For me, one of the most gratifying parts of life on the farm is watching the land change over the years in positive ways. When we first arrived here at our home site along Harkins Slough sixteen years ago, the upper portion of the property was almost completely devoid of vegetation around the farm fields. In the first few years we planted hedgerows around most of the periphery of the farm, as well as riparian buffer strips and landscaping around the house and outbuildings. As the trees and shrubs that we planted over the years have matured, the number of birds that visit the farm has increased dramatically. There is something very special about seeing a black-shouldered kite perch on a tree that you planted. But some of the less obvious changes on the farm are arguably even more significant—such as the improvement in soil quality.
I’ve heard other farmers joke about how their soil changes every 100 feet, but here it is no joke. On the back slope of our property the soil transitions from heavy clay on top, to nearly pure sand at the bottom. The very best soil is in the fields surrounding our house—a dark, loose, clay loam that is studded with small shell fragments and which probably benefited from the manure produced during the many decades that this property served as a dairy in the mid-to-late 20th century.
Underlying most of the farm at between 12 and 24 inches deep is a clay pan—a layer of dense, sticky yellow clay that would be well suited for throwing pots. In the years before we arrived, when the property was leased out and farmed intensively, the repeated tillage passes had the effect of leveling the fields—knocking down the high spots and filling in the low ones. This exposed the clay pan in places and it is in these areas that we face our biggest problems. Magnesium is the binding element in clay and in excess it is effectively toxic to plants. Apparently excess magnesium is a major problem affecting soils worldwide, and it was through a conversation with Joji Muramoto, a researcher at UCSC, that I heard about the successful strategy that one Japanese farmer used to address this problem—adding large amounts of organic material high in carbon, rice hulls in his case.
Instead of using rice hulls, we focused on growing high carbon, cereal cover crops in these areas and in one particularly bad place I took the unusual step of incorporating finely ground wood chips. Incorporating wood chips is something that would be unthinkable for most growers. While the soilborne microbes are breaking down the wood, something that can take years to complete, they consume loads of nitrogen, effectively “tying it up” so the plants can’t use it. In this field however, I figured I had nothing to lose—crops were growing very poorly here to begin with so it really couldn’t make matters worse.
It’s been six years since the wood chip application and, with yearly cover crops, the difference in soil tilth is drama
tic. It was nearly impossible to work up a nice seedbed before—the soil was either too wet and formed clods when it was worked, or it was too dry and became rock hard, there was no in-between. Now, I am gratified to find that the soil in this field works up easily into a loose, fluffy seedbed. It has a great earthy smell, and a much larger population of earthworms than it used to. Crops are growing well. In fact, this is the strawberry field where we’ve been holding the u-picks this year.
I notice that the large organic growers in the area seem to be cover cropping only minimally these days. Perhaps the economics just don’t favor the extra time and expense of keeping a field out of production long enough to grow a proper cover crop, and certainly not to adopt a strategy that takes years to work. We are fortunate to be able to farm on a scale and model that allows us to invest in the long term health of our soil. The birds may be more obvious, but the complex environment of a living soil with a thriving microenvironment is truly at the base of our food chain.
(This article has been updated from the original printed in 2013.)
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