Mineralization Of Organic Nitrogen Research Articles

Rate of soil acidification under wheat in a semi-arid environment

The rate of acidification under wheat in south-eastern Australia was examined by measuring the fluxes of protons entering and leaving the soil, using the theoretical framework of Helyar and Porter (1989). Monthly proton budgets were estimated for the root zone (0–90 cm layer) and for the 0–25 and 25–90 cm layers. After an annual cycle, the root zone was alkalinized by 0.5 to 3.1 kmol OH- ha-1. The alkalinity originated from the mineralization of the organic anions contained in the organic matter. The budget was near neutrality in the 0–25 cm layer (range: −1.0 to 1.4 kmol H+ ha-1), whereas there was net alkalinization in the 25–90 cm layer (1.7 to 2.3 kmol OH- ha-1). In the 0–25 cm layer, the acidity produced in autumn by mineralization of organic nitrogen was counterbalanced by the alkalinity released from crop residues. The main acidifying factor in this layer was leaching of NO3 - during early winter (2.4 kmol H+ ha-1). Nitrate added through leaching was the main alkalinizing factor in the 25–90 cm layer, as added NO3 - was taken up by the roots or denitrified in this layer. Urea fertilization had almost no effect on the rate of acidification, as little NO3 - was leached out of the root zone. The factors acidifying the soil under wheat were limited in this environment because of the small amout of NO3 - leached and the retention of the crop residues.

Organic nitrogen mineralization in temperate humid-zone soils after two and six weeks of aerobic incubation

The N mineralization rate in 11 soils was studied by aerobic incubation at 28°C and at a moisture content of 75% of field capacity for 2 weeks (short term) and 6 weeks (medium term). Relationships between the N mineralization indices for each period were evaluated. Ammonification largely predominated during the first 2 weeks of incubation, whereas nitrification was the predominant process between weeks 2 and 6. The net N mineralized in the different soils varied from 0 to 2.85% of the organic N after 2 weeks of incubation and from 0.32 to 3.36% of the organic N after 6 weeks of incubation, the mean values for each period being 0.82 and 1.51% of the organic N, respectively. The quantities of NHinf4sup+-N, NOinf3sup--N, and total inorganic N produced and the percentage of organic N mineralized after 2 weeks of incubation were highly and positively correlated with the coresponding values after 6 weeks of incubation. These results showed that either length of incubation could be used to determine the potential N mineralization capacity of the soils. Information obtained from two incubation periods was largely supplementary for the kinetic study of N mineralization, ammonification, and nitrification; therefore a medium-term incubation with intermediate measurements of N mineralization over a short term may be more useful than a single measurement using either of the two incubation periods.

Nitrification in the Hyporheic Zone of a Desert Stream Ecosystem

Nitrification in the hyporheic zone of Sycamore Creek, a Sonoran Desert stream, was examined, focusing on the association between respiration and nitrate production. Subsurface respiration in Sycamore Creek is highest in regions of hydrologic downwelling where organic matter derived from the stream surface is transported into the hyporheic zone. Similarly, nitrification was closely related to hydrologic exchange between the surface and hyporheic zone. Nitrification in downwelling regions averaged 13.1 μ gNO₃-N· L sediments^-1· h^-1 compared with 1.7 μ gNO₃-N· L sediments^-1· h^-1 in upwelling regions. Hyporheic respiration also varies temporally as a result of flash floods which scour and remove algae from the stream and thus reduce the pool of organic matter to support subsurface metabolism. Nitrification was also significantly affected by flooding; nitrification increased from an average of only 3.0 μ gNO₃-N· L sediments^-1· h^-1 immediately following floods to 38.5 μ gNO₃-N· L sediments^-1· h^-1 late in succession. Nitrification was significantly correlated with hyporheic respiration, supporting the hypothesis that nitrification is fueled by mineralization of organic nitrogen to ammonium. The coupling between subsurface respiration and nitrification is one step in a cyclic interaction between surface and hyporheic zones and serves to transform nitrogen from an organic to inorganic form.

