In a recent webinar, the Soil Health Institute’s President and CEO, Dr. Wayne Honeycutt, provided an introduction on how farmers can manage their soils to increase soil organic carbon. He laid out the facts with four essential questions:
- What is soil organic carbon?
- How does it benefit farming?
- How can you increase soil organic carbon?
- How long does it take?
Read on to learn more about retaining organic carbon in your soil and the benefits it brings to your farm.
What is soil organic carbon?
Let’s start with soil organic matter, which consists of elements like carbon, nitrogen and phosphorus. It starts as materials from plants and animals that are then further transformed during the decomposition process by microorganisms. Soil organic matter and soil organic carbon are often used interchangeably as organic matter is about half carbon. However, different methods are used to measure them. Put simply, soil organic carbon is the carbon in soil organic matter.
How does it benefit farming?
Here are the seven most important benefits of soil organic carbon:
- Increased water holding capacity in soils. This builds drought resilience.
- Lower soil density. As you increase carbon, density decreases because organic compounds are less dense than the soil minerals. When soil is less dense, the roots can travel through the soil and scavenge for nutrients and water more easily. This makes for a healthier plant overall.
- Increased water infiltration. Organic carbon helps to form soil aggregates, where organic molecules produced by microorganisms bind mineral particles together. The no-till process helps to preserve these aggregates, increasing carbon in surface soils, which allows more aggregates to form, further stabilizing the soil structure. Tilled fields typically have less carbon and poorer water infiltration – this is evident of ponded water on fields after heavy rainfall.
- Increased nutrient availability. When microbes feed on soil organic carbon (in order to get energy), they release nitrogen and phosphorus that were tied to that carbon, thereby providing more nutrients for the plant.
- Improved trafficability, meaning that the soil structure is improved and allows farming equipment to traverse the field more days in a given year.
- Increased yield stability. Although there is not a lot of experimental data on this, many farmers have found this benefit to be true. When compared to their neighbors, who do not use soil health practices that increase carbon, farmers that do find they have more stable yields from year-to-year. This is often most evident during drought years, likely because of the greater water-holding capacity, reduced density and other benefits that increasing soil organic carbon has for farmers.
- Finally, soil organic carbon increases profitability. Soil Health Institute (SHI) scientists recently interviewed 125 farmers about their profitability since they started using soil health systems. While the Institute will be releasing those results in the coming months, Dr. Honeycutt said that almost all of the farmers interviewed reported higher profitability after adopting soil health systems that increase soil organic carbon.
How can you increase soil organic carbon?
As SHI’s soil scientists have proven, the benefits of soil organic carbon are numerous. However, the question remains for how farmers can increase the amount of carbon in their soil.
One of the first things to think about is the carbon cycle at a fundamental level. It’s important to note that carbon is always coming in and out of the soil. The amount of soil organic carbon is the net balance of how much organic carbon is put into the soil mostly from plants, such as dead leaves, roots, and compounds released by living roots, and how much organic carbon is removed by harvest or returned to the atmosphere as carbon dioxide by microbial processes.
Therefore, the goal is to add more carbon in the soil than you lose to the air or remove through harvest.
So, how do you achieve that? According to Dr. Honeycutt, this is done through the management choices that alter the carbon balance.
It is much easier to lose soil organic carbon than it is to gain it. Research shows that continuous no-till builds soil organic carbon in surface soils over time. In the United States, many of our cropland soils have lost 40-50% of their precious soil organic carbon. Much of this has been through tillage. No-tillage results in more organic carbon accumulation in the surface soil and therefore results in the on-farm benefits described above.
The use of cover crops is also a great opportunity for incorporating more carbon to your soil. Cover crops also protect the soil from erosion and help recycle nutrients from deeper in the soil back to the surface. Their residue provides a mulch to keep the soil cool and moist, and as that residue decomposes, some ends up as soil organic carbon.
Other important management decisions also affect carbon in your soil. For example, choice of crop rotation and residue management can dramatically affect the amount carbon that is added to your soil.
Additionally, farmers who integrate livestock in their operation have a wonderful opportunity to increase carbon in their soils through the direct application of animal manure while livestock graze cover crops or crop residue for forage.
How long does it take?
The golden question: When can you expect to see results? As Dr. Honeycutt says, you’re not going to like his answer.
The answer: It all depends.
It can usually take about three to five years after changing management before you can have a measurable change in your soil due to background variability, including weather and soil type. Of course, this doesn’t mean that you aren’t having change before that. In general, it takes a bit longer to show a measurable increase in soil organic carbon in hot or dry climates and in very sandy soils. Landscape positions can also influence those results. For example, a lower landscape position may retain more water, allowing plants to grow better and therefore return more carbon to the soil. Those same moist conditions can also slow decomposition processes, resulting in greater carbon build-up in those landscape position soils.
Dr. Honeycutt’s best advice is to focus on the management choices that you make and keep a positive outlook.
“If you think you can, you can. If you think you can’t, you're right.”
Properly managing the soil organic carbon content is fundamental to regenerative agriculture. It can provide many benefits to farmers who are committed to implementing soil health systems. You want to think of yourself as a carbon manager and ask how you can increase the amount of carbon in soil to improve soil health and provide benefits for you and your farm.
Please use the following resources for more information and to answer questions you may have: