Location: Soil and Water Management ResearchTitle: Temperature alters dicyandiamide (DCD) efficacy for multiple reactive nitrogen species in urea-amended soils: Experiments and modeling
|Venterea, Rodney - Rod|
|CLOUGH, TIMOTHY - Lincoln University - New Zealand|
|COULTER, JEFFREY - University Of Minnesota|
|SOUZA, EMERSON - University Of Minnesota|
|BREUILLIN-SESSOMS, FLORENCE - University Of Minnesota|
|SADOWSKY, MICHAEL - University Of Minnesota|
|GUPTA, SANJAY - University Of Minnesota|
Submitted to: Soil Biology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/14/2021
Publication Date: 6/23/2021
Citation: Venterea, R.T., Clough, T.J., Coulter, J.A., Souza, E.F., Breuillin-Sessoms, F., Spokas, K.A., Sadowsky, M.J., Gupta, S.K., Bronson, K.F. 2021. Temperature alters dicyandiamide (DCD) efficacy for multiple reactive nitrogen species in urea-amended soils: Experiments and modeling. Soil Biology and Biochemistry. 160. Article 108341. https://doi.org/10.1016/j.soilbio.2021.108341.
Interpretive Summary: Dicyandiamide (DCD) is an organic chemical that is co-applied with nitrogen fertilizers to slow down the process of microbial nitrification, which helps to reduce losses of nitrogen to the environment and make more of the fertilizer available to the crop. While commonly used, the effectiveness of DCD varies widely. Few studies have measured DCD and temperature effects on a complete set of soil N variables. Here the DCD reduction efficiencies (RE) for nine nitrogen availability metrics were measured in two soils (a loam and silt loam) using aerobic laboratory microcosms at five temperatures from 5 to 30oC. The effectiveness of DCD for reducing the production of all forms of nitrogen decreased as temperature increased. Also, the effectiveness of DCD was greater, and less sensitive to temperature, for certain forms of nitrogen, including nitrite and nitric oxide, compared to other forms. One form of nitrogen, ammonia, was increased by up to 200% when DCD was added. A soil nitrogen cycling process model was modified to account for the effects of DCD. The modeling results indicated the DCD had indirect effects on the first step of nitrification as well indirect effects on the second step of nitrification. The results of this study will help land managers to reduce nitrogen losses and allow scientists to make better predictions of the effectiveness of nitrification inhibitors.
Technical Abstract: Dicyandiamide (DCD) is a nitrification inhibitor (NI) used to reduce reactive nitrogen (N) losses from soils. While commonly used, its effectiveness varies widely. Few studies have measured DCD and temperature effects on a complete set of soil N variables, including nitrite (NO2-) measured separately from nitrate (NO3-). Here the DCD reduction efficiencies (RE) for nine N availability metrics were quantified in two soils (a loam and silt loam) using aerobic laboratory microcosms at 5 to 30oC. Both regression analysis and process modeling were used to characterize the responses. Four metrics accounted for NO3- production and included total mobilized N, net nitrification, maximum nitrification rate, and cumulative NO3- (cNO3-). The REs for these NO3--associated production variables decreased linearly with temperature, and in all cases were below 60% at temperatures =22oC, except for cNO3- in one soil. In contrast, RE for NO2- and nitric oxide (NO) gas production were less sensitive to temperature, ranging from 80-99% at 22oC and 50-95% at 30oC. Addition of DCD suppressed nitrous oxide (N2O) production in both soils by 20-80%, but increased ammonia (NH3) volatilization by 36-210%. The time at which the maximum RE occurred decreased exponentially with increasing temperature for most variables. The two-step nitrification process model (2SN) was modified to include competitive inhibition coupled to first-order DCD decomposition. Model versus data comparisons suggested that DCD had indirect effects on NO2- kinetics that contributed to the greater suppression of NO2- and NO relative to NO3-. Better understanding of the simultaneous impacts of NIs on multiple soil processes will improve mitigation of reactive N losses and prediction of NI effectiveness.