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Nitrification Inhibition in Soil and Ecosystem Functioning An Overview
F. Azam,S. Farooq
Pakistan Journal of Biological Sciences , 2003,
Abstract: Form (NH4 or NO3) and availability of N has significant implications to the functioning and sustainability of agroecosystems. Most of the fertilizer nitrogen (N) applied to agricultural soils is in the form of NH4 or NH4-forming fertilizers. This form of N is rapidly oxidized to NO3 by nitrifying microorganisms leading to significant losses of N through NO3-leaching and denitrification. Both denitrification and NO3-leaching have environmental implications and economic concerns. Strategies have therefore been sought to regulate the process of nitrification leading to its complete or partial inhibition. Indeed, climax ecosystems are developed in such a way that the process of nitrification is already fairly inhibited. This paper presents an overview on: I) the process of nitrification, ii) microorganisms involved, iii) the implications of nitrification and nitrification inhibition to ecosystem functioning and finally iv) the methods to inhibit nitrification.
Nitrification inhibition of dicyandiamide on urea in the red soil of different textures

YANG Chun-Xia,LI Yong-Mei,

中国生态农业学报 , 2006,
Abstract: The nitrification inhibition of dicyandiamide on urea in the red soil of different textures was studied.The results show that the hydrolyzation rate of urea in the loam soil and the clay soil is quicker than that in the sandy loam soil,and dicyandiamide slows down the nitrification of urea in the loam soil and clay soil but improves it in the sandy soil.The transformation of urea in the sandy soil by adding or without adding dicyandiamide needs 49 days.It requires 35 days in the clay while it is prolonged for 14 days after adding dicyandiamide.However the nitrification time of urea in the loam needs further research.
Nitrification as Ecotoxicological Endpoint in Risk Assessment of Soil Heavy Metal Pollution

XIA Yue,ZHU Yong-guan,

生态毒理学报 , 2007,
Abstract: The establishment of standards for estimating soil quality is an important area in studies of soil pollution. At present, there are some ecotoxicological endpoints for assessing the risk in soil microbial process, including soil biomass, soil respiration, enzyme activity, nitrification and N fixation etc. Mitigating the problems associated with heavy metal pollution of soils is our important subject in environmental field. Because of its sensitivity to heavy metal and the key role in global N cycle, nitrification has been widely used in estimating heavy metal toxicity. This paper summarizes recent studies in the mechanism, application and the factors affecting nitrification.
Comparative studies on soil nitrification inhibition by pyridine compounds

LI Zhao-Jun,SONG A-Lin,FAN Fen-Liang,LIANG Yong-Chao,

中国生态农业学报 , 2012,
Abstract: Nitrification inhibition is a well-established fertilizer management that improves fertilizer use efficiency (FUE) in crop production aimed at enhanced profitability, crop quality and healthy environment. As a nitrification inhibitor, pyridine compound has been used for stabilization of fertilizer nitrogen (N) for more than 20 years now. However, pyridine compound represents a broad class of heterocyclic N compounds whose activity as nitrification inhibitors appears to be impacted by Cl and/or trichloromethl sub-stitution on C atoms immediately adjacent to the N ring. In addition, the solubility of pyridine compounds in water is very low; which decreases nitrification inhibitory activity. To prove nitrification inhibitory effects, 2-chloro-6(3-chloromethylthiazole)-sulfate, 2-chloro-6(3-chloromethylthiazole)-chloride, pyridine compounds mixture and pyridine X compounds were investigated for inhibi-tory effects on nitrification of fluvo-aquic soil, red soil and paddy soil using laboratory microcosm experiments. The results showed that nitrate contents in soils treated with pyridine compounds were significantly lower than those of the control. Nitrification inhibi- tion rate range was 2.91%~91.92%. Inhibitory effect of pyridine compounds on soil nitrification increased before 21 d, after which it decreased, with peak effect on 21st d. Differences were noted among inhibitory effects of different pyridine compounds. The effects of 2-chloro-6(3-chloromethylthiazole)-chloride were much stronger than those of other pyridine compounds. Differences were also noted in inhibitory effects of pyridine compounds on nitrification in fluo-aquic soil, red soil and paddy soil. Inhibitory effects of pyri-dine compounds in the different soils were in the order of: fluvo-aquic soil > paddy soil > red soil. Based on soil type, pyridine com-pound inhibition effect on nitrification increased with increasing application rate the compounds.
The Inhibition of Bean Plant Metabolism by Cd Metal and Atrazine: I. The Effect of Atrazine with Cd Metal on Growth, Photosynthesis, Nutritional Level and Rhizosphere of Soil  [PDF]
Rafia Azmat,Yasmeen Akhtar,Rukhsana Talat,Fahim Uddin
Biotechnology , 2005,
Abstract: Sublethal atrazine concentration with toxic Cd (cadmium) metal induced, general inhibition on growth, photosynthesis and nutritional level of bean plant. Progressive reduction in protein, amino acid and carbohydrate synthesis were associated with increasing herbicide concentration at all experimental periods. Nodulation failed to occur in roots of leguminous plant. The rhizosphere was found to be affected and colonies of helpful organism were observed in which Rhizobium species were not isolated from the roots. The results of these investigations allowed me to draw a conclusion that soil enriched with heavy metal kill the microbial life. Therefore they cannot degradate the atrazine herbicide, which is highly toxic to photosynthetic processes of the plant and translocated to the tips of leaves. But soil enriched with toxic metal was effected on the microbial life. This causes the lowering of the soil ability in mitigation of the dangerous herbicide activity.
Effects of lignin on nitrification in soil
HUANG Yi-zong,FENG Zong-wei,ZHANG Fu-zhu,LIU Shu-qin,
HUANG Yi-zong
,FENG Zong-wei,ZHANG Fu-zhu,LIU Shu-qin

