Nitrification of ammonium sulphate and urea in an acid red yellow podzolic tea soil in Sri Lanka in relation to soil fertility

Summary Two laboratory incubation experiments were carried out to study the rate of nitrification of ammonium sulphate and urea in an acid red yellow podzolic tea soil. One experiment was with a soil (A) collected from under a good cover of high yielding clonal tea and the other with a soil (B) collected from a bare plot adjoining the tea field. Soil pH was adjusted with calcium carbonate or calcium oxide. Nitrification was appreciable in soil A whereas it was very low in soil B. Elevation of pH substantially increased nitrification in soil A, slightly increased and even depressed nitrification, in certain treatments, in soil B. The difference in the rates of nitrification in the two soils is discussed in relation to soil fertility.     

Effects of addition of varying levels of copper,as oxide or phosphate,on nitrogen mineralisation and nitrification during incubation of a slightly calcareous soil receiving dried blood

Summary The addition of 100, 1000 and 10,000 ppm copper, as oxide or hydrogen phosphate, stimulated nitrogen mineralisation and nitrification during incubation of a sandy loam (0.5% calcium carbonate) treated with 200 ppm N as dried blood. The maximum effects occurred with 1000 ppm added copper and were similar with both sources of added copper. EDTA-extractable copper was higher where copper hydrogen phosphate than where copper oxide had been added.     

Optimization of Bifidobacterium longum growth by use of calcium carbonate-alginate beads

High concentrations of ammonium and sodium ions inhibited Bifidobacterium longum growth more than a high calcium ion concentration. The optimal pH for B. longum growth was determined to be 5.0 due to the lower accumulation of ammonium ion. To reduce the accumulation of ammonium ion and obtain an enhanced growth of B. longum, the pH of the culture containing immobilized calcium carbonate beads was controlled to 5.0 with ammonia water. The concentrations of ammonium, sodium, and calcium ions in the culture were maintained at the desired level. The maximum cell mass increased to 16.8 g/l, 1.23 times higher than cultures without calcium carbonate beads. The number of viable cells in the culture increased to 5.0 × 10¹⁰, 1.67 times more than cultures without calcium carbonate beads.     

Fertilization influences nitrogen dynamics in soils under Dalbergia sissoo

The influence of added ammonium, phosphorus, potassium, and gypsum on net nitrogen mineralization was studied in soil beneath a six-year-old plantation of the N₂-fixing tree Dalbergia sissoo in Pakistan. Soil with and without amendments was placed in polyethylene bags and incubated, buried in the soil, for 30 days. After that time the soil was analyzed and net ammonium and nitrate production and net nitrogen mineralization were calculated. The addition of ammonium stimulated nitrification indicating that the process was substrate limited. The inhibition of nitrification by Nitrapyrin showed that the process is autotrophic in these soils. Gypsum addition lowered soil pH from 8.0 to 7.2 and significantly stimulated ammonification, nitrification and net nitrogen mineralization. The addition of potassium more than tripled the soil K:Na ratio. Net ammonium and nitrate production and net nitrogen mineralization all increased in this treatment. The addition of phosphorus had no significant effect on soil nitrogen dynamics.     

Ammonium exchange and bioregeneration of bio-flocculated zeolite in a sequencing batch reactor

Natural zeolite was added to the sequencing batch reactors to assess its role in ammonium exchange. Even though the biofilm was fully developed on the zeolite surface, ammonium removal and the biological regeneration of the zeolite occurred constantly during the anoxic-fill phase and the reaction phase, respectively. However, the specific nitrification rate of the bio-flocculated zeolite was lower than that observed in the control on account of the limited ammonium release to the liquid phase.     

