Use of Enriched 15N Sources to study Soil N Transformations

Author(s):  
Ian R. P. Fillery ◽  
Sylvie Recous
Keyword(s):  
Soil N ◽  
1974 ◽  
Vol 54 (4) ◽  
pp. 403-412 ◽  
Author(s):  
C. A. CAMPBELL ◽  
D. W. STEWART ◽  
W. NICHOLAICHUK ◽  
V. O. BIEDERBECK

Wood Mountain loam was wetted with water or (NH4)2SO4 solution to provide a factorial combination among three moisture and three NH4-N levels. Samples in polyethylene bags were incubated at 2.5-cm depths in fallow, and in an incubator that simulated the diurnal patterns of temperature fluctuation recorded in the field. During the growing season, treatments were sampled regularly for moisture, NO3− and exchangeable NH4-N. Similar determinations were made on in situ samples taken in fallow Wood Mountain loam. The incubator simulated the effects of growing season temperatures on soil N transformations satisfactorily. Pronounced increases or decreases in temperature led to flushes in N mineralization. However, in the 1972 growing season, temperature was suboptimal and temperature changes were generally small. Consequently, when a stepwise multiple regression technique was used to analyze the data, neither ammonification nor nitrification showed a quantitative relationship to temperature. Comparison of the nitrification occurring in laboratory-incubated soils with that occurring in situ led to the conclusion that 70 to 90% of the NO3-N produced in surface soil resulted from wetting and drying. Estimates of potentially ammonifiable soil N(No) and its rate of mineralization (k) were derived from cumulative ammonification by assuming that the laws of first-order kinetics were applicable. In the 10, 15, and 20% moisture treatments the average No was 27, 41, and 82 ppm, respectively. Under the conditions of this study, the time required to mineralize half of No was about 7 wk.


2019 ◽  
Vol 16 (21) ◽  
pp. 4277-4291
Author(s):  
Yanxia Nie ◽  
Xiaoge Han ◽  
Jie Chen ◽  
Mengcen Wang ◽  
Weijun Shen

Abstract. Elevated nitrogen (N) deposition affects soil N transformations in the N-rich soil of tropical forests. However, the change in soil functional microorganisms responsible for soil N cycling remains largely unknown. Here, we investigated the variation in soil inorganic N content, net N mineralization (Rm), net nitrification (Rn), inorganic N leaching (Rl), N2O efflux and N-related functional gene abundance in a tropical forest soil over a 2-year period with four levels of N addition. The responses of soil net N transformations (in situ Rm and Rn) and Rl to N additions were negligible during the first year of N inputs. The Rm, Rn, and Rl increased with the medium nitrogen (MN) and high nitrogen (HN) treatments relative to the control treatments in the second year of N additions. Furthermore, the Rm, Rn, and Rl were higher in the wet season than in the dry season. The Rm and Rn were mainly associated with the N addition-induced lower C:N ratio in the dry season but with higher microbial biomass in the wet season. Throughout the study period, high N additions increased the annual N2O emissions by 78 %. Overall, N additions significantly facilitated Rm, Rn, Rl and N2O emission. In addition, the MN and HN treatments increased the ammonia-oxidizing archaea (AOA) abundance by 17.3 % and 7.5 %, respectively. Meanwhile, the HN addition significantly increased the abundance of nirK denitrifiers but significantly decreased the abundance of ammonia-oxidizing bacteria (AOB) and nosZ-containing N2O reducers. To some extent, the variation in functional gene abundance was related to the corresponding N-transformation processes. Partial least squares path modelling (PLS-PM) indicated that inorganic N contents had significantly negative direct effects on the abundances of N-related functional genes in the wet season, implying that chronic N deposition would have a negative effect on the N-cycling-related microbes and the function of N transformation. Our results provide evidence that elevated N deposition may impose consistent stimulatory effects on soil N-transformation rates but differentiated impacts on related microbial functional genes. Long-term experimentation or observations are needed to decipher the interrelations between the rate of soil N-transformation processes and the abundance or expression of related functional genes.


