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Why following newer fertilizer guidelines helps farmers, environment

Mike Starkey listens as Hans Kok speaks
STUDY LESSONS: Mike Starkey (far right) listens as conservation expert Hans Kok explains the value of sound practices like cover crops to legislators and personnel from The Nature Conservancy.
Continuous monitoring of nutrient levels confirms that one fertilizer application recommendation is correct.

Editor’s note: This is the second of a two-part series discussing lessons learned after the first year of an extensive water-quality monitoring project. Read the first story, "Early on-farm water-quality monitoring results revealing," on this website, as well.

Bob Barr feels vindicated by first-year data from a six-year edge-of-field monitoring project underway in a stream feeding Eagle Creek Reservoir near Indianapolis. The researcher with the Center for Earth and Environmental Science at Indiana University-Purdue University Indianapolis strongly believes fewer nutrients come out of tile draining land where farmers practice intensive conservation tillage. Average data from the first year of a new study indicate he may be correct.

“Since we didn’t have data on continuous flow every hour of every day all year long before, critics could argue nutrients came out of the tile when we weren’t monitoring,” Barr says. “With automatic sampling equipment, we now know if something happens all year.”

Barr cautions that they only have one year of data. He also notes that there were issues with some sampling equipment, but they’ve been resolved. That doesn’t negate the early findings, however, that average nutrient levels coming from tile draining Mike Starkey’s land were lower than the average nutrient flow for the entire stream that flows by his farm.

Data suggests higher levels of nutrients enter the stream elsewhere. Starkey’s tile water appears to help draw down average nutrient levels in the stream. Starkey farms near Brownsburg.

Phosphorus spike
Just because average nutrient levels from field tile during the entire year were lower doesn’t mean there weren’t spikes when nutrient levels were higher. In fact, Barr observes a significant but short-lived spike in phosphorus levels in water from the field in late-winter 2016.

So what caused the spike? Barr was able to piece together a reasonable explanation, he says.

“One requirement of the project was to apply fertilizer by tristate university [Purdue, Ohio State and Michigan State universities] fertilizer recommendations at the start of the project to create a baseline,” Barr says. Starkey typically applies significantly less fertilizer on his fields, all of which are no-tilled and cover-cropped, than university recommendations suggest. However, to follow protocol for the long-term project, he applied more fertilizer before the 2016 cropping season.

“Some phosphorus ended up going on in February on frozen ground,” Barr says. Conditions didn’t allow application the previous fall. Rain events occurred after fertilizer application.

“That’s when we saw spikes,” Barr says. “Timing coincided with recent fertilizer application."

Lesson confirmed
In retrospect, the phosphorus applied was in a soluble form, enhancing its ability to move. “We’ve always recommended that you don’t apply fertilizer on frozen ground, and this example affirms what we’ve always said,” says Barry Fisher, regional soil health manager with the Natural Resources Conservation Service.

Fisher says the situation also points to a new lesson. “Apparently, soluble phosphorus moving along the surface can find its way into tile lines fairly quickly,” he notes. “Most fields have risers or other features that would allow a point of entry.”

Observation of the spike confirms two things, Fisher says. First, it’s essential economically and environmentally to avoid fertilizer application on frozen ground. Second, it’s important to consider how nutrients may move after application   

 

 

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