Learning points from 5 years towards emission-free Pot Anthurium cultivation

The road towards this goal was rich in experiences. Recently we looked back at the many learning points from this long research period together with the dedicated supervisory committee (BCO). They visited the trial once every two weeks and supplied the thousands of plants grown.

More control options

Over time, the BCO has gained more control possibilities (nutrition, climate, energy, spectrum, EC and water). To increase the stability of the moisture content in the pot, the watering frequency was slowly increased from once every 4 to 7 daysto once to even twice per day for some varieties; to the surprise of the BCO members, this had a very positive effect on growth, root quality and even flower colour for varieties whose color normally fades by light excess.

With the LED spectrum and day length, excessive flower stem elongation and leaf quality can be controlled. When implementing LED, BCO members still encounter a number of questions; we will be discussing these with them in the coming weeks.

Increasing the insulation level of the greenhouse

The insulation level was gradually increased over the years (an extra screen - which does not let moisture through -, bubble plastic at the outer walls, unperforated foil and a greenhouse cover of low-ε glass). All this has greatly contributed to reduce the heat demand. Pot Anthurium can be grown much more energy-efficiently than thought; it turns out that the minimum temperature can be lowered significantly: thanks to the good insulation, you can let descend the temperature slowly during the night without actively using the heat pipe; the lamps and/or the sun will increase the temperature during the day.

Fossil-free, but imbalance in heat production and heat demand remains

With the system used (good insulation, high-intensity LED lighting and latent heat harvesting), it was possible to cultivate a whole year with only 123 kWh/m² of electricity for the lamps and the heat pump. This was enough to light, heat and climatize the entire crop without fossil fuels input. Due to the imbalance in moments of heat harvesting and heat demand, the system does require a seasonal storage of about 60 kWh/m², such as an aquifer. For the practical implementation, this is one of the biggest hurdles to overcome because of the large costs involved and the possibility of applying an aquifer at the farm. Another requirement is that fossil-free power must be able to be generated or stored properly and affordably.

That it is possible to grow a beautiful plant with many leaves and flowers with a very low input of CO₂ (less than 2kg/m² year) is endorsed as a learning point by some of the BCO members but also disputed by some others, arguing that it remains a Demonstration, not a comparison test with different CO₂ concentrations. Because CO₂ supply will become a bottleneck in fossil-free cultivation, this topic needs attention (and maybe research).

Healthy crop with very limited use of chemicals

The crop health was repeatedly challenged by exotic pests. Nevertheless we managed to cultivate several years without chemicals or with very limited chemical (local) corrections. This research has directed attention to spiders as potential pest controllers. The strategy using predatory mites, lacewing larvae and spiders resulted in minimal use of correctives. These were only needed in the first outbreaks of new, exotic pests, such as pepper thrips in year 4 and cycads in the last summer, for which no natural enemies are known (yet). For practice, this means that the fight against new exotic pests will continue and crop protection strategies will have to be adjusted in the future.

This project was carried out by the Greenhouse Horticulture Business Unit of Wageningen University & Research and financed and coordinated by the innovation programme of the Ministry of LVVN and Glastuinbouw Nederland “Greenhouse as source of energy”. The trial was intensively monitored and supervised by a growers comittee.