Total Nitrogen Yield Research Articles

A hydrological and nutrient load balance for the Lake Clearwater catchment, Canterbury, New Zealand

Nitrogen and phosphorus entering waterways from diffuse agricultural sources is a major problem in New Zealand and internationally. This problem is well documented for lowland areas but little is known about nutrient enrichment from farming in high country areas. The Lake Clearwater catchment, in the Canterbury high country of New Zealand, has a native ecosystem that has adapted to low-nutrient conditions. The Department of Conservation's Arawai Kakariki Wetland Restoration Programme identifies wetlands in the catchment as one of three key endemic wetland types. Uncertainty regarding diffuse nutrient load from agriculture into the lake and wetland is limiting effective management of this unique catchment. This study investigated the hydrological regimes and nitrogen and phosphorus concentrations and loads in five key surface waterways at ten surface water sites and three groundwater seeps for two years. It aims to improve knowledge of nutrient sources, characteristics and loads from agricultural land use in this 46 km2 high country catchment. Additionally, nutrient load predictions from the Catchment Land Use for Environmental Sustainability (CLUES) model were compared to measured nutrient loads to assess the applicability of the model in high country catchments. The CLUES model was developed, primarily for lowland areas, to predict changes in water quality and nutrient loads from land-use change. The total nitrogen concentrations downstream of farmland were typically above the Australia and New Zealand Environment and Conservation Council (ANZECC) water quality guideline and the median concentration for upland Canterbury waterways. Specifically, the nitrate concentration (0.19-0.29 g m-3) in farmland subsurface runoff was elevated, compared to streams in the Lake Clearwater catchment with unfarmed catchments, and was estimated to contribute 52% of total nitrogen yield from farmland. The total nitrogen yield (1.96-2.94 kg ha-1 year-1) for farmed land was comparable to minimum values for New Zealand pastoral land use reported in the literature. The total estimated nitrogen export from Lake Clearwater (2518 kg year-1) was 83% greater than the estimated diffuse input from all land in the catchment (1375 kg year-1). This indicated an additional source of nitrogen into the lake and seasonal nitrogen saturation. Total phosphorus yields (0.093-0.123 kg ha-1 year-1) downstream of farmland were well below yields for New Zealand pastoral land use reported in the literature. Total estimated phosphorus export from the lake (58 kg year-1) was 24% less than total estimated diffuse loads into the lake (76 kg year-1). The ratio of total nitrogen to total phosphorus in Lake Clearwater (49:1) indicated that phosphorus is the limiting nutrient and that nitrogen loads into the lake are above natural levels. Total nitrogen loads predicted by the CLUES model in the Lake Clearwater catchment were reasonable, providing land-use area inputs are accurate and nutrient loads exit catchments in surface water. However, CLUES greatly overestimated phosphorus loads from farmed and unfarmed land.

Characterization of the seed and seed extracts of the pumpkins Cucurbita maxima D. and Cucurbita pepo l. from Macedonia

Chemical composition of seeds of C. maxima D. and C. pepo L. cultivated in the Republic of Macedonia and physico-chemical characteristics, fatty acid profiles, and sterol and tocopherol contents in pumpkin seed extracts were determined. Higher kernel yield and content of moisture, ash, total nitrogen, proteins and carbohydrates were measured in the C. pepo than in C. maxima seed. The highest extract yield of 487.4 g/kg dry matter was obtained from C. pepo kernel, while 388.2 g/kg dry matter was extracted from C. maxima kernel, when n-hexane was used as solvent. In all extracts, the palmitic, stearic, oleic and linoleic acids were predominant. The linoleic/oleic acid ratio was higher in C. maxima extracts. D7-Sterols were predominant in all extracts, while D5-sterols content was higher in the whole seed than in the kernel extracts. Higher tocopherol content was determined in the extracts of C. pepo whole seed and kernel (153.79 mg/kg and 117.81 mg/kg, respectively), than in those of C. maxima (121.24 mg/kg and 117.55 mg/kg, respectively). In all extracts γ-tocopherol content was higher than α-tocopherol.

Evaluation of spatial variability on hydrology and nutrient source loads at watershed scale using a modeling approach

Understanding the effects of spatial variability on hydrologic parameters and nutrient source load distribution is essential to develop water quality improvement programs. The objective of this research was to evaluate spatially distributed hydrologic variability, nutrient sources, and their loadings at the watershed scale using a modeling approach. The Soil and Water Assessment Tool (SWAT) was applied to assess spatial variability of annual average water, sediment, total phosphorus (TP), and total nitrogen (TN) yields from the Upper Pearl River Watershed (UPRW) in Mississippi, USA. The SWAT model was successfully calibrated, validated, and verified with good model efficiency (R2 = 0.70 and E = 0.59) using monthly measured stream flow, daily observed flow, sediment, TP, and TN yields. The SWAT model results determined that spatial variability of annual average pollutant loads of water yield ranged from 877 to 206 mm, sediment yield ranged from 1.71 to 0.17 t ha−1, TP ranged from 1.39 to 0.02 kg ha−1, and TN ranged from 10.22 to 0.69 kg ha−1 in the watershed sub-basins. Understanding of the spatial variability of hydrologic and nutrient source loads distribution helps watershed managers focus their management efforts to the most needy watershed sub-basins.

