In the video, it creates sparks – are these possibly a fire risk?
Yes, while the spark itself has no thermal mass, the treatment wand can heat up and set fire to dry leaves. In dry conditions, our recommendation is to not treat directly onto dry grass, clear out dried leaves near target weeds, wet down the area with water before operation and check carefully for signs of smoldering before leaving an operating are.
What are the differences in effectiveness when the soil is dry, to when the soil and surrounding plants are wet?
Dry conditions are better as more energy is used treating the weed rather than heating any water in the soil. You might get an issue with the earth return not being able to find a route if your fixed earth is 25m away in extremely dry soil, however, we have had success in summer on sand dunes.
How far down does the effect travel? So if you have a plant that has underground runners, how far/deep would the plants be controlled? eg, blackberry runners.
The RootWave Pro has been treating Japanese Knotweed in the UK which has a really deep root structure. We cannot control the path of electricity and therefore guarantee it will kill all the roots, but the longer you treat the weed, the more likely it is do the necessary damage, especially since the hypocotyl and meristem (control and growth centres) of many plants are found just below the surface of the ground.
Does the plant need to be in an active growth phase?
You can shock the weed anytime. It is best if the plant has plenty of water in its tissues, and some plants will change their water holding seasonally.
Can you cut back and then treat without waiting for regrowth? (eg cut down gorse and treat the cut stem to reach the roots?)
Yes, this would be our advice for large infestations as there is no point in wasting energy on the overall bush. We recommend for all weeds to be cut back to below gumboot height prior to operation, however, some regrowth may allow the operator to target the plant more accurately.
Have you done any studies/trials on the effect of the soil biology after treatment? In particular, what is the effect on worms or fungal mycorrhiza?
RootWave are doing this as part of an EU Grant project with NIAB. Evidence to-date suggests no issues as the surrounding soil heats up less than on a hot summers day, and initial results (of a 2-year programme) are expected at the end of 2018.
Worms, due to their soft body contact with the soil water, can be affected by the electricity, and are frequently seen coming to the surface and leaving the treatment area. Worms will be more greatly affected when the soil is wet. Unfortunately, the mortality rate the worms that come to the surface in wet condition is around 18%, although that is considerably lower than those affected by rotary hoeing, stock compacting soil, or tractors.
What trials have been conducted?
Contact us for a copy of the case studies. So far there have been detailed trials in NZ on lawn edges, agapanthus, acanthus mollus, and wooly nightshade. We have more informal ‘before and after’ photos of various other key invasive weed species, including wild ginger, tradescantia and wild asparagus.
What is the environmental impact of the construction of the device? Have you incorporated any recycled material in the construction, or traced the source of the materials and checked for sustainable practices? Do you have a ‘cradle to cradle’ policy?
This is our intention, but at the moment, we have not. Assume no recycled materials in the construction. The lease model allows us to follow reverse logistics and recycle any components that have reached their end point.
Do you have as part of your mission statement any further environmental or sustainable practices other than the replacement of chemicals by the use of the RootWave Pro?
Yes, Hot Grass owns only electric/hybrid vehicles, we use 100% renewable energy to power our offices and cars, recycle, and we do choose green solutions wherever we have a choice. At the moment, our focus is on reducing the use of chemical herbicides.
Is there an operator risk from electromagnetic radiation?
There is no comparable risk because the operator would not have continuous exposure and currents and therefore field densities are orders of magnitude lower than high voltage power pylons.