环境科学学报(英文版) , 2003,
Abstract: The effects of two lignins isolated from black liquor from pulping process on nitrification in soils after addition of urea, (NH4)2SO4 and (NH4)2HPO4 were investigated by incubation at 20 or 30 degrees C for 7 or 14 d. The effects of lignin on nitrous oxide emissions from soil were also determined. Results showed that both lignins were more effective for inhibiting nitrification of NH4(+)-N as (NH4)2SO4 or (NH4)2HPO4 as compared to urea-N. The effectiveness of lignin on nitrification was markedly affected by different soil type and temperature. Nitrous oxide emissions from soil declined when lignin was used. Urea plus 20 and 50 g/kg lignin reduced N2O emissions by about 83% and 96%. respectively, while (NH4)2HPO4 plus 20 and 50 g/kg lignin respectively reduced emissions by 83% and 93%. Because of its low cost and nonhazardous characteristics, lignin has potential value as a fertilizer amendment to improve N fertilizer efficiency.
Biodegradation of plastics in soil and effects on nitrification activity. A laboratory approach.  [PDF]
Giulia Bettas Ardisson,Francesco Degli-Innocenti
Frontiers in Microbiology , 2014, DOI: 10.3389/fmicb.2014.00710
Abstract: The progressive application of new biodegradable plastics in agriculture calls for improved testing approaches to assure their environmental safety. Full biodegradation (≥ 90%) prevents accumulation in soil, which is the first tier of testing. The application of specific ecotoxicity tests is the second tier of testing needed to show safety for the soil ecosystem. Soil microbial nitrification is widely used as a bioindicator for evaluating the impact of chemicals on soil but it is not applied for evaluating the impact of biodegradable plastics. In this work the International Standard test for biodegradation of plastics in soil (ISO 17556, 2012) was applied both to measure biodegradation and to prepare soil samples needed for a subsequent nitrification test based on another International Standard (ISO 14238, 2012). The plastic mulch film tested in this work showed full biodegradability and no inhibition of the nitrification potential of the soil in comparison with the controls. The laboratory approach suggested in this Technology Report enables (i) to follow the course of biodegradation, (ii) a strict control of variables and environmental conditions, (iii) the application of very high concentrations of test material (to maximize the possible effects). This testing approach could be taken into consideration in improved testing schemes aimed at defining the biodegradability of plastics in soil.
The Inhibition of Bean Plant Metabolism by Cd Metal and Atrazine III: Effect of Seaweed Codium iyengarii on Metal, Herbicide Toxicity and Rhizosphere of the Soil  [PDF]
Rafia Azmat,Aliya Hayat,Tanveer Khanum,Rukhsana Talat
Biotechnology , 2006,
Abstract: A seaweed-dried powder of Codium iyengarii was used to investigate the effect on bean plants. These cultivated in metal contaminated and atrazine herbicide environment. The use of seaweed increased the growth of seedlings under toxicity of metal and herbicide. Seaweed contains all trace elements and major and minor plant nutrients such as alganic acid, vitamins, auxins, gibberllins and antibiotics. Results were interpreted in relation with metabolic activity of plant, bioremediation of atrazine and soil rhizosphere. It was observed that seaweeds containing alganic acid act as a soil conditioner, which improved the water holding characteristics of soil and helped in the formation of crumb structure. The toxicity of heavy metal Cd in conjunction with atrazine herbicide was inhibited up to 100 ppm of metal concentration. Significant improvement in seed germination, morphology and physiological processes were observed. Seaweeds helps in improving the rhizosphere of the contaminated soil which results in the bioremediation of atrazine by soil bacteria. This can be attributed with the growth of the plant in heavy metal contaminated environment and also controls the toxicity of trizine herbicide. While an increase in the concentration of Cd metal shows that it retarded the growth of the bean plant in the presence of seaweeds too.
Nitrification inhibition and dose-dependent effect of dicyandiamide on sandy, loamy and clayey soils
DCD 在不同质地土壤上的硝化抑制效果和剂量效应研究

