Organic farming has become increasingly reliant on external inputs for sources of fertility. All too often these inputs have their origins from a dysfunctional agricultural system, whose foundation lies on monocultures, genetically modified organisms, and questionable animal welfare standards.
Arguably, reliance on inputs derived from industrial agriculture may be overshadowed by the unquestioning adherence to farming practices that have their origins in a “N-P-K science” that has little concern on farm profitability and environmental sustainability. Many of the fertility management strategies employed by farmers have little to do with plant requirements, and more to do with large-scale farm management, which unfortunately some organic farmers and gardeners have often adopted as the norm.
The common idiom that the greatest change when transitioning to organic agriculture is between the ears has validity when it comes to plant fertility. Placing an organic lens on fertility should encompass a systems approach that is respectful of the soil, as well as the plant. The three ‘R’s–reduce, reuse, and recycle–can serve as a lens to help organic farmers “take-back” fertility. This framework allows the farm to optimize production for profitability, while not creating adverse impacts on the health of the farm ecosystem.
Most fertility recommendations are based on soil tests, which by definition are a reasonable facsimile of what nutrients might be immediately available to the plant at a point in time. Most soil tests give no value to soil organic matter (SOM), other than listing it as a percentage. Depending on soil type and climate, alternative interpretations of SOM will credit 10 to 20lbs of N per acre for each percent OM. In other words, a soil test reading 4.5% SOM will make available 45 to 90lbs of N during the active growing season–a value that can meet the N demands of many crops. So, farmers and gardeners that place greater emphasis on increasing soil organic matter and enhancing nutrient cycling through use of compost, compost teas, and plant teas may meet or exceed their crops nutrient demands.
Plant fertility adjustments are recommended as split applications, but often the worst-case scenario–where all nutrients are supplied at once–is the common approach. Unfortunately, plants cannot and will not use the vast majority of these nutrients, and depending on the soil and climatic conditions, many of these nutrients can become unavailable to the plant through leaching. Farmers who have soils high in soil organic matter or high in clay may be able to secure some of these nutrients, but there is a limit as to how much can be held. A general rule of thumb is that a moderate feeder will use 10lbs of N per acre per week, so any amount above and beyond may be subject to loss. It is here that the advantage slants to the smaller-scale enterprise, which may be better able to cater to the specific needs of the plant in a timely manner.
The concept of reusing in terms of fertility may be a little bit of a stretch, but the loss of livestock from the typical organic farm has removed an integral component in the cycling of nutrients. Long-term perennial forages, cover crops, and green manures work incredibly well in building soil structure and soil organic matter, but in some way that is only half of the story they could tell. The divorce of livestock from crop production within a farm system has led to a single-purpose, or compartmentalized view, of farm components.
Through incorporating livestock on the farm, plants take on another purpose–that of a food source. Many farmers who have re-introduced livestock into their operations comment on how they soon feel “whole”–that their farming system has plugged up some leaks. Livestock, in particular ruminants, can take organic material, and through their manure, provide plant available nutrients and billions and billions of beneficial microorganisms for soil health.
The early organic movement was synonymous with weeds, in large part because of its dependence on manures. The recent resurgence in alternative approaches in agriculture, such as permaculture and biodynamic, have brought a new perspective on weeds, giving them a facelift by focussing on their positive qualities. Many weeds are highlighted as scavengers or as miners, or better yet, as dynamic accumulators. This term specifically denotes a weed’s ability to take up nutrients from deep within the soil and subsequently releasing those same nutrients (upon the plant’s death) to soil closer to the surface.
Recycling of nutrients through the use of “weeds” can be done in a passive way or in a more proactive manner, in which the farmer is exploiting the competitive advantage of these so called “weeds”. Passively, organic farmers and gardeners can simply pull out weeds where they are growing and place them as mulch (as long as the weeds have not gone to seed). These plants will gradually release their nutrients as they decompose, all the while serving as a weed barrier, soil moisture and temperature regulator, and a food source for soil microbes. Most commonly, nitrate scavengers like lambsquarters and redroot pigweed, usually found in the vicinity of well-fertilized vegetables, can be harvested and placed right back where they were growing. This ensures the weed plants releases the very same nutrients that scavenged at a time when the intentional plants can actually use them.
