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Information - The FFC Bulletin - 2016 V1 January

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Back to the future - electrothermal, systemic, weedkiller

By Charles Merfield

Introduction - systemic thermal weeding

To date, the only practical and successful thermal weeding techniques have been steam and flame.  While effective in defoliating plants, these techniques only kill the parts they contact, i.e., they are a contact kill, not systemic weed kill, unlike systemic herbicides that kill the whole plant.  This is a key reason why thermal weeding has been unable to supplant herbicides, especially broad-spectrum, systemic herbicides, and also because thermal treatment costs are much higher.  For thermal weeding to have a chance to supplant herbicides, it needs to be systemic and cheaper than flame and steam.  That is what makes electrothermal weeding stand out.  It is both systemic and is lower cost than steam and flame which is why its resurrection reopens a window for non-chemical weed control for both urban / amenity areas and agri/horticulture. 

This article gives a brief overview of the history and physics of electrothermal weeding, analyses its potential for a range of uses from amenity to agriculture and forestry and concludes with information on the newly available electrothermal weeder.  

Electrothermal weeding history

Electrothermal weeding has a long history, going back at least to the 1890s when patents were issued for ‘electric vegetation exterminators’.  There was a upsurge of research in the 1970s and 80s including in the USA where the Lasco Corporation manufactured machines for sale [10], in Russia, and in the UK where there was particular interest in using it to control bolters in sugar beet crops [1, 2, 3, 4, 5].  However, the technique did not achieve commercial success, mainly due to herbicides being much cheaper while having similar efficacy, that electrothermal machines, in what was then a small market [4]. 

Surfing the zeitgeist - alternatives to herbicides

Things have changed considerably in the past 30 years: herbicides are facing multiple problems including evolved resistance, legislative prohibition and disquiet among consumers and retail chains - being able to claim to be ‘spray free’ is often a significant marketing advantage.  There is therefore a growing need for non-chemical weed control techniques to replace herbicides. Electrothermal weeding may be one of those technologies from the past that is about to come back to the future. 

How electrothermal works

Electrothermal weeding uses high voltage (5,000 - 30,000 volts), but low amperage (0.5 - 2 amps) electricity to kill plants [9].  When the electrode touches the plant, electricity flows down the stem from the point of contact, into the roots and then into the soil, where it completes the circuit though an earth on the weeding machine.  The electricity rapidly heats the plant to the point that the water in the tissues boils into steam which then causes cell destruction, which results in plant death. 

This contrasts with flame and steam, the heat is typically applied to the foliage because it is not practical to get the heat into the ground, and therefore kill the roots, due to the huge thermal mass of soil.  In addition, the heat from steam and flame has to transfer from the surface to inside the plant by conduction - which is very slow.  This means that as plants grow, and have thicker stems, it becomes harder and harder to get the heat into the meristems (buds) from which plants grow.  If the buds are not killed the plant simply regrows after treatment. 

Systemic kill - penetrating the root system

In electrothermal weeding, the electricity instantaneously spreads through the plant’s tissues between the electrode and the soil, so the entire stem and roots are heated to lethal temperatures.  And by focusing on the ground level stem, less plant tissue has to be heated, so less energy is used.  By killing the plant tissues where the stem and roots join (the hypocotyl) it is akin to strangling a plant or ‘going for the jugular’ and it is even more effective than the equivalent treatment of ring-barking as both phloem and xylem are destroyed - plants cannot survive such treatment. 

There is a limit to how deep the electricity will penetrate the root system, as it is will be ‘leaking’ out of the roots and into the soil to return to the earth by the path of least resistance.  The rate of leakage will therefore depend on the relative conductivity of the root and soil.  In favour of the electricity travelling through the root is that there is water in the vascular system of the plant and dissolved mineral salts.  If the soil is also moist or wet then leakage will be faster, while in dry soil, the electricity is likely to travel further down the roots as they will have lower resistance than the soil.  As an example of what is possible a Californian thistle (Cirsium arvense) root was killed 23 cm below ground level [5]. 

No possibility of resistance

All living things have a thermal death point, so it is impossible for weeds to developed resistance to thermal weeding techniques, so there is no risk of weeds becoming resistant in the future. 

Energy efficiency

The core reason for the very poor energy efficiency of flame and steam is that it is very difficult to get the heat into the plants without also heating the surroundings, i.e., air, soil, and machinery, which is why flame and steam weeding often have heat transfer efficiencies below 1% [6].  Electrothermal has the advantage that ancillary heating is kept to a minimum, because there is highly efficient energy transfer between electrode and plant, with the main energy loss being to the soil, but only after, it has done its job of heating the plant.  So coupled with targeting the stem of the plant, electrothermal is much more energy efficient than both flame and steam. 

Weather conditions

Electrothermal is effective in windy conditions and immediately before rain is due, that would prohibit or reduce the efficacy of herbicides due to spray drift and wash-off, and mechanical weeding due to rain increasing survival rates of cut weeds.  However, rain, or plants that are wet, will prohibit electrothermal use due to the electricity earthing through the water on the outside of plants.  Electrothermal poses a fire risk due to the intense heat at the point of contact with the plant which can produce sparks and small flames.  Its use in dry conditions would represent a significant fire hazard, and fire fighting equipment should be considered essential in all weather conditions. 


Finally, the high voltages of 5,000 to 30,000 volts used in electrothermal weeding are highly dangerous i.e., lethal (as a comparison, welders use low voltages, e.g., 10-40 volts but high amperages, e.g., 300-500 amps).  Comprehensive safety procedures are therefore essential for the use of electrothermal weeders [4]. 

The potential

With its unique properties, electrothermal is considered to have a wide range of potential uses, including:

  • Amenity / urban areas;
  • Control of woody weeds such as gorse, broom and wilding pines;
  • Cropping, (e.g., arable and vegetables) particularly for control of intrarow weeds overtopping the crop;
  • Pasture, for killing tall weeds, e.g., thistles, ragweed, and docks.

Amenity / urban areas

The use of herbicides in amenity and urban areas is under pressure from citizens and governments, with some European countries already banning their use.  However, alternatives such as flame, steam, and mechanical control, e.g., brushing, are far from optimal replacements, due to their higher costs, fire hazards and particularly lack of systemic kill [8].  Thermoelectric is the only non-chemical alternative that has a systemic effect and therefore is comparable to herbicides in effectiveness. 

