The emissions of nitrogen from the cultivation of potted orchids are relatively high and in businesses that don't recirculate, is far above the norm. In order to comply with the norm, recirculation is necessary and a lot of effort is required.

Growers who have already started with reusing drain water have indicated that in practice an emission norm of 300 kg N/ha/year seems achievable. In September 2014, research was started to discover if it is possible to get the emissions even lower.

In a test glasshouse at Wageningen UR Glastuinbouw, three treatments were tested during the vegetative stages with the Phalaenopsis cultivars, Springtime and Zamora:

• Reusing drain water so that the emissions stay within the norm for 2018 (emission maximum 150 kg N/ha/year);
• Reusing as much drain water as possible with the exception of the rinsing water from the UV disinfection unit;
• No reusage of drain water (control treatment).

The reuse of drain water during the propagation phase didn't show any adverse reactions. During the two-weekly growing measurement and the destructive measurement at the end of the propagation phase (at the beginning of March 2015), no consistent differences were noticed between the treatment with or without reused drain water.

Because it is important to discover if there are no subsequent adverse effects on the number of flowers and flower stems produced, the research is being continued in the generative phase. In March 2015, the cool phase was started to induce flowering.

The treatment with the reuse of drain water is being continued in a similar way.

Photo: In the test glasshouse in Wageningen UR Glastuinbouw (Photo: LTO)

Source: LTO Glaskracht Nederland/Wageningen UR