Its back into the archives today for this great blog on the importance of earthworms and their agronomic value to farmers in terms of all the functions they perform. Although this article is 7 years old, it's just as relevant today as it was then. Happy reading!
An agricultural system that is dependent upon petrochemicals is absurdly vulnerable as peak oil approaches. Smart operators, the world over, have recognised this vulnerability and are seeking to reduce their reliance upon oil. The focus changes from oil to soil as growers come to recognise that their chemical approach has been self perpetuating. The more you use, the more you lose and the higher your requirement for chemical intervention.In contrast, a biological approach involves ever reducing inputs as the biology kicks in. The emphasis is upon soil life and there is one creature in this equation that epitomises the profit potential of biology.
Imagine a worker who can aerate your soil while fertilising, soil conditioning, liming, and creating humus. This same creature can mineralise soil and repopulate beneficial biology while also improving structure. If your soil contains good numbers of these workers then it is a good indication that you have a happy and productive soil food web. It has been suggested that the presence of this remarkable life form can be seen as a marker of the success and sustainability of any given society. I refer here to the humble earthworm.
All Important Oxygen
It could be argued that oxygen is the single most important element for plant production. Plant roots need an abundant supply and the organisms that crowd around those roots can’t function without it. The calcium to magnesium ratio is the single most important ratio in the soil because it governs oxygen delivery. The lower your soil-life counts the higher your requirement for aeration to introduce oxygen. It is always much more cost-effective to use your earthworms to aerate rather than hauling a spiked roller all over the farm! Earthworms create the perfect passageways to improve gas exchange and improve water infiltration. The earthworm castings also increase crumb structure which also improves oxygen availability.
There is a massive difference in the nutrient analysis of the surrounding soil compared to what comes out of the back end of an earthworm. In fact, these slimy strands are essentially fertiliser factories. The castings contain 7 times more phosphorus, 10 times more potassium, 5 times more nitrogen, 3 times more magnesium and 1.5 times more calcium than surrounding soil. At the Gatton field days, several years ago, the DPI conducted trials on several organic fertilisers, including manure, feedlot compost and vermi-compost. The vermi-compost completely outperformed all other inputs in the trial. In fact, there were impressive results at application rates of just 1 tonne per acre or 2.5 tonnes per hectare. Here’s the holy grail of biological farming. If you can achieve counts of 25 earthworms per shovelful then your days of buying fertiliser are over. This number of earthworms will produce 300 tonnes of earthwork castings per year. The cost of commercial castings exceeds $200 per tonne so you are effectively receiving $60,000 of free fertiliser from your earthworms and why would you need to apply any more?
Repopulating Your Workforce
The earthworm does not digest with enzymes when plant matter passes through its system. Instead it employs microorganisms for this energy intensive task. A unique range of microbes are incubated within the earthworm and are excreted amongst the castings to introduce these organisms to the soil. That is why growers have achieved such good results from earthworm juice (water that has passed through the worm beds and accumulated these organisms). If you do not have earthworms in your soil then you do not have this valuable range of organisms and there will be good gains in introducing them. As always it is a “give and you shall receive” deal in nature. The earthworm is seeking as much plant matter and beneficial biology as possible because that is what it eats. The bacteria it delivers sponsor production of more biomass, which means more food for the earthworm. These bacteria are also a food source for protozoa which, in turn, are the favourite food of earthworms. In this manner, the system becomes self supporting as is the case with many natural systems. The problems usually emerge when we intervene and disrupt the balance.
Since 1850 the loss of humus from our soils equates to 470 gigatonnes and this accounts for a great deal of the offending CO2 in the atmosphere. There is an urgent need to return this CO2 to the soil as humus and it is here that the earthworm has a hugely important role to play. Earthworms compost 4 times faster than conventional composting and composting is about humus production, whether that occurs in the field or in the composting plant. If your earthworms are delivering 300 tonnes of humus rich castings per hectare then you will see an associated increase in organic matter (for which you will soon be paid). Increasing your earthworm numbers is a prime humus building strategy and yet most conventional farms have very few remaining earthworms at work.
Lime For Free
I often suggest that there is little need for fertiliser inputs if you can fire up your earthworms. Seminar patrons often ask “what about liming?”. It’s a good question because calcium is the most important nutrient and it is removed with every crop. Earthworms are like little lime works; they have a calciferous gland that adds calcium carbonate to everything that passes through them. They are also burrowing deep in the profile bringing calcium and other minerals up into the root zone.
What Drives Out the Worm Workers?
Earthworms follow food. They love to eat fungi and protozoa so if these creatures are missing in your soil, so too will be the creatures that feed upon them. Earthworms also love dead plant matter. I have graphic childhood memories of digging in Dad’s lupin cover crop at the end of winter and an army of earthworms would appear overnight to enjoy the feast.
