Different responses of terrestrial soil microbial biomass to the
addition of varied types of nitrogen fertilizers
Atmospheric deposition of nitrogen (N) compounds have significantly
increased worldwide in the recent decades, mainly in the form of
ammonium (NH4+-N), nitrate
(NO3−-N) and urea
(CO(NH2)2). Here, we used meta-analysis
to compare the influence of different N types on terrestrial soil
microbial biomass based on 1585 paired observations from 178 articles.
In all N types, NH4+-N addition
displayed the greatest negative affects on soil microbial biomass (-18.9
%) followed by. NH4NO3 (-7.51 %) and
NO3−-N (-7.26 %).
CO(NH2)2 addition resulted in the
smallest total microbial biomass declines among all N types (-6.99 %).
All the soil microbial characteristics, such as fungi and bacteria,
revealed the same trends across all ecosystems, especially for
arbuscular mycorrhizal fungi, F/B, and G+/G− ratio. In addition, the
response sizes were significantly correlated with the accumulated N
amount (N addition rate × application duration). The results indicated
that the response sizes were significantly N-type dependent.