Mineral Forms Of Nitrogen Research Articles

Microbiological analysis of technozems of the Abagura agglomeration and concentration factory tailings dump

Microorganisms participate in the processes of restoration of contaminated soil ecosystems. Analysis of the processes is important for the biomonitoring of reclaimed territories and can improve the accuracy of forecasts of detoxification processes of the formed technozems. In the process of study of the microbiological state of the technozems of the Abagur agglomeration and concentration plant tailings dump, Novokuznetsk, changes in the group and species composition of soil aerobic heterotrophic microorganisms were studied and a quantitative assessment of the saprotrophic microflora content was presented. A microbiological analysis of the original sewage sludge (WWS) shows their initially high biological contamination by a wide taxonomic spectrum of microorganisms. It was shown, that the use of WWS for the enrichment of iron ore wastes by an organic substance contributes to the microbiological saturation of the latter at the level of ecological trophic diversity. The overall level of microbial population increases sharply compared with the control man-caused option, regardless of the way the WWS placing and its “quality”. At that, the WWS material neutralized by quicklime is most available to microorganisms, as evidenced by stimulation of the growth of representatives of various taxonomic affiliations and a high mineralization coefficient of the organic substance of the used ameliorant. The control man-caused substrate - soil mixture without organic additives is characterized by weak microbiological contamination. A microbiological analysis shows that small amounts of ammonifying microorganisms of various taxonomic affiliations, as well as bacteria and proactinomycetes with a trophic strategy for utilization of mineral forms of nitrogen, can be found in small amounts on the surface of the tailings dump. Biological testing of microbiological samples showed that in rehabilitated ecosystems with WWS during the microbiological mineralization of organic substance by active pathogens, actinomycetes and fungi participate in the destruction of protein compounds along with bacteria.

The Influence of Environmental Factors on Phytoplankton Varietya Case Study of Three Ponds of Western Poland

Abstract The structure of phytoplankton assemblages in three small water bodies was compared and abiotic factors were described. It indicated considerable differences in the species abundance and biomass of the phytoplankton as well as the chemical composition of water between artificial pond (No. 2) and others. A total of 455 phytoplankton taxa were recorded. All ponds were characterized by greatest species richness of Chlorophyta. The highest biomass was noted in August-September 2015, and it was true for each pond. The CCA models showed dependences between the variables under study and phytoplankton groups. They indicated which environmental variables had the greatest influence on the biomass of phytoplankton in the waterbodies under analysis. The biomass of most of the taxonomic group in the phytoplankton (except Miozoa) depended on the presence of nitrogen not only in form of nitrates but also in the form of mineral nitrogen. The research findings suggest the trend of future studies on the phytoplankton in these ponds. The analysis of its variability should also include the influence of light and the influence of consumers on the food chain in the ecosystem.

Зональные особенности химического состава вод малых рек бассейна Рыбинского водохранилища

The work is devoted to the study of the chemical composition of small rivers in the southwestern part of the territory of the Vologda region, which form the river flow of the Rybinsk reservoir basin. The determination of the chemical composition of water in rivers is carried out by generally accepted methods according to standard procedures. A distinctive feature of the river waters of the studied drainage basin is their significant difference in color and color intensity, total iron ion content, and ratio of basic anions. Most of the catchment area of this territory is represented by swamps and numerous lakes, many of them are sources of small and medium length watercourses. A comparative analysis of the ion-salt composition of the waters of rivers shows a certain similarity in the manifestation of the zonal features of the formation of their chemical composition. The composition of the water of the rivers in its salt part is mainly due to the climatic conditions. The waters of the rivers have a hydrocarbonate and sulphate-hydrocarbonate magnesium-calcium composition and relatively low mineralization. Statistical processing of the results of analytical data shows a high correlation in terms of color, permanganate oxidation and chemical oxygen consumption of the investigated water samples. Nutrients represented by the mineral forms of nitrogen and phosphorus in river waters within the studied catchment basin are determined by similar concentrations. A single directivity has been established in the distributions of the contents of heavy metal ions. From the number of heavy metal ions (iron, manganese, aluminum, copper, zinc, nickel, lead, arsenic, chromium, cadmium), which were determined in the analyzed samples, the excess of water quality standards for fishery water bodies was established of by iron and manganese ions. Excess of the established standards of quality of natural waters for other identified ions was not detected.

Growth and development of Alfalfa depending on the type of nitrogen nutrition

Mineral and symbiotrophic types of nitrogen nutrition of plants were compared in experiments with the blue-hybrid alfalfa. Variants with seed inoculation by high-mountain strains of nodule bacteria (In-1800 and N30+In) had the maximum height of plants during all experimental years (40-70 cm), which is explained by the better nitrogen provision of plants. At the same time, the effect of the mineral forms of nitrogen appeared only in the year of sowing at the beginning of the growing season to the first mowing, in the future the differences between these options were neutralized. The foliage intensity of plants was in the range of 41.4-54.8%, increasing due to the improved availability of biologically bound nitrogen in plants. Mineral forms of nitrogen reduced plants’ foliage coverage in all experimental years, however, this decrease was noted only in the initial periods of vegetation. The maximum indicators of foliage coverage were noted in the In-1800 variant. By the end of the third year of crops use, the plant stand density was 980-1100 thousand units/ha, and the total thinning of alfalfa crops reached 45-51%. At the same time, the symbiotrophic type of nitrogen nutrition made it possible to significantly increase the competitiveness of plants, which ultimately affected the persistence of the crop density.

Seasonal dynamics of nitrogen-containing substances in the Black Sea coastal zone by example Gelendzhik and Golubaya bay

In the course of studies of hydrochemical monitoring data for the period from 2017 to 2019, we found that the Gelendzhik bay, which belongs to semi-closed water areas, has an increased background of mineral and organic nitrogen forms compared to the background in the Golubaya bay corresponding to the open coast. Increased concentrations of mineral forms of nitrogen in the Gelendzhik bay we detected, probably due to anthropogenic impact.

Influence of the adoption of phosphogips and seros-containing fertilizers on the microbial population of south chernozem

The following field experiences were performed on the Chernozem southern carbonate: 1.Control, 2. Sulphoammophos – 150 kg/ha, 3. Sulphoammophos – 250 kg/ha, 4.Phosphogypsum – 3 t/ha, 5.Phosphogypsum – 6 t/ha, 6.Phosphogypsum – 12 t/ha, 7. Phosphogypsum – 3 t/ha ammophos –70 kg/ha ammonium nitrate, 100 kg/ha 8. Phosphogypsum – 6 t/ha ammophos -70 kg/ha ammonium nitrate, 100 kg/ha 9. Phosphogypsum – 12 t/ha ammophos–70 kg/ha ammonium nitrate, 100 kg/ha. 10. ammophos-70 kg/ha + ammonium nitrate 100 kg/ha. The determination of the number of microorganisms produced in the phase of milky-wax ripeness of winter wheat on the selective nutrient medium: meat-peptone agar – number of ammonifiers; on starch and ammonia agar – microorganisms that assimilate mineral forms of nitrogen on the Hutchinson medium – calculatorsreal the number of microorganisms on the Czapek-Dox medium – the number of micromycetes on the Ashby medium – the number of aerobic nitrogen-fixing bacteria of the genus Azotobacter. Introduction phosphogypsum, sulphoammophos, ammophos and ammonium nitrate contributes to the increase in the numbers of various physiological groups of microorganisms. The highest values of the studied indicators in comparison with the control was achieved through the joint application of phosphogypsum – 12 t/ha ammophos-70kg/ha and ammonium nitrate-100kg/ha: ammonifiers on 123.4 million CFU/g (or 2.5 times); nitrifiers at 138 million CFU/g (3.3 times), microscopic fungi on 90,0 thousand CFU/g (1.7 times); cellulose-fermenting microorganisms on 250.6 thousand CFU/g (more than 2 times); aerobic nitrogen-fixing bacteria of the genus Azotobacter by 30.7 thousand CFU/g (1.5 times). Thus, the most responsive to the introduction of phosphogypsum and fertilizers microorganisms that convert mineral and organic nitrogen compounds.

МЕТОДИКА ВИДІЛЕННЯ ЗОН, ВРАЗЛИВИХ ДО ЗАБРУДНЕННЯ ПОВЕРХНЕВИХ І ПІДЗЕМНИХ ВОД НІТРАТНИМИ СПОЛУКАМИ

The article presents the national methodology for the identification of vulnerable areas to pollution of surface and ground water by nutrients compounds. The designation of nitrate vulnerable zones is an effective tool to reduce the impact of agricultural activities on water pollution by nutrients and is used for managing of diffuse pollution within river basins to achieve “good” ecological status. The analysis of heterogeneity of natural conditions in Ukraine and intensity of agricultural activity allows to determine 3 types of zones which differ in vulnerability: 1. Zones of high risk of water pollution, where nitrogen surplus in soil and washing and periodic washing regime are favorable for the nitrate leaching; 2. Zones of potential water pollution, where a deficient nitrogen balance in soil is observed in conditions of washing and periodic washing regime; 3. Zones of short-term pollution, where positive nitrogen balance in soil is noted by the unwashed water regime. The content of dissolved forms of mineral nitrogen (Nminer) in water and the presence of eutrophication process in the water body were recommended to use as criterias for designation of vulnerable zones. For the small rivers with a Strahler coefficient < 5, the nitrate vulnerable zones designation is recommended using the criterion of the nitrogen mineral forms content with a threshold value of 11,3 mgN/l. For the rivers with a Strahler coefficient ≥ 5, reservoirs, estuaries and coastal waters the designation is carried out on the basis of eutrophication. For the groundwater, it is based on the content of nitrogen mineral forms less than 9,7 mgN/l. This method was developed in Ukraine for the first time.

ЕКОЛОГІЧНА ХАРАКТЕРИСТИКА Р. ПІВДЕННИЙ БУГ ТА ОЛЕКСАНДРІВСЬКОГО ВОДОСХОВИЩА ЗА ГІДРОХІМІЧНИМИ ПОКАЗНИКАМИ

The paper presents the results of researches of the modern ecological state South Bug and Aleksandrovskogo of storage pool the affected of the South Ukrainian power complex zone on hydrochemical indexes (main ions, mineralization of water, biogenic matters), which are the indicators of the ecological state of natural reservoirs. Research of the hydrochemical mode South Bug and Aleksandrovskogo of storage pool within the limits of the South Ukrainian power complex conducted during 2019. An analysis of the got data is as compared to those, which took place more early, rotined that the water masses South Bug tested substantial changes (on the indexes of the chemical state). The conducted researches rotined that chemical composition of water S.Bug and Aleksandrovskogo of storage pool had been characterized sufficiently by the high values of mineralization of water, maintenance of main ions, especially sulfate and to general inflexibility.The features of spatio-temporal changeability of the main hydrochemical indicators of quality of water environment are set. Tendency of gradual increase of maintenance of main ions and of mineralization of water is traced on the longitudinal type of the river. The gradual diminishing from the winter to the summer and increase of mineralization of water and main ions an autumn is traced in a seasonal aspect. It is known that the important index of the sanitary-hygenic state of natural reservoirs is content of biogenic matters. Worsening of the ecological state South Bug and Aleksandrovskogo of storage pool is set on maintenance biogenic matters. Modern researches rotined that and here took place changes are certain, namely: on an area in the district of South Ukrainian power complex zone something the concentrations of nitrate and ammoniacal forms of mineral nitrogen and phosphatic ions grew, that testifies to the decline of selfcleansing ability of the river and is the index of process second contaminations of the river.

