Mean Nitrate Concentrations Research Articles

Trends and occurrences of nitrate in the groundwater of the West Bank, Palestine

Groundwater is the major source of water to the Palestinians. Efficient management of this resource requires a good understanding of its status. This understanding necessitates a characterization of the quality of the utilizable volumes. This paper focuses on the assessment of nitrate concentrations in the aquifers of the West Bank, Palestine. A preliminary statistical analysis is carried out for the spatial and temporal distributions of the nitrate concentrations. GIS is utilized to facilitate the analysis and to efficiently account for the spatiality of nitrate concentrations. The analysis was carried out at different spatial levels and key parameters including soil type, watersheds, depth, population, and rainfall. It is observed that elevated nitrate concentrations in the groundwater greatly coincide with increasing rainfall, particularly in the last few years. Results confirm that the annual mean nitrate concentration in the Western groundwater basin has an increasing trend over the period from 1982 to 2004 indicating its vulnerability to contamination. This result can be attributed to the agricultural activities along with the high groundwater recharge. However, leaking septic and sewer systems are considerably causing nitrate contamination of groundwater in populated areas. Overall, the recommendations call for an immediate intervention to manage the quality problems in the West Bank aquifers.

Determination of nitrogen reduction levels necessary to reach groundwater quality targets in large river basins: the Weser basin case study, Germany

We used the interdisciplinary model network REGFLUD to predict the actual mean nitrate concentration in percolation water at the scale of the Weser river basin (Germany) using an area—differentiated (100 m × 100 m) approach. REGFLUD combines the agro-economic model RAUMIS for estimating nitrogen surpluses and the hydrological models GROWA/DENUZ for assessing the nitrate leaching from the soil. The areas showing predicted nitrate concentrations in percolation water above the EU groundwater quality standard of 50 mg NO3/l, have been identified as priority areas for implementing nitrogen reduction measures. For these “hot spot” areas a backward modelling approach was used to quantify the maximal permissible nitrogen surplus levels in agriculture to guarantee a mean long-term nitrate concentration in percolation water below 50 mg NO3/l. Research work will directly support the implementation of the EU-Water Framework Directive in the Weser basin, e.g. by using the maximal permissible nitrogen surplus levels as a framework for the derivation of regionally adapted and hence effective nitrogen reduction measures.

Effect of Nitrogen Fertilization on the Yield and Quality of Field-grown Leaf Lettuce for Spring Harvest

Effect of Nitrogen Fertilization on the Yield and Quality of Field-grown Leaf Lettuce for Spring Harvest Two field experiments with leaf lettuce were carried out in 2006-2008. Each of them was set up in a random sub-block design in 3 replications and a two-factorial system. The first factor represented different nitrogen doses that were used to obtain the required N level in the soil prior to planting the seedlings, the levels being: 50, 100 and 150 mg N·dm-3. The second factor incorporated 4 nitrogenous fertilizers which were different in terms of chemical composition, and, more importantly, contained different nitrogen forms for introduction to the soil: ammonium nitrate 34% N-[NH4NO3], calcium nitrate 15.5% N-[Ca(NO3)2xH2O+NH4NO3], ammonium sulphate 20.0% N-[(NH4)2SO4], and ENTEC 26% N-[NH4NO3+(NH4)2SO4+0.8% DMPP]. Two varieties of leaf lettuce were used: Casabella (of the type Lollo Bionda) with green leaves, and Klausia (of the type Lollo Rosa) with red leaves. The best sources of nitrogen for the lettuce plants were the fertilizers ENTEC 26 and ammonium nitrate, which in contrast to calcium nitrate and ammonium sulphate made it possible to obtain significantly higher yields of lettuce. Irrespective of the kind of the nitrogenous fertilizer used, increasing the concentration of nitrogen in the soil from 50 mg N·dm-3 to 100 mg N·dm-3 resulted in a significant increase in the marketable yield of lettuce. At 150 mg N·dm-3 this yield remained at a level similar to that at 100 mg N·dm-3. The lettuce fertilized with ammonium sulphate was marked by the lowest mean nitrate content in the leaves before harvest. The use of gradually higher doses of nitrogen resulted in a reduced dry weight content and lower levels of total and reducing sugars in lettuce leaves. With respect to yield size and quality, the recommended concentration of nitrogen in the soil for leaf lettuce should not exceed 100 mg N·dm-3.

