“Where can I get some good topsoil?” That’s a question I hear frequently at our nursery. And I often look wistfully towards the plains and say, only half-jokingly, “You can get good topsoil about 800 miles east of here.” That’s where I grew up, in Iowa, and where two tomato plants feed a family of six. It’s not that local suppliers are trying to deceive us when they sell Colorado clay as topsoil; it’s just that the glaciers didn’t dump three feet of loam on top of our clay.
In this article, Mikl explains why Soil Health matters.
From Peak Soil to Soil Revolution
We are having a real revolution in our relationship with our soils. The turning point is our change in focus from soil fertility to soil health. In the last 60 years of the “Green Revolution” (i.e. the petrochemical boom), soil was viewed as a physical structure and fertility was viewed as a measure of chemicals in the soil — primarily NPK, nitrogen, phosphorus and potassium. The petroleum industry could make these macronutrients from natural gas, which make plants grow but often in poor health. Weak plants attract insect pests and fungal diseases, so more petroleum in the forms of insecticides and fungicides added to the success of the oil industry. But this approach has led to “Peak Soil” where land is losing productivity, crops are losing nutritional value, the soil is eroding at extreme rates, and the health of animals and people has declined.
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?
Flood recovery is not a problem most of us have had to deal with before so we can only try to solve the problems individually and make adjustments in the future.
The main problems seem to be:
1) Soil washed away-erosion
2) Soil dumped on top of plants, trees and existing soil
3) Plants washed away
4) Weed seeds deposited on the soil 5) manure and sewage and unknown contaminants deposited on the land
MULCHING THE GARDEN
Benefits of Mulching:
1) prevents evaporation; holds moisture
2) reduces weeding; makes weeding easier
3) reduces fungal diseases; prevents splashing of spores onto bottom leaves
4) feeds the soil; as mulch decomposes, worms take nutrients into the soil
Applying a mulch around our plants can be one of the most effective ways to improve their health and success, especially during hot and dry conditions like we had in 2012. Mulches have many benefits, but it is important to know how to use them to avoid problems.
Mulch conserves water by reducing evaporation 10%-50%. Usually a 2”-4” deep layer is best, and the material needs to be open enough to admit rain and irrigation and dense enough to resist evaporation. It is a good idea to apply mulch after the soil has been deeply watered or soaked with a good rain. Then the mulch will hold the moisture. Beware of materials like unshredded leaves which can act like shingles, and dry compost or sawdust which are hydrophobic, meaning they are difficult to wet. These problems are worse on a slope where water can run off instead of penetrating.
Normally when we think of fungi relating to plants, what comes to mind is infection and disease: powdery mildew, blackspot, slime flux and canker; Oh, NO!! However there is a growing awareness of the far more extensive benefits that fungi contribute to our world. Decomposing fungi are primary agents in the composting process which to us recyclers is the magic of turning garbage into gold. Not only do our plants love the rich humus and organic matter, but pesticides and herbicides are also broken down. Much of the body of soil itself is made up of fungi, especially loamy, well-aerated soil. And then there are the symbiotic fungi, the ones forming mutually beneficial relationships with plants. These associations of absorbing roots with fungal mycelium are known as mycorrhizae, from “mycor”- fungus and “rhiza”-root. Even though these beneficial relationships were discovered in 1885, it is not widely known today that 95 % of all plants on earth intermingle their roots with mycorrhizal fungi.
Nitrogen is an essential nutrient for all living things. Where does that nitrogen come from? It comes from the atmosphere, which is composed of 78% nitrogen; but that gas is quite inert, meaning it can’t combine with other elements until it is broken into a simpler form. This process takes a lot of energy to “fix” the nitrogen. There are three processes that can fix nitrogen: atmospheric, Haber Process and biological.
Atmospheric fixation occurs when the high temperature of lightning splits the nitrogen gas so it bonds with oxygen and moisture in the air to form nitrates that fall to the earth with rain. This natural fertilization benefits plants. Some people have asked, Is it my imagination that my grass looks greener after a thunderstorm? Maybe not; it could be due to the nitrogen as much as to the water.
Do any of you have dirt under your fingernails? Good. You and all gardeners have direct experience with soil. Those of you who don’t get your hands in the dirt probably will, because soil and soil building is the next frontier. Why do I say that?
Because until recently our understanding of soil and our approach to soil fertility was steeped in ignorance and misunderstanding. We’ve been in the Dark Ages.
Does anybody know the meaning of a new paradigm? It does not mean coming up with a new idea; it means coming up with a new perspective, a new ground from which to begin our thinking. We are entering a new paradigm in relation to the earth.
A very old Chinese saying goes “Man comes and deserts follow.” So it has been known since early times that human activities, including agriculture, deplete the soil and reduce the capacity of the soil to sustain life. Restoring fertility has, therefore, always been an important goal for human civilization.
The first known renewal technique was slash and burn: when the soil’s productivity went down, early farmers moved on, burned the bushes and trees and planted in the ash and charcoal. This technique improved short-term productivity. But when land became less plentiful, farmers learned to put animal manures on spent soils to gain fertility. Later they learned to let the land stand fallow for a time, and they learned to rotate crops. After growing a heavy-feeder crop like corn, they grew a nitrogen-fixing crop like beans or they would grow corn, then alfalfa, then beans and again corn. Manuring and crop rotation were the main fertility practices, I believe, until the late 1940’s.