Soil and plant microbial communities have a mutualistic relationship where they provide what the other needs to thrive. There are many factors that can influence this relationship, such as soil structure, composition, and humidity, but soil pH has one of the most profound impacts on the growth and survival of plants and microbes.
When we measure pH, we’re actually measuring the local concentration of protons (hydrogen ions, known as H+). When there are too many H+ ions, the soil is acidic, resulting in a low pH. When the proton concentration is low (or a scarcity of H+ ions), the soil is alkaline (or basic) and has a high pH. Soil chemistry largely determines which microbial communities can get established in the soil.
Soil microbes are just as much affected by high pH as they are by low pH. When soil pH is in a neutral range (6.0-7.5, which is close to the pH of water), plants are more easily able to uptake the nutrients they need. For that reason, this is generally their optimal range. However, there are some plants such as blueberries or Rhododendron, that favor a more acidic soils. Not all microbes necessarily favor a neutral pH – fungi actually prefer soils with a lower pH. As acidic soils reduce the availability of certain nutrients, fungi are able to increase access to those limited nutrients for the plant to uptake. Still, challenges can arise for microbial communities when the soil pH deviates from its optimal range. While soil pH will naturally lower in time due to geochemical and metabolic processes, the soil pH can decrease rapidly with the input of certain fertilizers.
For example, when ammonium-based fertilizers are applied to the soil, bacteria use oxygen to convert the ammonium nitrogen (NH4+) to nitrate (NO3–), a more plant-usable form, and H+ ions, through a process called nitrification. Bacteria do this to obtain energy. If a plant needs some potassium, it will exchange one of its positive hydrogen (H+) ions for a potassium cation (K+) in the soil. This exchange helps maintain electrical balance through a natural process called cation exchange. However, this balance can be thrown off by over-application of fertilizers. As plants take up certain nutrients, it leaves a deficit of other nutrients, which can cause a decrease in pH levels.
If more fertilizer is continuously applied, more H+ ions are released, which can cause an imbalance in the soil and lead to soil acidification. The increased amount of H+ ions will directly affect the functionality and structure of the soil microbial communities. A low soil pH can disrupt plant cell membranes – altering enzyme production and limiting cell reproduction. Enzyme production and activity work best in more neutral pH ranges. As well, low soil pH can limit the exchange signals between root bacteria (rhizobia) and plants, which reduces root nodule formation, and alters the symbiosis that allows plants to fix nitrogen.
Overall, maintaining a balanced soil pH is crucial for ensuring nutrient availability and more importantly, microbial diversity in your soil. As deviations in pH can disrupt essential processes like nutrient uptake, enzyme activity, and the communication and functioning of symbiotic relationships between plants and soil microbes.
Healthy soil is brimming with beneficial microbes, and those microbes are one of the important keys to ensuring the health of your plants. Along with breaking down key nutrients for your plants, they’ll aerate the soil so nutrients are evenly distributed, and fend off parasitic microbes so your garden can grow in peace.
Considering the wealth of benefits, it’s no surprise that it is recommended that you do everything you can to maximize the microbial biomass in your soil. While there’s complicated science behind it, nourishing and increasing the amount of microbes in your soil is simple, and can be accomplished with a few tried and true methods. And thanks to the microBIOMETER® soil test, even amateur gardeners can track their microbial biomass levels.
First, let’s detail how you can take care of those important microbes and enhance their numbers. It’ll involve shedding some old gardening habits, along with taking on some new ones, but we promise the end results will be worth it.
What To Avoid
Before you start taking extra steps to care for and increase your microbial biomass, you should ensure you’re avoiding certain tactics that are known to hinder their growth.
While you might think avoiding pesticides wouldn’t enhance plant health, a close look at the ingredients of most pesticides will show you they do far more harm than good. Amongst a variety of issues, one of the most harmful is the fact they decimate microbial populations in the soil. If you want to ensure pests will stay away in the absence of pesticides, try utilizing companion plants instead.
While pesticides are bad, fungicides are even more of a threat. Some of the most vital microbes in your soil, being fungi, would be directly targeted by these treatments. The harshness of these chemicals would also wreak havoc on the non-fungi microbes, all but eliminating any trace of a microbial biomass. Even if you can’t do everything on this list, ensure you at least abide by this particular rule.
Lastly, while many gardeners and farmers consider tilling a standard gardening process, you’ll want to abstain from it if you’re focusing on your soil’s microbes. That, of course, is due to the level of soil disturbance that occurs during the process. The process leads to lost microbes (especially fungi), and any benefits gained from additions made to the soil end up being cancelled out. By avoiding tilling, you’ll allow the delicate environment in your soil to function undisturbed and, in turn, at full capacity.
What To Do
Now that you’ve cut those bad habits out of your gardening routine, you have room for a few that’ll greatly benefit your soil in the long run.
Nothing gets microbes into the soil like a nice big pile of compost! All that food breaking down in one big pile is basically a feast for all the helpful microbes you want around your plants. Once you add it onto your soil, then turn it to make sure air hits every part of it, you’ll be ensuring the microbes have plenty of energy to break down nutrients. To ensure the best compost possible, make sure you add in natural components like grass clippings, fruits, vegetables, wood chips, and straw. There’s no need to exclude other foods, even processed ones, but a healthy blend of green and brown material is a must.
Following the same logic, compost teas can do wonders for the microbes in your soil. All you have to do is take some compost and put it in a water permeable pouch, add some microbe feeding nutrients (perhaps like molasses), and let it brew (bubbling air into it) until the microbes in the compost have multiplied and the tea is full of microbes. Once done, pour it all around the base of your plants. One round will do your plants good, but repeating this process a few times during your growing process will really make a difference.
This last step is actually three steps and if these conditions aren’t met, virtually nothing else on this list will have a noticeable effect. To start, making sure you have adequate moisture is as simple as regularly watering your plants. You may also want to consider purchasing a moisture meter to assure your levels are ideal. Next, the ideal pH range for soil is between 6.0 and 7.0, so you’ll have to test your soil to see where you’re at. If your soil pH is too low try adding limestone and if your pH is too high you can add aluminum sulfate and sulfur to get things balanced. Lastly, mulching is a great way to help your soil maintain an even temperature.
Incorporating these simple tactics into your crop management is an important first step to building the microbial biomass in your soil. Another critical step is testing and quantifying the results of these inputs since decision making without data is like driving blindfolded. microBIOMETER® is a rapid, on-site soil test for microbial biomass. Microbes respond very quickly to any changes in the soil, therefore, you can set a baseline then retest within a week to see if you are heading in the right direction.