Statistical analysis of nitrate concentrations from the Rivers Frome and Piddle (Dorset, UK) for the period 1965–2007

AbstractThe results presented here update those of Casey and Clarke (Freshwater Biology, 1979), ecologists who studied nitrate concentrations in the River Frome in southern England from 1965 to 1976, finding that average annual nitrate concentrations were increasing at the rate of around 0·11 mg NO3N l−1 year−1. Statistical analyses at the same East Stoke site for the period 1978 to 2003 are presented and results are compared with the neighbouring River Piddle for the period 1978 to 2007 which, unlike the Frome, lies entirely within the Chalk in its upper reaches. The method of Casey and Clarke (1979) is followed in applying general linear and nonlinear estimation models (NEMs) to explore the sources of variation in the nitrate concentration data. The proportions of the total variation in nitrate concentration attributable to differences between years and to differences between months are similar for the Frome in both periods. For the Frome and Piddle models from 1978 onwards, an even greater proportion of variation is explained by differences between years rather than differences between months, suggesting that long‐term change is the dominant effect. Analyses of annual mean nitrate concentration data show a sustained linear trend over the study period for both rivers and indicate that the rate of increase of annual mean nitrate concentration continues at a rate not significantly different from that found by Casey and Clarke (1979). Four versions of a NEM were applied, including the original Casey and Clarke (1979) model. The inclusion of flow variables adds little to the overall explanation and a cosine index remains the most effective descriptor of seasonal variations in nitrate concentration, suggesting seasonal in‐stream biological uptake as a dominant control, rather than hydrological catchment response. Copyright © 2008 John Wiley & Sons, Ltd.

Evaluation of the soil crop model STICS over 8 years against the “on farm” database of Bruyères catchment

The European Water Framework Directive (2000) offers a new challenge for farmers and water policy makers. It requires the establishment of quantitative environmental diagnosis of water quality. This can be done using crop models properly tested in the short and long-terms and taking into account current farming practices. The aim of this paper is to check the robustness of a crop model (STICS) for predicting the nitrogen uptake and nitrate leaching in various fields during 8 successive years. The model was evaluated on the soil–crop database of a small catchment in northern France. It includes data of crop production and N uptake, water and mineral nitrogen contents in soil measured three times a year at 36 sampling sites representative of crops (wheat, sugar beet, pea, barley, oilseed rape) and soil parent materials (loam, loamy clay and rocks, sandy loam and limestone, sand). A few crop parameters of STICS were recalibrated on independent databases in order to improve the predictions obtained with the standard parameterization. STICS was then evaluated either by resetting simulations each year (RS) or during continuous simulations (CS) over the 8 years. A reasonable agreement was obtained between observed and simulated values, except for soil N mineral content at harvest and N content in crop residues. The model efficiencies using CS mode were 0.53, 0.94 and 0.38 for N uptake, soil water and mineral N in late autumn, respectively. The mean calculated drainage was 192 mm y −1 and N leaching was estimated at 20 kg N ha −1 y −1, respectively. Averaging the outputs according to soil and crop type improved the quality of fit. The outputs of CS simulations were close to those obtained with RS. The mean nitrate concentration in water drainage was estimated as 46 and 45 mg NO 3 l −1 with RS and CS, respectively. Continuous simulations did not induce a substantial drift in mineral N in late autumn and can be trusted for predicting nitrate leaching. However, the leaching predictions were more sensitive to spatially variable parameters such as maximal rooting depth and potential mineralisation rate for CS than for RS. This emphasizes the difficulty in extrapolating the model over the long-term for large spatial areas. Another important uncertainty concerns fertiliser use efficiency, which had a small effect on leaching but a marked influence on gaseous N losses. Further assessments of the model will concern the whole N balance prediction over the long-term.