Salt fertilisers dehydrate fungi and bacteria and thereby reduce earthworm food. These inputs also irritate the worms and they disappear quite rapidly. There has not been a lot of work looking at the effect of farm chemicals on earthworms but we do know that fungicides kill fungi (good and bad) and several herbicides appear to kill fungi as efficiently as they kick out weeds.
Compacted soils with a poor calcium to magnesium ratio are inhospitable to earthworms. Why battle your way through the hard stuff when you can so easily travel elsewhere for easier pickings.
Cultivation also impacts earthworms. It obviously chops them up and opens the soil to feathered predators but there is another dynamic involved. Native earthworms burrow down to 30 cms, line those burrows with slime and organic material which attracts other organisms and these visitors serve as a food source. Every time they head to the surface they vacuum this supplementary tucker from their burrows en route. Tillage tears apart these pantry passageways and discourages the return of earthworm workers. This is why research has shown that minimum till and no till agriculture usually encourages more earthworms and associated humus production.
Bringing Back the Fertility Builders
How do you recover your earthworm populations to profit from this wondrous workforce? There are several foods that stimulate earthworms. Anything that increases the number of fungi in your soil will boost earthworm populations because fungi are a major food source for these creatures. Humic acid is the most powerful promoter of fungi followed very closely by kelp. Both of these materials offer a wide range of other benefits and this is why they have become integral components of the biological approach. The other biological essential which can have a magical effect upon earthworms is liquid fish fertiliser. It is common to see an immediate marked increase in earthworm numbers following the application of fish to the soil. It is actually like they come from nowhere to enjoy this concentrated mix of protein, fatty acids, carbohydrates and minerals. The one secret here is that you need to source a liquid fish fertiliser that still contains the full oil component (Nutri-Sea Liquid Fish) as the fish oil is a major attractant.
The other way to increase numbers is to feed the soil with plant matter by building a cover crop or green manure crop into your program. Ideally, there should be no time at which your soil is left bare. Whenever the opportunity presents, the aim is to produce some soil food rather than fallow your soil. Some people argue that they do not want a cover crop to steal moisture that they are trying to conserve for the following crop. This is not what occurs. The cover crop increases organic matter and biological activity. Bacteria produce a sticky, alkaline film that works just like water crystals in the soil. The more bacteria you have, the greater your potential to retain moisture. Similarly, an increase in organic matter means more moisture retention. A 1% increase in organic matter means that your soil can retain 170,000 extra litters per hectare. In a home garden this represents 17 liters per square meter.
The other worm building tip involves a creature called protozoa. Protozoa are to earthworms what potatoes are to humans. Potatoes are our favourite vegetable (often linked to our huge consumption of chips). Protozoa numbers are often depleted due to their susceptibility to farm chemicals and, in this case, the earthworms go elsewhere in search of their favourite food. If you want to return your farm to a fast food heaven for earthworms then you need to bring back the protozoa. It turns out that this is not that difficult to achieve and it involves something called Lucerne tea.
For some reason, protozoa love Lucerne and all three species are found in abundant numbers in Lucerne hay. The idea is to harvest these creatures from the hay and multiply their numbers prior to introducing them to the soil. The one caution here relates to chemical contamination of the hay. The safe option is to source organic Lucerne as it appears that the chemical used to control Lucerne flea can seriously impact protozoa populations living on the Lucerne.
Here’s how to make a Lucerne tea. Add 7 kg of Lucerne hay to 200 litres of water. The best idea is to place the hay into a simple, drawstring bag made of shadecloth so that it will not clog the pump. However, this is not necessary if you are using brewing apparatus based upon air compressors rather than impeller pumps. Next you add some food to feed the protozoa. We have developed a food called LMF™ (Liquid Microbe Food) that works well for this purpose. Two litres of LMF™ is required for the 200 litre drum (1%) and then you leave the mix to brew for at least 24 hours. You will then need to filter the end product (if it is not in a drawstring bag) before applying it via boom spray or fertigation at a rate of 100 litres per hectare.
In turbulent times when agriculture is threatened with the twin spectres of peak oil and climate change, those who are earliest to adopt viable solutions will be those most likely to profit amidst the turmoil. The earthworm offers exactly that kind of edge. The presence of these remarkable life forms in your soil heralds a disease suppressive soil with more carbon building potential and less requirement for chemical intervention. The food produced on these soils will be more nutrient dense and the cost of production significantly less. Bring back the earthworms to your soil and you will also have a lot more fun in your chosen profession. Farming with nature is dominated by pride, purpose and pleasure and life is too short to compromise.