Modelling Nitrate Output from Agricultural Watersheds Using a Hydrological Model

Abstract A distributed area model called CEQNIT (CEQUEAU-NITRATE) to predict nitrate concentration and load from agricultural watersheds has been developed. The model application requires that the watershed be divided into partial squares. At partial-square scale, the model simulates nitrogen reactions within the soil and nitrate leaching. Nitrogen budget in the CEQNIT model includes the leaching of nitrate, plant uptake, denitrification, mineralization of organic nitrogen, immobilisation, nitrification, input by fertilizer and precipitation. Nitrogen dynamics were simulated as first-order kinetic reactions, and the influence of soil temperature and moisture were included. The model requires input from the CEQUEAU hydrological model that provides temporal and spatial estimation of flow discharge over the watershed. Using two-year data from a small agricultural watershed (78 ha), the model was calibrated with first-year data and tested with the second-year data. Results obtained from this study showed that the model was able to reproduce the seasonal nitrate fluctuations accurately.

Transformations of nitrogen fertilizers in Brazilian Amazonia soils

We have compared the effect of 15N urea and 15N ammonium sulfate on the process of stabilization in organic matter and mineralization in three soils of central Amazonia, classified as Oxisol, Ultisol, and low‐humic gley. During the first month of incubation in the laboratory, the nitrogen fertilizer amendment slightly increased mineralization of organic nitrogen in both acid soils (Oxisol and Ultisol). In these soils, 60% of the nitrogen added was recovered as NH4 + after 2 months incubation, while in the low‐humic gley soil, 50% of the applied nitrogen was nitrified. The incorporation of 15N fertilizer in the organic matter of the latter soil was higher (30%) than in the acid soils. Incorporation in the acid soils, though low, was more important for N derived from urea than ammonium sulfate. For the Oxisol, nitrogen incorporation in organic matter values varied between 12% and 19%, and 7–9% for the Ultisol.

Mineralization of Soil Organic Nitrogen and Nitrogen Absorption by Rice Plant as Affected by Drying Duration

Mineralization of Soil Organic Nitrogen and Nitrogen Absorption by Rice Plant as Affected by Drying Duration

Case Studies on Nitrate Leaching in Arable Fields of Organic Farms

ABSTRACT Nitrogen supply of crops on organic farming systems mainly depends on mineralization of soil organic matter nitrogen. Mineralization was studied by taking soil samples from 30 plots in the crop rotation of two organic farms at intervals of 7 to 14 days during the growing season. On fallow plots net-mineralization alternated with net-immobilization three times from April to November. These soil inherent dynamics were modified by cultivation and the growing cycles of the different crops. Several cases could be observed which led to high accumulations of leacheable nitrate in soils: 1. fallow during growing season, 2. fallow during autumn and winter, 3. manuring in autumn, 4. leaching of chopped green manure by rain, 5. low nitrogen uptake of crops because of diseases, 6. transfer of mineralizable nitrogen from spring to autumn. The concept of the soil merely as a storage place for plant nutrients was one of the main factors for mistakes in nitrogen management. Understanding the interactions of plan...

Effect of Application of Ammonium Nitrogen on Mineralization of Soil Organic Nitrogen in Paddy Soils

Effect of Application of Ammonium Nitrogen on Mineralization of Soil Organic Nitrogen in Paddy Soils

Assessing nitrogen mineralization from soil organic matter using anion exchange membranes