Partitioning the effects of changes in nitrate availability and phytoplankton community structure on relative nitrate uptake

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 359:51-68 (2008) - DOI: https://doi.org/10.3354/meps07417 Partitioning the effects of changes in nitrate availability and phytoplankton community structure on relative nitrate uptake Jesús M. Mercado1,*, Teodoro Ramírez1, Dolores Cortés1, Marta Sebastián2, Esperanza Liger3, Begoña Bautista2 1Instituto Español de Oceanografía, Centro Oceanográfico de Málaga, Puerto Pesquero s/n, Apdo. 285, 29640 Fuengirola (Malaga), Spain 2Departamento de Ecología, Universidad de Málaga, Facultad de Ciencias, Campus Universitario de Teatinos, 29074 Malaga, Spain 3Departamento de Física Aplicada II, Universidad de Málaga, E.T.S.I. Informática, Campus de Teatinos s/n, 29071 Malaga, Spain *Email: jesus.mercado@ma.ieo.es ABSTRACT: The uptake of dissolved nitrogen by different assemblages of phytoplankton was determined during 4 seasonal surveys carried out in the northwest sector of the Alboran Sea. The study area was characterized by stratification of the water column from spring to autumn, leading to very low nutrient concentrations in the euphotic zone; in particular, nitrate was below the detection limit at numerous stations in autumn. In winter and spring, the potential limitation of phytoplankton growth by nitrate was alleviated at some stations by upwelling of the nutrient-enriched Levantine Intermediate Water (LIW). The values of relative NO3– uptake (the proportion of nitrate to total N uptake) were highly variable (ranging from 0.01 to 0.8), even during single surveys. At most of the sampling stations during the stratification period, the relative nitrate uptake was <0.2 at the surface, but increased at the depth of the sub-surface chlorophyll a fluorescence maximum (SFM). At the surface, relative nitrate uptake and nitrate concentrations were strongly correlated, and about 82% of the relative nitrate uptake variability was accounted for by simultaneous changes in the nitrate concentrations and the micro-plankton chlorophyll a size fractions. These changes were related to modifications in upwelling intensity, as determined by variability in surface salinity. In contrast, relative nitrate uptake was not correlated with nitrate concentrations in the SFM samples, where the mean nitrate concentration increased 3-fold with respect to the surface value. On average, the micro-phytoplankton in these samples collected at the SFM was dominated by diatoms, the abundance of which ranged from 24 to 960 cells ml–1. This variability in diatom cell abundance explained about 52% of the variability of relative nitrate uptake at this depth level. Therefore, our data demonstrate that the proposed relationship between relative nitrate uptake and large phytoplankton was most evident at non-limiting nitrate concentrations. KEY WORDS: Nitrogen uptake · Diatoms · Phytoplankton · Primary production · Upwelling · Alboran Sea · Mediterranean Sea Full text in pdf format PreviousNextCite this article as: Mercado JM, Ramírez T, Cortés D, Sebastián M, Liger E, Bautista B (2008) Partitioning the effects of changes in nitrate availability and phytoplankton community structure on relative nitrate uptake. Mar Ecol Prog Ser 359:51-68. https://doi.org/10.3354/meps07417 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 359. Online publication date: May 05, 2008 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2008 Inter-Research.

