While traditionally reserved for outdoor weather monitoring, weather stations are increasingly proving their value in greenhouse applications. Changes in temperature, humidity, light, and other greenhouse conditions can have a profound effect on the productivity and quality of plant growth, and many growers today have integrated weather station technology as part of their overall climate-control strategy. By continuously monitoring numerous environmental conditions at once, a grower is better able to understand how climate conditions are fluctuating, and react to those changes in order to maximize yield and efficiency.
Such is the case at Tega Hills Greenhouse in Fort Mill, South Carolina. The greenhouse produces approximately 25,000 pounds of tomatoes a year, the sales of which are divided up between wholesalers, the farmer’s market, and the general public via a road-side stand. Greenhouse owner Mark Robinson, a computer systems administrator-turned greenhouse grower, has been continuously monitoring conditions in his 28’ x 144' greenhouse with a battery-powered weather station since 1999.
“One of my primary concerns was to make sure the tomato plants were getting enough sunlight,” he explains. “Tomato production can decrease drastically as light intensity drops. Although we usually have good sunshine in this area, every percent of PAR you lose through the plastic covering of the greenhouse is that much lost in plant production.”
According to Robinson, it was also important to be able to continuously record air temperature, in order to make sure the greenhouse’s environmental computers were working properly, as well as soil temperature, in order to keep an eye on the root zone temperature of the plants.
Robinson chose to equip the greenhouse with a HOBO® Weather Station from Onset. The station is based on “smart sensor” technology, which means that Robinson was able to simply plug individual sensors for PAR, air temperature, and soil temperature into the station, and the station immediately recognized each one without complicated wiring, programming, or calibration. The entire system, including sensors, can run for a full year on just four AA batteries, thus eliminating the need for solar panels or large battery packs.
At Tega Hills, the weather station is mounted on a pole located on one of the greenhouse’s end walls. At the top of the station is the photosynthetic light sensor, which is affixed to an “arm” Robinson constructed that can swing inside and outside of the greenhouse. Robinson explains that once a month, he pivots the PAR sensor outside to collect actual sunlight data and compares that with light data from inside. “This tells me how much PAR I’m losing through the double-polyethylene cover.” Robinson adds that by measuring the “transparency” of the cover, the weather station may indicate that the cover needs to be scrubbed free of dirt, or potentially discarded and replaced. “The industry suggests getting a new cover every three years, but if there’s a significant reduction in PAR values anytime before then, it’s important to know.”
The weather station’s temperature sensor, mounted just below the PAR sensor, continuously monitors the greenhouse air temperature to give Robinson a clear picture of the overall growing conditions. Collected data is offloaded to a computer once a month, at which time Robinson can analyze the data using the weather station’s data graphing and analysis software, and understand any visible trends in climate shift. This information can be useful in troubleshooting the facility’s environmental-control systems.
To measure soil temperature, a third sensor is placed directly into a Bato bucket where two tomato plants grow in a perlite soil mix. The goal, according to Robinson, is to keep the root zone temperature of the plants at an optimal level. “Studies have shown that if you can maintain the ideal temperature, yield will be better. So, if I see that the temperature has become too low, then I know to heat up my irrigation water.”
Since implementing the HOBO Weather Station, Robinson has been able to maintain tighter control over his greenhouse environment, and feels that it has helped him change the way he grows.
“I think of the weather station as a centralized, multi-port data-gathering device,” states Robinson. “Growers are very busy people, and the fact that you can just plug things in and go is a huge advantage. For me, the biggest advantage of having a weather station is that it can answer the question, ‘What can I do to make the environment more hospitable to these plants?’ ”