Gypsum applications reviewed for effects on soil, crops

Ray Mueller
Now Media Group


A interrelated series of national events has led to the development of a relatively new soil amendment product that is the subject of several public and private sector evaluations on farms in eastern Wisconsin.

A leading commercial name for that product is Gypsoil (a mix of calcium and sulfur). It is obtained from coal-fired electric power plants which are using scrubbers to collect the emissions which had traditionally been dispersed into the air.

When new federal air pollution rules forced those plants to reduce those emissions within the past decade, a number of electric power generators opted for installing the scrubbers which supply the product that's known as gypsum. In the past, the sulfur emissions were in effect a free source of a nutrient that is vital for growing healthy alfalfa and several other crops.

Gypsum as soil amendment

Since about 2009, the gypsum recovered at the coal-fired plants has been developed as a commercial product that's a source of sulfur for crops and as a soil amendment for which most of the research findings have been quite favorable. One of the leading companies in the gypsum market is Gypsoil, which is a division of Beneficial Resource Management — a national company with a corporate office in Chicago.

Gypsoil works closely with WE Energies, which has several coal-fired electric power plants in Wisconsin. Pure gypsum has 23 percent calcium and 19 percent sulfur. The flue gas desulfurization (FGD) gypsum from WE Energies has 20 percent calcium and 16 percent sulfate sulfur, according to Ron Chamberlain, chief agronomist and director of research for Gypsoil.

On-farm projects

Chamberlain was a presenter at the 2016 spring advisory board meeting of the Glacierland Resource Conservation and Development Council, which is involved in gypsum project funding and research. That meeting was held in Outagamie County on the Greg and Karon Nettekoven farm, which is one of four northeast Wisconsin farms on which the use of gypsum as a soil amendment is being demonstrated and researched with a $29,640 grant from the Great Lakes Commission.

Since the Nettekovens took over the family farm in 1988, they have revised the production practices on the 760 acres that were once used to grow feed for beef cattle and hogs in addition to raising vegetable crops. Today, they grow a rotation of corn, soybeans, and winter wheat and have recently begun to plant cover crops such as red clover, cereal rye, spring barley, tillage radio and Austrian winter peas.

Greg Nettekoven told the meeting attendees that some land has been enrolled in the federal Conservation Stewardship Program, that federal Environmental Quality Incentive Program funds have been obtained, that mulch tilling has been introduced and that no-till practices have yielded both failure and success.

Four farm projects

As part of the four-farm project, the application of FGD gypsum began in 2014 on the Nettekoven farm. Designed for comparison purposes, the latest application was one ton per acre on 12 acres of a 25-acre field, he noted. The 1-ton rate converts to 400 pounds of calcium and 320 pounds of sulfur per acre.

The projects on those farms, which have included spring and fall applications of one-half ton per acre, are being monitored by Molly Meyers, an agricultural conservation specialist with the Glacierland Council. She pointed out that soil structure trait and water infiltration rate comparisons are being conducted in the wake of the gypsum applications.

In addition to cooperating with the projects on the initial four farms, WE Energies is providing $60,000 for a project on a Lower Fox River Valley farm where field tile has been installed and a gypsum application is planned for this spring. A focus of that project, which will continue through 2017, will be the measurement of volumes and the components in the discharges through the tile drain system.

Milwaukee River projects

A similar paired watershed comparative study is being carried out with the application of gypsum in the upland part of the Milwaukee River basin, according to Greg Olson, who is the project director for the Sand County Foundation. He is working with Francisco Arriaga, who is a soil scientist with the University of Wisconsin Extension Service.

Begun in 2014 on agricultural land which features some steep slopes, that project is designed to evaluate how the application of gypsum affects the runoff of phosphorus in surface water, Olson reported. The paired sites are on two farms at rural Campbellsport (one with livestock and grain crops and another with only grain cropping) and one at rural Kewaskum with both livestock and grain crops.