Effect of the Form of Mineral Nitrogen on the Growth and Heterotrophic Fixation of 14С-Bicarbonate in Chlamydomonas reinhardtii

The earlier-detected effect of the mineral nitrogen form in the nutrient medium (ammonium or nitrate) on the quantity of ribosomes in the cells of chlamydomonas and the callus of soybean requires experimental corroboration of the proposed interpretation of the discovered phenomenon. In order to elucidate the mechanism of ammonium’s action on the formation of protein-producing structures (ribosomes) in the cells of green alga chlamydomonas (Chlamydomonas reinhardtii, strain gr 21), we compared the effect of the form of mineral nitrogen (nitrate and ammonium) on the growth and heterotrophic fixation of 14С-bicarbonate. Our experiments have shown that the process of cell division (mitosis) was hampered at the beginning of the growing cycle (on days 1–3) when the cells were cultured on nitrate medium. By the end of the growing cycle (days 7–10), the number of cells and the content of dry matter in the cells equalized. It was found that the cells grown on TAP medium with ammonium fixed Н14С$${\text{O}}_{3}^{ - }$$ at a higher rate than the cells cultured on TAP medium with nitrate. The obtained results have shown that the rate of dark fixation of Н14С$${\text{O}}_{3}^{ - }$$ in the cells grown in the medium with ammonium was higher than in the cells on nitrate medium irrespective of the mode of calculation: on the number of cells or per dry weight unit. An assumption that ammonium present in the nutrient medium can activate synthesis of extra amino acids participating in the formation of protein components of ribosomes in the alga chlamydomonas is discussed.

Ufa forestry-technical school, of the Ministry of Forestry of the Republic of Bashkortostan, Ufa, Russia

In the Republic of Bashkortostan, in the greenhouse of the year-round operation of the experimental farm of the state-run vocational training school "Ufa forestry-technical school" (Limonary in Ufa city), tropical and subtropical fruit crops have been cultivated for many years. The farm constantly monitors the agrochemical, physico-chemical, biochemical indicators of soil grounds. The agrochemical characteristics of soils during the cultivation of exotic fruit crops have been studied. For fertilizing all cultivated plants of the farm, organic and mineral macro- and micronutrient fertilizers are regularly added at regular intervals. When using fertilizers, the need for nutrient elements of crops is taken into account for successful growth and fruiting by periods of growth and agrochemical data. The study presents a comparative characteristic of soil grounds for 2016 and 2018, which shows: humus content, mobile forms of P2O5 and K2O, mineral forms of nitrogen, pH (salt). The results of agrochemical surveys allow you to adjust the dose of fertilizers for the cultivation of major crops, planting material and for the formation of the crop.

The content of organic carbon, nitrogen and phosphorus in deep-water biocenoses of coralline algae of the South China sea

The study on the influence of the depth of habitation on the content of organic carbon (Corg), organic and mineral forms of nitrogen (N) and phosphorus (P) in the biocenosis of coralline algae, was carried out in spring in the South China Sea at depths of 5 to 150 m. It was shown that with an increase in depth to 150 m, the content of Corg in the tissues decreased from 72 to 42 g/m2. The content of N also decreased with depth, but to a lesser extent — from 15 to 10 g/m2, while the content of P increased linearly from 0.75 to 4.29 g/m2. The atomic ratio C/N/P in the biocenosis at depths of 5–10 m does not vary significantly and is on the average 187:31:1, which is comparable to the mean values obtained for mass species of reef-building corals. Unlike organic carbon and nitrogen, the phosphorus content in the algal biocenosis increased with depth more than 5 times. Correspondingly, the C/N/P ratio becomes 24:5:1 at a depth of 150 m. Such depth-dependent increase in the proportion of phosphorus in the biocenosis, with a simultaneous decline in the contents of organic carbon and, to a lesser extent, nitrogen, can be explained by release of phosphorus during destruction of the organic matter in the biocoenosis of coralline algae with the formation of insoluble calcium phosphates.

Content of Organic Carbon, Nitrogen, and Phosphorus in Deep-Water Coralline Algae Biocenoses, South China Sea

The influence of habitat depth on the content of organic carbon (Corg), as well as organic and mineral forms of nitrogen (N) and phosphorus (P), in the biocenosis of coralline algae at depths of 5 to 150 m was studied in spring in the South China Sea. It has been found that the Corg content in tissues decreased from 72 to 42 g/m2 with increasing depth to 150 m. The N content also decreased with depth but to a lesser extent, from 15 to 10 g/m2, while the P content increased linearly from 0.75 to 4.29 g/m2. The atomic ratio C/N/P in the biocenosis at depths of 5–10 m did not vary significantly and averaged at 187 : 31 : 1, which is comparable to the mean values obtained for the common species of reef-building corals. Unlike Corg and N, the P content in the algal biocenosis increased with depth more than fivefold. Correspondingly, the C/N/P ratio amounted to 24 : 5 : 1 at a depth of 150 m. Such a depth-dependent increase in the proportion of phosphorus in the biocenosis, with simultaneous reduction in the Corg and, to a lesser extent, N contents, can be explained by the release of phosphorus during in the breakdown of organic matter in the biocenosis of coralline algae with the formation of insoluble calcium phosphates.

