Brandon – Zero-till fields at different stages of development – infancy, adolescence and maturity – offer insights into how fields gradually change under the practice, according to researchers and farmers experienced with zero-till.
Garth Butcher of Birtle, Man., has seen the soil changes closeup. He has fields in all three stages of zero-till evolution.
Butcher seeded his first zero-till fields in 1979. By 1981, his entire 1,350 acre farm was under zero till. He calls these fields his mature zero-till land.
He bought a second 500-acre parcel of land 10 years ago and put it into zero till.
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He bought another 800 acres five years ago and also put it into zero till.
He said the stages of development in the three ages of zero-till soil are obvious.
The zero-till soil evolution was explained by Butcher and fertility specialist John Heard, in a joint presentation to the 25th annual Manitoba-North Dakota Zero Till Workshop held in Brandon at the end of January.
Butcher, who conducts soil tests in October, said there’s a difference in nitrates of 20 pounds per acre between fields. That difference affects how much nitrogen fertilizer he must buy for each field.
On a first-year zero-till field, with a typical clay loam soil, his average nitrate level from 1990 to 1994 was 22 lb. per acre. On that same field the average nitrate level from 1998 to 2002 jumped to 41 lb. per acre.
He said it costs more money to farm the newer fields. He gets the highest nitrate levels on the oldest zero-till fields, lower levels on the medium fields and the lowest on the newest zero-till fields.
“On these new fields, I apply more fertilizer, according to the recommendations, but I still end up with less residual nitrate in my soil test results.”
Butcher thinks the soil improvement is due to higher organic matter levels and more active mineralization of organic matter.
Greater mineralization is due to a higher concentration of soil organisms and better soil moisture.
Earthworms are one of the first differences he notices as a new field starts settling into a zero-till regime.
“The earthworms are a sign the soil is becoming healthier and more active,” he said. “After the worms increase in numbers, you begin to notice a difference in soil tilth, sometime around the five-year point. You see the aggregates form and soil particles start to cling together instead of crumbling.”
Excess crop residue on some mature zero-till fields may act as an insulating blanket, creating a frost problem, but Butcher said it’s not enough of a threat to cultivate.
He fall bands anhydrous an average of two out of three years, and feels this is enough tillage for his fields. He has also started baling straw to reduce potential residue problems.
“The market for straw is expanding, so it’s not a bad compromise. A lot of farmers have been cutting back on annual crop acreage because they’re expanding their cattle operations. They need more straw for the cattle, but they’re growing less of it, so this is a good fit.”
Straw baling also prepares fields for seeding winter wheat, Butcher said.
He believes the most noticeable changes to fields converted to zero-till occurred at about the 15-year mark.
“But nobody really has a way of knowing what a mature zero-till field looks like because 25 years is about the oldest samples we have anywhere. Nobody knows what will happen at year 35 or 45.”
Heard said that Butcher’s soil maturity assessment coincides with the timeline European farmers and researchers have found.
“Researchers in Germany call it the new equilibrium.
“They have found that at about 15 years, zero-till soils settle into a steady state that balances nitrogen immobilization with mineralization. The previously immobilized nitrogen in the surface layers is released to the crop at a faster rate than the microorganisms can immobilize it again.”
At this point, zero-till farmers report more crop-lodging caused by excess nitrogen, protein levels too high for malting barley, lower rates of nitrogen fertilizer with equal yields and higher than normal fall soil nitrate levels, he said.
These factors point to the need for a new soil test that accounts for the mineralization
occurring in zero-till soils, Heard said.