Woody weeds

Woody weeds, such as gorse (Ulex europaeus), broom (Cytisus scoparius) and wilding pines (Pinus spp.) are often difficult to control by any current means: they can have high tolerance to herbicides, and if they are cut down, many will regrow from the stump (i.e., true stem).  To kill them either the stump has to be removed or treated with weedkiller, which increases costs, and root removal disturbs the soil which encourages seed to germinate and on slopes can result in soil loss.  In theory flame and steam could be used to ring-bark woody weeds, but in practice it is very difficult to ensure sufficient heat is applied around the full circumference of the stem, all the way down to the true roots to prevent the plants re-growing.  Electrothermal, targeted at the base of the stem or trunk, can kill all of the stem below the contact point and into the root system.  Once this hypocotyl zone is killed then the plant cannot regrow and the foliage dies for lack of water.  Electrodes can be fitted to long poles so they can reach through the foliage to the stem, so there is a reduced need to cut foliage back to reach the stem. 

Cropping (vegetables and arable, aka row crops) is the production system for which electrothermal was originally targeted in the 1980s.  The main current use for flame weeding in cropping is killing newly germinated weeds for stale seedbeds [7].  However, it is considered hard for electrothermal to kill newly emerged weeds as they are small and very close to the soil, so it is difficult to ensure the electricity travels through the weeds and does not bypass them and earth directly to the soil.  It is therefore considered that electrothermal is unlikely to replace flame weeders for this purpose. 

However, there are many situations were weeds stand above the crop which is where electrothermal should be a valuable new weeding solution.  Killing such tall weeds was the original aim of the machines in the 1980s where they targeted weeds such as sugarbeet bolters and fat hen / lambs quarters (Chenopodium album).  A key point is that weeds in both the interrow, and much more importantly, the intrarow would be killed, and as intrarow weeds are much more difficult to control once they are established, this could be a particular advantage for electrothermal. 

It is also possible to create an electrothermal interrow hoe, where the electrodes replace the hoe blades, travelling a few centimetres above the soil surface to kill weeds between the crop rows.  Where weeds are small, e.g., less than four true leaves / 5 cm high), interrow hoes will probably still be cheaper, especially as they can operate at high speeds, e.g., up to 20 kph, but their effectiveness reduces considerably once weeds get bigger.  This could be an important niche for electrothermal as it will still be effective at killing larger weeds.  It could therefore be a valuable compliment and backup to interrow hoeing, which sometimes fails due to problems such as the field being too wet for horizontal hoe blades to work effectively, which allows the weeds to get away.  Electrothermal interrow weeders could come to the rescue and they could kill bigger weeds that hoeing missed, and electrothermal could kill weeds when soil moisture is too high for hoe blades to work effectively.  In addition, unlike most mechanical weeding techniques that benefit from hot dry windy conditions to help kill the weeds, electrothermal directly kills the plants so it should still achieve high kill rates in cool wet conditions. 


Pasture weeds often stand proud above the pasture, especially after grazing as they are unpalatable to stock.  So, like weeds that stand tall over crops, (see 5.3 above) these are ideal targets for electrothermal weeding, in the same way they are good targets for weed-wipers.  An additional point is that pasture weeds typically have protected growing points at their base or just below the soil surface, such as biennial thistles e.g., scotch thistle (Onopordum acanthium), ragwort (Jacobaea vulgaris), and docks (Rumex spp.) as this is what allows them to survive grazing and mowing.  To physically kill the plant it has to be removed down to the roots.  Electrothermal weeding should be able to kill these plants as the electricity kills all the way down the stem and into the roots, while leaving surrounding pasture unharmed. 

Commercial machines

The reason for this article and the renewed interest in electrothermal weeding, is that after a 30 year hiatus, the idea has been resurrected by Ubiqutek which was established by the sons of Dr Mike Diprose, who was a key researcher looking at thermoelectric weeding in sugarbeet and other crops in the UK in the 1970s and 80s (see references).  The machinery and science behind it is considered to have a solid scientific pedigree.


The above analysis is based on the electrothermal publications listed in the references and other sources.  While the analysis concludes there is considerable potential, there is a clear need for independent evaluation of this machine, for all its potential uses, including determining optimum treatment durations for a wide range of weeds over a range of soil moistures, as well as working out work rates and therefore total operating costs.

A number of land managers, connected to the Future Farming Centre are discussing the potential for evaluating a Ubiqutek machine.  If you are would like information on this group, please email This email address is being protected from spambots. You need JavaScript enabled to view it. for more information. 


Neither the Future Farming Centre or any of its staff have any commercial or other interest in Ubiqutek.  This article is an independent analysis of electrothermal technology as a whole and has been provided to inform land managers of a newly available, potentially valuable, thermal weeding technology.  It is not an endorsement or otherwise of Ubiqutek. 

This article has been prepared by The BHU Future Farming Centre, which is part of The Biological Husbandry Unit Organics Trust. While every effort has been made to ensure that the information herein is accurate, The Biological Husbandry Unit Organics Trust takes no responsibility for any errors, omissions in, or for the correctness of, the information contained in this article. The Biological Husbandry Unit Organics Trust does not accept liability for error or fact or opinion, which may be present, nor for the consequences of any decisions based on this information.


1.  Diprose, M.F. and Benson, F.A., Electrical methods of killing plants. Journal of Agricultural Engineering Research, 1984. 30: p. 197-209.

2.  Diprose, M.F., Benson, F.A., and Hackam, R., Electrothermal control of weed beet and bolting sugar beet. Weed Research, 1980. 20(5): p. 311-322

3.  Diprose, M.F., Benson, F.A., and Turner, N.V. The use of high voltage electricity for weed beet control. in British Crop Protection Conference - Weeds. 1980. Brighton, UK: British Crop Protection Council

4.  Diprose, M.F., Fletcher, R., Longden, P.C., and Champion, M.J., Use of electricity to control bolters in sugar beet (Beta vulgaris L.): a comparison of the electrothermal with chemical and mechanical cutting methods. Weed Research, 1985. 25: p. 53-60

5.  Diprose, M.F., Hackam, R., and Benson, F.A. Weed control by high voltage electric shocks. in British Crop Protection Conference - weeds. 1978. Brighton, UK: British Crop Protection Council

6.  Merfield, C.N., Organic F1 hybrid carrot seed (Daucus carota L.) production: the effect of crop density on seed yield and quality, thermal weeding and fungal pathogen management, in Bio-Protection and Ecology Division. 2006, Lincoln University.