Both in the spring and December of 2014, the sites where gypsum had been applied had less surface runoff, Olson indicated. He said all of the initial findings have been favorable and noted that plans are underway to add two farms in the Kaukauna area to the project.

Gypsum basics

The WE Energies plants have been generating about 300,000 tons of gypsum annually since 2009. One half of it is being applied on agricultural land. Gypsoil is a major buyer of that gypsum and seller of it to farmers.

In his presentation at the meeting, Ron Chamberlain of Gypsoil said that Benjamin Franklin was one of the earliest known advocates and demonstrators of how gypsum is beneficial to plant growth. Gypsum is a water soluble mineral that is readily available for use by plants and is commonly used to fertilize potatoes and peanuts, he explained.

Crop research with gypsum in states such as Ohio, Georgia and Arkansas has shown that it is beneficial for root growth, particularly for corn, Chamberlain reported. One reason for that is how gypsum can neutralizes the effect of excess soil aluminum, which has a toxicity that can burn roots, he stated.

Major benefits of gypsum

Multiple studies of gypsum are showing improvement in the physical, chemical and biological health of soil, better water infiltration and water quality, and a reduction of the runoff of soil and pathogens. He said the Natural Resources Conservation Service agrees with those findings.

Specifically, Chamberlain cited studies in which water infiltration rates rose to 1.8 inches per hour after the application of gypsum, turbidity in tile drain water flowing toward Lake Erie was greatly reduced, phosphorus runoff volume was down by 62 to 39 percent during the three years after applications, and gypsum was found at depths of 36 inches in the soil.

Don't expect immediate results on those points with gypsum applications, Chamberlain emphasized. He said it takes three years in most cases to document significant differences and suggested applications be repeated every three years.

Landowners should notice the effects of gypsum with reductions in field ponding, soil surface sealing or crusting, and erosion along with improvements in the root size of plants and crop production, Chamberlain promised. It usually takes three years to notice a difference in crop yields.

Application strategies

Depending on conditions, the typical application rates for gypsum range from 500 to 4,000 pounds per acre, Chamberlain pointed out. He recommended the higher rates for soil amendment and the lower ones for crop nutrients.

Gypsum is appropriate only for soils which have clay as a component — not for soils which are nearly pure sand or silt, Chamberlain stressed. Any soil with a high percentage of organic matter also needs gypsum.

Clay soil tends to have too little calcium and too much magnesium, Chamberlain said. Other problems with soil structure and health could be due to excess limestone, frequent tillage and high amounts of salt from manure.

Calcium attracts clay, leading to good traits in the soil structure, while magnesium acts completely in the opposite, causing soil compaction, erosion and crusting, Chamberlain explained. He said gypsum is very beneficial because it binds to the magnesium to create a new compound that provides soil with a strong structure while also keeping it loose.

Base saturation concept

Good soil will have 70 to 80 percent calcium and 10 to 13 percent magnesium, Chamberlain said. Other components would be about 10 percent hydrogen and 2 to 5 percent potassium.

One term that soil scientists use to describe that balance of soil components and nutrients is 'base saturation.' Chamberlain acknowledged that there are two distinct camps among soil scientists about the importance of that concept.

The parties disagree about the appropriateness of the ratio between calcium and magnesium, which Chamberlain indicates should be about seven to one with an allowance for more magnesium in sandy soils. The dispute often pits Extension Service soil scientists against those in the private sector.

Chamberlain observed that parties on both sides of the dispute could be wrong on what starting point they choose to establish a calcium to magnesium ratio. To learn about those traits and to identify the related cation exchange capacity of their soils, he urges landowners to ask for those tests when submitting soil samples.

For getting that information, Chamberlain prefers to use Midwest Labs in Omaha and A & L Labs at Fort Wayne, Indiana for those soil tests. He noted, however, that all major soil testing services can provide that information for an additional fee.