By Sonja Begemann and Darrell Smith
Learn to manage soil to avoid yield loss from deficiencies
Knowing the value of soil health tests isn’t the biggest challenge. Doing is. Do you make it a priority to conduct soil health tests on your fields?
“The most important thing is to have a soil test,” says Brian Kuehl, director of product development at West Central Distribution. “It’s the roadmap that tells you where the soil has been and where it needs to go.”
Extensive efforts by Pioneer and USDA provide a soil health report card of sorts, specifically on phosphorus and potassium.
“The general theme we saw in the central Corn Belt is a lot of states are low in potassium,” says Andy Heggenstaller, Pioneer agronomy research manager. “However, the western Corn Belt is low in phosphorus.”
Low testing soil has a significant risk of yield loss, he adds.
If you identify deficiencies in your soil consider the following factors when adjusting nutrient needs:
- Yield history. Higher yields take more nutrients out of the soil.
- Yield goals. If you’re going to push yield, you’ll likely need to push nutrients.
- pH level. The ease at which nutrients are absorbed depends on pH.
- Extent of deficiency. Application rate and method influence how fast you resolve the deficiency.
- What surplus nutrients might be tying up others. For example, nitrogen and sulfur work in tandem.
- Patience. It will likely take a few years before you notice progress. Continue soil health tests to monitor progress. As long as the soil is moving in the right direction keep on keeping on.
Soil composition changes, so be diligent about conducting soil health tests and be ready to change your fertilizer program. “Take your soil samples and measurements in the spring when soil moisture is close to capacity,” says Farm Journal Field Agronomist Ken Ferrie. “Record the locations using GPS so you can return every three to six years and measure progress as you implement your soil health improvement strategy.”
Soil health tests help you avoid losing yield and money from mismanaged fertilizer.
You can perform some soil health tests, such as water infiltration, soil respiration, aggregate stability, pH, surface hardness, compaction and density. Other aspects, including stability, texture analysis, active organic matter and mineralizable nitrogen, need to be tested in a lab.
Soil health tests offer a more comprehensive look at what’s going on below the ground. “Besides testing for macronutrients nitrogen, phosphorus and potassium we now need to test for micronutrients,” Ferrie says. “Over-applying or underapplying any macro- or micronutrient might be detrimental to soil health.”
When balanced, the various components of soil work together like a well-oiled machine. When off balance, they can work against each other. For example, if you apply excess nitrogen to a soil with optimum pH, the extra nitrogen stimulates microbial populations, Ferrie explains. Those microbes release soil carbon, which might be lost as carbon dioxide.
“Down the road, you might need to apply more nitrogen fertilizer because you reduced the supply of nitrogen stored in the soil,” he adds. “If you apply an ammoniacal source of nitrogen, which creates acidity, soil microbial activity might be reduced. Then you will need to apply more limestone to correct the acidity.”
Farmers who irrigate or apply manure should also test for sodium. “Excess sodium prevents clay particles from flocculating [just like hydrogen in an acid soil], so the soil particles run together and structure is destroyed,” Ferrie explains.
It takes extra time and effort, but soil testing and management can help make your soils more productive.