7.  Merfield, C.N., False and Stale Seedbeds: The most effective non-chemical weed management tools for cropping and pasture establishment. The FFC Bulletin, 2015. 2015(V4): p. 25

8.  Rask, A.M. and Kristoffersen, P., A review of non-chemical weed control on hard surfaces. Weed Research, 2007. 47(5): p. 370-380.

9.  Vigneault, C. and Benoît, D.L., Electrical weed control: Theory and applications, in Physical control methods in plant protection, Vincent, C., Panneton, B., and Fleurat-Lessard, F., Editors. 2001, Springer-Verlag: Berlin, Germany. ISBN 3-540-64562-4.

10.       Wilson, R.G.J. and Anderson, F.N., Control of three weed species in sugarbeets (Beta vulgaris) with an electrical discharge system. Weed Science, 1981. 29(1): p. 93-98

The BHU Future Farming Centre

Information - The FFC Bulletin - 2016 V1 January

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Understanding biostimulants, biofertilisers and on-farm trials

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By Charles Merfield and Marion Johnson


There has been a phenomenal growth over the last decade of biostimulants and biological fertiliser (biofertilisers) products. A wide range of claims are made for these products and it can be hard for farmers and growers to tell fact from fiction. There has also been something of a factional spilt on this issue between academics and farmers & growers: many mainstream academics have been sceptical of these products, considering they are not based on ‘real’ science, while some farmers and growers have been buying and using them successfully in increasing amounts. The opposite is also true, in that some farmers and growers have been sceptical about some of the claims being made and there are academics who have been passionate advocates. The whole topic is therefore something of a mare’s nest.

So, diving in where angels fear to tread, this report aims to give you the guidance you need to work out which biostimulant and biofertiliser products have real potential to help you farm better and more profitably and those that should be treated with scepticism. It is going to be a somewhat windy road, as there is no simple answer, there is no simple list of what works and what does not. You need to understand some of the complexities and niceties of scientific experiments, but hopefully the knowledge you gain will be valuable in other areas of your decision making.

What are biostimulants and biofertilisers?

There are no formally agreed definitions of biostimulants or biofertilisers, in part because new forms and types have been rapidly appearing and the industries as a whole are evolving quickly.

Broadly, a biostimulant is a substance or microorganism that when applied to plants or the soil, stimulates existing biological & chemical processes in the plant and/or associated microbes (e.g., mycorrhizal fungi) to enhance the plants growth, yield and/or quality through improving nutrient update, nutrient use efficiency and/or tolerance to abiotic stress (e.g., heat, saline soils).

Biofertilisers are materials of biological origin, e.g., plants, seaweed, fish, land animals, etc., that contain sufficient levels of plant nutrients (nitrogen, phosphorus, potassium, calcium, magnesium, etc.), in forms that are either directly absorbed by plants, or are sufficiently quickly decomposed to available forms, to cause an increase in plant growth and/or quality.

The main difference therefore is that biostimulants don't contain many nutrients, while biofertilisers do.

The term biofertilisers has both a narrow and broad meaning. Taking the term at face value, it means anything with a fertiliser value that is biological in origin. However, some consider biofertilisers to mean processed, commercial / proprietary products - the narrow meaning. The broader meaning therefore includes traditional, and widely used, materials such as manures and composts. However there is no clear dividing line between the narrow and broad definitions, for example biodigestates (the material produced by biodigesters / anaerobic digestion) come from a controlled process and are heavily modified from the starting material, while some proprietary products are only slightly altered from their raw state. This report therefore uses the wider definition but notes which type of product is being referred to.

Biological controls are not biofertilisers or biostimulants

It is also important to differentiate between biofertilisers & biostimulants and biological controls (biocontrols). Biocontrols use one or more living organisms, typically microbes and insects, to control pests, such as diseases, insects and weeds. The biocontrol agent therefore has no direct effect on the crop plant, only the benefit of having the pest controlled (although the impact of that can be a profound increase in growth). Biopesticides are a sub-group of microbial biocontrol agents that are applied / used like chemical pesticides, i.e., sprayed onto crops. These may appear to be similar to biostimulants (many of which are also microbes) but they are different. Confusingly some products, for example Trichoderma fungi can act as both a biostimulant and a biocontrol. Adding to the confusion is that a number of biocontrols are marketed as biostimulants to get around the extensive safety and efficacy testing that is required for pest control products which has been designed for agrichemicals, not biological organisms.


Biostimulants are in-turn divided into four major sub-types, some with sub-types of their own [1]

  • Microbial inoculants
    • Free-living fungi
    • Arbuscular mycorrhizal fungi (AMF)
    • Free-living bacteria
  • Protein hydrolysates and amino acids
  • Humic Substances
    • Humic acids
    • Fulvic acids
  • Seaweed extracts

This is not an exhaustive or exclusive list, for example, compost teas contain microbes, so they could be included in ‘1. Microbial Inoculants’, even though they contain more microbe species than are listed, they may also contain proteins, amino acids and humic substances. Seaweeds, while the most common, are not the only plants that extracts are made from - many terrestrial plants are also used in both commercial and farm-made extracts. Despite these limitations the framework highlights the main types and shows the broad range of organisms and substances that are classed as biostimulants.


As biofertilisers can be made from any previously living entity, either animal or plant, there is no equivalent categorisation as for biostimulants. Generally they can be grouped by how processed or decomposed they are. For the broad definition of biofertiliser, materials that are in a raw, or close to raw state, include slurry and farm yard manure (FYM) while those that are well decomposed include compost and biodigestate. For the narrower definition raw (undecomposed) seaweed can be used as a fertiliser, while proprietary biological seaweed fertilisers and biostimulants process the raw seaweed using a range of techniques to concentrate the desired components and/or enhance certain components to create the final product.

How to decide if a product works?

Determining whether any particular product works is where things get complex and a bit tricky. Perhaps a good way to start is with an anecdote...