A Whole‐Farm Strategy to Reduce Environmental Impacts of Nitrogen

Dutch regulations for ammonia emission require farmers to inject slurry into the soil (shallow) or to apply it in narrow bands at the surface. For one commercial dairy farm in the Netherlands it was hypothesized that its alternative farming strategy, including low-protein feeding and surface spreading, could be an equally effective tool for ammonia emission abatement. The overall objective of the research was to investigate how management at this farm is related to nitrogen (N) losses to the environment, including groundwater and surface water. Gaseous emission of ammonia and greenhouse gasses from the naturally ventilated stables were 8.1 and 3.1 kg yr(-1) AU(-1) on average using the internal tracer (SF(6))-ratio method. Measurements on volatilization of ammonia from slurry application to the field using an integrated horizontal flux method and the micrometeorological mass balance method yielded relatively low values of ammonia emissions per ha (3.5-10.9 kg NH(3)-N ha(-1)). The mean nitrate concentration in the upper ground water was 6.7 mg L(-1) for 2004 and 3.0 mg L(-1) for 2005, and the half-year summer means of N in surface water were 2.3 mg N L(-1) and 3.4 mg N L(-1) for 2004 and 2005, respectively. Using a nutrient budget model for this farm, partly based on these findings, it was found that the calculated ammonia loss per ton milk (range 5.3-7.5 kg N Mg(-1)) is comparable with the estimated ammonia loss of a conventional farm that applies animal slurry using prescribed technologies.

Assessment of a sinkhole filter for removing agricultural contaminants

The impact on water quality by agricultural activity in karst terrain is an important consideration for resource management within the Appalachian Region. Three USDA Natural Resource Conservation Service-designed sinkhole filters for removing contaminants from manure-impacted infiltrating water were assessed for removal efficiency of indicator bacteria and nitrate. Geometric mean fecal coliform bacteria concentrations decreased 85% to 96%. Mean nitrate concentrations increased 130% at two of the filter locations. The sinkhole filters probably filtered out sediment and associated contaminants, such as fecal coliform bacteria, but had no filtering effect on solutes like nitrate. Nitrate concentrations might have increased because of nitrification in the filter media between runoff events. The sinkhole filter appears to be an effective management tool in order to reduce inputs of pathogens to karst groundwater aquifers.

Relation of nitrate contamination of groundwater with methaemoglobin level among infants in Gaza

A descriptive, cross-sectional and analytical study was carried out in 3 areas of the Gaza Strip, Palestine, in 2002, to determine the factors associated with high methaemoglobin (Met-Hb) levels in infants and the relationship with nitrate concentration in drinking water wells. Drinking water sources were likely to be the main factor for high levels of Met-Hb. Out of 338 infants attending for vaccination, having supplemental feeding, use of boiled water and age 3-6 months were associated with high Met-Hb levels. The highest mean Met-Hb level was in Khan-Younis, where the highest mean nitrate concentration was recorded in drinking water. The results emphasize the importance of exclusive breastfeeding for infants < 6 months old, and the choice of a suitable source of water for these infants.

The Use of the Weights-of-Evidence Modeling Technique to Estimate the Vulnerability of Groundwater to Nitrate Contamination

The occurrence of elevated nitrate (NO 3 − ) concentration in the aquifer of the Province of Milan (northern Italy) is related to both natural and anthropogenic variables. Using the weights-of-evidence modeling technique a specific vulnerability assessment has been performed. This study presents an evolution of previous applications of the proposed methodology as a consequence of an updating of the available database, in terms of data type, quality, and accuracy, and of a more specific and enhanced statistical controls onto the final results. A comparison between the spatial distribution of vulnerability classes and the frequency of occurrences of nitrate in wells shows a high degree of correlation, both for low and high nitrate concentration. Similar results may be evidenced considering the correlation between posterior probability classes and mean nitrate concentrations in wells located in each of these classes: a high R 2 value (0.99) and the agreement with the threshold concentration value used to define prior probability testifies a general good quality of results. Groundwater-specific vulnerability has been classified in terms of vulnerability classes and, according to the outcomes of the model, the density of population can be considered the most impacting source of nitrate. Mean annual irrigation and groundwater depth can be identified as influencing factors in the distribution of nitrate, while agricultural practice appears a negligible factor.

