Slurry & Manure
Side-by-side barn trial: treated manure held about 13% more ammonium nitrogen and 13% more phosphate.
Two Ohio finishing farms — university-coordinated trial · Seneca and Crawford counties, Ohio, USA · 22 October 2026
The challenge
Most slurry results are farm reports with nothing to compare against. This trial set out to measure whether biological treatment changes the fertiliser value of manure, using treated and untreated pits side by side on two finishing farms.
The approach
From May 2013, one barn on each farm was treated (8 gallons at the start, 2 gallons on days 7 and 14, then 2 gallons a month) and a neighbouring barn was left untreated. Samples from both were analysed for ammonium nitrogen, organic nitrogen, phosphate, potash and moisture.
Results
+3.84 lb per 1,000 gal (+13%)
Ammonium-N (Seneca farm)
+2.57 lb per 1,000 gal (+13%)
Phosphate (Seneca farm)
+2.89 lb per 1,000 gal (+10%)
Potash (Seneca farm)
+3.33 lb per 1,000 gal
Phosphate (Crawford farm)
On the Seneca farm, which agitated before pumping, every main nutrient was higher in the treated barn. On the Crawford farm, which did not agitate, the gains were smaller and potash was slightly lower, but phosphate rose strongly and total nitrogen was higher in the treated pit on both farms. The authors put the fertiliser gain at $3.96 per 1,000 gallons on Seneca and $1.90 on Crawford, before counting any handling or agitation savings. This was pig slurry treated with PIT PERFECT®, not dairy slurry with DFP, so we present it as evidence for the technology, not a promise for a particular farm.
Source documentation
Ecological Laboratories case studies (opens in a new tab)