A simple method to assess differences in potential contribution of organic nitrogen mineralization to plant available N among soils may be useful in fertility research as well as routine soil testing. We deployed a method to assess mineralizable soil organic N using anion exchange membrane (AEM) burial. The method is based on a simple closed incubation system in which strips of AEM are buried directly in soil to adsorb NO 3 - released from organic matter. An index of mineralization was obtained using the amount of NO 3 - adsorbed on an AEM strip removed at the end of each incubation. The same incubation system but using 0.001M CaCl2 solution to extract NO3-N was used as the reference method. The mineralization indices obtained from both methods were compared with each other and with plant uptake. A total of 74 soils from across Saskatchewan were used in the study to provide a range of soil properties. Correlations between test values and N uptake by plants in two separate experiments showed the 2 week AEM incubation to be more closely correlated with plant N uptake (r2 = 0.86**** and 0.57****, respectively) than the reference method (r2 = 0.60**** and 0.48****, respectively). With this method, we were able to determine the influence of different tillage systems and landscape positions on mineralizable N. The results showed that the NO 3 - released from soil organic matter and accumulated on the AEM reflected the expected effect of three different tillage systems and two landscape positions on mineralizable N. Cropping systems with continuous alfalfa (Medicago sativa) showed higher N release from soil organic matter than a canola (Brassica napus)-lentil (Lens culinaris)-barley (Hordeum vulgare) rotation did. Higher N mineralization was found in the lower slope positions of the landscape where organic matter contents are highest. Direct burial of AEM appears to be a simple and effective method of including a measure of N mineralization in a soil test.

Notes on protozoa in agricultural soil with emphasis on heterotrophic flagellates and naked amoebae and their ecology.

Heterotrophic flagellates and naked amoebae are usually very numerous in agricultural soils; with numbers in the magnitude of 10,000 to 100,000 (active+encysted) cells per gram of soil. In 'hotspots' influenced by living roots or by dead organic material, the number may occasionally be as high as several millions per gram of soil. An exact enumeration of these organisms is virtually impossible. As they most often adhere closely to the soil particles, direct counting will underestimate numbers since the organisms will be masked. The method usually applied for enumeration of these organisms, the 'most probable number (MPN) method', is based on the ability of the organisms to grow on particular culture media. This method will in many cases underestimate the total protozoan number (active+encysted). It is uncertain how many of the heterotrophic flagellates and naked amoebae are actively moving and how many are encysted at a particular time; the 'HCl-method' which has usually been used to discriminate between active and encysted has proven to be highly unreliable. Despite the methodological difficulties many investigations of these organisms indicate that they play an important role in agricultural soils as bacterial consumers, and to a minor extent as consumers of fungi. Because of their small size and their flexible body they are able to graze bacteria in small pores in the soil in which larger organisms are precluded from coming. Key factors restricting the number and activity of heterotrophic flagellates and naked amoebae in soils seem to be water potential and soil structure and texture. In micro-cosm experiments, small heterotrophic flagellates and naked amoebae regulate the size and composition of the bacterial community. Bacterial activity seems to be stimulated by these organisms in most cases as well as the mineralization of carbon and nitrogen and possibly other mineral nutrients. In the rhizosphere of living plants the activity of protozoa has proven to stimulate uptake of nitrogen in pot experiments, and it has been hypothesized that organic matter liberated by plants in the root zone will stimulate bacterial and protozoan activity, leading to mineralization of organic soil nitrogen which is subsequently taken up by the plants.

Notes on protozoa in agricultural soil with emphasis on heterotrophic flagellates and naked amoebae and their ecology

Heterotrophic flagellates and naked amoebae are usually very numerous in agricultural soils; with numbers in the magnitude of 10000 to 100000 (active+ encysted) cells per gram of soil. In ‘hotspots’ influenced by living roots or by dead organic material, the number may occasionally be as high as several millions per gram of soil. An exact enumeration of these organisms is virtually impossible. As they most often adhere closely to the soil particles, direct counting will underestimate numbers since the organisms will be masked. The method usually applied for enumeration of these organisms, the ‘most probable umber (MPN) method’, is based on the ability of the organisms to grow on particular culture media. This method will in many cases underestimate the total protozoan number (active+ encysted). It is uncertain how many of the heterotrophic flagellates and naked amoebae are actively moving and how many are encysted at a particular time; the ‘HCI-method’ which has usually been used to discriminate between active and encysted has proven to be highly unreliable. Despite the methodological difficulties many investigations of these organisms indicate that they play an important role in agricultural soils as bacterial consumers, and to a minor extent as consumers of fungi. Because of their small size and their flexible body they are able to graze bacteria in small pores in the soil in which larger organisms are precluded from coming. Key factors restricting the number and activity of heterotrophic flagellates and naked amoebae in soils seem to be water potential and soil structure and texture. In micro-corm experiments, small heterotrophic flagellates and naked amoebae regulate the size and composition of the bacterial community. Bacterial activity seems to be stimulated by these organisms in most cases as well as the mineralization of carbon and nitrogen and possibly other mineral nutrients. In the rhizosphere of living plants the activity of protozoa has proven to stimulate uptake of nitrogen inpot experiments, and it has been hypothesized that organic matter liberated by plants in the root zone will stimulate bacterial and protozoan activity, leading to mineralization of organic soil nitrogen which is subsequently taken up by the plants.

Isotope ratios and concentrations of sulfur and nitrogen in needles and soils of Picea abies stands as influenced by atmospheric deposition of sulfur and nitrogen compounds

Concentrations and natural isotope abundance of total sulfur and nitrogen as well as sulfate and nitrate concentrations were measured in needles of different age classes and in soil samples of different horizons from a healthy and a declining Norway spruce (Picea abies (L.) Karst.) forest in the Fichtelgebirge (NE Bavaria, Germany), in order to study the fate of atmospheric depositions of sulfur and nitrogen compounds. The mean δ15N of the needles ranged between −3.7 and −2.1 ‰ and for δ34S a range between −0.4 and +0.9 ‰ was observed. δ34S and sulfur concentrations in the needles of both stands increased continuously with needle age and thus, were closely correlated. The δ15N values of the needles showed an initial decrease followed by an increase with needle age. The healthy stand showed more negative δ15N values in old needles than the declining stand. Nitrogen concentrations decreased with needle age. For soil samples at both sites the mean δ15N and δ34S values increased from −3 ‰ (δ15N) or +0.9 ‰ (δ34S) in the uppermost organic layer to about +4 ‰ (δ15N) or +4.5 ‰ (δ34S) in the mineral soil. This depth-dependent increase in abundance of 15N and 34S was accompanied by a decrease in total nitrogen and sulfur concentrations in the soil. δ15N values and nitrogen concentrations were closely correlated (slope −0.0061 ‰ δ15N per μmol eq N gdw −1), and δ34S values were linearly correlated with sulfur concentrations (slope −0.0576 ‰ δ34S per μmol eq S gdw −1). It follows that in the same soil samples sulfur concentrations were linearly correlated with the nitrogen concentrations (slope 0.0527), and δ34S values were linearly correlated with δ15N values (slope 0.459). A correlation of the sulfur and nitrogen isotope abundances on a Δ basis (which considers the different relative frequencies of 15N and 34S), however, revealed an isotope fractionation that was higher by a factor of 5 for sulfur than for nitrogen (slope 5.292). These correlations indicate a long term synchronous mineralization of organic nitrogen and sulfur compounds in the soil accompanied by element-specific isotope fractionations. Based on different sulfur isotope abundance of the soil (δ34S=0.9 ‰ for total sulfur of the organic layer was assumed to be equivalent to about −1.0 ‰ for soil sulfate) and of the atmospheric SO2 deposition (δ34S=2.0 ‰ at the healthy site and 2.3 ‰ at the declining site) the contribution of atmospheric SO2 to total sulfur of the needles was estimated. This contribution increased from about 20 % in current-year needles to more than 50 % in 3-year-old needles. The proportion of sulfur from atmospheric deposition was equivalent to the age dependent sulfate accumulation in the needles. In contrast to the accumulation of atmospheric sulfur compounds nitrogen compounds from atmospheric deposition were metabolized and were used for growth. The implications of both responses to atmospheric deposition are discussed.