Measurement of in situ rates of nitrification in sediment

A method has been developed for the measurement of nitrification rates in intact sediment cores without disturbing the concentration gradients of oxygen and ammonium. N-serve (2-chloro-6-trichloromethyl-pyridine), a specific inhibitor of the autotrophic ammonium oxidation, was injected into a 0–2 cm surface layer of the sediment (20 ppm) and added to the water column of sediment cores (5 ppm). N-serve in these concentrations was sufficient to inhibit nitrification, but did not change the rate of ammonium production or incorporation in sediment suspensions, which were incubated aerobically and anaerobically. The ammonium accumulation in cores injected with N-serve was thus equal to the amount of ammonium which was oxidized to nitrate in the control cores. Nitrification rates were in the range of 0–3 mmol N m^{–2 –1}     

The evaluation of enhanced nitrification by immobilized biofilm on a clinoptilolite carrier

This study was conducted to evaluate the effect of clinoptilolite on nitrification in activated sludge (AS), and was focused on a relationship between ammonium exchange capacity of this mineral and improvement of nitrification. In batch experiments, the adsorption property of biofilm-attached clinoptilolite did not show substantial difference from that of natural clinoptilolite, indicating that bioregeneration became completely achieved without any regenerant in the AS. The AS with added clinoptilolite (ZR) was compared to the control AS (CR) when the ratio of chemical oxygen demand (COD) to total kjeldahl nitrogen (TKN) of influent, i.e. C/N ratio, was varied from 3.25 to 7.5 at a hydraulic retention time (HRT) of 3 h. Enhanced nitrification was comparatively observed for the ZR as C/N ratio gradually increased. The results indicated that the clinoptilolite provided a relatively low C/N ratio for nitrifiers, due to ammonium adsorption of this mineral, and consequently nitrification was accelerated.     

Nitrification and Autotrophic Nitrifying Bacteria in a Hydrocarbon-Polluted Soil

In vitro ammonia-oxidizing bacteria are capable of oxidizing hydrocarbons incompletely. This transformation is accompanied by competitive inhibition of ammonia monooxygenase, the first key enzyme in nitrification. The effect of hydrocarbon pollution on soil nitrification was examined in situ. In a microcosm study, adding diesel fuel hydrocarbon to an uncontaminated soil (agricultural unfertilized soil) treated with ammonium sulfate dramatically reduced the amount of KCl-extractable nitrate but stimulated ammonium consumption. In a soil with long history of pollution that was treated with ammonium sulfate, 90% of the ammonium was transformed into nitrate after 3 weeks of incubation. Nitrate production was twofold higher in the contaminated soil than in the agricultural soil to which hydrocarbon was not added. To assess if ammonia-oxidizing bacteria acquired resistance to inhibition by hydrocarbon, the contaminated soil was reexposed to diesel fuel. Ammonium consumption was not affected, but nitrate production was 30% lower than nitrate production in the absence of hydrocarbon. The apparent reduction in nitrification resulted from immobilization of ammonium by hydrocarbon-stimulated microbial activity. These results indicated that the hydrocarbon inhibited nitrification in the noncontaminated soil (agricultural soil) and that ammonia-oxidizing bacteria in the polluted soil acquired resistance to inhibition by the hydrocarbon, possibly by increasing the affinity of nitrifying bacteria for ammonium in the soil.     

Nitrification and autotrophic nitrifying bacteria in a hydrocarbon-polluted soil.

In vitro ammonia-oxidizing bacteria are capable of oxidizing hydrocarbons incompletely. This transformation is accompanied by competitive inhibition of ammonia monooxygenase, the first key enzyme in nitrification. The effect of hydrocarbon pollution on soil nitrification was examined in situ. In a microcosm study, adding diesel fuel hydrocarbon to an uncontaminated soil (agricultural unfertilized soil) treated with ammonium sulfate dramatically reduced the amount of KCl-extractable nitrate but stimulated ammonium consumption. In a soil with long history of pollution that was treated with ammonium sulfate, 90% of the ammonium was transformed into nitrate after 3 weeks of incubation. Nitrate production was twofold higher in the contaminated soil than in the agricultural soil to which hydrocarbon was not added. To assess if ammonia-oxidizing bacteria acquired resistance to inhibition by hydrocarbon, the contaminated soil was reexposed to diesel fuel. Ammonium consumption was not affected, but nitrate production was 30% lower than nitrate production in the absence of hydrocarbon. The apparent reduction in nitrification resulted from immobilization of ammonium by hydrocarbon-stimulated microbial activity. These results indicated that the hydrocarbon inhibited nitrification in the noncontaminated soil (agricultural soil) and that ammonia-oxidizing bacteria in the polluted soil acquired resistance to inhibition by the hydrocarbon, possibly by increasing the affinity of nitrifying bacteria for ammonium in the soil.     