Back in the 1980s the first wave of seaweed biostimulants came to market. A vining pea grower in the UK was interested in the claims being made, but though he would test the products before using them on the whole farm. Sensibly, he set up a simple experiment in his field by spraying several strips of the seaweed product up his field of peas with unsprayed strips in-between. It was soon pretty obvious where the peas had been sprayed, as the plants were both bigger and greener, a property that lasted until harvest time. To test the effect on yield he drove the harvester across the strips: every time he hit one of the sprayed strips the harvester groaned and he had to put it down a gear and hit the throttle, so he assumed that it was from all the weight of extra peas that he had grown. Fortunately his farm adviser was there and suggested that he get off the harvester and actually have a close look at the crop itself. It did not take long for the grower to realise that the extra work the harvester was doing on the sprayed strips was nothing to do with peas, because there were hardly any pods on the sprayed vines, let alone peas. The seaweed biostimulant was one that contained plant hormones (phytohormones) which are chemicals that regulate plant growth. In this case the phytohormone was one that encouraged vegetative growth in peas - i.e., making vine, and suppressed reproductive growth - i.e., making pods and peas. The strain on the harvester was not lots of peas, it was lots of vine!

There are a couple of key lessons to take from this true story.

  • The plant-soil-climate system is one of the most complex things in the universe. It is simply impossible to predict the effect of complex products (i.e., those containing several ingredients, as opposed to one or two) on plants and the rest of the system. The only way to determine the effects is by empirical scientific experiment (spraying strips up the field). However, you must make a direct measurement of the results (counting the number of pods and peas on the vines) not rely on indirect measurements (the response of the harvester).
  • Where products have real and consistent effect, it may not be the one you want (vine instead of peas). It is essential that the product has been tested on your specific crop (even specific cultivars), for the effect you want to achieve, at the point in the crops lifecycle you plan to use it (e.g., early growth, post flowering). Just as there are selective herbicides that will kill weeds and not the crop, any one biofertilisers or biostimulant may have quite different results on one crop species than another as well as different effects at different growth stages.
  • Farm advisers can sometimes be worth their weight in gold (well nearly)!

Understanding the science

Having said that empirical scientific experiments are the only way to determine the effectiveness of a product, designing the experiments to truly measure outcomes and responses can be a quagmire. The key over arching questions are:

  • Does the research replicate real-world use.
  • Is the experimental methodology appropriate.
  • Does the experimental design measure the correct parameters
  • Do we know what to measure?
  • Is the experiment run over a long enough time frame

Real-world use

A recent review paper on biostimulants [1] listed a wide range and number of experiments that had been undertaken. However, a majority of these were not undertaken in real-world conditions - an important caveat. Typically when scientists start working on a biostimulant, or undertaking other research using living thing, such as biocontrol agents or allelopathic chemicals, they start work in the laboratory (in vitro (meaning in glass) in the jargon). Mostly this is because it is quick and cheap and they can get a research publication out of the work. If the lab work looks promising, and just as often when it does not, they then proceed to pot trials, i.e., growing plants in pots in a glasshouse. This is more expensive than the lab, but more realistic, and it produces another paper. However, those scientists that have been in the game for a long time know that the results of lab trials, and often pot trials, bear no relation to performance in the real world. Therefore, experienced scientists, as a starting, not an end point, often undertake trials in situations as close to real world use as possible, and skip the whole lab and pot trial, publication gravy train.

What that means is research, even high quality research, that is not conducted under real-world conditions that match your crop and farm, i.e., the exact crop species, even the same cultivars for some species (e.g., grapes), on similar soils and similar climates may not be relevant to your operation. Due to the huge number of soils and climates around the world you can’t be too picky about the conditions being similar, e.g., in New Zealand, Canterbury and Hawkes Bay results should be considered comparable, but anywhere in NZ with Australian dryland would not be comparable. So, as farmers and growers you should pretty much just ignore lab and pot based experiments - their results are signposts but almost meaningless as far as your crops and pasture are concerned. Results from experiments that sound like they could have been done on your farm, orchard, vineyard etc., are the ones you should pay the closest attention to.

Appropriate methodology

Experimental methodology is science jargon for how an experiment was done. It covers things such as the treatments, e.g., amount and type of fertiliser, the untreated ‘null’ controls, the statistical analysis, the general setup, e.g., in-vitro lab experiment, pot experiment, field experiment, and all the details, e.g., soil type, soil tests, soil moisture, weather for the whole experiment, plant species & cultivar, age, when planted, and uncle Tom Cobley and all.

Determining if the experimental methodology is appropriate is unfortunately where the quagmire gives way to the snake pit. It is surprisingly easy for scientists to set experiments up to get the result they want, and it is even easier for scientists that don’t have the right expertise, to set an experiment up that fools them into thinking they have an accurate result. Then there is the interpretation: scientists can disagree over what the results mean - one of the most famous was the UK’s multi-million dollar experiments culling badgers for TB (tuberculosis) control in cattle - where opposing camps of scientists, very politely, tore strips off each other in public over their contrary interpretation of the results.

Also just because a paper has been “published in a peer reviewed journal” does not mean that the information is inviolable.. Often when scientists undertake a ‘meta-analysis’ (taking all the experiments in journal papers that have researched a particular topic (e.g., culling badgers to reduce TB in cattle) and combining the results into one giant statistical analysis, they often throw out 10 to 40% of the papers due to invalid methodology, i.e., they consider the results of those trials to be unreliable. It is also pretty common for different experiments to give contrary results, due to the vagaries of nature, and agricultural science. As an example, in the European Union, cultivar comparison experiments have to comply with the 5 × 5 rule: the comparisons have to be done in at least five locations for a minimum of five years for the data to be considered reliable - 25 repeats of the same field experiment!

It takes a lot of scientific training and even more experience to make a good call on the methods for an individual experiment, and in the end it is a subjective decision. Therefore there is little chance that the layperson can make that judgement, so if you want a view on a particular experiment, then you need to find an independent scientist who is trained and experienced in the same specialism as the experiment, to give you advice, and then, it is only an opinion.

At the end of the day, individual papers count for little, it is the amassed results from across a large number of experiments, across many years, plus the experiences from farmers and growers using products and techniques for real, that eventually determines if an effect is real or not. Until such broad consensus it built up, caveat emptor applies.

Measuring the correct parameters

From a farmer and growers perspective, it may seam pretty obvious what parameters to measure - the ones that get turned into profit, i.e., the stuff you harvest: lambs, grapes, apples, lettuces, wheat grains, etc.  Disappointingly this is too frequently the measurement that gets missed by scientists.  However, it is also important to measure ‘intermediate’ parameters, such as growth during the whole season, plant nutrient levels, etc., as these are important for helping understand what is going on, i.e., the cause and effect relationships.  There is a mantra in science that ‘correlation does not imply causation’. What this means is if you only measure yield, you don't know why the yield increased, so you only have a correlation, which is weak science, while if you measure other parameters these can point to how the increase was cause, then you have stronger science. 

