Manure spreading

Iowa is the country’s No. 1 producer of manure and no region creates more of it than N’West Iowa.

REGIONAL—Not only is N’West Iowa an abundant crop production region but it also is one of the top crap producers as well.

A blog post titled “50 Shades of Brown” penned by Chris Jones, a research engineer for IIHR Hydroscience and Engineering at the University of Iowa in Iowa City, deduced that Iowa produces more excrement than any other state.

According to Jones’ research, three of the Hawkeye State’s top 10 highest poop producing counties are in N’West Iowa.

While Iowa’s human population is a sparse 3.1 million, it is home to a considerable amount of livestock.

Jones included livestock in his methodology specifically beef cattle, broiler chickens, dairy cattle, hogs, laying hen and turkeys. Counting livestock, Jones places Iowa’s true population at 168 million.

Using that number, which is based on information from the 2017 U.S. Census of Agriculture and the State Data Center of Iowa, Jones calculated a “fecal equivalent population” to determine how much waste is generated.

“I looked at reference values for the amount of nitrogen, phosphorus, and total solids generated by each type of animal, and converted that to a human equivalent,” he wrote. “I then added that number to the human population to get a ‘fecal equivalent population,’ which I will call FEP for brevity from here on out. Since U.S. states vary in size from 1,545 (Rhode Island) to 665,000 square miles (Alaska), I divided the FEP by the states’ areas to get an FEP density, if you will.”

Based on that formula, Iowa was easily America’s No. 1 state when it came to going No. 2 and had an FEP of 2,979 per square mile.

Delaware, a smaller state in size and population but with a huge poultry population, is the runner-up with an FEP of 2,371 per square mile.

In a follow-up interview, Jones explained what inspired his post.

“Me and my collaborators had done some work on some western Iowa watersheds about a year ago looking at the nitrate levels in streams draining into the Missouri River,” he said. “It seems that in those streams, nitrate concentrations correlate very closely with the density of livestock that’s in those watersheds.”

Jones said they studied nine watersheds and the two with the highest concentration of nitrates and livestock were the Rock and Floyd watersheds, which flow throughout parts of N’West Iowa.

A county-by-county breakdown of Jones’ data shows that Sioux County has the highest FEP in the state at 11,795,788 followed by Lyon County’s 7,248,358. Both counties typically rank one and two in livestock production in Iowa.

While slightly lower than their western counterparts, O’Brien and Osceola counties also had high FEPs. O’Brien County has an FEP of 3,231,668 and Osceola’s is 2,580,833. Both rank in the top 15 for Iowa.

“Manure is a good fertilizer and in many ways it’s preferable to commercial chemical fertilizers,” Jones said. “But one of the problems that we see is that the availability of manure does not have that big of an effect on commercial fertilizer sales. Sioux County, for example, we have a very high density of livestock but there is still quite a lot of commercial fertilizer sold in that county. It’s usually in the top 20 if not the top 10 or 15 counties in the state for commercial fertilizer sales.”

Although there is a bounty of boo-boo in N’West Iowa, Jones said that is not solely to blame for some of the water quality issues his team has detected in the region’s waterways.

“The manure in and of itself is not causing this impairment of the streams for nitrogen; it’s the overall (application) rates,” he said. “That’s where management of the manure becomes important and how does it fit into a fertilization scheme where they are also using commercial fertilizer.”

Jones understands that runoffs that lead to manure reaching the streams happen from time to time; however, his big point is that it should be applied to fields with more caution and with standards set by Iowa State University.

“I know it’s a sensitive issue up there and I’m not trying to make any enemies,” he said.

Top 15

Here are the top 15 poop-producing counties in N’West Iowa, based on a study by research engineer Chris Jones:

Field 1 Field 2 Field 3 Field 4
County Livestock Humans Fecal equivalent population
SIOUX 11,760,879 34,909 11,795,788
LYON 7,236,547 11,811 7,248,358
WASHINGTON 5,589,942 22,141 5,612,083
PLYMOUTH 5,175,043 25,095 5,200,138
HAMILTON 4,089,815 14,952 4,104,767
WRIGHT 3,881,648 12,690 3,894,338
CARROLL 3,765,196 20,154 3,785,350
DELAWARE 3,522,836 17,069 3,539,905
O BRIEN 3,217,828 13,840 3,231,668
DUBUQUE 3,059,082 96,854 3,155,936
HARDIN 2,997,426 16,868 3,014,294
KOSSUTH 2,714,221 14,908 2,729,129
OSCEOLA 2,574,793 6,040 2,580,833
CLAYTON 2,528,294 17,556 2,545,850
PALO ALTO 2,502,507 8,929 2,511,436