Growers use high tunnels (HTs) specifically to create environments near their crops that would be unavailable otherwise. Those environments can be very beneficial but difficult to achieve and maintain during many cropping periods. This article summarizes key observations about the challenges and opportunities presented to growers when setting the ventilation status of their HT(s).
HTs are essentially square or rectangular boxes with sides, ends, and, occasionally, tops that can be closed or partially to fully opened. The combined relative positions of a HT’s sidewall curtains, end wall doors, and end wall and/or ridge vents (if present) comprise its ventilation status. Farming inside this box, HT growers must use its ventilation status to manage key conditions inside it (e.g., temperature, relative humidity, air movement/exchange). This process is the HT grower’s opportunity and challenge. Setting the ventilation status is an opportunity because it allows the grower to respond to changing external conditions in their attempt to maintain target conditions inside the HT. Setting the ventilation status is difficult because it can demand large amounts of time, energy, and other resources and create questions and stress.
For example, while many vents operate automatically on temperature-sensitive pistons or controls, they generally do not take wind, rain, or other factors that may influence the grower’s interests into account. Also, very important, opening and closing end wall doors and sidewall curtains is typically done manually. Dynamic weather conditions and specific crop needs may then require repeated trips to the HT(s) to change ventilation status, robbing time and energy from other activities and costing fuel, etc. Further, once at the HT(s), there is the question as to what the ventilation status should be. Answering that question can be very difficult. Consider that the relative positions of two sidewall curtains and two sets of end wall doors represents eighty-one combinations at 0%, 50%, and 100% open for each (3x3x3x3=81) and a more realistic use of these four options at five positions each represents 625 combinations. Adding two end wall vents at three positions each to this list brings the total number of possible ventilation status positions to 5,625 (625x3x3). When growers consider tunnel compass orientation, outdoor temperature, wind speed and direction, sunlight and cloud cover levels, crop needs, that relatively small differences in ventilation status can have large effects on conditions inside the HT (e.g., https://u.osu.edu/vegnetnews/2023/02/11/efficient-and-effective-management-of-high-tunnel-environments-1-the-need-and-challenge/), and other factors, selecting the most sensible ventilation status understandably becomes important and potentially difficult.
Some growers simplify by setting a “compromise” status at some point each day or night and moving on, unable or unwilling to change the ventilation status more frequently and, thereby, possibly exposing crops to non-optimal conditions as outside conditions change. Stress created by that scenario has been clear to me in conversations with growers and it appears to be increasing as weather patterns become more dynamic and extreme.
We partner with growers, the research-extension community, and members of industry to improve growers’ success and efficiency at managing conditions inside their HTs, especially through setting their ventilation status. Participation in the Ohio Controlled Environment Agricultural Center and local to international professional working groups and recent support from the USDA-Ohio Department of Agriculture Specialty Crop Block Grant Competition (“Advancing High Tunnel Production: Research-based Support and Technologies to Speed and Enhance Grower Success”) assist in that process. Please contact Matt Kleinhenz (kleinhenz.1@osu.edu; 330.263.3810) for more information.
