By Thomas Kilcer
Why do we manage poorly drained soils like they are well-drained? This sounds like a dumb question, but it is very apropos.
It happens on farms across the Northeast and Midwest. Multiple years of corn makes drainage worse as the soil structure collapses and machinery compaction squeezes out what little porosity the soil originally had.
In Canada, on silt soils, they now tile on 25-foot space as 50 foot no longer works because of compaction and overworked soils.
As I have mentioned before, 15 years of alfalfa grass sod does not remove the yield- and root-limiting pan that restricts roots to only 7 inches of soil. It is like a paved road underneath.
Nearly every poorly drained or silty or clay field I have dug in has a yield or root or drainage limiting compaction problem due to it being plowed while too wet at some point in the past.
There are long-term and short-term steps that you can take to increase the quantity and consistency of yields from these soils.
First off, you should establish a plan to remove the limiting pan. Yes, I know the layer under that may be even more poorly drained. Nearly every farmer who wins yield contests has worked at gradually increasing the rooting depth and root mass.
You are not going to do it using a chisel or moleboard, or by planting radishes; it is a comprehensive approach. When the soil is dry, deep tillage followed by a fibrous rooted crop, like winter forage or alfalfa grass, will help keep the soil structure open.
My ideal system would simultaneously inject manure behind the deep-zone tillage shank to coat with organic matter the loosened soil particles of the shattered compaction to prevent them from reconsolidating. Immediately follow with a fibrous rooted sod or winter forage crop.
A farmer I know who has been using this process says that his marginal soils are now producing as well as his better soils. He simultaneously removed the old compacted layers and increased the rooting depth.
After a couple of years, you will not need to work that deep as the compaction is out, unless you harvested last fall.
On a silty clay soil where we deep-tilled, that was the only part of the farm dry enough to work in the spring. When we dug a hole at 16 inches down, we had liquid water that we could have pumped out. The surface water moved to the deeper voids created and dried the surface.
We changed the internal moisture composition of the profile and significantly increased the opportunity to get on the ground for no-till or harvesting with properly deflated low-compaction tires.
All this is a complete waste of time and money if you continue recreational tillage and long row-crop rotations suited for better-drained soils.
Short-season rotation optimizes no-till planting. No-till saves time, soil and keeps the compacting tillage equipment out of the deeper portion of these fragile soils. Short-season puts you higher on the yield curve, so average yield over the life of the rotation is significantly higher.
A three-year corn and six-year alfalfa over the nine-year life of the rotation on good soils will produce an average of 4.6 tons of dry matter per year. For less well-drained soils, two years of corn followed each year with winter forage, then a short three-year alfalfa or clover rotation will improve both the soil and the economic return.
The system involves fall-killing a sod; no-till planting corn when the soil is dry the next spring; harvesting the slightly shorter-season corn; no-till planting winter triticale on time — two weeks before wheat grain; harvesting the winter forage and no-tilling corn — use a clearing coulter to remove allopathy; a no-till winter triticale followed by no-till red clover into the harvested triticale stubble; and two more years of red clover.
At the end of the third year of clover or alfalfa, the sod is killed in late fall for next spring’s no-till corn. This is a simple system that works. This rotation can produce an average of 5.99 tons of dry matter per year, or a 30% yield increase. The higher yield occurs because you are capturing the yield of just the peak years.
First-year corn is 15% to 20% higher yielding than corn following corn. This reduces the cost of putting a ton of silage in front of your cows.
As the number of years of repeated corn occur, soil structure rapidly deteriorates and yields fluctuate greatly, with blame placed on the weather. Short rotations minimize this impact.
By the third year, rootworms have moved in and need to be controlled, which means more cost for that same ton of silage.
In long rotations, more nitrogen is needed either as fertilizer or manure. With short rotations, the first-year corn — 50% of corn acres in this rotation — will not need additional nitrogen beyond starter.
As seedings get stretched out, especially on somewhat poorly drained soils, yields are often lower than seeding year and are composed more of less nutritious weeds. Seeding year in this short rotation is planted into a harvested triticale crop.
Keep it covered
The key points are to remove prior damage and then use no-till to minimize ongoing damage to the soil.
Don’t leave these sensitive soils bare. Always have something growing on it over the winter. The only exception might be the sod killed the first half of October for early no-till the next spring.
The other winter forage benefit is that research has found a seven-fold increase in air and water movement in and out of a clay soil after a winter grain.
Kilcer is a certified crop adviser from Kinderhook, N.Y.