As organic gardeners, we believe that healthy productive plants do not grow in a vacuum. On the contrary, our plants thrive in a rich environment, in harmony with all surroundings, both natural and artificially-placed.
Careful planning must be the very first step of every garden, beginning with taking general cues from the biome where we live: the types of plants that grow naturally and abundantly in our area; the seasons when they grow and flower; the insects attracted to them; and the pests, both small and large, that feed on them. The biome – or ecological community where we plan to garden – is large, and we can easily identify its many aspects just by looking around.
Understanding the Microbiome
Perhaps even more important than the visible biome is the microbiome: the entire world of microscopic organisms living in the soil that is undetectable by the naked eye. Especially in the practice of organic gardening – when we do not use man-made chemical fertilizers or pesticides – it is critical to help the microbiome thrive. Living in the soil are bacteria, fungi, protozoa, nematodes, mites, and microarthropods. Some are not only beneficial to our plants but actually necessary to gardening – while others can indeed be detrimental.
The beneficial microorganisms are generally referred to as probiotics, because they enhance plant growth or prevent disease in plants by increasing bioavailability of nutrients and minerals to plants, producing hormones for growth, stimulating plant immunity, and affecting stress response. The addition of beneficial microorganisms to your existing living soil base can help a range of common and rare plant problems.
Scientists studying soil microbiomes have reported many interesting observations, such as the fact that microbiomes are extremely localized – meaning that they have very distinct characteristics – and vary widely from one another over short distances. As we have mentioned before, it is very important to become familiar with the conditions in YOUR area and add amendments as appropriate.
Your Soil’s pH & How It Affects Nutrient Uptake
Another interesting fact about microbiomes relates to soil pH. When soil pH is raised, the actual soil composition is not changed. However, the nutrients in the soil become more “available” to the plants. A healthy soil microbiome also increases decomposition of organic materials in the soil, which increases mineral nutrients and organic compounds that can be used by plants. The use of commercial fertilizers and pesticides reduces or depletes over time, the microbiome. Because of this, certain practices are ill-advised, such as soil solarization to kill weeds or “zero tillage” through deep sheet mulching to create a growing medium. These methods either kill the microbiome or prevent plant roots from reaching into the soil where the microbiome is located.
Tilling & How It Affects Nutrient Uptake
Deep tillage and double-digging can also destroy the microbiome, while minimal tillage, usually accomplished once early in the plant’s life cycle with hand tools, is shown to enhance the biodiversity of the microbiome while conserving moisture and preventing soil compaction. Other practices that have a long history in natural and organic gardening have also been shown through scientific study to preserve and enhance the microbiome while increasing plant health and productivity. Crop rotation, cover cropping, and legume rotations are now shown to improve the abilities of plants to produce, despite drought and heat. This is especially important as we face both climate change and increasing population.
Keeping Your Garden Healthy
The importance of the microbiome to garden health and plant production cannot be overstated. Mycorrhiza, for example, is a fungus found in all healthy microbiomes. It develops a symbiotic relationship with plant roots, delivering water and nutrients to the roots while gaining sustenance in return. When this fungus is not present in your growing medium, plants will be smaller and produce less. Rhizobium, a bacterium, is very important for legumes. It colonizes the root system and draws nitrogen from the air, fixing it in the soil. Without it, legume growth is stunted and production is poor. And these are just two examples of specific microbes. In healthy soil that is well fed with organic matter regularly, microbes will number in the hundreds of millions per gram of soil. So, whether your goal is a backyard garden, a small farm, permaculture, or edible forestry, the health and vigor of your soil microbiome is the key to the productivity of your plants year after year.
Natural farming, a movement dating back to the 1970s, employs a few methods of feeding the microbiome. This is achieved through the use of fermented juices. The theory is that microflora grown through the fermentation process and then added to the soil will increase beneficial microorganisms living there. The benefits of culturing microorganisms and adding them to your living soil are widely acknowledged in tropical and subtropical areas. Scientific studies in other regions seem to be few and far between, though many natural and organic farmers around the world have been conducting trials on their own, often with good results.