review by Liz Henderson
This little book, only 75 pages long, is a great introduction to caring for the health of your soil whether you are gardening or farming, small or large-scale. For non-beginners, rereading this book at the start of each new farming/gardening season would also be a helpful refresher. In Stika’s words, this book “is a soil-centric view on restoring the soil first and then realizing all of the crop production and environmental benefits that will follow.” (xvi) Before taking up a plow or fork, Stika wants us to understand how soils function so that when we maximize productivity, we do not undermine future yields and ecosystem health.
The manual starts by defining soil health as– “the capacity of a soil to function,” and lists the five main functions: “maintaining biodiversity and productivity, partitioning water and solute flow, filtering and buffering, nutrient cycling, and structural support.” (p. 1) To enable soils to fulfill these functions, farmers act as solar engineers, working with the photosynthesis naturally performed by plants to “harvest water and sunlight to manufacture carbohydrates, fat and protein.” (p. 2) Plants exchange the carbohydrates for the nutrients they need, of which 90% cycle through the living organisms in soil before they are available to the plants. As Michael Pollan wittily noted in The Botany of Desire, plants have much more agency than we give them credit for, exercising control by sending chemical signals and adjusting exudates to communicate their needs to the denizens of the soil.
Stika identifies three kinds of disturbance that cause soil dysfunction: physical, chemical and biological, making it very clear that tillage ranks among the guiltiest. Minimizing the physical disturbance of soil through tillage and cultivation is essential to unburdening soil life from human interventions. Tillage disrupts the fungi, especially the mychorrizae, that feed plants and exude the gooey substances that hold soil aggregates together. Most chemical fertilizers and pesticides also disrupt or kill off important elements of soil life. Excessive use of natural fertilizers, too much manure or compost, can also be disruptive.
A common farming error is to use starter fertilizer. The addition of fertilizer as a plant is just beginning to grow shortcircuits the development of the relationships with microorganisms. It takes much more energy for a plant to get them to start up when it needs their nutrients later in the season.
Healthy soil is a miraculously efficient and complex system that human beings have only begun to understand. Plants feed the microherd of visible and microscopic organisms which in turn feed the plants, and very little is lost. Carbon is the most important element – Stika calls it the “currency of the soil.” A diverse food web ensures that despite varying weather conditions, the soil is able to maintain its many functions. Soil erosion, Stika points out, “is not a problem. It is a symptom of unhealthy, dysfunctional soil.”
Although soil organic matter makes up a small percentage of the soil by weight, it includes the many living organisms as well as the decaying and dead organisms that together perform most of soil’s functions. The living fraction takes nitrogen from the air and makes nutrients and water available to plants. Stika sites research that shows that plant roots on their own can only reach 1% of the surrounding soil, but when fungi are associated with the roots, they reach 20% of the soil, enabling them to capture far more moisture and food. In Chapter Four, Stika covers the living organisms from the smallest bacteria through the largest arthropods, and concludes that when a soil serves as a beneficial habitat for all the members of the soil food web, they build aggregates that restore the soil’s capacity to infiltrate water and cycle nutrients.
Fortunately, it is possible to restore degraded soil and there is no limit to what we can achieve if we observe these simple guidelines:
reduce soil disturbance
increase plant diversity
keep living plants growing as much of the time as possible
do not leave the soil naked
Stika does not dictate how to accomplish this on every farm. He urges each farmer to develop the approach that works best for individual conditions and provides some helpful pointers. A key to the decomposition of crop residues lies in understanding the CN ratio: soil microorganisms need a diet with a CN ratio of 24:1. When the ratio is higher or lower either all the nitrogen present will go into breaking down the residues or the microorganisms will quickly consume the residue leaving the soil bare. Once soil has been degraded it takes 3 to 5 years to bring it back, so Stika counsels patience.
Stika concludes his manual with suggestions for assessing the health of your soil. Cornell offers a series of tests for soil biology that cost $110. There is also the Haney test. NRCS has a soil health website with assessment information. I like Stika’s do-it-yourself ideas – take a handful, examine it for worms and other critters, smell it – a healthy soil smells earthy, place some aggregates in water and see how long it takes them to dissolve, dig a small hole, pour water in and time how long it takes to sink in. Read Stika’s little book, be inspired and get started!