01 February 2023
We might talk about planning our approach to crop production ‘from the bottom up’, but how often does that include a critical appraisal of what is arguably the most fundamental aspect of nursery infrastructure – the surface on which we stand down pot and container crops?
In the last few years, as growers around the world are being asked either by their customers or legislation to cut water use and run-off, which can contain nutrients and crop protection products, the choice of growing surface is receiving more attention as it can play a key role in achieving a ‘closed system’.
A recent study by Netherlands-based nursery floor manufacturer ErfGoed suggests your choice of growing surface, whether for protected or outdoor production, can make a significant difference not just to water management but in other areas ranging from labour and energy efficiency to crop wastage and overall profitability.
“We used a questionnaire to gather feedback from growers about their experiences with different kinds of growing surfaces,” says Jack Ford, ErfGoed’s North America sales manager. The results were used to score six of the most common growing systems for their performance against various criteria, from their ability to capture and reuse water to uniformity of growing environment, labour efficiency and return on investment.
Of three different ebb and flood systems included in the review, automated Dutch benches and the ErfGoed floor achieved maximum points because of water delivery and drainage uniformity.
The third, bare concrete floors, rated less well for two reasons. “They are never quite even, however well laid,” says Mr Ford. “They also rely on being sloped to the water’s entry and drain points, so the plants nearest those points are in the water longer than those furthest away. The ErfGoed floor includes a capillary mat that pulls water out of the growing medium during the drainage cycle, which doesn’t happen on concrete.”
All three systems scored equally well for recapturing and recycling the water. He pointed out that water could be collected from static benches if lined and from some gravel or fabric-covered beds, depending on their construction.
Concrete floors and crushed stone or fabric-covered beds were down-scored because they can be uneven and prone to puddling, however well laid, and rely on a slope for drainage. “That’s a concern as puddles run the risk of uneven growth and consequent crop losses,” he says. “In these days of tight margins losing just 5-10 per cent of the crop can mean most of your profit is gone.”
Choice of surface can affect your ability to manage the crop’s growing environment, says Ford. For example, how the material conducts heat dictates whether you can give the crop bottom heating and how evenly the area warms up. “You can heat benches from below, but not very efficiently,” he says. “You can have underfloor heating with concrete, but while it does conduct heat reasonably well, there can be hotspots above the pipes.
“The combination of stone, air and water in the ErfGoed floor means heat is evenly spread. You can cool from below, too, by bringing water up to just below the surface.
“It’s also possible to have cool-air movement under benches, but this can be costly if it involves fans or chillers.”
Unsurprisingly, with its ability to be fully automated, the Dutch container-bench system scored best for labour efficiency. Concrete floors and the ErfGoed floor were ranked second because they can withstand being driven on by different types of machinery.
More hand labour is needed to pick up and stand pots down on crushed stone and fabric-covered beds, as the surface may move if driven over. Still, the advent of new conveyor systems and low ground-pressure ‘flying forks’ or robots offer opportunities to cut labour use, says ErfGoed.
Workers find conditions most comfortable in static and mobile bench set-ups, particularly with the automated system, because crops are delivered to a purpose-designed workstation. Where working at floor level is the only option, the ErfGoed and concrete floors keep driest and have the least risk of trip hazards.
How much of the area can be utilised is integral to efficiency. No paths are needed for crushed stone, fabric-covered beds, or the Erfgoed floor, so the total area is available to the crop. Concrete ranks lower because any puddles must be avoided.
Their evenness of surface means the ErfGoed floor and Dutch mobile benches rate highest for the range of pot sizes they can be used for, while it is harder to stand smaller pots down on a crushed stone, for example. “Some species don’t really like concrete because it’s harder to control humidity and temperature,” adds Ford.
Regarding capital outlay, fabric-covered beds are the most affordable and concrete floors, and Dutch automated benches are the most expensive. However, return on investment must also consider the system’s impact in areas such as energy and labour inputs.
Ford suggests that if money were no object, Dutch mobile benching could be the first choice for flowering pot plants.
“ErfGoed floors come a close second because of the consistency of results,” he says. “You’ll also see a particularly good return on investment because of superior crop quality, minimal losses, and potential energy savings.”
Concrete ebb and flood floor: laid with a slight slope and filled/drained from gutters or holes
ErfGoed ebb and flood floor: a closed system with crushed stone overlaid with capillary mat and fabric, designed to flood and drain simultaneously across the entire surface.
‘Dutch’ container system: computer-controlled mobile benches that move automatically through the greenhouse, usually including the ebb and flood irrigation
Static benching: drained onto the floor beneath
Crushed-stone bed: indoor or outside, 4 to 15cm deep and fabric covered
Fabric-covered bed: cloth laid over sand or gravel, irrigated from overhead
This article was first published in the February 2023 FloraCulture International.