There has never been more interest in the concept of on-farm production of microbial inoculants. This can involve task-specific organisms like nitrogen fixers, phosphate solubilisers, or humus-building microbes. Alternatively, the intention might simply involve a desire to increase all-important biodiversity, in recognition that,“the more the merrier,” is what effectively drives low problem, high-production agriculture.
The sponsors of that increased interest in microbe brewing include rising input costs and increasing chemical resistance. Often, we are effectively putting on more of everything, each season, for more cost and less response. It’s the definition of unsustainable, and many farmers are now seeking more viable alternatives.
One of those more cost-effective options involves the on-farm multiplication of beneficial organisms. You can source a good proportion of your N requirements from the atmosphere for free, for example. You can manage disease and insects with antagonistic microbes, and you can unlock frozen reserves of phosphate by multiplying up creatures capable of releasing this lode.
However, as is always the case, there can be traps for young players. This article will provide key guidelines to help ensure that this new venture proves productive. In fact, there are ten considerations when creating your own living fertilisers.
1. Hygiene is critical
The first thing to understand is that microbes are everywhere and it is so easy to contaminate a microbe brew with unwanted intruders. You need to flush the tank after each brew. Otherwise, post-brew residues are left to effectively rot, until your next brew. Some of the organisms that multiply in the leftovers might well multiply during your next brew, and that is not desirable.
I have found at my farms that the best strategy is to clear the decks before starting the microbe multiplication process. This disinfectant strategy is not just about ensuring that you sterilize the equipment. The water source may be more important. I suggest that you put some dam water under a microscope, or through a microbiometer, and you will find it is teaming with microbes, some of which may well compete with the good guys you are trying to multiply.
So, we always fill the brewing tank with dam water and then add chlorine to sterilize both the water and the equipment. That typically involves 40 mls of pool chlorine in a 1000 litre brewing tank.
Now you have to get rid of the chlorine, or it will kill your inoculum, just as it killed the bugs in the dam water. The secret here is to bubble off the chlorine with your aerator running, until there is zero smell of outgassing chlorine. Some suggest that 30 minutes is sufficient but we find it takes much longer. We typically bubble overnight, before adding the food and inoculum, just to be absolutely sure.
2. Clean, chemical-free tanks
The second consideration relates to your spray tank or fertigation tank. You can’t use the same tank you use for chemicals, or residues might impact your brewed inoculum. Most growers have a dedicated tank for nutrients and microbes. Hydrogen peroxide can often be used to clean out chemically contaminated tanks, as it oxidises the unwanted contaminants.
3. Delivering enough oxygen
If you are using A DIY brewing tank, you need to be sure than you are providing enough oxygen throughout the brewing process. Bacteria, for example, are subdividing every twenty minutes, and,12 hours into the brewing process, there are trillions of organisms demanding oxygen. If you do not maintain a minimum 6 ppm of dissolved oxygen throughout the brewing process, then your workforce has often suffocated half-way through the cycle. You brewed a bunch of dead guys, and you are often none the wiser!
If you have a commercial brewer you can assume that the manufacturers have done the work to ensure adequate oxygen delivery, but if the brewer is your own creation, it is best to beg, borrow or steal a dissolved oxygen meter, to monitor your brew. You only need do this once, but it is important. The key to dissolved oxygen is the generation of thousands of tiny bubbles. There is no point in wildly swirling water with large bubbles. This will not deliver sufficient oxygen. Tiny bubbles have a greater surface area and this ensures a good level of dissolved oxygen.
4. Feeding your brew
The next key factor relates to the microbe food you will require to multiply your inoculum. The accepted rate of microbe food is 1%, but some prefer a little more. Microbes are seeking the same things we need. They want fats, carbohydrates and protein, and a smattering of trace minerals also helps. You can make your own food using things like liquid fish, amino acids, kelp, fulvic acid, humic acid, trace minerals and a little molasses. Remember that you just need a little more than 1 litre per 100 litres of water. We have developed a very popular microbe food involving all of these inputs and more, if you want simplicity. It is called Nutri-Life LMF (Liquid Microbe Food) and it is used at one litre per 100 litres (1%).
The most important thing about microbe food is that all inputs are fully stabilised. Theoretically, you could use something like soy meal as a food source, as it contains the three key food groups. However, it can also contain bacteria from the atmosphere that are seeking those fats, proteins and carbohydrates. Commercial sources of fish, kelp and humates have usually been stabilised, but be careful if you are making your own. Theses DIY liquid fertilisers are fine on the farm, but they may be a liability when brewing, as potential contaminants can also multiply.
