It is widely known that nitrogen is essential for plants. It is a major component of amino acids, DNA and chlorophyll. It is necessary for photosynthesis, the alchemical process of turning sunlight, carbon dioxide, minerals and water into oxygen and sugars that is the food that feeds life on earth. In Colorado, most of our soils are deficient in nitrogen.
But too much nitrogen can be a problem, especially high nitrogen chemical fertilizers. Bill McKibben, author of The Art of Balancing Soil Nutrients states, “Although all plant nutrients are critical, none seem to produce such quick and dramatic effect on plant growth as nitrogen does. It is because of this reason that nitrogen has been over-used and abused.” A 20%-30% nitrogen fertilizer can make a spring lawn turn bright green practically overnight, and can make plants in a greenhouse or garden grow and look mature really fast. So what’s the problem?
Here are some problems of plants over-fertilized with nitrogen:
1) Shoot growth is stimulated at the expense of root growth
2) Fast growth produces soft, thin tissues that dehydrate quickly, requiring more frequent watering, and reducing the tolerance to summer heat stress.
3) Soft tissues from fast growth are more attractive and vulnerable to sucking insects like aphids and spider mites, and also to fungal diseases.
4) When more energy is directed to vegetative growth, less energy goes to flowers and fruits, so fewer flowers and fruits are formed or they drop off.
5) Salts in strong nitrogen fertilizers can burn plant roots and harm soil life.
6) Microbes are overstimulated and multiply so much they consume the carbon in the soil, releasing carbon dioxide and leaving the soil depleted of nutrients. Then microbe populations collapse.
7) Plants cannot use excessive nitrogen, so it leaches into the groundwater, causing the 8,000 square mile dead zone in the Gulf of Mexico.
8) Higher quantities of greenhouse gases are produced (carbon dioxide and nitrous oxide), especially if the nitrogen is from a chemical fertilizer.
It has taken 60 years of industrial farming and gardening with chemicals for us to realize that if a little nitrogen is good, more is not better. Fast forward to December 14, 2017 when in Longmont, Colorado, there was a “Soil Revolution Conference” presented by Boulder County. Participants were invited to “dig deeper into the science, benefits and practical applications of farming for soil health.”
The keynote speaker was potato farmer Brendon Rockey from Center, Colorado. He said eliminating pesticides, fungicides and herbicides and growing cover crops has improved the soil life populations and the soil structure, resulting in fewer pests, better nutrition and water retention, and better production on his farm.
The key points to soil health as presented by the USDA Natural Resources Conservation Service are: 1) Minimize soil disturbance, which means plowing, tilling, over-grazing, and over application of fertilizers and pesticides. 2) Keep the soil covered with mulch, stubble or cover crops 3) Plant diversity: plant communities of plants that support a diversity of bacteria and fungi in the soil which are more capable of converting raw materials into nutrients available to the plants. 4) Maintain Continual live plants: using cover crops to keep feeding the mycorrhizal fungi and other soil life during the off-season, and to provide nitrogen and organic matter when they are mowed or turned into the soil, and 5) Integrate livestock into the soil system: grazing stimulates grasses and manure adds carbon and nitrogen.
Carbon and Carbon Farming were mentioned again and again. “Carbon is the key driver of the nutrient-microbial system.” Nitrogen feeds the plant, but organic matter feeds the soil life, and healthy soil is the key to healthy plants. Everything we say about soil is an over-simplification, because so much is going on. But this Soil Revolution is turning attention from the use of fossil-fuel inputs to the soil-based intelligence of Nature that recycles nutrients from wastes.
Nitrogen, instead of being produced from natural gas can be brought into the soil through the use of cover crops like Hairy Vetch and Chickling Vetch, Winter Peas, beans and other legumes through the activity of nitrogen-fixing bacteria. And nitrogen can be obtained from recycling animal manures and fish and meat wastes. In addition, when our soils are full of life and diversity, the millions of microorganisms can extract nitrogen from dead plant and animal matter.
This Soil Revolution, this shift from dependence on fossil fuels for crop production to reliance on Nature’s own Soil Life system of nutrient cycling is really not a new idea. But the last 10 years of microbiology research has illuminated the incredible wealth that exists in the soil if we learn how to partner with the Soil Food Web.
Resources: USDA Natural Resources Conservation Service: NRCS Soil Health, plus their recommended reading list
Sustainable Agriculture Research and Education: Building Soils
Sequester Carbon at Home: Elizabeth@nullElizabethBlackArt.com
Organic Gardener’s Companion-Jane Shellenberger
Teaming With Microbes-Jeff Lowenfels
Many ACRES USA publications
Christine Jones: AmazingCarbon.com