Estimating nutrient concentrations from catchment characteristics across the UK

Abstract. Within a Geographical Information System (GIS) framework, the distributions of nitrate and orthophosphate concentrations at monitoring sites across the UK were examined and empirical relationships with catchment characteristics were established. The mean orthophosphate concentrations were linked strongly with the urban component, and less significantly with effective rainfall and agricultural coverage. This is of strategic importance in relation to phosphorus and the Water Framework Directive. Correspondingly, mean nitrate concentrations were linked to land-use types, base flow index and effective rainfall. Within-catchment residence times and effective-rainfall (runoff) were important in relation to nitrate. The issue of nitrate and the Water Framework Directive is more complex than that for orthophosphate and involves a strong agricultural as well as an urban component.

Seasonal Change of Nitrate and Oxalate Concentration in Relation to the Growth Rate of Spinach Cultivars

Reduction of nitrate and oxalate content in spinach (Spinacia oleracea L.) has become the major concern in terms of their toxicity to human health. The primary objectives of this study were 1) to determine the seasonal change in nitrate and oxalate concentrations and 2) to elucidate the relationship between growth rate and concentration of nitrate and oxalate in spinach. In a replicated field experiment in Hiratsuka, Japan, the authors grew 182 cultivars of spinach over four growing seasons (winter, spring, summer, and fall) under the nitrogen application rate of 100 kg N·ha–1. The average number of days required for harvest was the shortest in summer (32.7days) and was longest in the winter (85.7 days). Mean nitrate concentration in spinach was significantly low in the winter (3797 mg·kg–1 fresh weight) compared with the other three seasons (4122–4328 mg·kg–1 fresh weight) in which no significant differences were found in mean nitrate levels. In contrast, oxalate concentrations showed a distinct seasonal variation, being the lowest in the fall (6149 mg·kg–1 fresh weight), followed by the summer (7525 mg·kg–1 fresh weight) and the spring (8903 mg·kg–1 fresh weight), and was the highest in the winter (10,929 mg·kg–1 fresh weight). Relative nitrate concentration showed a moderate negative correlation with relative days required for harvest (r = 0.411, P &lt; 0.001), whereas relative oxalate concentration showed a strong positive correlation with relative days required for harvest (r = 0.566, P &lt; 0.001). Accordingly, a moderate negative correlation (r = 0.325, P &lt; 0.001) was detected between nitrate and oxalate concentrations. Moreover, fast-growing cultivars contained higher nitrate and lower oxalate, whereas slow-growing cultivars contained lower nitrate and higher oxalate. These results indicate that the growth rate primarily accounts for the nitrate and oxalate concentration in spinach, and nitrate and oxalate might play a counterrole to each other.

Assessment of nitrate pollution in the Grand Morin aquifers (France): Combined use of geostatistics and physically based modeling

The objective of this work is to combine several approaches to better understand nitrate fate in the Grand Morin aquifers (2700 km 2), part of the Seine basin. cawaqs results from the coupling of the hydrogeological model newsam with the hydrodynamic and biogeochemical model of river ProSe. cawaqs is coupled with the agronomic model Stics in order to simulate nitrate migration in basins. First, kriging provides a satisfactory representation of aquifer nitrate contamination from local observations, to set initial conditions for the physically based model. Then associated confidence intervals, derived from data using geostatistics, are used to validate cawaqs results. Results and evaluation obtained from the combination of these approaches are given (period 1977–1988). Then cawaqs is used to simulate nitrate fate for a 20-year period (1977–1996). The mean nitrate concentrations increase in aquifers is 0.09 mgN L −1 yr −1, resulting from an average infiltration flux of 3500 kgN.km −2 yr −1.

Nitrate leaching and bread-making quality of spring wheat following cultivation of different grasslands

