Urease and Nitrification Inhibitors

Increasing nitrogen efficiency of pig slurry

Nutrient leaching into water sources and gaseous emissions from slurry are one of the major sources of pollution from Irish agriculture. Pig farmers don’t need slurry, but it must go somewhere. It can lower the need for artificial fertiliser on beef, sheep, and dairy farms. Research published this year in the Journal of Animal Bioscience tested advancements in nitrogen efficiency of pig slurry on perennial rye grass swards.

Urease and nitrification inhibitors were added to pig slurry which was applied to separate plots at a rate of 200kgN/ha to harvested pasture. The effect of these inhibitors on reduction of ammonia and nitrous oxide emissions were measured along with leaching. Slurry with inhibitors was compared with plots without, testing the efficiency of nitrogen used for grass regrowth (Park et al. 2021).

‘’Proper application of urease and nitrification inhibitors would be an efficient strategy to improve the N use efficiency of pig slurry’’-Authors concluded.

Urease and nitrification inhibitors increased nitrogen recovered by grass by 25-42%, leading to improved regrowth. Nitrogen conversion to soil inorganic nitrogen was enhanced by nearly a third with use of inhibitors. Nitrogen losses were lower on plots with inhibitors, 25.5% nitrogen loss compared to 38% for the control. Overall pig slurry ammonia losses were reduced by 27%, nitrous oxide by 50% and nitrate leaching by 10% (Park et al. 2021).

‘’Scientists still have many obstacles to overcome, for example: the isolation of natural inhibitors from plant material and the production of those inhibitors on a large scale, which will definitely be far more complicated than is the case with the currently known and used inhibitors’’-

Authors of a paper reviewing the effectiveness of various urease inhibitors suggest. The inhibitors used in the pig slurry trial were synthetic inhibitors which are very cost effective. This review article suggested that they perform well, however, there are not enough long-term studies done on these compounds. Adding that, natural sourced inhibitors from plants should be sought after (Matczuk and Siczek 2021). The main barrier being of course cost and availability.

Nitrogen emissions make up a great deal of Irish agricultural greenhouse gas emissions. Research findings on pig slurry suggest that urease and nitrate inhibitors are effective at reducing gaseous ammonia and nitrous oxide emissions, as well as nitrate leaching. Grass growth was also enhanced. It was suggested that natural plant sourced inhibitors should be the sought-after products. My take is that long term effect of synthetic and natural inhibitors needs to be compared. I understand that natural might be better long term but cost effectiveness and speed of implementation are factors also. Reducing gaseous emissions and eutrophication should be priority number one. Followed by the eventual move to natural inhibitors and lowering of its production cost. Meaning it can be used practically at farm level across all animal production systems.

By:         Neal Folliard M.Sc.

References:

Matczuk, D. and Siczek, A. (2021) ‘Effectiveness of the use of urease inhibitors in agriculture: a review’, International Agrophysics, 35(2), 197-208, available: http://dx.doi.org/10.31545/intagr/139714.

Park, S.H., Lee, B.R. and Kim, T.H. (2021) ‘Urease and nitrification inhibitors with pig slurry effects on ammonia and nitrous oxide emissions, nitrate leaching, and nitrogen use efficiency in perennial ryegrass sward’, Animal bioscience, 34(12), 2023-2033, available: http://dx.doi.org/10.5713/ab.21.0046.