Estimating the Sources and Transport of Nitrogen Pollution in the Ishikari River Basin, Japan

The hybrid mechanistic-statistical watershed model SPARROW (Spatially Referenced Regression on Watershed Attributes) was applied to estimate the sources and transport of total nitrogen (TN) in surface waters of Ishikari River Basin (14,330 km2), the largest watershed on the Hokkaido Island of Japan. The loads from atmospheric deposition, point sources and erosion are routed through the drainage network (900 streams) with first-order stream decay. Then we calibrated the model using measurements of TN from 31 monitoring sites of mixed spatial data on topography, soils and stream hydrography. The R2 and MSE are 0.82 and 0.62 separately. On this basis, the predication of TN distribution was evaluated, and the mean incremental annual TN yield was 11.61kg/ha/yr.

Estimating Nitrogen Yield for a Catchment of Lake Taihu Based on Distributed Hydrological Modelling

Nitrogen and phosphorous pollution is common in China and worldwide. The pollution deteriorates water quality and even causes significant change of the freshwater ecosystem. Management must be strengthened in order to reduce the pollution to secure water supply safety and to maintain healthy ecosystems. This paper investigated the yield of total nitrogen (TN) for different land use types, exemplified in the Xitiaoxi catchment of Lake Taihu basin, where catchment-generated nitrogen pollution is severe. Extensive water quality sampling was performed for different river levels and various land use types. A distributed hydrological model was also employed to simulate the river discharges at locations where flow observation is not available, and the simulated river discharges were used for the calculation of nitrogen yield. It is found that generally the catchment’s nitrogen export is still as high as 2.6 t/km2/year. The yield for forest is 0.8-1.0 t/km2/year, while the yields for arable land and for the river sections immediately downstream of urban area are higher than the average ranging 2.8-3.3 t/km2/year. It is also concluded that the hydrological modelling using a spatially distributed model is helpful and essential in obtaining flows at any locations, which can subsequently be used jointly with the water quality data to identify the critical source areas with high nitrogen yields.

Sources and Delivery of Nutrients to the Northwestern Gulf of Mexico from Streams in the South-Central United States1

SPAtially Referenced Regressions On Watershed attributes (SPARROW) models were developed to estimate nutrient inputs [total nitrogen (TN) and total phosphorus (TP)] to the northwestern part of the Gulf of Mexico from streams in the South-Central United States (U.S.). This area included drainages of the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf hydrologic regions. The models were standardized to reflect nutrient sources and stream conditions during 2002. Model predictions of nutrient loads (mass per time) and yields (mass per area per time) generally were greatest in streams in the eastern part of the region and along reaches near the Texas and Louisiana shoreline. The Mississippi River and Atchafalaya River watersheds, which drain nearly two-thirds of the conterminous U.S., delivered the largest nutrient loads to the Gulf of Mexico, as expected. However, the three largest delivered TN yields were from the Trinity River/Galveston Bay, Calcasieu River, and Aransas River watersheds, while the three largest delivered TP yields were from the Calcasieu River, Mermentau River, and Trinity River/Galveston Bay watersheds. Model output indicated that the three largest sources of nitrogen from the region were atmospheric deposition (42%), commercial fertilizer (20%), and livestock manure (unconfined, 17%). The three largest sources of phosphorus were commercial fertilizer (28%), urban runoff (23%), and livestock manure (confined and unconfined, 23%).

Seasonal changes of nutrient fluxes in the Upper Changjiang basin: An example of the Longchuanjiang River, China

summary Fluxes of dissolved and particulate nitrogen (N) and phosphorus (P) variables were measured monthly from September 2007 to March 2009 in the upper Longchuanjiang River (Yunnan Province, China) to determine annual loads and seasonal variability. Dissolved N (DN) and particle associated P (PAP) contributed 56% and 99% of the total nitrogen (TN) and total phosphorus (TP) yields of 549 and 608 kg/km 2 /yr. Fluxes of particulate N (PN), dissolved P (DP), PAP and TP exhibited great seasonality because they were highly correlated with water discharge. Areal export rates of NH þ 4 –N, PN, PAP and TP were higher than in the main channel and most tributaries of the Changjiang River. High particulate loads were contributed to erosion of phosphorus-rich soils during heavily rains in the wet season. Median measured concentrations of TN, NH þ 4 –N and TP exceeded the maximum permissible limit for domestic and recreational use in China. High nitrogen and phosphorus concentrations draw attention to the potential for additional nutrient loading to foster the formation of algal blooms in locations where free-flowing river sections are changing into cascades of reservoirs. Importantly, the great seasonality in the data shows necessity of sufficient sampling for determining annual fluxes.

