Beyond NPK: Farming by plant nutrition
June 25, 2012
Natural and sustainable farming is often described by what it is not; it is the opposite of the single cropped systems of industrial agriculture. However, industrial agriculture has some good ideas—high input and high yields. Of course, the inputs of industrial agriculture are fossil fuel based, are often applied in excess, causing environmental destruction through runoff. These inputs fit into the reductionist science of NPK: focusing on the major nutrients required by plants and ignoring the trace minerals necessary for proper plant development, to withstand pests and disease, and to produce nutritious vegetables. However, this heavy fertilization scheme does support the common sense idea that you have to put a lot in to get a lot out. Certainly, organic farming should be high yielding, too!
There is a romantic idea of the organic farm, a closed loop system, in which outside fertility is unnecessary. What a dream!–a dream not impossible to achieve, though difficult, time-consuming, and mostly impractical. Plants need rock phosphate, sea minerals, biological communities on their leaves and roots, limestone, and more. Good luck finding farmland with all of that! Of course there are a lot of inputs that can be made more easily on the farm: compost and compost tea, mulch… However, like I’ve mentioned before, most organic/sustainable vegetable operations would rather buy in fertilizer (in addition to making compost), so it can be checked off the list. Many organic farms even operate under the NPK principle. Their fertilizers come from organic sources rather than from a lab, but probably still do not make up a complete diet for plants.
There is a group of sustainable farmers focused on nutrient dense cropping—including micronutrients into the fertility plan to promote optimal plant health. These fertility plans include the more common good farming practices of cover cropping, building soil organic matter, and promoting soil biology. In addition to a soil-based focus, the nutrient density theory hones in on the plants themselves. The basic concept is to give the plant everything it needs for peak photosynthesis and health. A plant that is able to produce complete complex carbohydrates, proteins, and fats, is relatively unsusceptible to pests and disease compared to its nutrient-deprived counterparts. The primitive stomachs of bugs are unable to digest the robust compounds of healthy plants.
It turns out that healthy plants need even more than macro- and micronutrients; they need minerals made available to them by microorganisms that inhabit the soil. In order to provide plants with these minerals, the soil biology must be fed. Only healthy plants with high photosynthetic capacity can supply the microorganisms with food. The nutrient density philosophy calls for jump starting this system by increasing photosynthesis. The leaf is a great place to start! Foliar feeding is a process of spraying or misting leaves with a nutrient solution diluted to homeopathic concentrations in water and compost tea. Plants absorb nutrients through their leaves much more efficiently than through their roots. Foliar feeding thus jump-starts photosynthesis, increasing sugar concentrations within the plant and also increasing root exudation, in which plants leak sugars into the soil. Soil microbes then eat this up and provide the plants with health-giving minerals in return.
Nutrient density farmers are out their spraying leaves or offering nutrients through their irrigation systems weekly, or if pests rear their heads, daily. This may seem time-consuming and it is. I attended a workshop about foliar feeding given by the spiritual, yet practical Derek Christianson. His take on time is to both delineate X amount of hours/week to the task, working it into the weekly schedule and to re-conceptualize the time. Instead of fighting the fire (pests) by spraying pesticides, build the fire within the plant by foliar feeding. Offer the plant nutrients through a positive approach rather than the negative approach of pest control.
I’d been interested in nutrient density since I was introduced to biodynamics and its unconventional approach to soil amending and spiritual farming. The theory made sense to me from a scientific point of view, and stirred my interest in biology and chemistry. As I watched Christianson stir up a foliar spray during the workshop, creating a vortex with his arm as he energized the water molecules with nutrients and human energy, I felt the excitement of a science joined by spirit, an unabashedly subjective, holistic, and practical science, much like Steiner envisioned.
Julie Rawson, executive director of NOFA/MA and my new mentor through the organization’s program, has been sharing her success with foliar feeding and nutrient density in our bi-weekly calls. She explained that the finicky and mysterious science of farming is impossible to master, but foliar feeding and a plant health focus offer promising results. When the Colorado potato beetles came by, she foliar fed her patch daily, and now has a thriving, virtually larvae free crop. Her fruit trees on the other hand, have yet to respond to her foliar plan, encouraging her to keep tweaking.
I’m also interested in the science beyond specific crops: How does the nutritional content of vegetables from foliar fed plants differ from those produced by strictly NPK fed crops? How do yields compare? If it’s high input, it should be high output too!