Nitrogen transformations in a soil of the Lower Burdekin, Queensland. 2. Laboratory incubation studies

1979 ◽  
Vol 19 (101) ◽  
pp. 739 ◽  
Author(s):  
RE Reid ◽  
SA Waring
Keyword(s):  
Soil Water ◽  
Low Ph ◽  
Nitrogen Transformations ◽  
Laboratory Incubation ◽  
Pasture Soil ◽  
Nitrate Production ◽  
Incubation Experiments ◽  
Net Mineralization ◽  
Initial Ph ◽  
Nitrification And Denitrification

Two laboratory incubation experiments were carried out to investigate the relation between soil water, Eh 7, nitrification and denitrification and to examine the relation between pH and nitrification. Samples were incubated for 16 days under aerobic and waterlogged conditions with 50 mg N kg-1 of added nitrate or ammonium. Apparent denitrification on waterlogging was rapid with 50% of nitrate disappearing in three days, but the presence of more than 7 mg N kg-1 as nitrate prevented Eh, falling below 270 mV. An initial wetting to 0.1 bar tension after drying and grinding caused apparent denitrification but a subsequent wetting to the same tension did not. If high nitrate levels occurred in the field, denitrification losses would be important. Net mineralization and nitrification were independent of soil water in the range 2 to 30% gravimetric. Samples of a pasture soil of initial pH about 4.2 were incubated aerobically with added ammonium and increasing amounts of K2CO3 to increase pH. Nitrate production increased with increasing pH and the relation between pH and nitrate production changed between pH 5.0 and 5.1. Denitrification losses from ammonium-containing fertilizers on waterlogging will be reduced if low pH has inhibited nitrification.

NITROGEN TRANSFORMATIONS NEAR UREA IN SOIL WITH DIFFERENT WATER POTENTIALS

1988 ◽  
Vol 68 (3) ◽  
pp. 569-576 ◽  
Author(s):  
YADVINDER SINGH ◽  
E. G. BEAUCHAMP
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Incubation Period ◽  
Relative Rate ◽  
Soil Water Potential ◽  
Nitrification Inhibitor ◽  
Silt Loam ◽  
Nitrogen Transformations ◽  
Water Potentials ◽  
Initial Soil

Two laboratory incubation experiments were conducted to determine the effect of initial soil water potential on the transformation of urea in large granules to nitrite and nitrate. In the first experiment two soils varying in initial soil water potentials (− 70 and − 140 kPa) were incubated with 2 g urea granules with and without a nitrification inhibitor (dicyandiamide) at 15 °C for 35 d. Only a trace of [Formula: see text] accumulated in a Brookston clay (pH 6.0) during the transformation of urea in 2 g granules. Accumulation of [Formula: see text] was also small (4–6 μg N g−1) in Conestogo silt loam (pH 7.6). Incorporation of dicyandiamide (DCD) into the urea granule at 50 g kg−1 urea significantly reduced the accumulation of [Formula: see text] in this soil. The relative rate of nitrification in the absence of DCD at −140 kPa water potential was 63.5% of that at −70 kPa (average of two soils). DCD reduced the nitrification of urea in 2 g granules by 85% during the 35-d period. In the second experiment a uniform layer of 2 g urea was placed in the center of 20-cm-long cores of Conestogo silt loam with three initial water potentials (−35, −60 and −120 kPa) and the soil was incubated at 15 °C for 45 d. The rate of urea hydrolysis was lowest at −120 kPa and greatest at −35 kPa. Soil pH in the vicinity of the urea layer increased from 7.6 to 9.1 and [Formula: see text] concentration was greater than 3000 μg g−1 soil. There were no significant differences in pH or [Formula: see text] concentration with the three soil water potential treatments at the 10th day of the incubation period. But, in the latter part of the incubation period, pH and [Formula: see text] concentration decreased with increasing soil water potential due to a higher rate of nitrification. Diffusion of various N species including [Formula: see text] was probably greater with the highest water potential treatment. Only small quantities of [Formula: see text] accumulated during nitrification of urea – N. Nitrification of urea increased with increasing water potential. After 35 d of incubation, 19.3, 15.4 and 8.9% of the applied urea had apparently nitrified at −35, −60 and −120 kPa, respectively. Nitrifier activity was completely inhibited in the 0- to 2-cm zone near the urea layer for 35 days. Nitrifier activity increased from an initial level of 8.5 to 73 μg [Formula: see text] in the 3- to 7-cm zone over the 35-d period. Nitrifier activity also increased with increasing soil water potential. Key words: Urea transformation, nitrification, water potential, large granules, nitrifier activity, [Formula: see text] production

scholarly journals Oxygen isotope fractionation during N<sub>2</sub>O production by soil denitrification