Effect of Aeration on Mineralization of Organic Nitrogen in Brackishwater Fishpond Soil

The mineralization of organic nitrogen at different salinity levels of brackishwater fishpond soils upon addition of cowdung was studied under laboratory conditions at ambient temperature 28.8-30.G•c over 120 days. Upon aeration, percent-. age gains in mineralized nitrogen at 0.5, 10, 20 and 30 ppt. Salinity ranged between 26.1 and 28.5% and were not significantly different. However, the rate of mineraliza­tion was slower at higher salinities.

Model for Slurry and Manure in CERES and Similar Models

AbstractProceeding from the structures and hypotheses of the CERES and SALUS models a model for considering manures has been developed. The model includes the following processes: infiltration during application, ammonia volatilization, leaching of ammonium and organic bound nitrogen and mineralization before incorporation, incorporation, ammonia volatilization, mineralization and leaching of organic bound nitrogen after incorporation. With the CERES Maize model combined with the manure model simulations were calculated concerning the following problems:– influence of application time of slurry on nitrate leaching under German site conditions and– influence of long‐term slurry fertilization and of stopping slurry fertilization on organic N content, mineralization, uptake by maize and leaching under Southern Michigan site conditions.Results and conclusions are presented.

Mineralization of organic nitrogen and carbon (fish food) added to anoxic sediment microcosms: role of sulphate reduction

Mineralization of organic nitrogen and carbon (fish food) added to anoxic sediment microcosms: role of sulphate reduction

Effects of Sooty Shearwaters Puffinus griseus on Surface Soils on Motuara Island, New Zealand.

The chemical characteristics of the surface soils affected by Sooty Shearwaters were investigated by analysis of 10 core samples taken from within each of three types of quadrats in three sampling areas on Motuara Island, South Island, New Zealand. These were (a) areas within 50cm of burrow entrances, but where leaf fall and trampling by the birds had been excluded (BURROW QUADRATS), (b) areas away from burrows and with normal leaf fall and plant cover present (LEAF LITTER PRESENT QUADRATS) and (c) areas similar to Leaf Litter Present Quadrats, but where all litter and plants had been removed at the beginning of the study (3 July, 1990) in cool, damp, calm conditions (LEAF LITTER ABSENT QUADRATS). Statistically significant differences were found between Burrow and other Quadrats, the former soil having lower pH values but higher electrical conductivity (EC) and phosphate levels. This suggests that the guano of Sooty Shearwaters lowers soil pH through the nitrification from ammonium to nitrate after mineralization of organic nitrogen, and enhances the EC and phosphate content in the surface layers. On the other hand, there was no significant difference in soil pH, EC, phosphate, potassium and total carbon and nitrogen content between Leaf Litter Present Quadrats and Leaf Litter Absent Quadrats, indicating that the absence of leaf litter and plants for a short period in winter does not significantly effect the chemical characteristics of the surface soils on Motuara Island.

Mineralization of organic nitrogen and carbon (fish food) added to anoxic sediment microcosms: role of sulphate reduction

Mineralization of organic nitrogen and carbon (fish food) added to anoxic sediment microcosms: role of sulphate reduction

Mineralization pattern of soil organic n of several soils in the tropics

Abstract The kinetics of mineralization of soil organic nitrogen (N) in samples of several air-dried and fresh soils in the tropics was studied. Four different paddy soil samples in the IRRI lowland field were used. Parameters for mineralization of soil organic N were computed by using Arrhenius' law and Michaelis-Menten's equation. The following results were obtained: 1. The mineralization pattern of organic N in the wet soil samples were represented by an exponential equation as a function of reference days, which were determined by the duration of the incubation period and apparent activation energy. Although significant differences in the mineralization rate and mineralization potential among the soils were observed, there was no appreciable difference in the value of apparent activation energy, which were relatively low compared with those of Japanese paddy soils.2. The mineralization pattern of the dried soil samples was represented by an equation consisting of two exponential equations. When a large amount of extractable carbon was detected by diluted sulfate or hot water in the soils, the mineralization pattern was represented by an equation which consisted of three exponential equations.3. The difference in the amount of inorganic N between the dried and wet soil samples increased rapidly up to 5 weeks after the start of incubation and then became almost constant. The mineralization pattern of the decomposable organic N which appeared with the changes of the soil conditions from wet to dry (DON) could also be represented by an exponential function of reference days.4. There was no appreciable difference in the mineralization rate and apparent activation energy between the organic N of the fresh soil samples and slowly mineralizable organic N of the dried soil samples, and between DON and the rapidly mineralizable organic N of the dried soil samples.

