By Kurt Simon
Many of the benefits from improving soil health don’t happen overnight. They build over time, as farmers consistently implement soil health practices like no-till, cover crops and crop rotations. But there is a way to monitor your progress: measuring the amount of organic matter in your soil.
First conceived by the late Brad Harrison, with the Natural Resources Conservation Service in Adel in central Iowa, the 1% Challenge encourages farmers to commit to a long-term plan to increase their soil’s organic matter by 1%. Soil organic matter is decomposed plant and animal material in the soil. This material gives soil good tilth, a dark color, better water-holding capacity and improved water infiltration rates. It also contributes to overall soil fertility. And it happens to be a very good indicator of improved soil health.
Increase organic matter 1% in 10 years
How much will it take to increase your soil organic matter by 1%? Soil organic matter is increased through substantial increases in organic materials, like roots, residue, compost and manure in the soil. Only 10% of the organic material added each year actually remains in the soil. Because of this, building a 1% organic matter increase will require 200,000 pounds of material, or the equivalent of 167 round bales of cornstalks per acre.
Depending on your original organic matter levels, soil types and crop rotations, it is possible to increase organic matter at an average rate of 0.1% per acre per year through no-till farming and planting a mixed cover crop each fall. After 10 years, that’s a 1% increase.
Why is it worth it?
While each farming operation’s expenses are unique, these estimates illustrate the economic impact of improving soil organic matter:
• Each year, 1% of soil organic matter per acre releases $15.70 worth of nutrients.
• Eliminating tillage will save about $3.50 in fuel costs per acre per year.
• Using cover crops may reduce the need for herbicides by about $16.20 per acre per year.
• An average increase of 5 bushels per acre in soybean yields following cover crops can earn an additional $50 per acre per year.
Based on these calculations, in an average year of a corn-soybean rotation, your bottom line could improve by more than $60 per acre. Plus, this significant increase in organic matter can hold 9 or 10 inches of plant-available water, reducing the potential for erosion due to runoff by 15%.
Where to start
Establish a baseline by completing a routine soil test with an organic matter calculation. In addition, conduct a soil health assessment in your field by recording soil temperatures, counting earthworms, calculating water infiltration rates and testing for compaction. We also recommend having a certified lab conduct a soil health analysis, such as the Haney test or the Cornell Soil Health Test.
The next step is to develop a soil health management plan, and that’s where NRCS can help. After discussing your goals and evaluating your current operation plan, we can recommend the types of practices and changes in management that will help you improve soil health and build organic matter.
Finally, monitor and document your progress each year. Items to record include crops planted, fertilizer and pesticides applied, weed pressure, yield and soil health assessments results (temperature, earthworm counts, infiltration rates, etc.).
Then in year four or five, conduct another soil test battery. Did your soil organic matter increase by a half percent? If so, you are on the right track. If not, take time to evaluate your management (NRCS can help) and make adjustments if necessary.
Are you interested in taking The 1% Challenge? Visit your local NRCS office.
Simon is the NRCS state conservationist for Iowa, based in Des Moines.