Organic matter accumulation is one of the most effective methods of improving soil quality. Due to its high porosity and specific surface area, its ability to store both water and nutrients is much higher than that of mineral soils (organic matter can hold up to 6x its weight in water). By having a slow mineralization rate (only about 5% mineralizes each year), organic matter can serve as a steady source of nutrients throughout the year, especially during the warmer spring and summer months. When undisturbed, it naturally aggregates, forming a combination of inter and intra aggregate spaces that improve both water infiltration and drainage. Organic matter may take years to accumulate, and is commonly lost as a result of tilling. Tilling after harvests leaves organic matter exposed to the elements, resulting in increased rates of decomposition, and wind or water erosion. Fields with healthy levels of organic matter usually have higher yields and require less fertilizer and irrigation inputs. Implementing a long-term, no-till regime while simultaneously building your organic matter can save you money and labor in the long-run.
Building Organic Matter with No-Till
The key to accumulating organic matter is producing more than what is lost from decomposition and erosion. Fortunately, no-till farming practices reduce erosion by protecting the soil from exposure to the elements (wind and water), and the cooler temperatures that result from residue cover slow down the rate of decomposition. Unfortunately, no-till farming can pose as challenge to building organic matter, as it requires different methods than what could be implemented in a no-till regime. That does not mean that it cannot be done, however. With the appropriate knowledge and a new skill set, no-till farming can and will produce beneficial organic matter.
Rotating the cash and cover crops that you grow on your land is crucial for providing your soil with a diverse variety of organic matter.
- Legumes- legumes are nitrogen fixing plants that provide natural sources of nitrogen to your soil.
- Surface Residue- Plants like grain corns that produce lots of leaf litter are a good source of surface organic matter.
- Sub-Surface Residue (Roots)- Roots are just as important for adding organic matter as leaf litter and other above ground sources. Sod crops are a good choice for growing roots, and the taller they are allowed to grow, the deeper the roots will go.
Cover crops and Green Manure
Cover crops provide erosion protection to the soil surface between growing seasons, and can act as a green manure once it is time to plant cash crops. A roller/crimper tool can be used to kill the cover crops and leave it on the field, where it will continue to protect the soil surface, and release nutrients as it degrades into organic matter. Colder soil temperatures are another result of green manure, which can prevent organic matter from decomposing too quickly during Spring and Summer.
Fertilize your soils
While having a substantial presence of organic matter means you can eventually reduce fertilizer inputs, it is important that you are not depriving your soil of necessary nutrients in the process. Having an appropriately fertilized farm results in more plant residue that can turn into organic matter. Studies have shown that phosphorus and potash can be effectively applied on the surface when green manures are present. Nitrogen, however works best when injected directly into the soil, which can be done with equipment that slices through green manure and surface residue.
Monitor Soil Conditions
Frequent soil testing is important in order to adjust your practices based on the specific needs of your land. Fungal and bacterial communities are beneficial to plants, but when their populations are out of balance, they can negatively affect organic matter production. C:N ratios are also important, as too high a ratio can result in an excess of microbial activity and nitrogen deficiency. Consult a professional to determine what no-till practices will best assist you in accumulating organic matter.