Effects of Mineral Nitrogen Partitioning on Tree–Grass Coexistence in West African Savannas

Coexistence between trees and grasses in savannas is generally assumed to be due to a combination of partial niche separation for water acquisition and disturbances impacting the demography of trees and grasses. We propose a mechanism of coexistence solely based on the partitioning of the two dominant forms of mineral nitrogen (N), ammonium (NH4+) and nitrate (NO3−). We built a mean-field model taking into account the capacity of grasses and trees to alter nitrification fluxes as well as their relative preferences for NH4+ versus NO3−. Two models were studied and parameterized for the Lamto savanna (Cote d’Ivoire): In the first model, the nitrification only depends on the quantity of available NH4+, and in the second model the nitrification rate is also controlled by tree and grass biomass. Consistent with coexistence theories, our results show that taking these two forms of mineral N into account can allow coexistence when trees and grasses have contrasting preferences for NH4+ and NO3−. Moreover, coexistence is more likely to occur for intermediate nitrification rates. Assuming that grasses are able to inhibit nitrification while trees can stimulate it, as observed in the Lamto savanna, the most likely case of coexistence would be when grasses prefer NH4+ and trees NO3−. We propose that mineral N partitioning is a stabilizing coexistence mechanism that occurs in interaction with already described mechanisms based on disturbances by fire and herbivores. This mechanism is likely relevant in many N-limited African savannas with vegetation composition similar to the one at the Lamto site, but should be thoroughly tested through empirical studies and new models taking into account spatiotemporal heterogeneity in nitrification rates.

Effect of long-term organic and mineral fertilisation on selected physico-chemical soil properties in rye monoculture and five-year crop rotation

Abstract The research was carried out continuously since 1923 in a permanent fertilisation experiment at the Experimental Station of SGGW in Skierniewice. The objective of the research was to determine the effect of long-term fertilisation (Ca, CaNPK, NPK) and crop rotation systems (rye monoculture without fertilisation with manure and five-field rotation with legume crop and manure fertilisation) on selected physical and chemical soil properties. Long-term fertilisation caused various degrees of change in many physio-chemical properties in three soil horizons (Ap, Eet, Bt): pH in KCl, cation exchange capacity, total exchangeable bases, base saturation, content of carbon, nitrogen and mineral forms of nitrogen (NO3, NH4) as well as the carbon-nitrogen ratio. The combined manure and mineral fertilisation increased the sorption capacity, total exchangeable bases, base cation saturation and total content of C and N in comparison to organic or mineral fertilisation. As a result of lime application, an increase in these parameters was determined with the exception of total contents of carbon and nitrogen, showing no differences or a decrease. A positive effect was confirmed in five-field crop rotation, which improves physicochemical soil properties in comparison to cereal monoculture. The C:N ratio narrows down with growing depth because more nitrogen than carbon migrates down the soil profile.

Changes in mineral forms of nitrogen and sulfur and enzymatic activities during composting of lignocellulosic waste and chicken feathers

The aim of this study was to show the dynamics of changes in the activity of enzymes responsible for C, N, and S metabolism, i.e., cellulase, protease, urease, and arylsulfatase in two lignocellulosic composts as well as changes in the concentration of mineral forms important in plant nutrition (N-NH4+, N-NO3−, S-SO42−). Most of the enzyme activity was higher during 10 weeks of composting in compost I, containing higher amounts of easily available organic matter than in compost II. Enzymatic activities in compost II remained at a higher level for a longer time, but they increased at a slower rate. Mineral content changes in the compost mass consisted primarily of an increase in N-NO3− concentration and a decrease in N-NH4+ and S-SO42− levels, especially in compost I. The concentration of mineral nitrogen and sulfur forms in compost water extracts was about 10–100 times lower than in the compost mass. At the end of composting, the amount of sulfates in the compost mass was 30 and 150 mg kg−1 dw in compost II and I, respectively. In this context, the composts obtained should be considered valuable for fertilizing soils poor in this component and for cultivating plants with high sulfate S demand.