The influence of sward botanical composition and ley age on grassland residual effects, quality of spring wheat and subsequent nitrate leaching was investigated. Grazed grasslands of different age (1, 2 and 8 production years) and composition (unfertilised grass-clover and fertilised perennial ryegrass) were ploughed and followed by spring wheat and spring barley. For reference, an adjacent field without grassland history but with the same crop sequence in 2002–2003 was treated with increasing quantities of N fertiliser. Yields and N uptake of spring wheat following grasslands always exceeded those of the reference plots with a history of cereal production. The nitrogen fertiliser replacement values of grass-clover and ryegrass were 59–100 and 72–121 kg ha−1, respectively, with the highest values representing the 8-year-old leys. Grain yield and N uptake increased while those for straw decreased with increasing ley age. There were no effects of previous grassland type (grass-clover/ryegrass) on content of protein, starch and gluten, but grassland age significantly influenced protein (P < 0.05) and gluten (P < 0.01) contents. It is suggested that N mineralisation following the ploughing of older grass leys occurred later than when following the first year ley. The protein and gluten contents of wheat following unfertilised grass-clover corresponded to those following cereals given 125–150 kg N ha−1, but the rheological properties of the gluten were different to what could be achieved using equivalent quantities of mineral fertiliser. Probably, the slow release of N from decomposition of old grassland gave a better synchrony between N release and plant demand. Nitrate leaching in year 1 after ploughing was significantly influenced by type of grassland (P < 0.001) with 10 and 29 kg N ha−1 leached from grass-clover and ryegrass, respectively. Nitrate leaching following ploughing of 1-year-old leys averaged 11 kg N ha−1 which was significantly lower than the 24 kg N ha−1 following 2- or 8-year-old leys. The flow-weighted mean nitrate concentration decreased from 8.5 mg N l−1 in year 1 after grassland cultivation to 4.5 mg N l−1 in year 2. More N was released following ploughing of ryegrass swards and from grasslands of increasing age, but differences were moderate compared to the estimated N-surplus. This indicates that when organic matter in grasslands is partially decomposed and readily mineralisable N used, the remaining organic N is released only very slowly.

Effect of Long‐Term Application of Biosolids for Land Reclamation on Surface Water Chemistry

Biosolids are known to have a potential to restore degraded land, but the long-term impacts of this practice on the environment, including water quality, still need to be evaluated. The surface water chemistry (NO3-, NH4+, and total P, Cd, Cu, and Hg) was monitored for 31 yr from 1972 to 2002 in a 6000-ha watershed at Fulton County, Illinois, where the Metropolitan Water Reclamation District of Greater Chicago was restoring the productivity of strip-mined land using biosolids. The mean cumulative loading rates during the past 31 yr were 875 dry Mg ha(-1) for 1120-ha fields in the biosolids-amended watershed and 4.3 dry Mg ha(-1) for the 670-ha fields in the control watershed. Biosolids were injected into mine spoil fields as liquid fertilizer from 1972 to 1985, and incorporated as dewatered cake from 1980 to 1996 and air-dried solids from 1987 to 2002. The mean annual loadings of nutrients and trace elements from biosolids in 1 ha were 735 kg N, 530 kg P, 4.5 kg Cd, 30.7 kg Cu, and 0.11 kg Hg in the fields of the biosolids-amended watershed, and negligible in the fields of the control watershed. Sampling of surface water was conducted monthly in the 1970s, and three times per year in the 1980s and 1990s. The water samples were collected from 12 reservoirs and 2 creeks receiving drainage from the fields in the control watershed, and 8 reservoirs and 4 creeks associated with the fields in the biosolids-amended watershed for the analysis of NO3- -N (including NO2- N), NH4+-N, and total P, Cd, Cu, and Hg. Compared to the control (0.18 mg L(-1)), surface water NO3- -N in the biosolids-amended watershed (2.23 mg L(-1)) was consistently higher; however, it was still below the Illinois limit of 10 mg L(-1) for public and food-processing water supplies. Biosolids applications had a significant effect on mean concentrations of ammonium N (0.11 mg L(-1) for control and 0.24 mg L(-1) for biosolids) and total P (0.10 mg L(-1) for control and 0.16 mg L(-1) for biosolids) in surface water. Application of biosolids did not increase the concentrations of Cd and Hg in surface water. The elevation of Cu in surface water with biosolids application only occurred in some years of the first decade, when land-applied sludges contained high concentrations of trace metals, including Cu. In fact, following the promulgation of 40 CFR Part 503, the concentrations of all three metals fell below the method detection level (MDL) in surface water for nearly all samplings. Nitrate in the surface water tends to be higher in spring, and ammonium, total P, and total Hg in summer and fall. Mean nitrate, ammonium, and total phosphorus concentrations were found to be greater in creeks than reservoirs. The results indicate that application of biosolids for land reclamation at high loading rates from 1972 to 2002, with adequate runoff and soil erosion control, had only a minor impact on surface water quality.

