A new study conducted by Penn State’s College of Agricultural Sciences showed that shallow disk injection compared to the surface broadcast of manure into the soil considerably lowered estrogen in biosolids runoff. The former biosolids application method may be an effective strategy in controlling the mobilization of estrogen thereby significantly improving downstream water quality.
The research also looked into how shallow disk injection affected the levels of dissolved phosphorus and dissolved organic carbon in runoff. It was found that their concentrations were also lower than with the use of surface broadcast.
The use of livestock biosolids fertilizer has proven beneficial in providing crops the essential soil nutrients it needs. But discoveries of new contaminants such as estrogens in the runoff raises concern for the health and safety of the environment. According to Heather Gall, assistant professor of agricultural and biological engineering, manure also introduces emerging contaminants to the environment, including the natural estrogens 17 alpha-estradiol, 17 beta-estradiol, estrone and estriol.
Although the study focused more on manure from dairy cattle, estrogens are a common component in the waste stream of all livestock and even humans. And while studying ubiquitous natural estrogens is important, synthetic estrogens can also affect water quality such as ethinylestradiol, which is an active ingredient in birth control pills, and trenbolone, used as ear implants for beef cattle.
“The method of animal manure application can influence the availability of nutrients and estrogens to runoff water,” said lead researcher Odette Mina, a recent doctoral degree graduate. “Several studies have shown the potential benefits of shallow disk injection for reducing phosphorus and nitrate transport in biosolids runoff compared to surface broadcasting. Our research demonstrated significantly reduced estrogen transport in runoff from shallow disk injection plots relative to surface broadcast plots.”
The study was conducted at the Kepler Farm plots located at the Russell E. Larson Agricultural Research Center in Rock Springs, near Penn State’s University Park campus. They prepared 12 hydrologically isolated plots arranged in a downslope to collect surface runoff water and catch them through PVC pipes which eventually end up in tipping buckets to estimate the runoff flowrate and analyze the nutrient concentrations.
A remarkable difference was seen in the levels of estrogen in the runoff following precipitations events. There was a significantly higher concentration of estrogen in the the runoff from surface broadcast fertilized plots compared to the manure injected plots. A rainfall event that occurred two days after biosolids was applied caused a really big movement of estrogens, carbon and phosphorus from the surface-broadcast plots.
“But that same event was not enough to even trigger runoff from the plots that had undergone shallow disk injection of manure. That first flush washed off really high concentrations of phosphorus and estrogens relative to the entire rest of the study, but there was nothing from the shallow disk injection plots,” stated Mina.
Despite the promising potential of disk injection biosolids fertilizers, there needs to be safeguards to guarantee that estrogen in biosolids runoff will not impact the groundwater. One major concern is that shallow disk injection could promote leaching of estrogen into the groundwater affecting the quality of water from wells. Thus, more studies are planned in the near future.
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