Time frames

For products such as biostimulants that have an immediate and relatively short term effect, trial duration is typically one crop cycle, based on the assumption that there is little or no residual effect, i.e., if you stop using the product, then the effect stops after a week to a few months.  However, it is rare for effects to be truly short term, e.g., annual plants may be bigger, so if resources allow, the experiment should be run for three to five years to see what the long-term effects are - which is how they will be used for real. 

For products, such as biofertilisers, or anything that impact on soil processes, duration should be as long as possible.  This is because soil processes and performance change very slowly. It really can take decades for the long-term effects to be fully shown.  The truly  long-term soil experiments around the world have now been running for over a century.  Data from these shows that it takes up to 50 years (half a century) for soil to truly reach a new equilibrium.  When the first ten to 30 years data from these experiments are analysed they often give quite different results compared with analysing 50 years.  If scientists are being really hard core about such trials, they will throw out the data from the first five years, have a look to see if there are any trends in the next five years, and then consider data after the first decade as starting to become reliable.  So, if you are running experiments that effect the soil, a trial should really be kept running for five years at a very minimum, and ideally a decade.

How to rig a fertiliser experiment

The results from fertiliser experiments are particularly noteworthy for their ability to get the results required, it is worth explaining how and why. For the full details underpinning this see the FFC Bulletin article “The Fundamentals of Soil Nutrient Management, Soil Testing and Fertiliser Recommendations” [3], and also “Understanding biological / organic fertilisers using kelp (Macrocystis pyrifera) as an example" [2].

A plants response to fertiliser does not just depend on the fertiliser, its growth response is to the total amounts of nutrients supplied from both the soil (or potting mix) and the fertiliser. There is an optimum amount of each nutrient that any given plant needs to maximise yield (or any other measurement). If there are excessive amounts of nutrients it will harm the plant and suppress yield, and if there are too few nutrients yield will also be suppressed. So, if a plant is grown in nutrient deficient soil and nutrients are supplied via fertiliser, the plant will grow more, potentially a lot more if the soil is really deficient. If the soil is around optimum, applying the same amount of the same fertiliser will have no effect on yield. If the soil is already in excess, applying the same level of fertiliser will cause a decrease in yield. So, the same application of fertiliser will result in increased yield, no yield change, and a decrease in yield depending on the nutrient level in the soil used.

Clearly to sell more fertiliser, the companies selling it will want to do tests in nutrient deficient soil not soil with excessive nutrients. To pick this kind of trick up, the person looking at the experiment’s results needs to know what the nutrient level of the soil that was used in the tests and they then need to know if that is deficient, optimum or excessive, and then interpret the results on that basis. In short, always take the results of fertiliser trials with a pinch of salt.

The experimental dilemma

One of the ‘advantages’ of chemical agricultural technologies, such as herbicides and insecticides, is that they work pretty much the same pretty much anywhere in the world A herbicide or insecticide that kills a weed or insect in the UK will do the same in Africa. Conversely one of the ‘downsides’ with biostimulants and biofertilisers is that their effects can vary widely depending on things such as the crop species, soil type, soil nutrient levels, weather/climate etc. Therefore while a pot experiment that shows a particular weedkiller kills a given weed is transferable pretty much too any farm anywhere in the world, the same is not true for biofertilisers and especially biostimulants. Experiments on biofertilisers and biostimulants need to be done under local conditions, which means that lots and lots of experiments are required to demonstrate efficacy for all the different crops, soils, climates, countries, etc., around the world.

This is the ‘experimental dilemma’ - experiments are expensive, so to conduct all the experiments needed to demonstrate widespread efficacy of biostimulants and biofertilisers, would be prohibitively expensive. In addition there is very little reason for scientists that don't work for the companies producing biostimulants to test these products.  Such experiments are rote work and so are the least rewarding to undertake as they don't create valuable new knowledge or understanding.  And, they are almost worthless to scientists trying to travel their career path.  And they still cost significant amounts of money, that could be spent on ground-breaking, career boosting experiments, so the opportunity cost is pretty big for a scientist to test such products.  So they don't. 

However, with the wide range of products out there, there is likely to be one that will improve your production and profit, the question is how to identify them. The answer, DIY experiments.

How to do your own experiments

Scientific experiments can seem like they are shrouded in an aura of mystery. To be fair, there are some really insanely complicated experiments out there. However, we are blessed in agriculture in that many of our experiments are the simplest there are. The value of DIY experiments is that they are done on your crop or pasture so the results are 100% meaningful for your operation. It is therefore entirely possible for farmers and growers to conduct their own if you follow a few simple rules.


Treatments are the different products you want to test. More is not always merrier as the amount of work increases considerably the more treatments.

It is important to decide the application regime from the start: is the product to be applied once at the start of the trial, or sprayed on weekly? The application regime should match what would be done in the real crop.

A control

You need to have something to compare the treatment with which is called, a ‘null’ control i.e., nothing is applied to the crop, and/or, current practice, e.g., current fertilisers. The control needs to be replicated and randomised just the same as the treatments.


As noted in section "Time Frames" getting the experimental duration right is really important.  For biostimulants that is typically one crop cycle but ideally three or more, while for biofertilisers, that impact on soil processes, duration should be as long as possible, ideally a trial should last five years but a decade is much better.  For field crops, 10 × 10 meters is a good starting point, and for perennials at lest ten plants down a row / 20 meters. 


Like the farmer spraying several strips of seaweed fertiliser on his peas, you need to have replication, i.e., several applications of the treatments. Traditionally four replicates are used (really the minimum) but in a perfect world six to eight are best.


It is impossible to emphasise how important proper randomisation is. It would not have been good enough for the farmer spaying strips up his field to just spray every other spray bout. To do the job properly, he should of stood at the bottom of each bout, flipped a coin, head for spray, tails for a control, and kept going until he had enough replicates (spray strips) of the seaweed and unsprayed (control). Randomisation helps take chance out of the experiment, so you didn’t accidentally add all the treatment you are testing on an area that by chance had higher or lower fertility anyway.


The standard layout for field trials is the randomised complete block (RCB). Figure 1 shows a RCB experiment layout with four treatments (a,b,c,d) and four replicates. The key to blocking is that each of the four treatments (or however many there are) are found in each and every one of the blocks (hence complete block). Each one of the squares is referred to as a plot, i.e., it is a group of plants or area of pasture that has one treatment applied to it and is one replicate.

