On land that had traditionally been in a cereal-fallow rotation, we started using a longer rotation that included legumes, oilseeds, and a green manure. For a number of years, we held to a fairly rigid rotation of cereal-pulse-oilseed-plow down. And it worked fairly well. We saw erosion dramatically decrease, weeds were held to reasonable levels, and yields were decent in most years.
Then we started learning more about soil microbial life.
Now our focus is how we can use the five soil health principles as much as possible on our farm. Here are some of the techniques we are using to improve the health and functionality of our soils following these principles.
1. Minimize soil disturbance
We learned how devastating tillage is to the soil. Every time we were disking or cultivating we were not only drying out the soil, but we were breaking fungal hyphae, filling in root channels that were acting as infiltration pathways, breaking up aggregates, and reducing the trash on the surface. It made us sad when we learned the smell of freshly worked earth that we loved so much is actually organic matter oxidizing. We do still till, but we are really trying to reduce the frequency and the intensity of the tillage. One of the biggest ways we are doing this is by not plowing in our green manures. We’ve been using a roller crimper for a few years now, and we can crimp a cover crop into a mat on the soil surface in usually two passes.
2. Keep the soil covered
The mulch layer from the crimped cover crop does a great job at helping us achieve the 2nd principle, keeping the soil covered. This has also been referred to as “maintaining soil armour”. And that’s exactly what it is. The mulch protects the soil surface from evaporation from the sun and the wind. It prevents wind and water erosion. When a raindrop hits the mulch the energy is dispersed before it hits the soil. If the rain falls on bare soil it has the opportunity to displace that soil, and the soil will crust over. In June 2017 we used thermocouple dataloggers to record the temperature 1” below the soil surface in bare fallow, under crimped rye, and under living yellow clover. Over a 3 day recording period, the bare soil had a daytime high of 48.5°C and a nighttime low of 5.5°C. The rye had a high of 31°C and a low of 12.5°C. The clover had a high of 26.5°C and a low of 12°C. This shows by keeping the soil covered we can reduce the daily temperature swings and create a better growing environment for our crops.
One of the easiest ways to increase our diversity was to change the cover crops we were using. We started simple by adding oats to the forage peas used for a plow down. In 2018 we are planting 5 different cover crop blends, each with 3 to 10 different species. When planning a cover crop blend the first thing we think of is what is the issue we’re trying to address? We’ve heard it said that cover crops are like a Swiss Army knife. They can do anything, but they can only really do one thing at a time. Once we identify the issue, such as nitrogen building, weed suppression, grazing, or organic matter building, we pick a few plants that will be keystone players. We then pick some that will be complementary to those main ones. When adding additional species we try to add from different groups: warm and cool season, grasses and broadleafs. We then try to add different architectures of growth above and below ground. Tap roots and creeping roots, tubers and fibrous roots below ground. Above ground we try to capture as much sunlight as possible by picking upright plants and creeping plants. Sunflowers, buckwheat and flax might all be considered broadleaf plants, but their growth and leaf structures are radically different. Another aspect we’ve been trying to diversify lately is flower type and season. It is important to provide a habitat for pollinators, and if we have a diverse type of flowers (open like a sunflower or more closed like alfalfa) we will support a diverse number of species of pollinators and other beneficial insects. By having a full and diverse community of insects we promote a fully functioning food chain where one or two pest species can’t explode in numbers where a void exists.
4. Keep a living root in the soil as much as possible
The purpose of the 4th principle – Always have a living root in the soil – is to be feeding the soil microbes as much as possible throughout the year. When there is a green plant growing it is using the water and carbon dioxide to create sugar and oxygen. The sugar is used to build the plant, but research has shown that up to 60% can be exuded through the roots within 24 hours of being photosynthesized. These root exudates are traded to microbes for nutrients and is the start of the entire soil food web. When you are putting more carbon into the soil (in the form of exudates) than you are taking out to build the plants, you are increasing your soil organic matter. Organic matter acts as a great sponge for nutrients and water. Bare soil is a missed opportunity to be building more organic matter in your soils. Some of the ways we try to maximize photosynthesis periods is to use biannual crops such as yellow clover and fall rye. We seed clover in the spring with the cash crop, and is living under the canopy at harvest time, and continues growing right until freeze up. We will seed fall rye after a cash crop for the same effect.
5. Integrate livestock
The final soil health principle is to integrate livestock. 2018 marks our first year grazing cattle on our cover crop land. Where we would normally roller crimp we are going to graze cattle at high stocking rates. By concentrating the animals in a small area they eat the leaves of the cover crop and trample the rest to the ground. The goal is to eat approximately a third and trample two thirds. The cattle deposit the manure and urine on the soil right where it was grown.