FORT WAYNE, Ind. — When it comes to soil nutrient management, farmers must focus on not just the chemical side of soils, but the physical and biological sides, as well.

Allowing proper aeration and water flow is critical for soil health, said Joe Nester, agronomist and owner of Nester Ag Management. Gypsum, a byproduct of the process used to clean the air in coal-powered power plants, can help improve air and water movement through the soil.

Gypsum also affects the relationship between calcium and magnesium in soils.

“You want to pay attention to the calcium level in your soil,” Nester said. “There is a profound difference between calcium and magnesium and the way they react to clay.

“Calcium looks very large compared to magnesium. Calcium can flocculate, which means it puts particles together like a puzzle — the other disperses clay. We have to manage the small-, large-particle relationship.”

Gypsum helps move magnesium further down in the soil so that it doesn’t disperse soil particles as badly, he said. Gypsum also causes an average 55 percent reduction in phosphorus levels.

Adding this compound only works on clay soils, however. On sandy soils gypsum is ineffective and farmers should look at sufficient levels of available nutrients to determine what to add.

Nester discussed the results of a study done by the National Soil Erosion Lab in 2002. It took place on a field with high magnesium levels and non-tilled soils. Four separate plots were made, and fishbowls were placed to collect runoff water from a rain simulator.

The plots that had gypsum applied to the surface had much clearer runoff, while the other plots produced murky water. The dirty water was holding important nutrients, Nester said, while the fields with gypsum retained nutrients in the soil.

“Water infiltration is key,” the agronomist said.

Interested farmers with clay soils should speak with their agronomist about gypsum. Nester said that typically one ton is applied per acre.

Gypsum is affordable because it is a byproduct from power companies that need to get rid of the material.

“As land values, crop values, input costs and water quality impact all increase, it becomes more important,” Nester said. “Soil, water and air will have more impact on your yields than the nutrient levels you have.

“They work together, but the soil tests don’t show soil, water and air. The grower that can manage soil structure and health with their nutrients is going to make the most money. It’s all about minimizing stress and the duration of that stress.”

There are several ways to succeed in farming today, he said. Some farmers practice tilling, while others find no-till practices better. Both methods have advantages and disadvantages that affect soil aeration and water infiltration.

Tilling warms the soil, eliminates residue challenges, distributes nutrients and leads to smoother soils. Although it temporarily injects air, it decreases air flow in the long run, Nester said.

The disadvantages of tillage are that it disrupts soil aggregates, making it hard for water to move up and down. It also decrease carbon dioxide levels, disrupts earthworm and causes other damages.

Farmers must weigh the pros and cons to decide what practices are best for their soils, Nester said.