Continuous flow method in soil microbiology

The decomposition of glycine in soil was studied by the continuous flow method. Glycine solution was added continuously to soil samples of different weights, i.e. soil columns of different heights. It was found that the extent of glycine mineralization was related to the weight of the soil. Glycine was nitrified most effectively in the soil sample weighing 30 g., in which 65.8% of the added (91.6% of the retained) glycine nitrogen was oxidized to nitrites and nitrates. No steady state was observed in the rate of nitrite and nitrate formation. The rate of nitrification rose at first, in relation to the weight of the soil, but fell after reaching the maximum. The factor limiting the rate of nitrification was the adsorption of ammonium nitrogen in the soil. By using soil samples of different weights and heights it was found possible to localize the process of ammonia release and the oxidation of ammonia and nitrites in the soil column and to influence the ratio of ammonification and nitrification or of the oxidation of ammonium ions and nitrites.     

Some factors influencing production of sulphate by oxidation of elemental sulphur and thiosulphate in upper horizons of spruce forest soils

Some factors influencing the oxidative activity of upper horizons of spruce forest soils (a mixture of fermentative and humus layers) toward intermediates of the oxidative part of the sulphur cycle were investigated. Preincubation of the soil with added cysteine, sulphide, elemental sulphur or thiosulphate was found to stimulate enzyme systems oxidating any of these compounds. Sulphite and sulphate were ineffective in this respect. The oxidation of elemental sulphur was stimulated by CaCO3, technical urea and high doses of superphosphate and potassium sulphate. It was inhibited by KH2PO4, pure urea, 40 % potassium salt, ammonium nitrate with calcium carbonate and the fertilizer NPK I. It proceeded at the highest rate at approximately 60 % capillary capacity (61 % of mass water content). Oxidation of thiosulphate was stimulated by KH2PO4, pure urea, superphosphate, potassium sulphate and only slightly by the fertilizer NPK I. It was inhibited by CaCO3, 40 % potassium salt and only slightly by ammonium nitrate with calcium carbonate. Potassium chloride, glucose and technical urea were without effect. The oxidation proceeded at the highest rate at 35 % maximal capillary capacity (48 % mass water content).     

Effect of temperature on nitrogen transformation in Hawaiian soils

Summary In a field experiment soil samples buried at the warmer temperature regime nitrified added ammonium faster than soils buried at the cooler temperature regime. Nitrification occurred more rapidly under both regimes in a soil which had developed in a warm climatic zone than in two other soils developed under cooler conditions.The rate of nitrification of added ammonium in soils incubated at 5, 15, 25 and 40°C in the laboratory increased with increase in the temperature up to 25°C in three out of four soils. In the fourth soil nitrification was as active at 40°C as at 25°C. The temperature range for appreciable nitrification to occur in a soil was related to the environmental conditions where the soil was formed.Mineralization of organic nitrogen occurred to a greater extent at 40°C than at three lower incubating temperatures of 5, 15, and 25°C. Rapid and active mineralization was associated with high organic matter and C/N ratio in soils     

Model of ammonia volatilization from calcareous soils

A quantitative model of ammonia volatilization from the calcareous soil uppermost 1-cm layer was developed and tested. The model accounts for the following processes: ammonium-ammonia equilibration in the soil solution, cation exchange between calcium and ammonium which results in ammonium distribution between soil liquid and solid phases, nitrification of dissolved ammonium, distribution of ammonia between liquid and gaseous phases and diffusion of gaseous ammonia in the soil air. The combined effect of various characteristics such as soil pH, cation exchange capacity, water capacity and nitrification rate on ammonia losses from various soil types have been studied. The model was validated against experimental results of ammonia losses from different soils for its use as a predicting tool. The model shows that most of ammonia losses can be explained by the interactive effect of high soil pH and low cation exchange capacity. Computations show increased ammonia volatilization with decreasing soil water capacity. Increasing fertilizer application rate has a small effect on percentage of ammonia losses. Increased nitrification rate and shorter “lag” period of nitrification reduce ammonia losses considerably. Good agreement was obtained between model calculations and experimental results of ammonia volatilization from 13 soils.     

