Effects of Different Chabazite Zeolite Amendments to Sorption of Nitrification Inhibitor 3,4-Dimethylpyrazole Phosphate (DMPP) in Soil

Application of natural zeolitites (ZTs, rock with > 50% of zeolites) as a soil amendment is recognized as a suitable method for increasing substrate quality. ZT is used at natural state or pre-enriched with specific cations (e.g., NH4+) to slow-release nutrients. ZT at natural state has been shown to mitigate gaseous N losses and favor crop yield, while NH4-enriched ZT has been reported to show quick NO3- production and relatively high gaseous N losses. The use of nitrification inhibitors (NIs) could alleviate these losses. In this work, the sorption behavior of a synthetic NI 3,4-dimethylpyrazole phosphate (DMPP) on different soil-ZT mixtures as well as on pure ZTs (natural and NH4-enriched) was tested. High sorption of NI can reduce its inhibitory effects and consequently the nitrogen use efficiency (NUE). Results show that natural ZTs had a deficient capacity for DMPP sorption and thus decreased the possibility to retain DMPP once applied to the soil. The sorption capacity strongly positively correlated to soil organic C content, supporting that sorption was mainly driven by soil organic matter. Any types of ZT added to the soil, notably that at natural state, have decreased the potential sorption of DMPP principally because of a dilution of the total organic C which reduced substrate hydrophobicity. A lower DMPP sorption in the substrate can mean higher availability of DMPP to soil microbial biomass and thus a higher potential in inhibiting nitrification. These beneficial effects may result in an advantageous strategy for increasing NUE.