Block 1





Block 2





Block 3





Block 4





Figure 1. Randomised complete block experimental layout.

Plot size

Plots need to be big enough so that the natural variation found in agriculture is minimised. Therefore the bigger the plot the better.

Measure what matters

Don't make the mistake the pea grower did of taking his harvesters performance as a measure of pea volumes. It is essential to measure the final product, i.e., the thing you sell to make money. For most of horticulture this is easy, you harvest the crop for each plot and count or weigh it. For livestock it is very hard to measure the effect on the stock (very large plots and lots of stock are required), so for livestock the surrogate measure of pasture growth and laboratory analysis is mostly used.

Statistical analysis

The statistics is typically the most confusing part. Fortunately the ANOVA test, which can be found in most spreadsheets is typically used. However, if you are not comfortable with statistics, as many aren’t there are a number of people who can help.

Getting some advice

While the basics of an experiment, as outlined above, are really pretty straight forward, there are niceties in the details that take experience to get right. Getting advice from a real scientist is therefore important. However, what the above illustrates is that it perfectly possible for a farmer or grower to carry out the experiment themselves, with some expert advice, and create their own empirical evidence about the effectiveness of any given biostimulant or biofertiliser.

Return on investment

Finally, the fundamental reason for applying any type of fertiliser, pesticides, biostimulants and all the other agricultural inputs available is to increase yield and therefore profit. If the product you are applying costs $200/ha to use and increases income by $100 you are $100 out of pocket (profit has reduced $100). Unless there is some other benefit, e.g., increasing soil organic matter over the longer term, which results in bigger yields in future, using products that lose you money is not a great idea. So, the ultimate measurement of an experiment, is not yield, it is profit, so it is critical that gross margins for all the treatments are calculated to test for the level of profit or loss.

How they work

Explaining how biofertilisers and biostimulants work as a whole is impossible as just about every single one has a different mode of action. This is why it is so hard to generalise about the products - they all work in different ways. A few examples, to give a flavour of the mechanisms involved, are given below.

Starting with biofertilisers. Foliar applied biofertilisers (and mineral fertilisers) can boost nutrient uptake even when soil nutrient levels are at an optimum - i.e., adding more nutrients to the soil does not increase yield. This is because they bypass the roots’ limitations on nutrient update. In some cases this can increase yield and quality but in other cases it can also lead to luxury uptake which can have negative effects, such as lodging, sappy growth, increased pest attack etc. So, more is not aways better.

Soil applied biofertilisers cannot be taken up by plant roots because the molecules are mostly too big to get across the root epidermis. They have to be decomposed (mineralised) into inorganic salts / minerals to be absorbed. Nutrients supplied by biofertilisers therefore sit in the same queue for plant uptake as the existing soil nutrients, so the potential for a biological form of a nutrient to have a markedly different effect to a mineral form on immediate plant uptake is small.

There are however important system level effects to take into account. Mineral fertilisers don't contain biological forms of carbon so they don't supply energy to soil biology so they can cause a reduction in soil organic matter as microbes use up the soil organic matter to make use of the extra mineral nutrients. By definition, biofertilisers do contain biological carbon so there is a much reduced likelihood that they will cause microbes to consume soil organic matter. Whether they cause a significant increase in soil organic matter depends on how much is applied. For example, compost, manure, biodigestate, wood chips and similar bulky materials, applied at tens of tonnes per hectare on a regular basis, are just about guaranteed to noticeably increase soil organic matter. Highly processed products applied at kilos per hectare are unlikely to result comparable increases in soil organic matter.

Biostimulants are where things get really complex. The range of mechanisms by which these products can impact plant growth and quality are almost limitless. They include:

Enhancing nutrient availability in soil, for example, through increased mineralisation of soil organic matter by microbes.

Increasing root biomass or root surface area, e.g., bacteria that release plant growth promoting chemicals.

Increasing the plant’s nutrient uptake capacity, e.g., mycorrhizal fungal association and, bacterial inoculants for legumes increase nitrogen uptake, and can therefore be considered a biostimulant.

Resistance to drought and salinity stress, through microbes that produce protective compounds or induce the plants to produce more of their own protectants.

Putting it all together

So, what conclusions can we draw about biostimulants and biofertilisers? Going back to the start, there are some good reasons for mainstream academics to have be sceptical of these products: their modes of action were outside of accepted wisdom at the time, and therefore, the required standard of proof that the effects were real, was, justifiably higher, or as Carl Sagan, one of the worlds great scientists and science popularisers, said “Extraordinary claims require extraordinary evidence.” However, many academics dismissed biostimulants and biofertilisers out of hand, regardless of the evidence, or without any evidence at all, which in-turn is also clearly unscientific.

On the other side of the ledger Carl also has a pearl of wisdom for academics and producers who have been insufficiently sceptical and promoted and used biostimulants & biofertilisers on the basis that they all work. “Keep an open mind, but not so open that your brains fall out.”

Dismissing ideas out of hand is not scientific, but uncritically accepting them, is also unscientific: Somewhere in the murky middle ground between these two extremes, the truth lives. The most effective way for navigating through the murk is empirical evidence, i.e., an experiment.

Evidence based

The only way to reliably determine if a biostimulant or biofertiliser does what it claims on the tin is to check if it has a body of experimental evidence to back it up. This means not just one peer reviewed paper, but a suite of them that are relevant to your production system. Due to the experimental dilemma (see the section "The experimental dilemma") there is a dearth of good experiments on biostimulants and biofertilisers. There are many biostimulants and biofertilisers that are backed up by large amounts of good quality science. There are many, many more that don't have experimental backing. Some of these will be effective and profitable, some won’t be. The answer to the experimental dilemma is therefore to do your own experiments, or get a group of your mates together to do them, or as a whole industry, with some good advice from independent scientists.

In a nutshell, the only way only way to sort the wheat from the chaff is to do the experiments yourself on your land. That way you will really know for sure. 

Futher information

The very informative "On-Farm Trial Guide" was produced a while back by MAF (!) FAR and LandWISE and hardcopy can still be purchased via their website


1. Calvo, P., Nelson, L., and Kloepper, J.W., Agricultural uses of plant biostimulants. Plant and Soil, 2014. 383(1): p. 3-41.

