SFF Project Summary
Rotation of Crops in Rockwool
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Quarterly Update: December 2005
Objectives
1. To survey collate and publish information on sustainable re-use of roockwool (spun basalt rock) slabs, a widely used rooting medium for growing both vegetable and ornamental crops in hydroponic cropping systems.
2. To conduct and publish results of trials to assess sustainable re-use methods which are appropriate for the relatively small (c 600m3) but growing (estimated rise to 2,000 -3,000m3 in five years) volume of slabs being used annually in New Zealand.
For objective 1. the Commonwealth Agricultural Bureaux Abstracts (1973-2003) were searched for relevant papers in scientific and grower journals.
For objective 2. a replicated field trial on one of the appropriate re-use methods for New Zealand was conducted. The method chosen was the incorporation of finely ground used rockwool slabs into potting mix.
Outcomes
Only very small amounts of long life rockwool slabs are used in New Zealand, primarily by growers of perennial ornamental crops such as roses.
Short life rockwool slabs, used once only by tomato, capsicum and egg plant growers or up to three times by cucumber growers, can be re-used in many ways but volumes are small by world standards.
Shoot growth of Hebe was similar in all treatments of our ground rockwool- potting mix trial. Root growth was least in the potting mix only treatment. This trial sufficiently demonstrated the potential of this rockwool reuse option.
Information from the project has been published as scientific papers and as articles published in the GROWER magazine.
The project has raised awareness about means of sustainable re-use of rockwool in New Zealand. Recently an assessment has begun of large machinery (not available in New Zealand when this project started) to fine grind both old stem and spent rooting substrate in one operation. Stakeholders of this project will continue to monitor developments in the re-use of rockwool.
It is intended to publish an updated article on the re-use and disposal of rockwool for publication in the GROWER and dissemination direct to relevant growers, by 31 December 2005. The issues and options are different to what they were 12 months ago.
W T Bussell, School of Natural Sciences
Unitec New Zealand
Quarterly Update: to December 2005
The most recent development has been the publication of "NZ Stonewool substrate slab re-use" in the November 2005 issue of Horticulture News.
One of the project's industry participants VegGro Supplies Ltd (VG Horticentre) is conjunction with Typhoon Glass has been exploring the potential to recycle stonewool slabs used in greenhouses.
The two companies are working to establish a mechanical process to allow growers in NZ to re-use stonewool in growing media mixes, or incorporate used slabs back into cropping soil, for the benefit of outdoor growers.
The preferred solution is to include stonewool (rockwool) slabs with other slab substrate, such as coco fibre, that has been screened to remove the plastic wrapping to provide a second-use option.
