Synergistic benefits of lime and 3,4-dimethylpyrazole phosphate application to mitigate the nitrous oxide emissions from acidic soils.

Acidic soils cover approximately 50 % of the arable land with high NO emission potential. 3,4-dimethylpyrazole phosphate (DMPP) inhibits NO emission from soils; however, its efficiency is affected by acidity. Liming is used for soil conditioning to ameliorate the effects of acidity. In the present study, we investigated the effects of liming on the efficiency of DMPP in inhibiting NO emission in acidic soils and the mechanisms involved. We evaluated the impact of liming, DMPP, and combined application and its microbial responses in two acidic soils from Zengcheng (ZC) and Shaoguan (SG) City, Guangdong Province, China. Soils were subjected to four treatments: un-limed soil (low soil pH) + urea (LU), un-limed soil + urea + DMPP (LD), limed soil (high soil pH) + urea (HU), and limed soil + urea + DMPP (HD) for analyses of the mineral N, NO emissions, and full-length 16S and metagenome sequencing. The results revealed that, HU significantly decreased and increased the NO emission by 17.8 % and 235.0 % in ZC and SG, respectively, compared with LU. This was caused by a trade-off between NO production and consumption after liming, where microbial communities and N-cycling functional genes show various compositions in different acidic soils. LD reduced NO emission by 23.5 % in ZC, whereas decreased 1.5 % was observed in SG. Interestingly, DMPP efficiency considerably improved after liming in two acidic soils. Compared with LU, HD significantly reduced NO emissions by 61.2 % and 48.5 % in ZC and SG, respectively. Synergy of mitigation efficiency was observed by lime and DMPP application, which was attributed to the changes in the dominant nitrifiers and the increase in NO consumption by denitrifiers. The combined application of lime and DMPP is a high-efficiency strategy for NO mitigation can ensure agricultural sustainability in acidic arable soils with minimal environmental damage.