Oct 15

Better irrigation in greenhouses and nurseries saves both money and water

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The US greenhouse and nursery industry supplies consumers with ornamental plants, vegetable seedlings, and fruit trees for use in gardens throughout North America. Irrigation in greenhouses and nurseries can be difficult to manage, because many of the plants are grown in fairly small pots that may need to be watered several times per day. And most greenhouse and nurseries grow a wide variety of crops; adjusting irrigation of all these crops based on the actual watering needs is too time-consuming for growers.
To address this challenge, we have developed wireless sensor networks to help growers automate irrigation based on the actual water needs of their crops. The principle is simple: soil moisture sensors are inserted into the pots and they measure how much water is present. The sensors are connected to a ‘node’, which radios the data to a computer, where the data is presented in charts. Growers can see whether the various crops have adequate water. More importantly, they can use this computer to instruct each node when and for how long to turn on the irrigation. This way, plants get watered only when needed and only with the amount of water required.
We are testing this system in a commercial nursery in Georgia. For the testing, we decided to pick gardenia ‘Radicans’, one of the most challenging crops produced by this nursery. Typically, this nursery loses about 20 – 30% of the plants during the production, and most of these losses are due to watering too much.
Using the wireless sensor networks to automate the irrigation of this crop eliminated these losses. And just as importantly, we found that we could actually grow the crop much faster; the normal production cycle for these plants is 14 months, but with precision irrigation we were able to grow them in only eight months.
The precision irrigation had various benefits to the nursery: since none of the plants died because of overwatering, the nursery could sell 2,000 more plants than they anticipated. And shortening the production cycle from 14 to 8 months reduced the production inputs (labor, fertilizer, pesticides). Combined, the extra plants that were sold and the reduced production costs resulted in an economic gain of $20,700 or approximately $1/sq. ft. The required hardware only costs about $6,000, so the return on investment was just a few months.
This research not only benefited this nursery, but also society at large: by irrigation more precisely, the nursery withdraws les ground water, leaving more water for other uses. And after seeing the benefits of better irrigation practices, the nursery has adjusted their irrigation practices throughout the entire nursery. We conservatively estimate that this has reduced their water use by 100,000,000 gallons per year, enough water to supply about 800 households or about 2,000 people.