Effect of soil covering on nitrogen availability of vineyards soils in Champagne area

&lt;p style="text-align: justify;"&gt;We studied the effect of soil cover (bare soil, mulch of barks or composted organic materials, grass cover) on soil N dynamics in various experimental vineyards located in Champagne area (France). Soil cores were sampled periodically to measure water and mineral N in soil profile during autumn and winter. These measurements were used in a simple dynamic model (LIXIM) to calculate nitrate leaching and N mineralization. N mineralization potential of soils were also determined in laboratory incubations in controlled conditions. In most sites, soil inorganic N contents (0-75 cm) varied between 20 and 60 kg N ha-1, depending of the season. Soil inorganic N in plots receiving barks or composted barks or covered with grass did not differ significantly from control plots. Higher amounts of inorganic N were found in soils amended with refuse compost, peat or mixed compost (barks + farmyard manure) or composted farmyard manure. The model indicated that N leached varied from 8 to 77 kg N ha-1 and that the mean nitrate concentration in drained water was less than 50 mg NO3- L-1 except for plots receiving refuse compost or bark + farmyard manure compost. The calculated N mineralization varied from 9 to 45 kg N ha-1 over the autumn-winter period, i.e. 118 to 182 days. The N mineralization rate (Vp), expressed per 'normalised day' i.e. day at 15°C and field capacity, varied from 0.15 to 0.82 kg N ha-1 nd-1, including all sites and experimental treatments. Effect of organic matter addition on Vp was only observed for long-term experimental sites where large amounts of organic nitrogen had been added to soil using peat, refuse compost or compost mixtures with barks and farmyard manure. The Vp values measured in laboratory incubations showed the same trends and were in the same order of magnitude than those calculated with LIXIM model using in situ data. In average, the values measured in laboratory incubations underestimated the actual N mineralization in field conditions. The model was used to predict N mineralization and inorganic N in soil during the vegetative period using Vp values. It allowed to estimate the N uptake by vine: 10 ± 5 kg N ha-1 at flowering and 57 ± 5 kg N ha-1 over the whole growing period. These results show that soil N availability was sufficient to feed the vine during the whole growing period and that no inorganic N fertilisation was necessary, even in the grass covered soil. In this soil, water availability is probably the limiting factor when depressive effects are observed. On the long-term, it is necessary to manage the amount and quality of added organic matter since organic inputs may modify N availability and therefore vine behaviour, wine quality and environmental risks.&lt;/p&gt;

Nitrogen Fluxes in Silage Maize Production: Relationship between Nitrogen Content at Silage Maturity and Nitrate Concentration in Soil Leachate

A challenge with respect to environmental soundness of agricultural production is the development of suitable indicators, which support an improved understanding and measurement of agricultural activities on environmental quality. The objective of this study was to investigate whether N concentration (Nc) of silage maize at silage maturity, a routinely recorded quality parameter, can serve as an indicator of nitrate concentration in the soil leachate (NO3C). The study was based on a 5-year experiment (1997–2001), conducted on sandy soil in Northern Germany. The experiment involved four mineral N fertilization rates (0, 50, 100, 150 kg N ha−1) and three slurry treatments (0, 20, 40 m3 ha−1). The water and N balance model HERMES was applied to simulate the N flows within the soil–plant system. The model performed satisfactorily for aboveground biomass accumulation, N uptake, soil mineral N, and nitrate leaching. Statistical analysis of the relationship between measured crop N concentration (Nc, g N kg−1) at silage maturity and simulated mean nitrate concentration (NO3C, mg NO31−1) of the leachate (October–March) revealed a significant impact of rainfall amount during spring/summer. Two exponential functions were estimated to describe the relationship for (i) ℈wet’ years: NO3C = 3.4253 × exp(0.3426 × Nc), and (ii) ℈dry’ years: NO3C = 6.8538 × exp(0.1811 × Nc). While in ℈dry’ years nitrate concentration exceeded the drinking water threshold even at very low N concentrations, the risk of high nitrate concentrations was negligible in ℈wet’ years. It is concluded that the newly developed indicator can provide a useful tool for assessing the potential risk of groundwater nitrate contamination in silage maize production.

