Housing cattle in a slatted floor with a pit below can double the cash value of your manure, according to Nicole Kenney-Rambo, assistant extension professor at the University of Minnesota.

A four-year study was conducted by the University of Minnesota to determine the impact of facility and feedlot design on the concentration of nutrient in manure and the resulting value of the manure as fertilizer.

Results show that confinement facilities capture the greatest amount of manure nutrients, and this translates to great manure value on a per-headspace basis.

Kenney-Rambo says increases in the price of commercial fertilizers over the past decade “have resulted in dramatic differences in the impact of feedlot facility design on manure value."

"In 2004, the value of manure captured by each facility design was small, less than $6 per head, and favored open lots as a result of the low expense of hauling manure in this facility design; however, a decade later the value of manure has increased up to tenfold, and the greatest return is realized with slatted-floor-over-deep-pit facilities due to increased nutrient capture.”

Using 2014 prices, Kenney-Rambo and colleagues calculated that per headspace, the annual value of manure from a confinement facility is $63.99, a manure pack is $41.71, and an open lot is $30.05.

“There has been a renewed interest in confinement cattle facilities in the upper Midwest due to a variety of reasons, but one major incentive is the potential to improve manure nutrient capture to remain in compliance with regulations and simultaneously improve the fertilizer value of manure,” she says.

“Manure may have been previously viewed as a byproduct of cattle production that needed to be disposed; however, producers with integrated livestock and crop operations are increasingly recognizing the value of manure as a fertilizer, especially in light of increased commercial fertilizer prices.”

Kenney-Rambo says the study’s results matched their hypothesis that confinement buildings increased nutrient capture, which was already readily apparent. “The true value in the results generated by this project was the ability to generate an estimate of nutrient capture by each facility type and also explore factors outside of physical environment that influence manure nutrient retention.”

When calculating the value of the manure, the study took into account the annual average fertilizer prices as reported by the USDA and estimated hauling costs for each type of facility ($4 a ton for manure pack, $3 a ton for open lot and $0.015 a gallon for slatted-floor confinement pits).

The University of Minnesota study looked at manure analysis results for solids and liquids along with the impact of facility design (open lot, bed pack from confinement barn, stockpiled manure, pit under slatted floor or lagoon) and cattle type (beef or dairy) on nutrient concentrations.

When looking at the estimated annual manure nutrient yields, manure stored in pits had the highest amounts of nitrogen, at 129 pounds per headspace compared to 86 pounds for bedded packs and 53 pounds for outdoor lots.

Manure from pits also had the highest potassium, at 89 pounds per headspace compared to 80 pounds with a bedded pack and 49 pounds for outdoor lots, and highest phosphorous, at 55 pounds per headspace compared to 50 pounds with bedded pack and 33 with outdoor lots.

Nutrient concentrations in solid manure samples were greater for beef cattle than dairy cattle. Dietary energy value did not impact nutrient concentrations of solid manure samples. She explains, “The decreased nutrient concentration observed for dairy-type cattle in solid manure samples is likely due to the extended duration of time they require on feed as compared to beef cattle, resulting in a dilution of manure nutrients due to use of bedding materials.”

Nitrogen concentration of solid samples from beef cows was approximately 18 pounds per ton of manure compared to 15.4 pounds per ton of dairy manure. Phosphate levels in beef manure were approximately 12.8 pounds per ton compared to 8.8 pounds for dairy manure.

Potash levels were approximately 16.4 pounds per ton of beef manure compared to 14.3 pounds for dairy manure.

The results were not the same for liquid samples from slatted-floor pits.

Nitrogen concentration of liquid samples from dairy cows was approximately 32.9 pounds per 1,000 gallons of manure compared to 26 pounds per 1,000 gallons of beef manure. Phosphate levels in dairy manure were approximately 15.1 pounds per 1,000 gallons compared to 12.6 pounds for beef manure. Potash levels were approximately 27.8 pounds per 1,000 gallons of dairy manure compared to 22.8 pounds for beef manure.

All cattle manure serves as a source of nitrogen and phosphorus as well as sulfur and organic matter, but Kenney-Rambo says there is considerable variation in the nutrient concentration in manure.

“Cattle type, diet, utilization of co-products, among other variables, all contribute to the variability. Nutrient content, retention and the ultimate bioavailability of manure nutrients for plant uptake are high-impact aspects of economic and environmental importance to cattle feeders with crop operations.”

Facility and feedlot design must take into account optimal cattle performance, cattle comfort and the safe and effective working conditions for personnel, but environmental protection measures continue to be brought to the forefront with increased awareness and regulatory changes. The largest environmental concerns are usually based upon preventing excessive nutrient or waste discharges into waterways.

Kenney-Rambo offers this advice to cattlemen looking at designing new facilities: “Deciding upon the design for new feedlot facilities is a complex decision that involves a number of interrelated variables."

"Nutrient capture and its implications on fertilizer value are certainly an important part of the equation but need to be balanced with a number of other considerations. Location, permitting, construction, feedlot management, expected feedlot facility longevity, initial cost of investment, cattle type, feedstuff availability, bedding type and procurement, cattle welfare, days on feed and a host of other variables must be considered when building a new feedlot or expanding.”

Kenney-Rambo says cattlemen who have existing outdoor feedlots who would like to increase their manure’s fertilizer value can do so by increasing the frequency of scraping pens and by utilizing settling basins and runoff control basins.  

Kelli Boylen is a freelance writer based in Iowa.

PHOTO: Outdoor lots averaged 52 pounds of nitrogen based on annual manure nutrient yields. Staff photo.