There are two major categories of practices that are widely recommended to increase soil organic matter and increase soil health.
The physical disturbances of soil impacts soil health because it speeds up organic matter decomposition and releases breakdown products like carbon dioxide back into the atmosphere. Soil organic matter (SOM) declines over time as a result of soil disturbances.
There are numerous variations on how the agronomic practices of tillage reduction can be achieved dependent upon soil type, weather conditions, time of year, types of cash crops or types of livestock present, available mineral content (e.g., nitrogen) of soil, etc. Collectively these practices that cease/reduce plowing and/or utilize cover crops may be referred to as conservation practices. When these practices accompany tracking soil organic matter changes, they are more commonly referred to as regenerative or healthy soil practices. They are similar practices that prioritize building organic matter in the soil.
Cover crops may be used to diversify a farm’s crops by providing more options and opportunities to increase farm income and lower expenditures. Cover crop plant biomass may be left on the soil surface or mowed or rolled down and allowed to decompose and become a major mechanism for improving soil health by increasing soil organic matter. Farmers will need to choose cover crop species (or a mix of them) that grow best for their region and needed soil nutrient requirements, as well as reflect growth capabilities for the longest portion of the calendar year appropriate to main cash crop species and other practices. For example, cover crops may be planted following harvest of a cash crop. Cover crops that stay green and/or grow over winter and into spring may also provide an early, less expensive feed source for livestock.
There are four classes of cover crops:
Each class has its own distinct benefits depending upon numerous variables as mentioned above. Here is an extensive compilation of cover crop plant species to consider when deciding which seeds to purchase, when to plant, and the most likely soil impact from various species (what time of year to plant, annual, perennial, water requirements, saline tolerance, etc.).
Planting cover crops is increasingly popular. It requires about two tons of feedlot manure to replace the organic material in one ton of crop residue contributed by cover crops. In addition, manure won’t offer the same benefits as crop residue related to reduced evaporation and snow water capture. Manure, along with its environmental issues, has to be stored and eventually moved to a final site (using energy) while cover crops decompose and produce green manure in place.
You are not required to be an organic farmer if you are trying to increase soil organic matter. However, the use of weed killers like dicamba or glyphosate should be avoided in killing cover crops. This is because the biological plant decomposition mechanisms of microbes are reduced through pesticide use. The use of pesticides will slow the carbon sequestration processes and limit it in scope. Avoidance of pesticides saves money, reduces compaction in the field saving fuel and time, and avoids the slowdown of accumulated soil organic matter. By avoiding pesticides, substantial money can be saved that can actually pay for cover crop seeds.
As an alternative to pesticide use, covercrops may be knocked down by mowing, flailing, undercutting, or rolling down to compress or crimp them, stop growth, and to provide a non-living blanket or cover over the soil. Undercutting is when you draw a blade under the soil, and you slice the cover crop underneath the soil. For mowing use a sickle mower, a flail, a weed whacker, or a scythe depending upon the scale of the operation. The cut cover crops decompose and a portion of these plant residues are eventually incorporated into the soil. Rain and irrigation events facilitate the entry of soluble portions of decomposed cover crops into the soil over the first year and encourage beneficial soil insects to help break down the crop residue.
As mentioned above, maintaining soil physical structure and use of cover crops provide a consistent source of food, shelter and nutrients that support active microbial functions, and plant residue decomposition increases soil health and soil organic matter. Avoidance of major soil disturbances maintains soil health over longer periods. It should be acknowledged and understood that practices that encourage soil health require some specialized equipment, knowledge, and experience of use, along with potential added costs. The good news is that specialized equipment needs may be found in some Oregon Soil and Water Conservation Districts, and plans are developing to increase and diversify special equipment availability in other conservation district locations.
All practices that improve soil health are scalable from the smallest of farms to the largest. The equipment needed such as no-till drills, roller crimpers, sickles, etc., are also scalable based on farm size.
Here’s a YouTube presentation featuring how a large scale no-till drill works. Regardless of size, the principles are the same, just the available options and machine settings will differ with various models and sizes.
A no-till drill is a very heavy drill with a specialized disk set-up that cuts through surface (cover crop) plant residues, places the seed at the correct depth in soil and then presses the soil back over the seed for good soil to seed contact all in a single pass over the field. Advantages to planting no-till with decomposing surface plant residues in place, include erosion control, fuel and time savings, and a mechanism to increase soil organic matter and increase soil health. Seed planting and cover crop termination can be achieved through a single pass over the field if/when agronomic practices allow. Through this practice, soil compaction is reduced, fuel use is lower, and soil physical structure is maintained. See “Thinking beyond the plow.”
Many internet sites offer both used and new no till drills that range roughly from $5,000 and up.
Small sized compact tractors with 35 or more HP can accommodate small sized no-till drills of 5-6 ft width.
Walk behind tractors can be purchased for less than $3,000 (without implements) for smaller scale farms. Custom no-till drills and roller crimpers can be fabricated to suit these small tractors.
Soil cores for taking soil health check samples can be purchased for less than $100.
Soil testing labs are available throughout the country for receiving and testing soils for
organic carbon content. We suggest soil carbon analyses be conducted by the combustion method or loss on ignition. For establishing and maintaining the highest levels of consistency of results, it is imperative that the same person be involved in sample collection and shipping for these laboratory analyses.
Check with your local Soil and Water Conservation District (at least one in every county of the state) through this directory .
Author: Ray Seidler, PhD