Open AccessEffects of Enhanced-Efficiency Nitrogen Fertilizers on Soil Microbial Biomass and Respiration in Tropical Soil Under Upland Rice Cultivation
Author(s) -
Vinícius Almeida Oliveira,
Eliana Paula Fernandes Brasil,
Welldy Gonçalves Teixeira,
Felipe Corrêa Veloso dos Santos,
Átila Reis da Silva
Publication year - 2021
Publication title -
journal of agricultural science
Language(s) - English
Resource type - Journals
eISSN - 1916-9760
pISSN - 1916-9752
DOI - 10.5539/jas.v13n6p31
Subject(s) - biomass (ecology) , soil respiration , rhizosphere , agronomy , chemistry , urease , urea , respiration rate , randomized block design , respiration , nitrogen , environmental science , soil water , biology , botany , soil science , bacteria , genetics , organic chemistry
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-CO2 and qCO2) 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-CO2 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.