Fertilizing crops with inorganic nitrogen and phosphorus can greatly improve yields, but a University of Nebraska-Lincoln study released this week indicates that while the extended use of fertilizers may be good for the crops, it may adversely affect soil stability and lead to problems like soil instability and erosion.

The study, published in the May-June issue of the Journal of Environmental Quality, is the handiwork of lead author Dr. Humberto Blanco, assistant professor of soil physics at the University of Nebraska-Lincoln, and agronomist Alan J. Schlegel, Southwest Research-Extension Center, Kansas State University.

The study is based on a 50-year chronicle of inorganic fertilization of corn in western Kansas that was irrigated and conventionally tilled.

“While inorganic fertilization did increase soil organic carbon stocks in the long term experiment, it seemingly failed to enhance soil aggregate stability,” according to the study. Aggregate stability is a key indicator of soil structural quality and resistance to erosion, which depends on how water moves through soil.

Blanco reports the result of the study “were somewhat surprising.

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 “Fertilization typically leaves behind more crop residues in fields,” he said, “which in turn can boost soil organic carbon levels, but we didn’t see improvement in soil aggregate stability even though soil organic carbon concentration increased.”

He noted that soil particles usually bind together more strongly in aggregates as soil organic carbon concentrations rise.

“More research is needed over a wider range of management and climate conditions,” Blanco added, citing a shortage of long-term studies about fertilizer impacts. "Definitely, the effects of inorganic fertilizer application on soil properties will depend on tillage and cropping systems, so we need to look at this in other long-term experiments."