Effects of Nitrification Inhibitors on Soil Nitrification and Ammonia Volatilization in Three Soils with Different pH

Abstract

The application of nitrification inhibitors (NIs) is considered to be an efficient way to delay nitrification, but the effect of NIs combinations on soil nitrification and ammonia (NH3) volatilization are not clear in soils with different pH values. In this study, we explored the effect of nitrapyrin (CP) and its combinations with 3, 4-dimethylepyrazole phosphate (DMPP), dicyandiamide (DCD) on the transformation of nitrogen, potential nitrification rate (PNR), and ammonia (NH3) volatilization in a 120-day incubation experiment with three different pH values of black soil. Treatments included no fertilizer (Control), ammonium sulfate (AS), AS+CP (CP), AS+CP+DMPP (CP+DMPP), and AS+CP+DCD (CP+DCD). The application of NIs significantly decreased NO3−-N contents and potential nitrification rate (p < 0.05), while significantly increased NH4+-N contents (p < 0.05), especially CP+DCD and CP+DMPP were the most effective in the neutral and alkaline soils, respectively. In the acid soil, CP significantly increased total NH3 volatilization by 31%, while CP+DCD significantly reduced by 28% compared with AS. However, no significant difference was found in NH3 volatilization with and without NIs treatments (p > 0.05) in the neutral and alkaline soils. In conclusion, the combined nitrification inhibitors had the better efficiency in all three tested soils. CP+DCD and CP+DMPP are the most effective in inhibiting soil nitrification in the clay soils with higher pH value and lower organic matter, while CP+DCD had the potential in mitigating environment pollution by reducing N loss of NH3 volatilization in the loam soil with lower pH value and higher organic matter. It provided a theoretical basis for the application of high efficiency fertilizer in different soils. Further studies under field conditions are required to assess the effects of these nitrification inhibitors.

A meta-analysis to examine whether nitrification inhibitors work through selectively inhibiting ammonia-oxidizing bacteria

“…Soil pH has been considered as one of the most important factors controlling NI efficacy, because pH has potential to impact the degradation rate of the NIs in soils. Cui et al (2021) showed that DMPP performed better in alkaline soil compared to acid soil conditions, which may be caused by the shorter half-life time of DMPP in acidic soil compared to alkaline soil. DMPP undergoes degradation in soil through chemical reaction steps, potentially involving reactive oxygen species (ROS) generated through abiotic and/or biotic processes ( Sidhu et al, 2021 ), which would possibly be affected by pH.…”

“…Soil pH was an important explanatory variable for NI efficacy in reducing N 2 O emissions ( Cui et al, 2021 ). The results from the current meta-analysis showed that NIs had different effects on decreasing N 2 O emissions under different soil pH ( Figure 2A and Table 1 , P < 0.01), and NIs efficacy had a positive response to soil pH.…”

“…Previous studies have reported a negative correlation between NI efficacy and SOM and clay content ( Barth et al, 2008 ; Zhu et al, 2019 ). High SOM and clay content could easily adsorb NIs, which would influence their availability and effectiveness ( Zhang et al, 2020 ; Cui et al, 2021 ). Furthermore, SOM could be used by soil microorganisms as energy, carbon (C), and N source, which improve microbial bioactivity, leading to accelerated biodegradation of NIs ( Fisk et al, 2015 ).…”

“…Soil pH has been considered as one of the most important factors controlling NI efficacy, because pH has potential to impact the degradation rate of the NIs in soils. Cui et al (2021) showed that DMPP performed better in alkaline soil compared to acid soil conditions, which may be caused by the shorter half-life SOM and soil texture were also considered as main factors affecting NI performance (Jarvis et al, 2007). Previous studies have reported a negative correlation between NI efficacy and SOM and clay content (Barth et al, 2008;Zhu et al, 2019).…”

“…would influence their availability and effectiveness (Zhang et al, 2020;Cui et al, 2021). Furthermore, SOM could be used by soil microorganisms as energy, carbon (C), and N source, which improve microbial bioactivity, leading to accelerated biodegradation of NIs (Fisk et al, 2015).…”