Effect of Feedlot Manure Storage and Tillage On Steroid Hormone Losses After Land Application.

Manure generated from concentrated animal feeding operations is a source of steroid hormones and growth promoters found in the environment. The objective of this research was to determine the effects of manure handling (composting and stockpiling) and tillage (disk, no-till, and plow) on the overland transport of steroid hormones after land application. Rainfall simulation studies were conducted one and 30 days after manure application on a Nora silty clay loam (Fine-silty, mixed, mesic Udic Haplustoll)  soil at the Haskell Agricultural Laboratory near Concord, NE (Latitude: 42^o 23’ 33.6” N, Longitude:  96^o 57’ 18.0” W) in 2008 and repeated in 2009. In 2009, due to the low detection rate for these substances in 2008, a surrogate estrogen (17α-ethynyl estradiol, EE2)  was applied to several sub-treatments to determine the effect of tillage and manure application on runoff concentrations. The design was a split-plot (whole plots were tillage) with three replications. Runoff samples were collected at five minute intervals for thirty minutes after runoff initiation. Laboratory analyses of runoff samples were used to identify 17 hormones and metabolites expected in livestock manure. Results of the run-off analysis indicated overall very low concentrations of steroid hormones approaching or below detection limits in the vast majority of samples with no statistical trend in concentrations. In 2008, considering only detection frequency, fewer samples showed traces of steroids one day after manure application in comparison to those collected one month after the manure application, though there was no trend apparent in number of detected hormones or metabolites. Results in 2009 from the surrogate treated study found a 96% reduction in EE2 loss from tillage plots compared to no till plots. Moreover, plots fertilized with manure and receiving additional hormone as EE2 showed almost 50% less mass lost in runoff in comparison to bare soil treated with EE2.