Andy and I went to a workshop about soil recently, which was presented by a state soil scientist who said that even at a young age, his son knew not to use the word dirt, but to say soil instead. When I was a child I learned to identify different breeds of chickens, and I probably learned other unusual tidbits. Our children, too, will likely have a different set of experiences than most.
The most interesting part of the soil workshop was the soil scientist’s demonstration of how people dramatically alter the soil structure by plowing and tilling. Naturally, soil is structured in easily identifiable layers. Land that has been plowed, however, even 100 years ago, doesn’t show the same layers. He showed us how you can dig a soil pit and look for the layers to find out if a certain area of land has ever been used for growing crops. The history of human use lies just beneath the surface.
We’ve been thinking a lot about soil types ever since we started looking for land to start our own farm. For every property we’re interested in, we look up the soil types on the Web Soil Survey. This website tells us what soil types are found in any particular area, and whether these soils are prime farmland, farmland of statewide importance or not prime farmland. It’s amazing to think that soil maps are around because people literally walked transects of the entire state, testing soil every so often along the way. Soil types can vary quite a bit from one point to the next, even in a fairly small area.
So when we started thinking about our wedding garden, we looked up the soil map right away. Our garden is Peru fine sandy loam, which is classified as prime farmland.
We went a step further and sent a sample of our soil to the Maine Soil Testing Service, which is part of the University of Maine. It came back recently, with pretty good scores in several categories.
What we did was take a small sample of soil from around 15 different spots around our garden. Then we mixed the samples together and sent some off in a box to Orono. Several weeks later they sent us a report showing if our soil had low, medium or optimum amounts of different nutrients important for growing vegetables. We found out we have optimum organic matter and sulfur, medium potassium and phosphorus, and low calcium and magnesium. Our soil pH is 5.6, which is optimum for potatoes, but too acidic for other vegetables. The test report also showed results for micronutrients. More on that later.
It’s hard to know what to do with these results. Okay, so we don’t have enough calcium and magnesium. Will that really hinder our plants? How do we fix that?
I did some more reading. Lime, which is a common soil amendment to raise the pH (make the soil more basic), is also a primary source of calcium. Magnesium, too, can be provided by using dolomitic lime. That made things easier. All we had to do was spread lime to fix the soil pH and low levels of magnesium and calcium.
We also decided to spread wood ash from our wood stove. Wood ash provides potassium and raises the pH, so we decreased the amount of lime accordingly.
Like I mentioned before, our soil tests also listed micronutrient content for copper, iron, manganese and zinc. These elements are important for plants’ growth and productivity, but they are only needed in small amounts. I learned that the availability of the micronutrients is driven by pH and organic matter. When these two factors are at good levels, often micronutrients will follow.
On Saturday we spread our amendments and tilled them in, with some goat manure as well. It’s just empty soil, but it sure does look beautiful!