IN VITRO ALLELOPATHIC INHIBITION OF NITRIFICATION BY BALSAM POPLAR AND BALSAM FIR

A soil percolation apparatus was used to study the effect of plant extracts on nitrification. Foliar leachates, leaf extracts, and bud extracts of balsam fir (Abies balsamea) and balsam poplar (Populus balsamifera) were added to the ammonium percolation solution. Color tests and quantitative measurement of residual ammonium and formed nitrate were applied. Foliar leachates of balsam fir strongly inhibited nitrification; leachates of balsam poplar were slightly less inhibitory. Balsam fir needle and balsam poplar dormant bud extracts (5% w/v) completely prevented the oxidation of ammonium. The same estracts (2% w/v) still prevented the oxidation of ammonium to nitrate to a large extent. Once again balsam fir extracts inhibited the process more strongly than balsam poplar. No evidence was obtained for the presence of a specific inhibitor of nitrifier microorganisms.     

Comparative effects of varying levels of chlorides and sulphates of sodium,potassium, calcium,and magnesium on ammonification and nitrification during incubation of soil

Summary The effect of chlorides and sulphates of sodium, potassium, calcium, and magnesium, added at 01.% to 2.0% sodium chloride-equivalent (soil basis), on nitrogen mineralization and nitrification during incubation (3 weeks, 30°C) of soil was studied. For the chloride series the critical level for virtually complete suppression of nitrification was between 0.5% and 1.0% of the added salts. Nitrogen mineralization was reduced only where 1–2% of salts were added. In the sulphate series nitrogen mineralization and nitrification were reduced to a fair extent only by the 2% level of sodium sulphate, the other sulphates having little or no effect on these processes. At some levels the sulphates and chlorides of all cations, except sodium, resulted in a small but significant increase in nitrogen mineralization.     

Nitrite effect on ammonium and nitrite oxidizing processes in a nitrifying sludge

Nitrite accumulation can be undesirable in nitrifying reactors used for the biological elimination of nitrogen from wastewaters because the ammonium oxidation process was seen to be inhibited. There is a need to better understand the effects of nitrite on both ammonium and nitrite oxidizing processes. In this paper, the effect of nitrite on the nitrifying activity of a sludge produced in steady-state nitrification was evaluated in batch cultures. At 25 mg N/l of added nitrite, nitrification was successfully carried out. Addition of higher nitrite concentrations to nitrifying cultures (100 and 200 mg N/l) provoked inhibitory effects on the nitrification respiratory process. Nitrite at 100 and 200 mg N/l induced a significant decrease in the values for nitrate yield (−20% and −34%, respectively) and specific rate of nitrate formation (−26% and −67%, respectively), while the ammonium consumption efficiency kept high and the specific rate of ammonium oxidation did not significantly change. This showed that the nitrite oxidizing process was more sensitive to the presence of nitrite than the ammonium oxidizing process. These results showed that as a consequence of nitrite accumulation in nitrification systems, the activity of the nitrite oxidizing bacteria could be more inhibited than that of the ammonium oxidizing bacteria, provoking a higher accumulation of nitrite in the medium.     

Influence of Protozoa and Nutrient Availability on Nitrification Rates in Subsurface Sediments

