No-till seen as a dynamic system
By Larry Dreiling
Examining the philosophy of no-till cropping as a systems approach to farming and the importance of understanding no-till agriculture from the system dynamics perspective was a key part of this year's No-till on the Plains Winter Conference, held recently at Salina, Kan.
Greg Scott, Oklahoma state soil scientist for the Natural Resources Conservation Service, presented his ideas that because all of the no-till system components are connected, every action will have an impact on the rest of the farm ecosystem, and it is important to consider the implication of a decision to all components of the system.
"No-till as a system includes rotations, cover crops, good soil management, and an understanding of how they work together," Scott said.
"We use the word ecosystem a lot, but let's define what a system is. It's a set of interdependent components that form a whole. We tend not to think about systems but rather about individual actions. All of the components of the system, even though we think about them separately—such as the crop we are growing or the soil we are planting them into, the rainfall we're getting—is all going to work as a system whether I want it to or not, and I have to learn to work within that system."
If one component is removed, Scott said, the whole system fails.
"The one consistent message we've heard at this conference is that over the years we have destroyed this part of the ecosystem from bacteria on up," Scott said. "We have reaped a harvest of ignoring how this ecosystemhas to work together."
Scott told of the no-till conversion of his own Cimarron County, Okla., farm, noticing how the earthworm population began to recover, creating channels that came to the surface, that persist from year to year, since he's not tilling them up and destroying them.
The earthworms, meanwhile, are bringing up residue, varying last year's residue crop.
"When you start digging into that residue, you discover that those earthworm casts are chock full of mycorrhizal fungi and they've allowed that system to rebuild the nutrient dynamics and the earthworm population," Scott said. "I'm putting residue on the surface and letting it decompose. It's nature's place to do so. Residue buried 7 inches under surface is not where nature fixes residue.
"By rebuilding the infiltration capacity, I don't have any runoff and get more water into the ground. I get a better crop. That better crop leaves more residue behind. Year by year, I rebuild that system, because while all I think I've done is reduce my tillage, I've really allowed the rest of the system to begin to function."
Cimarron County sits over the Ogallala Aquifer. If Scott's farm has a year that gets enough rainfall to push rainfall down below the root zone, this water in that ecosystem can actually function to recharge the aquifer. Not a dramatic increment, he said, but an increment nonetheless.
"The reaction is the water began to run to the hill slopes and began to build saline seeps all around a field," Scott said. "The seeps are the response to my management changes that were good yet I failed to anticipate that I was going to have more water than I know what to do with.
"It's still good to consider that I can send water down to the aquifer when I don't need it, but I need to consider if I'm sending nutrients and chemicals with it when I do it."
While Scott said he is sold on no-till, he also is a cynic about it.
"Thirty-five years ago I could look at some soil and say it was in great condition. This soil has naturally good tilth. The soil is soft, easy to till and makes a good seedbed," Scott said. "Over about a 25-year period, however, we had seen where soil had degraded to the point where we couldn't say we saw a farm that was in good shape.
"It was in 2003 that I started looking at soils that were in good shape and discovered they all been no-tilled for five to ten years. The changes were startling, so dramatic, and so rapid that I became sold on it."
Scott gets upset when people approach him to say they no-till even if they do occasional tillage.
"Essentially, one tillage pass loses most of what you've gained with no-till," Scott said. "Penetration resistance goes up. That's important because the root uses energy to grow. The denser the soil is the more energy it takes for that plant to grow. Roots growing through compacted soil tend to be shorter, fatter, explore less of the soil. They have less association with mycorrhizal fungi, and they give the plant less energy to take back into the plant and yield. Bulk density and penetration resistance—even with one tillage—goes up about 30 percent.
"The aggregation of soil structure we've built up from the fungi, the mucus of the worms, the exodates from the roots are destroyed in one tillage. The water infiltration is gone because all the worm channels we built have been destroyed and the organic matter falls off if we till just once.
"That pool of organic matter is available, in the bank, loaded with nematodes and fungi and bacteria with no-till. One plowing destroys that revenue gain of organic matter."
In Oklahoma, Scott said, it's not uncommon to lose 2 percent of the organic matter in the soils through tillage.
"You've lost 20 tons of organic matter, which is 2 tons of nitrogen," Scott said. "At 60 cents a pound, that's $2,400.00. We've lost more nitrogen in our fields than the land is worth. If you value nitrogen, no-till is money in the bank."
Part of the system approach is the addition of cover crops, Scott said.
"You keep hearing the message over and over again at this conference, but it is a consistent one," Scott said. "No-till with cover crops gives us the most rapid increase in quality in our systems."
Cover crops are especially good at correcting something Scott thought he'd never see in farmground covered in no-till: saline seeps.
"We've done all the good things and received all the benefits of no-till, but the water we've saved has to go somewhere and we failed to anticipate these saline seeps we're seeing," Scott said. "One thing about them, saline seeps will attract deer to lick the salt."
Saline seeps create a depression in yields and a lack of residue that creates weeds. The challenge, Scott said, is to determine how to increase the intensity of cropping, to dramatically increase water use, and to move the water table down from the surface and heal the saline seep.
"We can do that by adding aggressive alfalfa varieties or sunflowers or other cover crops to use all that water," Scott said. "It will heal itself. Interestingly, you might discover your soils to be lacking chloride because we've leached it out of the soil and into the saline seeps."
In considering adding cover crops, Scott suggests looking to the unbroken prairie for inspiration.
"In a tallgrass prairie, you can find many species of grasses and sedges growing in January," Scott said. "Nature does not never leave much of the prairie green year-round. Look closely at the prairie close to the soil. You'll find lots of things growing."
Scott had a reminder to his seminar participants:
"The land reacts as a system whether we anticipate its actions or not," Scott said. "Most of us are surprised when our actions effect the environment. It's difficult to wrap your arms around, but if you can anticipate what will happen, you'll be ahead."
Larry Dreiling can be reached by phone at 785-628-1117, or by email at email@example.com.