Soil compaction concerns farmers; could hinder production for years

Many Iowa farmers got to know local tow-truck drivers on a first-name basis last fall. Plenty of combines and tractors got stuck in soggy soils at the start of harvest.

Unwanted towing bills, though, may not be the only consequence of driving heavy implements on saturated ground.

Farmers and agronomy experts say soil compaction could hinder production in some areas this year and for years to come.

?It?s a concern,? said April Hemmes, an Iowa Soybean Association board member from Hampton.

Hemmes said compaction worries were a topic of conversation recently among area farmers. She and nearly every farmer she knew got stuck at least once during the early part of harvest.

Compaction occurs when soil aggregates and particles are compressed into a smaller volume, according to Iowa State University Extension and Outreach. Most compaction occurs from farm machinery traversing fields at or near soil moisture holding capacity.

That certainly was the case in many parts of the state when relatively wet weather prevailed from the second week of July through late September. Two separate storms in August and September dumped 8 to 12 inches of rain in parts of northeast Iowa.

Excessively compacted soil causes poor root penetration, nutrient deficiencies, reduced internal soil drainage, reduced water infiltration and lack of aeriation.

Yield losses of 10 to 20 percent in compacted fields due to poor plant growth have been reported, according to ISU. Research data in Iowa and the Midwest indicate that if traffic and compaction are allowed to occur on wet soils and soil aeration is limited, yields over time may be reduced by 4 to 6 bushels per acre for corn and by 2 to 3 bushels per acre for soybeans.

Despite compaction fears, many farmers didn?t have a choice but to harvest in less than perfect conditions. Persistent rain narrowed the harvest window and ISU experts recommended farmers combine crops as soon as possible because of mold and stalk rot issues.

?A farmer has to do what he or she has to do. Sometimes that is not in harmony with nature, which can cause soil damage that can take a long time to fix,? said Elwynn Taylor, Extension climatologist and agronomist.

Mark Licht, ISU Extension cropping systems agronomist, doesn?t believe compaction will be widespread or particularly bad this year. Even though the early part of harvest was wet, he said the rain did subside in early October and the ground did sufficiently dry in many areas to minimize potential damage.

?It?s not as bad as it could have been,? he said.

Solutions

Old Man Winter can help break up compacted soils. Freeze/thaw cycles can reduce or reverse damage.

According to ISU Extension data, frost has penetrated the topsoil in most of the state. As of Jan. 10, the temperature of the top 4 inches of soil was below freezing almost statewide. Only a few northeast Iowa counties have topsoil temperatures above 32 degrees thanks to a blanket of snow.

For the most part, experts said frost is a foot deep statewide, give or take a few inches.

Taylor said it typically takes four freeze/thaw events to solve compaction problems. Some winters only have one, other times it can occur multiple times.

?It doesn?t have to be amazingly cold to create frost penetration, just consistent temperatures,? Taylor said. ?With an open winter [limited snow cover statewide] and current temperatures, the chances for freeze/thaw seems pretty good.?

Some farmers rely on deep tillage to break up compaction.

Mahdi Al-Kaisi, an ISU professor of soil of soil management/environment, said that should be avoided in the spring, especially if fields are saturated. If tiles are running, it?s a good indication they are, he said.

?Tillage will exacerbate the problem and destroy soil structure. Practices like no-till and cover crops are the best solution to reduce compaction,? Al-Kaisi said.

Expansion and contraction of frost does help break up compaction on a limited basis, he said, but the best solution ? if possible ? is to avoid field operations when soil moisture is at or near field capacity.

Other tips to avoid soil compaction:

? Dedicated travel lanes for grain cart operations.

? Don?t fill large carts to full capacity.

? Properly adjusted tire size and correct air pressure for the axle load being carried.

? Use larger tires to increase the ?footprint? on the soil.

Hemmes decided deep tillage isn?t the answer. However, she will take precautions to protect soybeans from sudden death syndrome. Hemmes said the disease can be exacerbated in wet, compacted fields.

?It?s an added concern of mine. I?ll use additional seed treatments and fungicides to fight SDS,? she said.

To learn more about soil health, including compaction and practices that can help minimize its effect, Al-Kaisi suggests farmers attend the 2017 ISU Soil Health Conference in Ames on Feb. 16-17.

To register go to www.register.extension.iastate.edu/soilhealth.