Geoderma (Oct 2023)
Diluted pyroligneous vinegar promoted Rhododendron growth by changing functional genes involved in N cycling in the rhizosphere
Abstract
Excessive chemical fertilization in protected horticulture has caused nutrient accumulation, reduction of soil biodiversity, and subsequently soil degradation. Pyroligneous vinegar is a byproduct of pyrolysis for biochar production. While there has been an increase in interest in using pyroligneous vinegar as an amendment to improve soil quality, a paucity of data exists of its effect on the growth of acidophilous plants such as azalea (Rhododendron). To address this, we investigated the changes in the growth of azalea and soil microbial abundance, specifically those involved in nitrogen cycling in the rhizosphere with amendment of conventional inorganic NPK fertilizer (NPK) and four dilutions of pyroligneous vinegar each with matched NPK content. The results showed that the treatments of pyroligneous vinegar increased plant biomass (51%-99%), root length (29%-81%) and surface area (63%-151%), and nitrogen use efficiency (83%-299%) compared to NPK alone. The pyroligneous vinegar treatments decreased soil pH and increased the contents of rhizosphere soil dissolved organic carbon and nitrate, and changed potential denitrification activity. Compared with NPK, pyroligneous vinegar increased archaeal and bacterial amoA genes (AOA and AOB) abundances (45% − 79% and 39% − 75%, respectively) in nitrification, but inhibited the denitrification gene abundances (i.e. nirS and nirK abundance up to 21% lower). Pyroligneous vinegar increased the ratio of nosZ/(nirS + nirK), suggesting an increased potential to lower nitrous oxide emissions. Correlation analysis indicated that nitrogen use efficiency correlated positively with AOA and AOB, but negatively with nirS and nirK abundance. Therefore, our study suggests that pyroligneous vinegar could improve the growth of acidophilous plants and increase their nitrogen use efficiency by changing nitrogen cycling related functional genes, and could be a potential soil amendment in protected horticulture.