2020 ◽  
Vol 20 (3) ◽  
pp. 1323-1331 ◽  
Author(s):  
Dianjie Wang ◽  
Zhihong Xu ◽  
Timothy J. Blumfield ◽  
Jacinta Zalucki

2016 ◽  
Vol 121 (6) ◽  
pp. 1409-1419 ◽  
Author(s):  
Jinbo Zhang ◽  
Peng Tian ◽  
Jialiang Tang ◽  
Lei Yuan ◽  
Yun Ke ◽  
...  

Geoderma ◽  
2017 ◽  
Vol 301 ◽  
pp. 42-46 ◽  
Author(s):  
Siyi Liu ◽  
Xiaoping Zhang ◽  
Jun Zhao ◽  
Jinbo Zhang ◽  
Christoph Müller ◽  
...  

2013 ◽  
Vol 29 (2) ◽  
pp. 147-159 ◽  
Author(s):  
Hilton G. T. Ndagurwa ◽  
John S. Dube ◽  
Donald Mlambo

Abstract:This study investigated the effects of mistletoe infection on N cycling in a semi–arid savanna, south-west Zimbabwe. We established five plots (10 × 10 m) which each included three large canopy-dominantAcacia karrootrees infected by one of three mistletoes (Erianthemum ngamicum,Plicosepalus kalachariensisandViscum verrucosum) and non-infectedA. karrootrees. In each plot, we measured litterfall, litter quality (N, phenolics, tannins and lignin), soil nutrient concentrations and N transformations beneath tree canopies. Soil N, P and Ca were greatest beneath trees infected byP.kalachariensisthan beneath non-infected trees. Litterfall and litter N returns were 1.5, 2 and 1.4 times more beneathA. karrootrees infected byE.ngamicum,P.kalachariensisandV. verrucosum, respectively. Mineral N increased with mistletoe infection but did not exceed 20%. Soil N transformations were greater beneath trees infected byE.ngamicum(> 40%), and lower beneath trees infected byP.kalachariensis(<50%) andV.verrucosum(<48%) than beneath non-infectedA. karrootrees. Soil N transformations were negatively correlated with condensed tannins, lignin and lignin : N. We conclude that the improved N concentration can increase resource heterogeneity, which may alter the ecosystem structure and functioning in the semi-arid savanna.


Author(s):  
Naoko Tokuchi ◽  
Muneto Hirobe ◽  
Keisuke Koba

2019 ◽  
Vol 131 ◽  
pp. 166-175 ◽  
Author(s):  
N. Fiorentino ◽  
M.A. Sánchez-Monedero ◽  
J. Lehmann ◽  
A. Enders ◽  
M. Fagnano ◽  
...  

2020 ◽  
Author(s):  
K. Scarlett ◽  
S. Denman ◽  
D. R. Clark ◽  
J. Forster ◽  
E. Vanguelova ◽  
...  

Abstract Tree decline is a global concern and the primary cause is often unknown. Complex interactions between fluctuations in nitrogen (N) and acidifying compounds have been proposed as factors causing nutrient imbalances and decreasing stress tolerance of oak trees. Microorganisms are crucial in regulating soil N available to plants, yet little is known about the relationships between soil N-cycling and tree health. Here, we combined high-throughput sequencing and qPCR analysis of key nitrification and denitrification genes with soil chemical analyses to characterise ammonia-oxidising bacteria (AOB), archaea (AOA) and denitrifying communities in soils associated with symptomatic (declining) and asymptomatic (apparently healthy) oak trees (Quercus robur and Q. petraea) in the United Kingdom. Asymptomatic trees were associated with a higher abundance of AOB that is driven positively by soil pH. No relationship was found between AOA abundance and tree health. However, AOA abundance was driven by lower concentrations of NH4+, further supporting the idea of AOA favouring lower soil NH4+ concentrations. Denitrifier abundance was influenced primarily by soil C:N ratio, and correlations with AOB regardless of tree health. These findings indicate that amelioration of soil acidification by balancing C:N may affect AOB abundance driving N transformations, reducing stress on declining oak trees.


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