How important is organic matter and how can you add more to your soil?
Soil organic matter is farming’s Holy Grail and every farmer should want more, says Peter Johnson, RealAgriculture’s resident agronomist. In this video, Johnson shares some simple strategies on how farmers can pump up organic matter levels to hold more water and nutrients in their fields and produce high yields. He notes that the basic strategy is akin to how dairy farmers make milk.
So how important is organic matter, really? When farmers add one half of one percentage point of dry matter to soil it can store an additional 23 millimetres of rainfall. In Ontario, that’s enough to grow 12 more bushels of corn.
It takes about 10,000 pounds of crop residue to increase soil organic matter by one half of one percent. But Johnson believes it’s important for farmers not to focus on that number but rather on maintaining strong crop rotations, including cover crops, and feeding soil bugs.
Johnson says new perspectives on organic matter are changing the strategies he and other soil scientists share with farmers. “We have stable organic matter and stuff we just return, but the main contributor to soil organic matter are the soil bugs – we didn’t realize that. As much as 80 percent of the organic matter in the soil is the residual from those soil bugs, after they have eaten the residue.”
To create that “soil poop” Johnson says farmers should feed their soil like dairy farmers feed their cows. “You’re not only feeding the cow, but the bugs in the cow’s stomach. You have to think like a nutritionist – that’s what drives milk production.”
Johnson explains that it’s also important for farmers to understand the carbon:nitrogen ratio of the crops they grow and ensure there’s diversity in their rotation. “When you grow corn, soybeans and wheat you get much higher organic matter because you have added diversity to the rotation.”
Growing 240-bushel-per-acre continuous corn, for example, creates lots of residue but it actually lowers organic matter, notes Johnson. “Once we mix it up and feed those bugs a more balanced diet, suddenly we get more organic matter.
“It’s important to include as many crops as you can because that will make you more organic matter and it will make you a better farmer,” says Johnson.