Сезонная и пространственная изменчивость химического состава воды реки Аргунь

The article discusses seasonal and spatial variability of the chemical composition of the waters of the Argun River which is the right component of the Amur river according to the Transbaikal AHEM (1962–1975 and 2016–2017), Russian-Chinese monitoring (2008, 2011–2013) and expeditionary observations in June 2018. The maximum concentrations of the main ions, mineral forms of nitrogen, iron compounds and manganese due to a deficiency of dissolved oxygen occurr during the winter low water period mainly in the upper part of the river. During the open channel period, the concentrations of nitrogen mineral forms was below the detection limit, the content of organic substances reaches the lowest values during the summer-autumn low-water period, and the main ions – in rain floods. We found differences in the main ions content along the river length caused by the natural and climatic features of the territory and economic activities in the catchment area. In 2018, observation of the river between Abagatuy and Priargunsk villages established the spatial variability of the main ions concentrations during the summer low water. The highest content of major ions due to mining is typical for the upper part of the river, the smallest – for the part of the river below the confluence of the Ganhe and Derbul rivers, which form the chemical composition on the western spurs of the Greater Khingan Range. An increase in the salt content in the water of the Argun River below the mouths of the rivers Urulyungui, Verkhnyaya Borzya and others draining the steppe and forest-steppe landscapes was noted. Key words: Argun River, water chemical composition, mineralization, main ions, biogenic and organic substances.

Emiliania huxleyi blooms in the Black Sea: influence of abiotic and biotic factors

Abstract Stelmakh L.V., Gorbunova T.I., 2018: Emiliania huxleyi blooms in the Black Sea: influence of abiotic and biotic factors. - Botanica, 24(2): 172-184. The studies were conducted in the Black Sea in deep and shallow water areas in October 2010 and May 2013. The main abiotic and biotic factors, which control spring and autumn coccolithophorid Emiliania huxleyi blooms, were identified. During late May this phenomenon was observed under optimal light and temperature conditions, and also optimal ratio between mineral forms of nitrogen and phosphorus (N/P) in the water. Biotic variables (the net growth rate of phytoplankton and relative dinoflagellates share in its total biomass) determined the uneven distribution of E. huxleyi within a bloom. In October, water temperature was almost 4ºС lower compared to that in May, and solar radiation intensity decreased approximately by 2-3 times. However, as a result of seasonal adaptation to light and temperature, E. huxleyi abundance reached blooming level. In that period, the variability of N/P ratio in the water and the relative share of diatoms in total biomass of phytoplankton played a major role in the uneven distribution of this coccolithophorid within the studied area. In the areas with low water salinity, a bloom was not developing. Within the main part of the studied water area, the major source of nitrogen was ammonium, which was favourable for the growth of E. huxleyi and dinoflagellates, but limited the growth of diatoms.

Effect of gap size and forest type on mineral nitrogen forms under different soil properties

Gaps play a key role in forest ecosystem development and result from either natural processes or targeted forest management activities. The aim of this study was to investigate the interrelationships of soil properties in each of three forest types and two treatments, and to identify factors that influence levels of soil mineral nitrogen forms. The relation between mineral nitrogen and factors of soil parameters and stand type (European beech, Norway spruce, mixed stand) categories were investigated. The spruce forest type stored significant nitrogen in both mineral forms of nitrogen. Moreover, there was a significant linear dependence between N–NO3− (nitrate anion) concentrations and cation exchange capacity (CEC) parameters such as base cation contents (S-CEC) and potential ureolytic activities (UreasePot), as well as between N–NH4+ (ammonium cation) concentrations and both hydrolytic acidities (Ha-CEC) and ureolytic activities. The dependence of N–NO3− concentrations on S-CEC contents and UreasePot was negative, especially in adjacent stand. The dependence of N–NH4+ concentrations on Ha-CEC and UreasePot was week in the beech and mixed forest types while it was significantly positive in the spruce forest type.

