Netpro Pty Ltd design and build protective structures to mitigate frost damage; NetPro also have a number of user-friendly products available.
Frost is a surface coating of frozen water vapour, the result of rapid heat loss.
Note that surface temperatures (of plants, soil etc) can fall below freezing, even though the air temperature remains above zero.
Location and local topography influence the incidence of frost. For example, the presence of a large body of water will act as a heat-bank, as do the tarred roads and large buildings found in cities. Evergreen trees can act as a protective blanket; and higher up, clouds do the same. Cold air tends to sink, so it will flow down into low areas like valleys and stream-sides. Slopes are less prone to frosts as the cold air is moving downhill, rather than settling; but an embankment (vegetation, sleepers or stone) can slow the flow and pool cold air.
Once frost itself and its conditions of occurrence are understood, it becomes easier to predict and prepare for frost mitigation. Conditions for rapid heat-loss include cloudless, still nights where the temperature drops close to freezing. Often, wind can reduce the occurrence of frost as it keeps the air moving and mixing, preventing formation of cold-sinks and inversion layers.
So, the ideal indicators of a potential frost are: cold, clear, still, starry nights.
It is common practice to cover frost-tender plants – using anything from old baskets and boxes, to bed-sheets and curtains, vinyl and plastic, shade-cloth and hessian (burlap) cloth. A commercially available product is frost-cloth or Horticultural Fleece - an extremely light, breathable fabric made from spun-bonded polypropylene or poly-ethylene.
On a sunny day, the soil will collect heat. Overnight, soil will lose heat as air temperatures fall. The idea of covers is to trap the warmth of the soil and to keep warmer air down close around the plant, thus preventing the rapid surface cooling conducive to frost formation. The second prong to this method is that the cover itself becomes the surface on which the moisture freezes, rather than the plant tissues.
‘Recycled’ covers must often be folded back or removed during the day-time, to allow light to reach the plant, and to prevent overheating such as can easily happen under plastic or vinyl. The advantage of the commercially available frost-cloth is that it can remain over the plants for long periods if necessary: it will provide an insulating layer whilst still allowing at least 70% light transmission; and, unlike plastic, it has a degree of permeability to both rain and air movement.
NetPro carries a range of frost cover options - suitable for both home gardeners and commercial growers.
We have a number of Reports on Trials completed by HIA (Horticulture Innovation Australia) on our Press Articles page. One Report of particular interest here is the one on the effectiveness of Frost cloth for weather mitigation.
Keep in mind how cold air settles and how frost forms; and simultaneously keep in mind how frost-cloth (Horticultural Fleece works as an insulating barrier and it becomes easier to use it most effectively.
Frost-cloth is light enough to be simply laid over the top of plants, but it is just as effective over cloches/hoops or trellis. It is important to ensure that the frost-cloth is securely anchored and sealed where it meets the ground. Remember this will hold the soil-warmth around the plant; and it will also prevent any breezes from removing the cloth.
One final note, no frost-cloth (horticultural fleece) - no matter how well it is deployed- is completely impermeable to heat loss. Eventually, over a continuous run of cold overcast days, soil-temperature (and air-temperature) will drop under the cloth. We recommend that on the first sunny day, the covers are folded back if possible, to allow the soil and mulch to collect warmth again.
Frost-cloth (or fleece) was originally developed in Europe and the USA but even in Australia, frost-cloth can be very effective at saving frost-sensitive plants and extending the growing season (at either end!). (Check out our "NetPro News" blog posts for links and ideas on using frost-cloth!)
In summary, frost-cloth can diminish the effect of frost in a number of ways, including capturing a pocket of warmer air and physically preventing ice from forming directly on or in plant tissues. Frost-cloth will not harm the plants if it remains on the plants for extended periods of time as it will provide a warm, light-filled and sheltered micro-climate for sensitive plants to flourish.
Three areas of influence have been identified in the efforts to quantify the effect of canopy netting and plant covers:
A more detailed discussion of results reported in these three areas can be found in the document Environmental Modification - Microclimate Adjustment, along with references to relevant reports.
While the large structures designed by NetPro are mainly utilized by the commercial horticultural sector, many of the materials developed are highly suitable for home gardens and small private orchards. Pre-packed nets can be purchased through our eBay shop, or by contacting our office. Material details can be found on the Product Sheets and in our Retail Catalogue. For larger quantities, please contact our sales office – either via the enquiry form or on the Toll Free number.
Success Stories View all
As major investors in the Australian horticulture industry, Rewards Group Ltd needs to ensure maximized returns on all funds invested, particularly in orchard infrastructure. Accordingly, our choice of contractors is critical to the final success of any project.
We currently have 250 acres of net – about 80% of our orchard area. Without the protective canopy, we wouldn’t be able to supply our market requirements. Quality is important to us and we wouldn’t be able to meet the specifications of our customers without net.
We particularly liked the product offered by NetPro – high quality was our main criteria. The option of wooden posts was also an important feature because of the highly-corrosive conditions in the feedlot environment. We were able to work through the construction plan and the materials options during the quoting process.
We chose NetPro to construct our protective canopies, as we know NetPro have been around for some time, we know their work and there are plenty of examples of their work around – we like the consistency of standard. In addition, NetPro are recognized by the Finance bodies, and it is much easier to get finance for a structure.
I think it has made all the difference to the quality of our product – it has saved us from bird attack and from hail damage." Since 2001, Robert Channon Wines have won 23 trophies, 17 gold medals, 26 silver and 55 bronze medals.
We live in North Queensland and have a nine metre pool. We needed to replace the pool cover but most local businesses we contacted wanted to replace it with a shade sail and the one quote we received to fabricate a new cover to our design seemed exceedingly high.
In 2003, Golden Valley Orchards were offered the opportunity to work with the NCEA (National Centre for Engineering in Agriculture) and NetPro Pty Ltd on a research project evaluating the effectiveness of (amongst others) NetPro's dam-covers.
"I think it has made all the difference to the quality of our product – it has saved us from bird attack and from hail damage." To date, Robert Channon Wines have won 23 trophies, 17 gold medals, 26 silver and 55 bronze medals since 2001."
Initially the idea of the net canopy over the landfill was discussed with Netpro as they are a local company and at the time Netpro was considering advancing into this area (protection of landfills). Netpro assisted Council with a very reasonable price which allowed the project to proceed.
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