2. Merfield, C.N., Understanding biological / organic fertilisers using kelp (Macrocystis pyrifera) as an example. 2012, The BHU Future Farming Centre: Lincoln

3. Merfield, C.N., The fundamentals of soil nutrient management, soil testing and fertiliser recommendations. The FFC Bulletin, 2015. 2015-V1.

The BHU Future Farming Centre

Information - The FFC Bulletin - 2016 V2 April

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New pollination opportunities using lucerne leafcutting bees

By Charles Merfield


The lucerne leafcutting bee (Megachile rotundata) (Figure 1) is the foundation of a multi-million dollar pollination industry in North America, not only for lucerne (Medicago sativa) but other crops such as oil seed rape (OSR) cranberries and blueberries, for example, in Canada half the OSR is pollinated by lucerne leafcutting bees [1]. 

Figure 1.  The lucerne leafcutting bee (Megachile rotundata) left image, right image Pennsylvania Department of Agriculture

The lucerne, or alfalfa leafcutting bee as the North Americans call it, accidentally reached the Americas in the 1940s from its native Europe, and was imported from the USA and Canada to New Zealand in 1971 to 1984, when a considerable amount of research was undertaken and an industry established, until the breakup of DSIR which resulted in disbandment of the project.  Fortunately one of the original scientists, Dr Barry Donovan (Figure 2), now of Donovan Scientific Insect Research, has recently been working to re-establish the industry.  This work is looking increasingly timely due to a number of factors. 

  • There is a gold rush into manuka honey by New Zealand bee keepers which is dramatically reducing the amount of honey bee hives availability for crop pollination and where they are available, the price is going up dramatically.
  • Honey bees have increasing health problems, starting with the varroa mite, then colony collapse disorder and there are now concerns about the newly identified parasite Lotmaria passim
  • Moving honey bees for pollination and ensuring sufficient bees not easy as bees have to be moved at night and it impacts the bees.  Leafcutting bees can be easily shipped and their emergence accurately timed with crop flowering. 
  • Lucerne is being promoted by Prof. Derrick Moot and team at Lincoln university as the smartest, sustainable and most profitable way to manage NZ dryland stock farms  The amount of lucerne being grown is increasing spectacularly, but most seed is imported because of a lack of local production.  Leafcutting bees can create a home grown lucerne seed industry and produce additional income for dryland farmers. 
  • Pollinating vegetable seed crops, especially carrots is difficult, but there are indications that leafcutting bees are a good, if not better, alternative to honey bees. 
  • The production of leafcutting bees for crop pollination in North America is now a multi-million dollar industry, and NZ has the potential, due to low leafcutting bee pest and disease levels, to sell bees into the N American market and elsewhere. 

Figure 2.  Dr Barry Donovan of Donovan Scientific Insect Research beside lucerne leafcutting bee hive

What are lucerne leafcutting bees?

Unlike honey bees that live in colonies, leafcutting bees are solitary but gregarious - i.e., they work alone but like each others company, which is what allows them to be managed.  Also, they will not sting unless squashed, so no protective clothing is required (Figure 2).  Their most preferred plant is lucerne, both as a source of pollen & nectar, and leaf material which they use to build the cells which house their young.  They will however use a range of other crop plants and weeds for food and leaves.  The females create their cells out of ovals cut from leaves, placing them in small holes and cracks, then provisioning them with pollen and nectar on which the larva feeds and then pupates in the cell.  Typically only one generation is produced per year, with the species overwintering as larvae in the cells.  This is the other aspect of leafcutting bees that makes them manageable and valuable for pollination.  Artificial nests / ‘hives’ are created which consists of lots of 6 mm diameter holes (Figure 3).  The bees create multiple leaf cells in these holes (Figure 4), which can then be recovered at the end of the season and refrigerated for about eight months.  In that time the cells can be shipped anywhere in NZ or overseas, ready for pollinating the next crop on time.  This compares very favourably with honey bees which have to be moved as whole hives, at night.  This is the basis for the leafcutting bee industry in N America - selling cells to farmers and growers to pollinate a range of crops.  Also, some leafcutting bee keepers run contract pollination services. 


Figure 3. Lucerne leafcutting bee hive. 


Figure 4.  Grooved bee nest boards and individual bee cells. 

Lucerne pollination

To be effectively pollinated the lucerne flower has to be ‘tripped’ which is where the anthers spring out of the flower and strike the bee on the underside.  The problem is that honey bees do not like this and they quickly learn to get the nectar without tripping the flower, so it fails to pollinate.  Also lucerne pollen is missing the essential amino acid isoleucine which means honey bees suffer protein stress when only working lucerne.  As a lucerne specialist, the leafcutting bee is unsurprisingly much better at pollinating lucerne.  Work done in the early 1980s in New Zealand showed that lucerne seed yields increased from around 70 kg / ha to between 350 to 517 kg / ha [2], a 370% to 590% increase!  Gross margins indicated that the entire capital cost would be more than recovered in the first year, indeed capital could be repaid several fold [2]. 

Management / lifecycle

Management of lucerne leafcutting bees is relatively straight forward, but, it has to be done correctly to be successful.  The downloads at the end of this article, and a wide range of information on the internet from N America, provide full details. 

As noted above the larvae in their leaf cells are kept refrigerated for about eight months of the year.  About 21 days prior to the crop starting flowering, the larvae in their cells are warmed up in controlled conditions which causes them to pupate and then emerge ready for action.  This is another valuable attribute as bee presence and activity can be precisely timed to crop requirements. 

The bees are then released into the field into simple, but carefully designed and placed shelters which houses the ‘hives’ - i.e., the 6 mm nesting holes.  Another benefit of leafcutting bees is they will work the first suitable available flowers and like to stay as close to their hives as possible, unlike honey bees which if they find more preferable flowers elsewhere can completely ignore the crop they are placed in.  The bees mate on emergence and although both sexes pollinate flowers only the females work to create the next generation while the males lounge around seeking to mate with females!  The females cut ovals out of leaves to create the cell which they place in the holes.  A lot of research was done in the United States to work out the best design of the hives and a system was developed where grooved boards when stacked up created the holes, so they could then be easily taken apart to retrieve the cells.  Lots of other approaches have been tried and are used, including paper drinking straws, and solid blocks of wood with holes drilled in them. 

