Innovations in irrigation

Staying ahead of the curve is not just an ecological good for a commercial greenhouse producer — it’s an economic necessity. Operators who can successfully implement the latest and most water-efficient technologies can improve their operational costs (OpEx) and attract discerning customers looking to support sustainable businesses.

We’ll explore the cutting-edge technologies, concepts and strategies that are reshaping irrigation practices, enhancing water efficiency and boosting crop yields.

Start at the source

The first place to start when evaluating water efficiency opportunities is determining your source water quality and how it may affect your downstream irrigation equipment. Many greenhouse operators use drip emitters (which can be highly efficient water delivery systems). However, water with a high dissolved solids content can clog drip emitters, explains Bill Perryman, a technical services manager at HyperLogic, a division of RII member the Hawthorne Gardening Company.

“Having the water as pure as possible from a dissolved solid standpoint helps prevent clogging and extends the life of the systems,” he says. “If you’re supplying drippers and misting systems when you have high amounts of calcium, you’ll quickly clog or even destroy some of the emitters and dripper tips.”

Similarly, chlorinated city water or well water may have binders that prevent nutrient solutions from properly dissolving, forming a precipitate that can clog emitters or irrigation lines. In those cases, some plants may receive high concentrations of nutrients while others receive barely any moisture.

Greenhouse operators may treat their source water with reverse osmosis (RO) purification systems to avoid these source-water problems. These units strip away all particles, like salts, bacteria and other impurities, dividing the incoming water into a pure and a waste stream. As noted in the WC BPG, “[d]epending on the efficiency of the unit, a staggering 1-9 gallons of rejected waste may be created for each gallon of purified water.”

If TDS levels are particularly high, or there are heavy metals or other hard-to-remove contaminants like boron, the use of RO systems becomes relatively unavoidable. That said, there are ways to ensure the RO system is operating at peak efficiency (without sacrificing water quality).

Perryman notes that “a properly designed RO system fit to your water chemistry and temperatures can help to achieve not only your desired water outcome but aid in preventing unnecessary by-product wastewater in the process.”

On the ground

Drip irrigation is a common and highly efficient strategy greenhouse operators use to water crops. As mentioned in the WC BPG, “water use for irrigation has decreased since 1980, when growers began adopting drip irrigation, indicating that new technology can reduce consumption.” Sensor-based irrigation is a newer strategy that has also had great efficiency impacts by ensuring growers don’t over- or under-water crops.

“Sensor technology is really revolutionizing the way that people water,” says Tera Lewandowski, a senior research scientist at Botanicare (a division of RII member the Hawthorne Gardening Company). “Using [drip irrigation and sensors] together is a great strategy. It is the best of both worlds.”

Drip irrigation allows growers to apply water and nutrients directly at the soil level rather than overhead watering that hits the foliage. This reduces the evaporative water loss and maximizes the water available to the plants. Adding moisture and EC sensors to the setup can help growers determine when irrigation and fertigation events need to happen. For example, crops on a timer or schedule-based drip irrigation system could receive too much water if there is a several-day stretch of cloudy weather. By using moisture sensors, irrigation events can be timed for when readings go beyond pre-set parameters.

What those parameters are is highly dependent on soil composition, Lewandowski says, which makes suggesting specific target ranges a challenge. A soil’s maximum airspace potential and porosity will greatly influence irrigation strategies, she notes. Generally, soils with lower maximum airspace potential are more water efficient as they retain more moisture. Comparing a soil mix with a 35% maximum airspace potential to one with a 25% maximum airspace potential that has the same porosity, the first will have better aeration.

“If you multi-pulse that 25% air soil, you’re never going to let it dry up,” Lewandowski explains.

A multi-pulse irrigation system delivers water to plants in several short bursts rather than one continuous flow. She suggests using fewer irrigation events when using soils with less airspace potential, “whereas multi-pulsing the high one might be a more appropriate strategy.”

The relationship between maximum airspace potential and soil porosity is direct and significant. That said, two soils with the same maximum airspace potential can have slightly different porosity depending on their exact composition. This can occur due to variations in the distribution, size and arrangement of soil particles and organic matter content. Of two soils with the same maximum airspace potential but slightly different porosity, the one with slightly lower porosity may still have appropriate drainage and will have better water retention, potentially reducing the frequency of irrigation events it needs.

When studying EC sensor readings, Lewandowski warns that the values may need to be taken with a grain of salt, as soil moisture content may artificially change the EC levels. “Without that background understanding, you might make decisions...that aren’t based on reality.”

The future of irrigation

The most advanced greenhouse operators are turning toward sophisticated climate control computers and advanced algorithms — some are even beginning to experiment with and implement artificial intelligence systems. Brandon Waghorn, a business development manager at greenhouse manufacturer and RII member South Essex Fabricating (SEF), says “In almost all high-tech commercial greenhouses, their irrigation will be fully integrated with the climate control system.”

Integrating irrigation into climate control systems enables growers to induce or avoid plant stress to maximize the production of desirable compounds and/or reduce pest and disease pressures. Some of these controllers will leverage advanced algorithms to unlock even more efficiencies and control.

“An advanced algorithm is essentially a logic-based program — ‘if this, then that.’ There is a wide variety of ‘ifs’ that can be weighted and set to different thresholds,” Waghorn explains.

On the cutting edge of irrigation and control technology, some greenhouse growers are adding AI technology to their operations. In this context, AI is “a program that is designed to continue to learn from the algorithm and continue to improve it,” says Waghorn, who describes it as “self-learning.” For example, these units can take historical climate data, future weather forecasts, past production parameters and crop quality/yield metrics to determine the best production conditions to replicate outcomes.

Greenhouse operators might be surprised by the relative ease that goes into training these systems. Based in Leamington, Ontario — sometimes referred to as “the tomato capital of Canada” — SEF and its partner Blue Radix have helped growers with little to no historical data collect that information and train AI systems to the point of fully automated greenhouse control within six months, Waghorn says.

“If there’s a significant amount of high-quality data available for many years, and the grower is able to conduct a good analysis of which chunks of that data were very good harvests to feed into the model, then it could be accelerated to as short as two months,” he adds.

The future of greenhouse irrigation is brimming with opportunities for innovation and efficiency. Advanced technologies such as AI-driven climate control systems and sensor-based irrigation are already reshaping water management practices, while tried and true best practices can help greenhouse growers get the most out of their water treatment systems.

In the near future, greenhouse operators could see adapted versions of tools like LIDAR drones, traditionally used in field farming, to evaluate crop health and identify high-temperature hot spots within their structures. Embracing these innovations will not only improve water efficiency and crop yields but also position greenhouse growers at the forefront of sustainable and technologically advanced agriculture.

Rob Eddy is RII's resource efficiency horticulturist. Rob has more than 30 years of experience in plant growth facility management, plant research and commercial production. rob@resourceinnovation.org