How sensors are changing the world of greenhouse growing

Agriculture is arguably one of the most important industries in the world. After all, with an estimated population of over 7 billion people, there are a lot of mouths to feed. Unfortunately, agriculture is also one of the most unpredictable industries. Crops are subject to the whims of nature with droughts, fire, rain, sun, and hail. In fact, 90 percent of all crop loss is caused by weather, according to the U.S. Department of Agriculture. Things like over-watering, temperature, and soil health, can require expensive testing machinery to assess and a large group of workers to manually spot-check the crops. Of course, spot checking isn’t 100 percent, so it’s a risky solution.

As technology started advancing, farmers realized they might be able to utilize some of the newer ideas in order to grow better crops and so, Precision Agriculture, was born. Precision Agriculture (or Precision Farming) is using technology like Global Positioning Monitors (GPS), sensors, wireless communications, and satellites to track crop growth, deliver information about conditions directly to the farmer, and generally making farming techniques more efficient and effective. Even NASA got in on the idea, working with the Department of Agriculture and NOAA, to use satellites and aerial remote sensing to help farmers manage farmland.

Eventually, this technology spread to greenhouse farming. There are approximately 17,639 nurseries and greenhouses in the U.S. making it about a 16.6 billion dollar industry (that also includes sod sales), according to the Environmental Protection Agency. Greenhouse, nursery and floriculture, make up about 2.5 percent of farms. Relatively speaking, they often hire more employees than regular farms, but have less acreage (around 72 acres versus 418 acres.)
The problems that plague farmers are centuries old—insects, heat, water problems—but recent improvements in sensor design allows the technology to function at the necessary granular level, delivering accurate and important information in real time.

Monitoring greenhouses
Much of technology for Precision Agriculture, particularly satellite technology, is designed for outdoor, large-scale farms. However, the same components can be used in greenhouses, to control the precise temperature and address the needs of the crops.

The technology is similar to that used to monitor the sensitive environment of a restaurant freezer, where an increase in heat of just a few degrees can mean financial loss and sick customers. In fact, Cellular Machines got their start in agriculture when a restaurant owner told a hydroponic farmer how he monitored his freezer. The farmer then requested sensors made specifically for greenhouses, a unique and somewhat challenging environment.
Greenhouses are particularly difficult because they must maintain a delicate balance in the atmosphere.

“The purpose of a greenhouse is to accelerate crop growth rate. The factors that can impact the ability to produce more crops are light, fertilizer, water (or soil), temperature, and humidity. Since the farmer can control all these variables, the growth rate can be significantly increased with almost no damage by insects or weather, such as hail,” says Gerry Cullen of Cellular Machines. “For example, the amount of light, if artificial light sources are used, can be controlled to provide the crop with the most efficient amount of light. Plants are even allowed to ‘sleep’ for periods to recover from light-fueled growth periods. Each plant type has different requirements.”

But all the benefits of being able to control factors come with drawbacks. Lights that are left on too long can damage the plants, fertilizer injected into the water tank can damage the root systems, the temperature can be too hot and chemicals must be closely monitored.

As a solution, Cellular Machines, created a system of sensors that can monitor the most important aspect for greenhouse growing including: temperature, humidity, light level, pH, door position and fertilizer (conductivity in parts per million.) The sensors wirelessly feed information back to the base-station, a “robot” that is usually housed on the wall of the greenhouse. The sensors are attached to parts of the greenhouse with high/low levels set. If any of the sensors detect a “high” or “low”, the system will send a text message to up to five different cellphones alerting the farmer to an issue. Plus, the system logs the general conditions in a Cloud server, so the farmer can review a history of all the information the sensors are gathering, which is beneficial for the farmer, but can also be shown to health inspectors or potential customers.

This system is particularly useful for smaller greenhouses as previous systems required complicated internet connections, expensive equipment and an IT technician to install and monitor. This works on a cellular network and consists of three parts: the cellular radio (Anaren’s Air Modules); a microprocessor to process the data, monitor conditions and control the radio; and a SIM card to monitor access to the cellular text message and data channel.

The idea of monitoring isn’t new, but allowing smaller greenhouses with a small staff to have the same advantages of an expensive monitoring system without the expense or manpower is a big benefit. As the sensors progress, they’ll be able to alert managers to problems earlier and grow more sensitive to the needs of the greenhouse.

Even more options
As the farmers discover what is beneficial to them, sensors are being used to measure a wider variety of conditions. For example, the Waspmote Sensor Board from Libelium offers the ability to monitor 14 environmental parameters via a wireless sensor network. The Waspmote is able to track: air temperature, air humidity, soil temperature, soil moisture, leaf wetness, atmospheric pressure, solar radiation, trunk/stem/fruit diameter, wind speed and direction, and rainfall.
This board is designed for vineyards or greenhouses and can deal more specifically with the issue of irrigation. Plus, these types of wireless sensor networks offer a higher level of precision than older techniques. The more precise the data is, the better the crop will be.

Even more exciting is the potential advances in technology. The Waspmote is already compatible with sensor add-ons—including air thermometer, hygrometer, anemometer, wind vane and pluviometer—that can turn on heaters or alert farmers to adverse weather conditions.

News Director, Design Engineering Group, and Editor, ECN