Nitrogen dynamics and yield response to minimal supplemental heating in high tunnel winter production

View the project final report

Commodities

• Vegetables: greens (leafy), greens (lettuces)

Practices

• Crop Production: fertilizers, high tunnels or hoop houses, nutrient cycling, nutrient management, organic fertilizers
• Soil Management: nutrient mineralization

Winter vegetable production in minimally heated high tunnels is becoming more popular in the Northeast as farms
attempt to increase farm income and maintain customer relationships through the winter. However, little
information exists on the relationships between temperature, nitrogen availability and uptake, marketable crop
yield, and economics for winter growers. This project proposes to study two anecdotally popular temperature
settings in identical, side-by-side tunnels for winter production and track the differences in propane use, soil
temperature, soil nitrate availability, nitrogen uptake, and crop yield of the popular winter grown vegetables
Winterbor kale, spinach, and mesclun lettuce mix. Collecting this data will allow us to assess the return on
investment of supplemental heating and enhance our understanding of nitrogen cycling in heated high tunnels
during the winter to better inform fertility management practices. The conclusions of the investigation will be
shared immediately amongst Cornell Cooperative Extension specialists to improve technical assistance to winter
growers as well as disseminated directly to farmers via trade publications and presentations at conferences. In
total, over 1000 growers will receive this information allowing them to make better-informed decisions about
whether supplemental heating for winter production is a sound economic choice.

The Poughkeepsie Farm Project erected two identical 42’ x 196’ side-by-side high tunnels in 2016 that are
equipped with high efficiency Modine 93 propane heaters. By using identical planting dates, fertilization rates, and
crop mixes in the two houses, it is possible to measure and compare the impact on marketable yield and nitrogen
availability and uptake in two different temperature zones. One house will operate with the thermostat set at 35-
degrees Fahrenheit while the second house operates at 42-degrees Fahrenheit. Installing in-line propane meters
in each house will allow for precise monitoring of fuel use and allow for a cost comparison at the end of the study.
Soil nitrate level tests and plant tissue sampling paired with soil temperature monitoring will demonstrate any
difference in nitrogen availability in the soil and actual plant uptake in the two temperature zones. This information
will allow farmers using season extension techniques to make more informed decisions about the costs and
benefits of heating to two different thresholds and impacts on nutrient management strategies under different
temperatures in high tunnels.