Organic matter key to soil health and no-till is best way to keep it in
In the decades since the advent of no-till farming practices, much has been learned about the life and health of the soil, and the enormous value of organic matter in the soil.
“An acre of soil that is 0.5% organic matter has about 500 pounds of nitrogen,” James Hoorman, an assistant professor of cover crops and water quality with Ohio State University Extension, told members of the South Center Kansas Residue Alliance at their 2012 Soil Improvement Workshop and Field Day in Kingman in March. “After 15 years of continuous no-till, the soil is about 4.5% organic matter and holds 4,500 pounds of nitrogen.”
Hoorman told the 220-plus farmers attending the workshop that there is no single measure of soil worth more significant than organic matter.
“Different tillage methods have a major impact on the rate of soil organic matter loss,” Hoorman said. “With chisel-plow tillage, there is loss; with a moldboard plow, there is twice as much; and with subsoil tillage, the loss is three times as great.”
• Adding cover crops increases the benefits of no-till.
• Cover crops mean more living roots and more microbial activity.
• More organic matter helps soil hold more water and nutrients.
More aggressive tillage adds oxygen to the soil, but that oxygen immediately bonds with carbon to create carbon dioxide that is lost to the atmosphere, he said.
“With tillage, between 60% and 80% of the carbon stored in the soil is released as carbon dioxide,” he said. “No-tilling keeps that carbon sequestered in the soil.
“All the carbon dioxide in the atmosphere can be sequestered by using only 40% of the soil’s capacity,” he said. “That has enormous implications.”
A handful of soil, 10 to 20 grams, is home to about 50 billion bacteria and up to 100 million fungi, Hoorman said. The fungi physically infect the plant, bringing nutrients such as nitrogen and phosphorus from the soil to the plant. In turn, the growing plant supplies sugar to the microbes, which keeps them alive and thriving.
“When you remove living roots from the soil, you also remove the food source for the microbes.”
In addition to food, the microbes need moderate temperatures to thrive. Cover crops serve an important role in keeping the soil cooler in summer and warmer in the winter.
With soil temperatures at 70 degrees F, 100% of the moisture in the soil is used for plant growth, he said. At 100 degrees F, only 15% of the moisture is used for growth.
Hoorman applies the term “ecofarming” to the no-tilling system that also integrates cover crops for nutrient management and weed control.
COMPARING NOTES: Arland Stephens (left) chats with fellow farmers Kenton Rosenhagen and Doug Bates during a break at the South Central Kansas Residue Alliance 2012 Soil Improvement Workshop. All are from Norwich.
This article published in the May, 2012 edition of KANSAS FARMER.