Statistical Analysis of Nitrate Movement through the Soil in Central Kansas

An earlier investigation by the Kansas Geological Survey in central Kansas studied the movement of nitrate from fertilizer through soil into the groundwater. Nitrate concentrations in soil water were measured on samples collected at three locations during a three-year span, from sets of lysimeters buried at different depths. Although patterns seemed apparent in the resulting measurements, no statistical analyses were performed to test their significance; this re-study of the data uses analyses of variance to test for differences in nitrate concentration attributable to time and to depth in the soil. The mean nitrate concentration of samples collected in the first year of the experiment was significantly higher than the means of second and third year samples at all three locations, perhaps reflecting the confounding influence of a previous flooding experiment. ANOVAs of depth across years determined few significant differences in nitrate concentration with depth. The wintertime gap in measurements and unequal sampling through time precludes formal time-series analyses, but graphs of concentration versus time show that peak concentration occurs at later times with increasing depth, and that maximum concentration decreases with depth. These statistical analyses support the conclusions from the original investigation.

Agricultural activities impact on groundwater nitrate pollution

Concern over agricultural diffuse pollution sources in integrated water quality management has been growing recently. High nitrogen fertilizers application rates may increase the potential groundwater pollution. These effects were investigated in Andimeshk and Susa plains that cover an area of 1100 km 2 between the Dez and Karkhe rivers in north of Khozestan-Iran. This region divided to 4 sub-regions A, B, C, and D. Additionally 168 groundwater samples were collected from 42 water wells during the months April, May, August, and September of 2004. The Hackspectrophotometer nitrate test was used to measure the NO3 - concentration in water samples. Information about further nitrate data was obtained. A questionnaire procedure was used for collection N-fertilizers application rate data in studied area. The results demonstrated that all of the groundwater samples have NO3 - concentration below the EPA MCL (44.27 mg/l) and WHO guideline (50 mg/l). The mean nitrate concentrations are 16.1, 19.5, 13.3, and 7.9 mg/l in sub-regions A, B, C, and D respectively. There are different amount of N-fertilizers applied in sub-regions A, B, C, and D. Correlation between NO3 concentrations and N-fertilizers rate suggests a inverse correlation between Nfertilizers application rate and ground waters nitrate concentrations in studied area (r=-0.69).

CHANGES IN RIVER NITRATE TRANSPORT OF THE WORLD RESULTED FROM INCREASE IN FERTILIZER USE

Nitrogenous fertilizer use of the world increased rapidly in the second half of 20th century. This change has been the main cause of human-induced disturbance of global nitrogen cycles. In this paper, we focus on river nitrate transport of the world. Much of river nitrate comes from soil layers of terrestrial areas. Thus, we first estimated nitrate leaching from soil layers using a terrestrial nitrogen cycle model using datasets of nitrogen fertilizer use, climate and soil conditions, and subsequently, simulated river nitrate transport. The terrestrial nitrogen cycle model consists of several flux calculations at daily time scale. A global river channel network data was used in the river nitrate transport simulation. These calculations were carried out using datasets of 1955, 1965, 1975, 1985 and 1995. The result of 1995 was compared with mean nitrate concentration data of several large rivers observed by GEMS/Water and agreed with it reasonably. The transported nitrate at river mouth was then aggregated to see its load to oceans. Finally, comparing each year result, significant impact of fertilizer increase was found.