Abstract

High tunnels are low cost temporary greenhouses that are often used to extend the growing season for high value crops such as tulips, muscari, sweet pea cultivars, and hyacinth beans. Profitability depends on selection and timing of crops to optimize use of these structures. Predicting soil temperatures in high tunnels as a function of outside temperature is a critical factor in crop selection and timing. However, predicting soil temperatures is difficult because air temperatures constantly change from hour to hour and day to day. We develop a model to account for temperature dynamics in high tunnels by modifying the fundamental differential equation in Newtonian law of cooling. We fit the model to data from high tunnels located in two states - Nebraska, Kansas and predict soil temperature as a function of external air temperatures. The model fits reasonably well at all high tunnel stations with most predictions being within 2° C of the observed value. We also found that the model could be used to adequately predict soil temperatures at one site based on parameter estimates of another nearby site. Thus we conclude that the model is an adequate tool in making high tunnel placement decisions and is useful for selection and timing of crops within established high tunnels.

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Apr 24th, 9:30 AM

PREDICTING SOIL TEMPERATURES IN HIGH TUNNELS USING A DYNAMIC MODEL BASED ON NEWTONIAN LAW OF COOLING

High tunnels are low cost temporary greenhouses that are often used to extend the growing season for high value crops such as tulips, muscari, sweet pea cultivars, and hyacinth beans. Profitability depends on selection and timing of crops to optimize use of these structures. Predicting soil temperatures in high tunnels as a function of outside temperature is a critical factor in crop selection and timing. However, predicting soil temperatures is difficult because air temperatures constantly change from hour to hour and day to day. We develop a model to account for temperature dynamics in high tunnels by modifying the fundamental differential equation in Newtonian law of cooling. We fit the model to data from high tunnels located in two states - Nebraska, Kansas and predict soil temperature as a function of external air temperatures. The model fits reasonably well at all high tunnel stations with most predictions being within 2° C of the observed value. We also found that the model could be used to adequately predict soil temperatures at one site based on parameter estimates of another nearby site. Thus we conclude that the model is an adequate tool in making high tunnel placement decisions and is useful for selection and timing of crops within established high tunnels.