmittance. Agribon 50 goes down to 24°F with only 50% transmittance. There is a a durable greenhouse plastic film with UV resistance. It offers a few more degrees worth of protection, but is harder to ventilate and looses more heat at night. What about combinations of covers being used or not used during the day or night depending on the weather? This will be investigated.

    During the fall, soil temperatures drop. For organic farmers or where non-chemical fertilizers are use, release of nutrients to the plant roots is made available by the biological activity of the soil. This activity slows as the soil temperature drops. This can restrict nutrient accessibility by the plants. We need to see if there are differences in plant growth with different types of fertilizers used, when applied, and at what temperatures do we see affects readily change. We also need to see if some leafy greens tend to accumulate levels of nitrates under low light and low temperatures to a point of possible toxicity.

    Hadad, R.G. 2000. Low Poly Tunnel Trial Update & Low Poly Tunnel Construction. In “Plow Sharing” newsletter, May 2000. North Carolina State Univ. Cooperative Extension
    Roos, D. & Jones, D. 2005. Season Extension.
    ATTRA 2005 Season Extension Techniques for Market Gardeners

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.