Effects of enhanced-efficiency nitrogen fertilizers on soil microbial biomass and respiration in tropical soil under upland rice cultivation
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2021
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While over-use of N fertilizers can suppress microbial biomass, application of urease inhibitors is known to be a
potential way to rebuilt microbial diversity and improve soil functions. However, the hypothesis of this study is
that the application of N fertilizers regardless of the source would increase soil microbial biomass and reduce
soil respiration. A two-year field experiment was conducted to assess the effects of enhanced-efficiency N
sources on soil microbial biomass, and soil respiration. The experiment was set up in a randomized block design
in a 3 × 4 + 1 factorial scheme, with four replicates. Treatments comprised three sources (conventional uncoated
urea, NBPT (N-(n-butyl) thiophosphoric triamide)-treated urea, and polymer-coated urea) and four rates (30, 60,
90 and 120 kg ha-1
) of N, in addition to a control treatment (no fertilizer application). Microbial biomass C
(MBC) and microbial biomass N (MBN), and soil respiration (C-CO 2 and qCO 2 ) were determined in upland rice
rhizosphere in each crop season. Responses of soil microbial properties to N fertilization were dependent on the
N rates, but no significant effect of the N sources was observed. All measured parameters, except MBC in the
first season and C-CO 2 in the second season, were increased with increasing N rates. However, the application of
N higher than 60 kg ha-1 suppressed soil microbial biomass, as well as soil respiration. Therefore, the lack of
response by added urease inhibitors to the N sources indicate that optimizing N rates for upland rice production
is a far more effective option for improving soil microbial community than using enhanced-efficiency N sources.
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Soil microbial activity, Fertilizer efficiency, N rate
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OLIVEIRA, Vinícius Almeida et al. Effects of enhanced-efficiency nitrogen fertilizers on soil microbial biomass and respiration in tropical soil under upland rice cultivation. Journal of Agricultural Science, v. 13, n. 6, 2021. DOI: 10.5539/jas.v13n6p31. Disponível em: https://www.ccsenet.org/journal/index.php/jas/article/view/0/45288. Acesso em: 8 out. 2024.