Nutrient Management Research Database

Dairy manure is often applied to cropped soils as a substitute for inorganic N fertilizers, but the impacts of manure on soil trace gas fluxes, yields, and soil N are uncertain in the semiarid western United States. Soil carbon dioxide (CO2-C), methane (CH4-C), nitrous oxide (N2O-N), and ammonia (NH3-N) emissions were monitored using surface chambers from five N treatments: (i) partially composted solid dairy manure (DM) (412 kg N ha(-1)), (ii) DM + AgrotainPlus (DM+AP), (iii) enhanced efficiency N fertilizer (SuperU [SU]) (179 kg N ha(-1)), (iv) urea (179 kg N ha(-1)), and (v) check (no N applied), to determine their effect on growing season (GS) and nongrowing season emissions from a tilled clay loam soil under irrigated, continuous corn production for 3 yr. SuperU and AgrotainPlus contain urease and nitrification inhibitors. Averaged over years, GS soil CO2-C emissions were greater for DM and DM+AP than for urea, SU, and check treatments due to the large amount of C added with the manure; CH4-C emissions did not vary among N treatments; and N2O-N emissions decreased in the order urea = DM = DM+AP > SU > check. AgrotainPlus added to the DM did not reduce N2O-N emissions compared with DM. Cumulative NH3-N emissions after manure application decreased in the order urea > SU > check, with no significant differences between SU, DM, and DM+AP. Dairy manure provided slow-release N with nitrate intensities lower than urea and N2O-N emissions similar to urea. These results highlight the importance of best-management practices such as immediate irrigation after N application and use of urease and nitrification inhibitors to minimize N losses.

• This study, in a corn silage system, compared greenhouse gas emissions resulting from the use of composted solid dairy manure, dairy manure with a commercial nitrification/urease inhibitor AgrotainPlus, enhanced efficiency urea fertilizer SuperU, and standard granular urea
• AgrotainPus was chosen to see if ammonia and nitrous oxide emissions could be reduced, as has been shown for its use with UAN.
• Ammonia loss, silage yields, and plant N uptake were also assessed.

• CO2 emissions were higher in the dairy manure treatments than either of the urea treatments. AgrotainPlus reduced CO2 emissions from the dairy manure by 15%
• AgrotainPlus did not reduce N2O emissions from dairy manure.
• While urea and SuperU both had lower N2O emissions, they lost more N in the form of ammonia, reflecting the importance of irrigating as quickly as possible after urea application to ensure the fertilizer enters the soil.
• SuperU enhanced efficiency fertilizer reduced ammonia and N2O losses as compared with normal granular urea.