Abstract Protozoan abundance, nitrification potential, and related factors in saturated subsurface sediments and the overlying soil were compared at a nonfertilized grassland and an agricultural cropland site. In a 6-week laboratory experiment, DOC, ammonium, and protozoan abundance were manipulated in flasks containing groundwater-sediment slurries. Microbial abundance (protozoa, actively respiring bacteria, and total bacteria) and nutrient concentrations (extractable ammonium and nitrate) were measured. Results from the soil profile analysis showed that protozoan abundance declined with depth at both sites, but significant numbers (392 cells g⁻¹dw) were found in groundwater sediments at the cropland site. Nitrification potential declined with depth at the grassland site and increased with depth at the cropland site. In the laboratory experiment, treatment responses generally were observed within 3 weeks, but had diminished by 6 weeks. Protozoa reduced bacterial populations through the first 3 weeks, but this effect was not significant by week 6. In the cropland sediments, increased net nitrate production occurred in the two reduced protozoa treatments that received ammonium, suggesting that nitrification was occurring and was limited by ammonium. High protozoan abundance in the cropland sediments increased the nitrate flux response, unless DOC was added; in this case, no response occurred. No such responses were recorded in the grassland sediments. Apparently, appreciable nitrification can occur in some groundwater sediments, if sufficient ammonium is present and DOC availability is low. Furthermore, nitrification can be enhanced when protozoan abundance is elevated. Finally, our results suggest that surface land use practices can alter subsurface nitrification rates and microbial community structure. Received: 12 July 1996; Accepted: 2 December 1996     

Nitrification inhibition in a flooded soil by hexachlorocyclohexane and carbofuran

Summary The effect of a commercial granular formulation of hexachlorocyclohexane (HCH) on nitrification in a flooded soil was studied at 10 and 100 ppm a.i. The oxidation of the added ammonium to nitrate was inhibited significantly at 10 ppm and almost completely at 100 ppm, concomitant with a proportional decrease in the, populations of ammonium- and nitrite-oxidising autotrophic bacteria. Of special interest is the synergistic increase in the inhibition of nitrification by a combined application of HCH and carbofuran.     

Effect of various salts on the growth and development of Geotrichum candidum,the causal agent of carrot sour rot

This study evaluated the efficacy of ammonium, calcium, potassium and sodium salts as possible alternatives to synthetic fungicides in the control of Geotrichum candidum, the causal agent of sour rot on carrots. In vitro mycelial growth of G. candidum was completely halted by ammonium bicarbonate and carbonate; calcium oxide; potassium benzoate, carbonate and sorbate; sodium benzoate, carbonate and fluoride (2% w/v). Potassium and sodium bicarbonate also reduced mycelial growth by 77.78% and 90.60%, respectively, and the difference between the effects of sodium bicarbonate and the first group of salts was not statistically significant (p < 0.05). With the exception of potassium and sodium bicarbonate, the above‐mentioned salts also halted or strongly reduced arthrospore germination. Potassium bicarbonate, and sodium bicarbonate, acetate and propionate significantly increased conidiation (p < 0.05). Of all the salts tested in vitro, only ammonium bicarbonate and carbonate, calcium oxide and sodium fluoride were toxic to G. candidum. In in vivo studies, all the calcium salts tested (acetate, chloride, citrate, formate, lactate, oxide, propionate and silicate), several of the sodium salts (acetate, bicarbonate, chloride and fluoride) and potassium bicarbonate exhibited both protective and curative activity against G. candidum, significantly reducing the severity of sour rot in comparison to pathogen‐inoculated controls (p < 0.05). Although no curative was observed with ammonium bicarbonate, ammonium carbonate, potassium carbonate, potassium chloride, sodium carbonate or sodium citrate, these salts also demonstrated significant protective activity against sour rot when compared to controls (p < 0.05). In sum, the study findings show that all of the selected salts may be used to control carrot sour rot, except for sodium fluoride, which exhibited phytotoxicity to carrots.     

Control of pH and its Effect on Ammonium Utilization by Nitrate Reductase Deficient Plants,Cells, and Protoplasts of Nicotiana tabacum

Nitrate reductase deficient plants of Nicotiana tabacum were unable to utilize ammonium efficiently unless the medium was buffered against excessive acidity accumulation. In addition to succinate, calcium carbonate, MES and phosphate buffers allowed plants to utilize ammonium efficiently. Similar observations were made regarding callus derived from stem tissue of these plants. Plants could be grown in compost, in a physiological state suitable for protoplast isolation, when watered with nutrient solutions containing NH₄NO₃ and MES buffer. Protoplast division and proliferation to the stage of plant regeneration was possible using Murashige and Skoog (1962) basal medium buffered with succinate, calcium carbonate or MES but not phosphate.