2016 ◽  
Vol 13 (4) ◽  
pp. 1129-1144 ◽  
Author(s):  
Dominika Lewicka-Szczebak ◽  
Jens Dyckmans ◽  
Jan Kaiser ◽  
Alina Marca ◽  
Jürgen Augustin ◽  
...  
Keyword(s):  
Oxygen Isotope ◽  
Soil Water ◽  
Isotope Effect ◽  
Isotope Exchange ◽  
Isotope Fractionation ◽  
Isotope Effects ◽  
N2o Production ◽  
Oxygen Isotope Fractionation ◽  
Oxygen Isotope Exchange ◽  
Incubation Experiments

Abstract. The isotopic composition of soil-derived N2O can help differentiate between N2O production pathways and estimate the fraction of N2O reduced to N2. Until now, δ18O of N2O has been rarely used in the interpretation of N2O isotopic signatures because of the rather complex oxygen isotope fractionations during N2O production by denitrification. The latter process involves nitrate reduction mediated through the following three enzymes: nitrate reductase (NAR), nitrite reductase (NIR) and nitric oxide reductase (NOR). Each step removes one oxygen atom as water (H2O), which gives rise to a branching isotope effect. Moreover, denitrification intermediates may partially or fully exchange oxygen isotopes with ambient water, which is associated with an exchange isotope effect. The main objective of this study was to decipher the mechanism of oxygen isotope fractionation during N2O production by soil denitrification and, in particular, to investigate the relationship between the extent of oxygen isotope exchange with soil water and the δ18O values of the produced N2O. In our soil incubation experiments Δ17O isotope tracing was applied for the first time to simultaneously determine the extent of oxygen isotope exchange and any associated oxygen isotope effect. We found that N2O formation in static anoxic incubation experiments was typically associated with oxygen isotope exchange close to 100 % and a stable difference between the 18O ∕ 16O ratio of soil water and the N2O product of δ18O(N2O ∕ H2O)  =  (17.5 ± 1.2) ‰. However, flow-through experiments gave lower oxygen isotope exchange down to 56 % and a higher δ18O(N2O ∕ H2O) of up to 37 ‰. The extent of isotope exchange and δ18O(N2O ∕ H2O) showed a significant correlation (R2 = 0.70, p <  0.00001). We hypothesize that this observation was due to the contribution of N2O from another production process, most probably fungal denitrification. An oxygen isotope fractionation model was used to test various scenarios with different magnitudes of branching isotope effects at different steps in the reduction process. The results suggest that during denitrification, isotope exchange occurs prior to isotope branching and that this exchange is mostly associated with the enzymatic nitrite reduction mediated by NIR. For bacterial denitrification, the branching isotope effect can be surprisingly low, about (0.0 ± 0.9) ‰, in contrast to fungal denitrification where higher values of up to 30 ‰ have been reported previously. This suggests that δ18O might be used as a tracer for differentiation between bacterial and fungal denitrification, due to their different magnitudes of branching isotope effects.

scholarly journals Effect of Salinity on Soil Respiration and Nitrogen Dynamics

2013 ◽  
Vol 20 (3) ◽  
pp. 519-530 ◽  
Author(s):  
Wen-Zhi Zeng ◽  
Chi Xu ◽  
Jing-Wei Wu ◽  
Jie-Sheng Huang ◽  
Tao Ma
Keyword(s):  
Soil Respiration ◽  
Soil Salinity ◽  
Nitrate Nitrogen ◽  
Threshold Value ◽  
Salinity Level ◽  
Soil Parameters ◽  
Incubation Experiments ◽  
Nitrogen Concentrations ◽  
Nitrification And Denitrification ◽  
Variation Tendency

Abstract A facility of BaPS (Barometric Process Separation) and indoor incubation experiments were used to determine the effect of soil salinity on soil respiration and nitrogen transformation. The rates of soil respiration, gross nitrification, denitrification, ammonium and nitrate nitrogen concentrations and relevant soil parameters were measured. Results showed that soil respiration and nitrification and denitrification rates were all affected by soil salinity. Furthermore, the effect of soil salinity level on nitrification and denitrification rates had a threshold value (EC1:5 = 1.13 dS/m). When soil salinity level was smaller to this threshold value, the rates of nitrification and denitrification increased with soil salinity while they were reduced when soil salinity level was larger than the threshold value. Moreover, the changing law of soil respiration rate with soil salinity was similar with the nitrification and denitrification rates while the variation tendency was opposite. In addition, the transformation form urea to ammonium and nitrate nitrogen was also reduced with the increase of soil salinity and the reduced effect could be expressed by exponential functions.