Nitrogen Addition Decreases Dissimilatory Nitrate Reduction to Ammonium in Rice Paddies.

Dissimilatory nitrate reduction to ammonium (DNRA), denitrification, anaerobic ammonium oxidation (anammox), and biological N2 fixation (BNF) can influence the nitrogen (N) use efficiency of rice production. While the effect of N application on BNF is known, little is known about its effect on NO3- partitioning between DNRA, denitrification, and anammox. Here, we investigated the effect of N application on DNRA, denitrification, anammox, and BNF and on the abundance of relevant genes in three paddy soils in Australia. Rice was grown in a glasshouse with N fertilizer (150 kg N ha-1) and without N fertilizer for 75 days, and the rhizosphere and bulk soils were collected separately for laboratory incubation and quantitative PCR analysis. Nitrogen application reduced DNRA rates by >16% in all the soils regardless of the rhizospheric zone, but it did not affect the nrfA gene abundance. Without N, the amount and proportion of NO3- reduced by DNRA (0.42 to 0.52 μg g-1 soil day-1 and 45 to 55%, respectively) were similar to or higher than the amount and proportion reduced by denitrification. However, with N the amount of NO3- reduced by DNRA (0.32 to 0.40 μg g-1 soil day-1) was 40 to 50% lower than the amount of NO3- reduced by denitrification. Denitrification loss increased by >20% with N addition and was affected by the rhizospheric zones. Nitrogen loss was minimal through anammox, while BNF added 0.02 to 0.25 μg N g-1 soil day-1 We found that DNRA plays a significant positive role in paddy soil N retention, as it accounts for up to 55% of the total NO3- reduction, but this is reduced by N application.IMPORTANCE This study provides evidence that nitrogen addition reduces nitrogen retention through DNRA and increases nitrogen loss via denitrification in a paddy soil ecosystem. DNRA is one of the major NO3- reduction processes, and it can outcompete denitrification in NO3- consumption when rice paddies are low in nitrogen. A significant level of DNRA activity in paddy soils indicates that DNRA plays an important role in retaining nitrogen by reducing NO3- availability for denitrification and leaching. Our study shows that by reducing N addition to rice paddies, there is a positive effect from reduced nitrogen loss but, more importantly, from the conversion of NO3- to NH4+, which is the favored form of mineral nitrogen for plant uptake.

Transfer of Nitrogen and Phosphorus Nutrients in Vegetated Buffer Zones Receiving Treatment Plant Effluent

Vegetated buffer zones (VBZs) are a type of constructed wetlands well known for their purifying capacity. They are built between wastewater treatment plants and receive compartments for a complementary treatment of eutrophicants. This study presents the results of the monitoring of nitrogen and phosphorus transfers in two VBZs with the objective to specify the processes and control factors. Two VBZs, located in Liebsdorf and Raon in the east of France, having contrasting characteristics of surface area, hydraulic load, soil texture and plant species, were monitored for 28 months in order to analyze mineral forms of nitrogen and phosphorus in water, sediment and plants. The decrease in nitrate at the Raon VBZ is linked to low dissolved oxygen (DO) in effluent, which probably triggered denitrification. By contrast, ammonium content remains high. At the Liebsdorf VBZ, high nitrate concentration in water and low ammonium content in soil show that nitrification could be the main process involved, favored by high DO in effluent and helophytes in the ditches. However, the low hydraulic retention time and large hydraulic load limit microbiological processes in the improvement of effluent water quality. Both zones show few changes in phosphorus concentration in water. The content of nutrients in plants is high by comparison with natural wetlands, and twice as high in Liebsdorf as in Raon. However, despite the high retention capacity of plants, the vegetation plays a minor role ( 20%). This study highlights the main factors (soil texture, ratio hydraulic load/surface) which managers can control in order to improve the efficiency of VBZs in nutrient removal.