Effects of Grazing by Flagellates on Competition for Ammonium between Nitrifying and Heterotrophic Bacteria in Chemostats

The enhanced mineralization of organic nitrogen by bacteriophagous protozoa is thought to favor the nitrification process in soils, in which nitrifying bacteria have to compete with heterotrophic bacteria for the available ammonium. To obtain more insight into this process, the influence of grazing by the bacteriovorous flagellate Adriamonas peritocrescens on the competition for limiting amounts of ammonium between the ammonium-oxidizing species Nitrosomonas europaea and the heterotrophic species Arthrobacter globiformis was studied in the presence of Nitrobacter winogradskyi in continuous cultures at dilution rates of 0.004 and 0.01 h. The ammonium concentration in the reservoir was maintained at 2 mM, whereas the glucose concentration was increased stepwise from 0 to 7 mM. A. globiformis won the competition for limiting amounts of ammonium when the glucose concentration in the reservoirs increased, in agreement with previously described experiments in which the flagellates were not included. The numbers of nitrifying bacteria decreased as the numbers of heterotrophic bacteria rose with increasing glucose concentrations. Critical C/N ratios, i.e., ratios between glucose and ammonium in the reservoirs at which no nitrate was found in the culture vessels, of 12.5 and 10.5 were determined at dilution rates of 0.004 and 0.01 h, respectively. Below these critical values, coexistence of the competing species was found. The numbers of nitrifying bacteria decreased more in the presence of flagellates than in their absence, presumably by selective predation on the nitrifying bacteria, either in the liquid culture or on the glass wall of the culture vessels. Despite this, the rate of nitrate production did not decrease more in the presence of flagellates than in their absence. This demonstrates that no correlation has to be expected between numbers of nitrifying bacteria and their activity and that a constant nitrification rate per cell cannot be assumed for nitrifying bacteria. Above the critical C/N ratios, low numbers of nitrifying bacteria were still found in the culture vessels, probably because of attachment of the nitrifying bacteria to the glass wall of the culture vessels. Like the numbers of heterotrophic bacteria, the numbers of flagellates increased when the glucose concentrations in the reservoirs increased. Numbers of 2 x 10 and 12 x 10 flagellates ml were found at 7 mM glucose at dilution rates of 0.004 and 0.01 h, respectively. It was concluded that the critical C/N ratios were practically unaffected by the presence of protozoa. Although nitrate production rates were equal in the presence and absence of flagellates, the numbers of nitrifying bacteria decreased more strongly in their presence. This indicates a higher activity per nitrifying cell in the presence of flagellates.

Rates of amino acid uptake and mineralization in Resurrection Bay (Alaska) sediments

The rates of uptake and mineralization of glutamic acid, alanine, lyslne, serine and glycine were measured in sediments from Resurrection Bay, Alaska, USA, using I4C-labeled amino acids. Amino acid concentrations and specific activities were determined by high performance liquid chromatography. The fate of radiolabeled amino acids added to killed control sediments was also investigated. Free amino acids were lost from the dissolved pool by both bacterial uptake and adsorption to sediment particles. Adsorption was the dominant process for the basic amino acid lysine and was responsible for about half of the glutamic acid and alanine removal from solution. Rates of bacterial mineralization of porewater amino acids, calculated using a model which corrects for the effects of adsorption, were 8 (glutamic acid), 1 (alanine), 0.7 (lysine), 1 (serine) and 3 (glycine) nmol cm?sed i ment d-'. These rates indicate that amino acids could be quantitatively important intermediates in the mineralization of organic nitrogen in this sediment.