In reading Ehrenfried Pfeiffer’s book, Weeds and What They Tell, you get a unique perspective of what role dandelions play in nature–that of a recycler of calcium. Dandelions with the large taproot will be ever-present in soils lacking calcium (or those with excess potassium) for the simple purpose of bringing calcium from the depths to the surface. Using this as a lens to view weeds, it becomes important to place harvested weeds where they appear to help remedy soil deficiencies.
Alternatively, in large part, as a result of David Jacke and Eric Toensmeier’s work, Edible Forest Gardens (Vol. II), and practitioners like Michael Phillips (The Holistic Orchard), the concept of brewing weed or plant teas has once again found promise. Some farmers purposefully plant dynamic accumulators in the margins of their fields and harvest them with the specific purpose of preparing nutrient teas.
Dandelion, burdock, curled dock, chickweed, chamomile, sorrel, yarrow are great scavengers of nutrients, packed full of calcium, phosphorus, magnesium, potassium, and trace elements. Lambsquarters, pigweed, clovers, quackgrass, lupins, alfalfa, purslane, and medics are excellent sources of nitrogen and work as stimulants for soil biological activity.
You may want to avoid rhubarb, black walnut, and wild carrot, as they contain pesticidal and plant inhibitory substances that may not be suitable in all spray situations. Also, try to harvest weeds before they have gone to seed, maximizing nutrient content, which is often highest just before flowering.
Below are some special teas brewed individually that are gaining more widespread adoption and appreciation:
Horsetail Tea: This ancient plant can be found in many undisturbed areas like drainage ditches and stream banks. Biodynamic farmers, at a metaphysical level, understand that the energy of horsetail has anti-fungal properties, preventing fungi like downy and powdery mildew from taking hold. At a biological level, many farmers recognize the high level of bioavailable silica in horsetail tea helps increase cellular strength and thus reduces disease incidence. The efficacy of horsetail has caught the attention of agribusiness and commercial extracts will be available soon. Just as an additional note, for those looking to make a more fungal-dominant compost tea, add some horsetail to the brewer and beneficial fungi counts will be notably higher.
Stinging Nettle Tea: If you have already eaten as much stinging nettle as you can for the season why not make some tea for your crops? Nettle tea can best be described as a stinky tonic. The overwhelming smell of rotten-eggs (hydrogen sulphide) should not discourage you (if you can’t handle the smell add some bonemeal). The tea is loaded with nitrogen, calcium, potassium, vitamins and trace minerals, like zinc, iron, and selenium. In addition to the nutrients, stinging nettle tea has high levels of silica which work to ward off fungal pests. Stinging nettle tea can be used weekly for most plants, but should be reduced when plants are fruit-filling.
Comfrey Tea: A sudden interest in certain aspects of permaculture has given new light to this amazing plant. Comfrey is referred to as a dynamic accumulator; in that it’s deep tangled roots are able to cycle nutrients from lower soil horizons, bringing them nearer to the soil surface. As such, many orchardists are planting comfrey around the base of their trees (it also attracts pollinators). Comfrey, noted for its high levels of calcium, is used to help regenerate bones and cartilage in our bodies and similarly it is used for supplementary calcium in plants. Calcium is not overly mobile in plants, especially if there are fluctuations in water availability; meaning that calcium in a leaf may not get to a developing fruit if there is a deficiency. Examples of calcium deficiencies include bitter pit in apples, cavity spot in carrots, black heart in celery, tip burn in lettuce, hollow heart in potatoes, and blossom end rot in tomatoes and peppers. A comfrey tea every other week will allow for adequate calcium absorption to help mitigate any deficiencies. Comfrey tea has had reported N-P-K analyses of 2-1-5, which is comparable to some fish or seaweed based liquid fertilizers.
Garlic Scape Tea: After you’ve finished selling, pickling, or sautéing your garlic scapes (the flowering stalk of hardneck garlic) why not make some tea with the remainder? Adding a few scapes to each batch of herbal tea will infuse the brew with ample organo-sulphur compounds, which act as transporters of other nutrients, as well as providing much needed sulphur to crops like brassicas (i.e., cabbages, Brussels sprouts, turnips, etc.) and alliums (i.e., onions, shallots, leeks, and garlic). A concentrated garlic scape spray may also serve as a deterrent from feeding insects, like striped cucumber beetle and tarnished plant bug.
For the past decade compost teas helped champion our need to look more closely at soil biology and soil health and a logical progression is to look at our sources of fertility. Using the philosophy that Nature knows what’s best, we can take her lead and attempt to mimic and tweak natural processes to meet our agricultural needs.