Generally there is only one generation a year, i.e., the bees that emerge from over winter produce lots of progeny, but that progeny do not hatch the same year, rather they remain as larvae and overwinter themselves.  Sometimes in good weather, the first generation may hatch and start producing a second generation, but in NZ conditions the second generation is not as large as the first, so it should be avoided.  This is done by timing the release of bees and putting the cells into cold storage at the correct time.  The correct time of cold storage is also the key to managing the main pest of leafcutting bees in NZ a small parasitic wasp Melittobia hawaiiensis that is native to NZ but found globally.  If the hives are left in the field too late in the season, parasitism levels rapidly increase to the point where all bee larvae can be lost.  The leaf cells are then kept refrigerated until they are required for the next season when they are then shipped, warmed up, and released to pollinate the next crop. 


Many thanks to Dr Barry Donavan for reviewing this article and providing most of the source material. 


If you are interested in producing lucerne leafcutting bees in New Zealand please contact Dr Ron van Toor at This email address is being protected from spambots. You need JavaScript enabled to view it. +64 27 285 2720.  Cells and small ‘starter’ hives can be purchased from Creative Woodcraft

All the key publications from NZ research from the 1980s is available below for download including the management handbook.  Each is a ZIP file and contains scans / images (JPGs) as the originals were typed so no electronic versions exist. 

There is also a wealth of information on the internet.  When searching, use the taxonomic name “Megachile rotundata”, or the American name "alfalfa leafcutting bee" and “alfalfa leafcutter bee” (lucerne leafcutting bee is the Entomological Society of NZ standard common name, but many producers, especially in N America, use the term leafcutter bee). 

Leafcutting bee life history, allocation details, and management techniques (main management handbook) 30 MB

Is leafcutting bee investment warranted? The answer is clearly "yes"! (NZ Journal of Agriculture article on financial benefits) 4 MB

Pitts-Singer, T. L. & Cane, J. H. (2011). The Alfalfa Leafcutting Bee, Megachile rotundata: The World's Most Intensively Managed Solitary Bee. Annual Review of Entomology, 56(1), 221-237. (open access review article)

The following pollination reports, cover annual research outputs and management advice.

Pollination report 1 1979.  4 MB

Pollination report 2 1980.  8 MB

Pollination report 3 1981.  23 MB

Pollination report 4 1982.  17 MB

Pollination report 5 1983.  11 MB

Pollination report 6 1984.  10 MB

Efficacy of lucerne leafcutting bees as pollinators of lucerne in New Zealand. Journal paper, 6 MB

Seed production of new cultivars of lucerne. Journal paper, 2 MB

Selection and importation of new pollinators to New Zealand. Journal paper, 3 MB


1. Darrach, M. and Page, S., Statistical Overview of the Canadian Honey and Bee Industry and the Economic Contribution of Honey Bee Pollination, 2013-2014. 2016, Ottawa, Ontario: Horticulture and Cross Sectoral Division, Agriculture and Agri-Food Canada. ISBN 1925-380X.

2. Donovan, B. and Read, P., Is leafcutting bee investment warranted? The answer is clearly "yes"! The New Zealand Joural of Agriculture, 1984. 149(4): p. 2-3 

The BHU Future Farming Centre

Information - The FFC Bulletin - 2016 V1 January

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New sustainable and ecological extension and information website launched

By Charles Merfield is a new website which is translating scientific research into practical advice to help farmers and growers become more profitable and sustainable.  It does this by providing unrivalled access to world‐class information resources and championing good farming practice based on ecological principles.

The site is a collaborative venture between leading organisations working to support sustainable farming in the UK including the Daylesford Foundation, the Organic Research Center, and Allerton Project, with the Daylesford Foundation having pledged £500,000 (NZ$ 1.1million) over the next five years.

Topics covered by the website include:

  • Soil management
  • Pests, diseases & weed management
  • Pasture management
  • Reducing antibiotic use
  • Encouraging biodiversity, especially pollinators and beneficial insects

While the site is unashamedly UK focused, and so has a number of topics (e.g., subsidies) that don't apply outside the UK, there is still a wide range of valuable information, being added to all the time, that will be of value to farmers and growers in other countries, especially those in temperate climates. 

The BHU Future Farming Centre

Information - The FFC Bulletin - 2016 V3 July

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Report on Indigenous Agroecology

By Marion Johnson

Download report (14 MB) from FFC or Nga pae o te Maramatanga website

This report edited by Dr Marion Johnson of the FFC and Chris Perley of Thoughtscapes looked at how mātauranga Māori (Māori traditional knowledge) and Totohungatanga Moriori (Moriori traditional knowedge) can inform and generate innovation in farm practices.

Agroecology in its simplest terms reconnects ecology to agriculture and to the people that draw their livelihoods from the land.  He Ahuwhenua Taketake, Indigenous Agroecology, weaves Maori and Moriori ways of seeing with agroecology to create a land management paradigm for Aotearoa New Zealand.
This report illustrates some of the areas of knowledge that are important to agroecology. It also highlights the necessity of farmers, whanau and specialists talking, working and adapting together for a common good.  Agroecology by necessity is complex, the land is complex. There is no universal recipe as each farm is individual but there a series of principles which can guide land management decisions. This document is only a beginning, making a contribution to the development of an alternative land management paradigm in Aotearoa New Zealand and providing a catalyst and context for dialogue and change.

The report begins by introducing the concepts of Agroecology and Indigenous Agroecology framed for Aotearoa New Zealand. Traditional land managements are explored as is the use of geographical information systems and visualisation to aid discussions of change.  Indigenous Agroecology requires a meeting of local culture and science so the challenges for communities in working with Mātauranga Māori and Science are discussed as are the problems faced by indigenous communities in retaining the participation of youth.  We depend on healthy water ways, healthy livestock and a broad diversity to support our lands and livelihoods, the multiple roles played by native plants in farm systems are enumerated and the problems of pollution and possibilities of bioremediation debated. Two final chapters illustrate the suggestions for local applications of Ahuwhenua Taketake on research link farms.
Agroecology has been endorsed internationally by the United Nations and others, as ‘the means by which we can mitigate climate change, rural equity, the various degrading environmental functions, as well as increase local food production’. Aotearoa New Zealand has an opportunity to embrace change, to safeguard our soils, water and biodiversity and to produce healthy nutrient dense food for local and export markets.

The Indigenous Agroecology, He Ahuwhenua Taketake, programme was developed and led by Dr Marion Johnson and funded by Nga pae o te Maramatanga.

Please do contact Marion, This email address is being protected from spambots. You need JavaScript enabled to view it. for any further information. 

We have a limited numbers of hard copies available; please email Marion with your postal address.