LIU Qian,CHU Gui-Xin,LIU Tao,WANG Jian,YE Jun,WANG Fei,LIANG Yong-Chao,

中国生态农业学报 , 2011,
Abstract: Ammonium and nitrate are the main forms of available nitrogen (N) for plant. Nitrate is the dominant form of N in upland soils in arid regions. However, nitrate can easily leach through soil profiles. Furthermore, N can easily be lost in the form of NOx via (de)nitrification. Inhibiting the processes of nitrification in soil through nitrification inhibitors is therefore critical for optimizing soil NH4+/NO3- ratio and improving the efficiency of N fertilizers. As one of the most common nitrification inhibitors, dicyandiamide (DCD) was applied at different rates (0%, 1.0%, 2.0%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 6.0% and 7.0% of applied N) in this study. And incubation experiment was conducted in sandy, loamy and clayey desert soils at 25 oC to investigate the inhibition effect, dose-dependent effects of DCD on soil nitrification in arid regions. The study may further enhance our existing knowledge on the mechanisms of DCD inhibited nitrification. The results showed that during 30 days of incubation, DCD exhibited significant inhibition effects on nitrification in all the tested soil types. Nitrification inhibition rates were 96.5%~99.4% in sandy soil, 66.9%~85.6% in clayey soil and 49.3%~79.4% in loamy soil. For the three soil types, DCD nitrification inhibition efficacy was in the following order: sandy soil > clayey soil > loamy soil. When DCD application rate increased from 1.0% to 7.0% of applied nitrogen, nitrate concentration in sandy soil merely increased from 1.9 to 10.7 mg·kg-1. This suggested that DCD dose did not significantly affect nitrification in sandy soils. However, soil nitrate concentration in loamy and clayey soils decreased sharply with increasing rates of DCD, indicating significant dose effect on soil nitrification. In conclusion, DCD significantly inhibited soil nitrification in calcareous desert soils. The recommended optimum application rates of DCD in sandy, clayey and loamy soils were 6.0%, 7.0% and 7.0% of applied nitrogen, respectively.
Brachiaria species affecting soil nitrification
Fernandes, Adalton Mazetti;Andrade, Gabriel José Massoni de;Souza, Emerson de Freitas Cordova de;Rosolem, Ciro Antonio;
Revista Brasileira de Ciência do Solo , 2011, DOI: 10.1590/S0100-06832011000500024
Abstract: nitrification can lead to substantial losses of the applied n through nitrate leaching and n2o emission. the regulation of nitrification may be a strategy to improve fertilizer n recovery and increase its agronomic efficiency. the objective of this study was to evaluate the inhibiting capacity of nitrification in soil by brachiaria species. the greenhouse experiment was conducted using pots with 10 dm3 of a red latosol sample. the treatments consisted of the cultivation of three forage species (brachiaria brizantha, b. ruziziensis and b. decumbens) and four n rates (0, 100, 200, and 300 mg/pot), and the control (without plants). in the absence of the forage plants, all n fertilization levels raised the n-no3- soil levels, as a result of nitrification. the mineralization of organic matter supplied much of the n requirement of the forage plants and nitrification was influenced in the rhizosphere of b. brizantha; however, this effect was not high enough to alter the n-nh4+ level in the total soil volume of the pot.
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