Assessing Greenhouse Gas Emissions of Dairy Manure from Tannin in Feeding Trials.

Dairy production systems, especially manure land applications, are responsible for a significant amount of total livestock based agriculture greenhouse gas emissions. Tannin additions to dairy cow diets are known to result in reduced ammonia emissions, enhanced N use efficiency, and higher N content in manure feces in laboratory incubations. However, research on the effects of large scale field application of tannin enhanced manures has not been studied. The objective of this project is to understand how dairy diets with tannin additives impacts land application of manure, specifically quantifying greenhouse gas emissions, N uptake, and corn silage yield response. Raw manure from an experimental dietary trial with tannin additions was field applied on 15 May 2014 in Prairie du Sac, WI. Three diets were studied (no tannin and diets 0.45% and 1.8% tannin by weight), each at two N application rates (240 kg ha^-1 and 360 kg ha^-1), accompanied with a control of no manure application to corn silage. Greenhouse gas measurements for CO₂, NH₃, N₂O, and CH₄ were made intensively during the first 68 hours after application, then measured every 7- 14 days through the growing season using Fourier Transform Infrared spectroscopy. Soil sampling from 0-10 and 10-20 cm accompanied GHG measurements and was analyzed for soil nitrate and ammonium. Silage was harvested and analyzed for plant tissue N and total yield from 9 m² plots. Experimental results will be presented from the 2014 growing season for greenhouse gas emissions, plant available N, and corn silage yield data.