Over the past few years we’ve been moving more and more towards the ideas expressed by Masanobu Fukuoka and Emilia Hazelip. But not entirely. We do intervene in the natural process in mostly benign ways. Because we grow vegetables intensively, we are extracting from the soil. Thus we have to replenish it by adding SOM either via mulch which breaks down into compost or by adding plant-based compost, either finished or partially finished to the beds. We also alternate feeding ourselves one year with feeding the soil the next year by planting green manure crops such as peas (a nitrogen fixer), buckwheat and Daikon radishes. Last year we started using a water based mycorrhizal fungi to assist in nutrient uptake and extend the roots’ access to water – I should probably talk about mycorrhizal fungi in a separate post.
But adding SOM and improving the microbiology of the soil is only part of the process. Planting peas in a crop rotation is meant to replenish nitrogen (You must chop and drop the peas before they begin to flower in order to capture all of the nitrogen attached to the roots). But nitrogen is only one of the nutrients that plants need. You need to add back the other macro and micro nutrients. One of the ways of doing this is thru remineralization. This takes you into the complicated world of soil amendments and soil testing. The more I read, the more I said “Wait a minute” and a few things began to emerge. Intuitively, soil testing makes sense. You want to know whether your soil is acidic or alkaline since this will affect how well your plants grow. You want to know what macro and micro nutrients are in your soil since that also will affect how well your plants grow. But then it begins to get messy. Once you have a lab result, what then? Most lab reports contain recommendations of how to amend your soil to get to the “ideal soil” . +100,000 hits!!!! WOW. So what do I add and in what proportions? If you really want to dive into the confusion, start here.
My confusion morphed into frustration. I know that we are mining our soil when we pull a carrot -an annual- or pluck an apple – a perennial. Had the apple not been plucked, it would have fallen to the ground and its nutrients re-cycled. The process of replacing what we are extracting involves a lot of science-based certainty applied to Nature. Enter Fukuoka at this point: We cannot comprehend the complexity of Nature.
And significantly, the process involves dollars for testing and for buying remedial products.
And then I remembered that one of the benefits of mycorrhizal fungi is their ability to convert mineral nutrients to a form that the plant can use.
There is strong evidence showing that fungi produce a large diversity of enzymes and chelating compounds that allow them to capture nutrients from the soil that are not normally accessible to plants (chelating compounds bind metals into different forms in the soil to prevent their interference with uptake of other nutrients)
Then I remembered that mycorrhizal fungi promote growth.
Plant growth-promoting rhizobacteria (PGPR) are naturally occurring soil bacteria that aggressively colonize plant roots and benefit plants by providing growth promotion. Inoculation of crop plants with certain strains of PGPR at an early stage of development improves biomass production through direct effects on root and shoots growth. Inoculation of ornamentals, forest trees, vegetables, and agricultural crops with PGPR may result in multiple effects on early-season plant growth, as seen in the enhancement of seedling germination, stand health, plant vigor, plant height, shoot weight, nutrient content of shoot tissues, early bloom, chlorophyll content, and increased nodulation in legumes.
PGPR are reported to influence the growth, yield, and nutrient uptake by an array of mechanisms. They help in increasing nitrogen fixation in legumes, help in promoting free-living nitrogen-fixing bacteria, increase supply of other nutrients, such as phosphorus, sulphur, iron and copper, produce plant hormones, enhance other beneficial bacteria or fungi, control fungal and bacterial diseases and help in controlling insect pests. There has been much research interest in PGPR and there is now an increasing number of PGPR being commercialized for various crops. Several reviews have discussed specific aspects of growth promotion by PGPR. In this review, we have discussed various bacteria which act as PGPR, mechanisms and the desirable properties exhibited by them.
Various species of bacteria like Pseudomonas, Azospirillum, Azotobacter, Klebsiella, Enterobacter, Alcaligenes, Arthrobacter, Burkholderia, Bacillus and Serratia have been reported to enhance the plant growth.
Working with James Duke’s Phytochemical and Ethnobotanical Databases, it’s possible to come up with the plants that contain the most quantities of the macro and micro nutrients that a remineralization programme would use. For our zone, the list is fairly short – lambsquarters (Chenopodium album), stinging nettle (Urtica dioica), pigweed (Amaranthus), dandelion (Taraxacum officinale), and horsetail (Equisetum arvense). Comfrey does not score particularly high but it does have an entrenched place in garden lore thanks to Lawrence D. Hills in the 1950s and 60s. The roots do reach very deep so it’s a bit surprising that the leaves don’t contain more minerals than they do. It’s easy enough to grow so why not include it. These plants can be added to the compost pile or they can be made into teas that are used for soil drenches or foliar sprays. Is this better than soil testing and soil amendments? Those with a science orientation would say no but they have no basis of comparison. It’s certainly cheaper and regenerative.
So that leaves us trying to do what Nature does – mining minerals with deep rooted plants and making those minerals available to plant roots through a mycorrhizal network as well as building soil organic matter. We just do it a bit differently – we harvest the deep rooted plants and turn them into compost or teas and we build soil organic matter by mulching and crop rotation.