Abstract
The application of nitrification inhibitors (NIs) based on ammonium (NH4+) is considered to be an efficient way to reduce nitrogen (N) loss by delaying the nitrification process through influencing ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). However, the inhibition mechanisms of NIs on AOA and AOB in different soils remain unclear. Hence, we explored the two commonly used NIs (3, 4-dimethylepyrazole phosphate (DMPP) and dicyandiamide (DCD) and their combination (DMPP + DCD) on the soil nitrification and abundance of ammonia oxidizers (AOA and AOB) in three black soils (HLJ, NA, and DA) with different physicochemical properties using a 120-day incubation experiment. The results demonstrated that NIs significantly increased NH4+-N concentrations and decreased NO3−-N concentrations in all three tested soils. There was no significant difference in inhibiting nitrification in HLJ among all NI treatments, while DCD was more efficient in NA, DMPP + DCD had better efficiency in DA. The potential nitrification rate (PNR) was greatly decreased by NIs addition, and PNR was significantly positively correlated with AOB (p < 0.05). AOA was dominant in the acid soil. All NI treatments significantly inhibited soil nitrification through inhibiting the growth of AOB in the two soils with higher pH. The abundance of AOA and AOB was significantly correlated with different soil types (positively correlated with soil pH, and negatively correlated with organic matter). Moreover, soil pH and soil organic matter were considered to be the most important factors influencing the inhibition efficiency of NIs and the abundance of AOA and AOB. The application of the NIs combination (DMPP + DCD) was considered to be the most cost-effective way to inhibit soil nitrification in soil with higher pH and lower SOM, which provides a theoretical basis for a field experiment.
Highlights
It is well known that nitrogen (N) is one of the most important nutrients for crops, and applying N-rich fertilization is a widespread practice in agriculture to ensure the higher yield and quality of plant
The NH4+-N concentration in N treatment rapidly decreased by 15–30% after day 3, though still 92–97% higher than that in the control only in HLJ, and no significant difference between CK and N treatments after day 14 and 70 in NA and DA, respectively (Figure 1A,C,E; Table S1)
In HLJ, no significant difference was found in nitrification inhibitors (NIs) treatments among the entire incubation time except for day 3 and maintained NH4+-N concentration > 346.35 mg kg−1 at least 120 days (Table S1)
Summary
It is well known that nitrogen (N) is one of the most important nutrients for crops, and applying N-rich fertilization is a widespread practice in agriculture to ensure the higher yield and quality of plant. NIs are chemical compounds that delay soil nitrification and decrease the emissions of the potent greenhouse gas nitrous oxide (N2O), leaching, and denitrification [5]. Nitrification inhibitors such as 3, 4-dimethylepyrazole phosphate (DMPP) and dicyandiamide (DCD) are the most widely used in agricultural soils [6]. A field experiment demonstrated that DCD with urea significantly reduced NO3− leaching by 58.5% and 36.2% in soils with pH 5.12 and 7.71, respectively [7] Another field study showed that DMPP with urea increased the nitrogen use efficiency by 10% [8]. Different NIs have different properties and price [6], it is essential to study the effect of combination NIs to find a more cost-effective way to inhibit soil nitrification
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