Scaling methane oxidation: From laboratory incubation experiments to landfill cover field conditions

2011 ◽  
Vol 31 (5) ◽  
pp. 978-986 ◽  
Author(s):  
Tarek Abichou ◽  
Koenraad Mahieu ◽  
Jeff Chanton ◽  
Mehrez Romdhane ◽  
Imane Mansouri
Keyword(s):  
Methane Oxidation ◽  
Field Conditions ◽  
Landfill Cover ◽  
Laboratory Incubation ◽  
Incubation Experiments

Synergistic Degradation of Acid Scarlet Dyeing Wastewater by the Ultrasound/Fenton Method

2013 ◽  
Vol 448-453 ◽  
pp. 34-37
Author(s):  
Tong Liu ◽  
Feng Wei He ◽  
Ya Qin Zhang
Keyword(s):  
Degradation Rate ◽  
Low Ph ◽  
Mass Ratio ◽  
Dyeing Wastewater ◽  
Fenton Reagent ◽  
Initial Concentration ◽  
A Value ◽  
Ultrasonic Technology ◽  
Initial Ph ◽  
Synergistic Degradation

Degradation of simulated acid scarlet (GR) wastewater by ultrasonic technology , Fenton reagentoxidation , and a combination of the two processes was studied. It was found that extent of degradation by ultrasonic technology or Fenton reagent oxidation alone was poor , with values of 4 % and 40 % respectively. The extent of degradation was significantly enhanced when the two processes were combined , with a value of up to 90 % , which shows that these two processes have a good synergistic effect and can shorten the reaction time.Also discussed the initial concentration, initial pH, Fe2+ and H2O2 dosage and other factors on the degradation of acid scarlet. The results show that the degradation rate of pH significant effect on the low pH is conducive to degradation. Degradation rate with the dosage of H2O2 and FeSO4 temperature increased, but when acid scarlet with H2O2 and Fe2+ the mass ratio of 100:15:41, the degradation rate reached 96.6%.

MINERALIZATION OF UREA–FORMALDEHYDE COMPOUNDS AT DIFFERENT pH LEVELS AND TEMPERATURES

1964 ◽  
Vol 44 (1) ◽  
pp. 131-136 ◽  
Author(s):  
J. Basaraba
Keyword(s):  
Incubation Period ◽  
Total Nitrogen ◽  
Main Product ◽  
Urea Formaldehyde ◽  
Growing Season ◽  
Nitrate Production ◽  
Laboratory Results ◽  
Initial Ph ◽  
Different Temperatures

Mineralization of urea-form fertilizer materials was studied in soils at two different pH levels and five different temperatures. Results show that the nitrogenous materials decomposed very slowly but progressively throughout the incubation period of 14 weeks, and that nitrate was the main product formed. The rates of nitrate production from the urea-form compounds were, in general, from 2 to 5% higher in soil with an initial pH 5.7 than in soil having an initial pH 7.0. At the end of the incubation period, the quantities of nitrate formed from the two urea-form compounds were about equal, amounting to 20, 28, 40, 50, and 58% of the total nitrogen added at 10, 15, 20, 25, and 30 °C respectively. The laboratory results suggested that the urea-form materials studied here could be of only limited value to plants if applied to soils with temperatures below 15 °C during the growing season.

scholarly journals Density Effects on Soil-Water Characteristics, Soil-Gas Diffusivity, and Emissions of N2 O and N2 from a Re-packed Pasture Soil

2019 ◽  
Vol 83 (1) ◽  
pp. 118-125 ◽  
Author(s):  
Deepagoda T. K. K. Chamindu ◽  
T. J. Clough ◽  
S. M. Thomas ◽  
N. Balaine ◽  
B. Elberling
Keyword(s):  
Soil Water ◽  
Soil Gas ◽  
Density Effects ◽  
Water Characteristics ◽  
Gas Diffusivity ◽  
Pasture Soil
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