Salix helps make container plant production more sustainable

Salix has installed the new Cleanleach leachate purfication system at its 20-acre Croxton Park nursery in the Thetford Forest, as part of a European research project.

The revolutionary system, which allows nurseries to treat and then recycle the leachates from their irrigation systems, has been developed in Spain by IRTA, the Spanish Government food and agricultural production research institute.

Water collection and recycling
Water collection and recycling

Container plant production facilitates the agronomic management, transport and transplanting of plants used in gardening, landscaping and reforestation. But it also generates leachates that cannot be released into the environment because they contain high concentrates of nitrates and sometimes phosphates.

IRTA’s Cleanleach system makes it possible to return these leachates into the irrigation system and take advantage of their nitrate and phosphate content as fertilizers.

The system was first installed by Naturalea at its Sale Graupera Nursery in Barcelona and Salix has now adapted the system to the needs of its own nursery, which specialises in growing native wetland and wildflower plant species.

The new technology combines slow horizontal sand filtering of leachates under the container area with constructed wetlands to transform the nitrates into nitrogen gas and render the phosphates less soluble.

David Holland, Technical Director for Salix, explains:

“In Europe, nurseries growing plants used in gardening, landscaping and reforestation take up over 127,000 hectares.

The new Cleanleach natural treatment process offers a much more sustainable alternative to traditional leachate management methods, making it possible to re-circulate the nutrients and irrigation water, and generating significant environmental improvements for the industry.

We are delighted to be involved in this exciting research project and have adapted the Cleanleach system to maximise the benefits to our own growing centre. Our pot grown plants are irrigated using rainwater collected from polytunnels and stored in tanks. The Cleanleach system cleans this water and recycles it back into the tanks. We’ve added a drainage layer under the sand filter and a floating wetland to give the water a final polishing before it is recycled for reuse on the nursery.”

Plant species grown in coir mats
Plant species grown in Coir Mats

During a recent visit to Croxton Park, the IRTA team collected samples and monitored the greenhouse emissions from Salix’s system as part of a Life Cycle Assessment of the Cleanleach system.

IRTA researcher, Dr Marc Vilnas explains how the information was collected:

The Cleanleach system is detailed in this PDF