5. Brewing times and conditions
Different organisms require different optimal brewing times, and climatic conditions can also impact this optimum. Microbes struggle to thrive in cold conditions, for example, and you might need a tank heater to get things started. I’ve even seen growers wrap an old electric blanket around their brewing tank in winter to improve conditions for microbe multiplication. Once the new workforce gets going, they tend to generate their own heat in their breeding frenzy.
Most organisms are brewed within 24 hours, but protozoa teas take 2 days and most fungal brews also have better counts after 36 hours.
6. Fungal inoculants
There is always a challenge in creating a fungal dominated inoculum. Whether it is trichoderma or a fungal dominated compost tea, it will always be more difficult, due to the nature of the beast. Bacteria divide more rapidly and release alkaline exudates, that slow fungal proliferation. Compost teas consequently become a bacterial soup. pH is the key here. If you can keep the brew below pH 4.7, then fungi tend to proliferate. That can be achieved with the addition of natural acids like vinegar or citric acid but this acidification often needs to be repeated a few times, as bacterial exudates keep pushing up the pH. The trick is to use a buffered pH modifier. We have developed something called Dominate (Fungi) which will hold down that pH and stimulate fungal proliferation. It is added to the tank at the rate of one litre per 100 litres (1%)
7. Attrition from pump pressure
Our next guideline relates to the application of microbial brews. Pump pressure can be destructive, and it is suggested that we should try not to exceed 60 to 70 psi. This problem, however, largely relates to what I call, “the splat factor”. It is about battering those single-celled creatures against a leaf, stem or trunk, and potentially damaging cell walls with the pressure. If you are using a blow mister, in an orchard situation, there is less likelihood of that kind of direct damage.
8. Putting the microbes behind the minerals
Another consideration involves using your brewed inoculum to magnify the uptake of nutrition. I call it “putting the microbes behind the minerals” or Microbially Enhanced Nutrient Delivery (MEND). You have wasted an opportunity if you do not include mineral nutrition with every inoculum. In a foliar scenario, the organisms involved represent a major source of CO2 release on the leaf surface. This triggers stomatal opening and better associated nutrient uptake.
9. Mineral/microbe tank compatibility
There are some minerals that can be biocidal, and hence counterproductive, when added to a tank full of microbes. The worst culprit is copper. Growers often think of this mineral as a fungi killer, but it can actually impacts almost everything. It is highly biocidal and hence the need to avoid large or regular repeated doses to the soil. Copper is a heavy metal that accumulates in the soil to the point that it can become a biological liability over time. It is never wise to add copper to any microbial brew, as it can compromise performance.
10. Monitoring your brew
It’s difficult to know how you are going because the targets of your efforts are invisible. It just looks like dirty water, so it can easily become a kind of “spray and pray” scenario.I like to use the microbiometer to see that everything has worked as planned. It will measure microbial biomass in your brew and if numbers are low then you need to sort out why!That’s how we discovered we were not off gassing chlorine for long enough at the farm brewing shed. For those of you capable of microscopic analysis, a good guideline for compost tea quality is the growing aggregation of fungi and bacteria during the brewing process. Early in the brewing cycle, bacteria and fungi remain visibly segregated. However, if the brew is progressing well, so is the interconnectedness and associated aggregation of fungi and bacteria. In the presence of good food and adequate oxygen, they become team players in the process of nutrient cycling.
On a more basic level, the completed brew should have a rich earthy smell and some bubbles or froth on top. If it has a bad smell, you have failed and should not apply that particular brew. I have actually seen rotten smelling end products that will kill grass. Perhaps there is even potential for a new herbicide here.
There are also some meters that can offer a guideline as to your likely success. These include ATP meters, as Adenosine Triphosphate is a direct measure of microbial activity. EC meters, pH meters and dissolved oxygen meters can all offer insight into the creation of ideal brewing conditions. Turbidity meters measure dissolved solids in the brew. The more active the microbes the higher the level of dissolved solids. Even a refractometer can offer some insight on this front.
One final suggestion to improve the performance of the end brew. Always send your new conscripts out to work with a lunchbox. Fungi love more complex foods like humic acid and kelp while bacteria like simpler options like sugar, molasses or fulvic acid. Fish hydrolysate feeds all organisms.
In Conclusion …..
You may have previous thought about on-farm production of microbial brews as some kind of “out there” concept that had no relevance to your operation. I’m suggesting that it might be of value to rethink that closed mind paradigm. We are demonstrably using more inputs for less response and the increasing costs of fertilisers and farm chemicals are threatening our viability. It makes perfect sense that we repopulate our soils and crops with beneficial biology as part of a strategy to escape this unsustainable cycle.