Capillary electrophoresis characterisation of humic acids: application to diverse forest soil samples

Environmental contextAnalysis of soil organic matter is important for understanding turnover and stabilisation processes of organic carbon in soils. Capillary electrophoresis is used here to investigate humic acids from soils of diverse forest sites, and show that the patterns of signals are indicative of soil characteristics. The method provides useful information of soil types and complements the existing set of methods for humic acid characterisation. AbstractAnalyses of humic substances provide very useful information about turnover characteristics and stabilisation processes of soil organic matter in environmental soil samples. The present study investigates 113 samples of forest soils from three different layers (undecomposed litter (L), if present, mixed samples of F (intermediate decomposed) and H (highly decomposed) organic matter (FH) and upper mineral soil layers (Ah horizon) from 0 to 5 cm) by extracting humic acids (HAs) and recording electropherograms. Five signals of these electropherograms were evaluated and correlated with basic parameters from soil (organic carbon, Corg, and total nitrogen, Nt, and extraction yields of HAs) and HAs (total carbon, Ct, and Nt), and with signals from photometry, mid-infrared and fluorescence spectroscopy. The developed method was able to separate HAs from different soil layers by calculating a discriminant function based on the five evaluated electrophoretic signals. The dataset of this work opened the opportunity to correlate the observed electrophoretic signals with the other determined soil parameters and spectroscopic signals. This can be seen as a very important step in the direction to assignments of the obtained electrophoretic signals. Soil characteristics were reflected quite well by this method and, combined with the other approaches, it is suitable for applications in further studies.

Effects of irrigation with treated wastewater on olive tree growth, yield and leaf mineral elements at short term

In arid regions, such as Tunisia, the reuse of treated wastewater (TWW) in agriculture can be a sustainable solution for water scarcity. A two-year field experiment was conducted in order to investigate the short-term effects of TWW on olive growth, yield and concentration of total nitrogen (N t), potassium (K), phosphorous (P), and heavy metals (i.e. Zn, Mn, Pb and Cd) in olive leaves. Olive trees were subjected to the following irrigation treatments: (i) trees irrigated with well water (WW) and (ii) trees irrigated with treated wastewater (TWW). For both treatments, the TWW and WW were applied at a rate of 4.5 m 3 day −1 tree −1 (5000 m 3 ha −1 year −1). After two years, non-significant injuries caused by salts and/or heavy metals were observed on shoot growth of trees irrigated with TWW. The application of TWW significantly increased concentration of N t, P and K in the leaves, whereas heavy metals (Zn and Mn) showed a significant increase only after the second year of irrigation.

A Synoptic Survey of Nitrogen and Phosphorus in Tributary Streams and Great Rivers of the Upper Mississippi, Missouri, and Ohio River Basins

We combined stream chemistry and hydrology data from surveys of 436 tributary stream sites and 447 great river sites in the Upper Mississippi, Missouri and Ohio River basins to provide a regional snapshot of baseflow total nitrogen (TN) and total phosphorus (TP) concentrations, and to investigate the relationships between land use and stream chemistry. Catchments in the Upper Mississippi River basin had more land in agricultural uses (51%) than the Missouri or Ohio River basin catchments (25% and 29%, respectively). The difference in agriculture is reflected in the TN concentrations in tributary streams and the great rivers: 5,431 and 2,112 μg L−1 for the Upper Mississippi, 1,751 and 978 μg L−1 for the Missouri, and 1,074 and 1,152 μg L−1 for the Ohio River basins. This agricultural effect was not as evident for tributary stream or great river TP concentrations: 165 and 181 μg L−1 in the Upper Mississippi, 177 and 171 μg L−1 in the Missouri, and 67 and 53 μg L−1 in the Ohio River basins. We set reference thresholds based on the 75th percentile TN and TP concentrations at our least disturbed sites. The TN threshold was exceeded for 50–63% of the tributary stream and 16–55% of great river lengths, with the greatest proportion in the Upper Mississippi River basin. The TP threshold was exceeded in 32–48% of tributary stream and 12–41% of great river lengths. Tributary stream N/P ranged from 67:1 (Ohio) to 210:1 (Upper Mississippi); river N/P ranged from 20:1 (Missouri) to 60:1 (Ohio). N/P indicated that potential N-limitation occurred in 10–21% of total tributary stream length and in 0–46% of great river length; potential P-limitation ranged from 60–83% of cumulative tributary stream length and from 21–98% of cumulative great river length. Total N flux (concentration × discharge) was highest in the Upper Mississippi River basin; TP flux was lowest in the Ohio River basin. River TN yields and TP yields for both tributary streams and great rivers, was not significantly different between the sub-basins. Our study empirically links catchment land use and stream chemistry, and demonstrates using monitoring data for estimating nutrient yields at a large regional scale.

Water Quality Response to Different Defarming Scenarios in Bai River Basin

In order to estimate non-point source pollution under different defarming scenarios in Bai River Basin. Geographic informational system (GIS) and the Soil and Water Assessment Tool (SWAT) was used to simulate the transport of runoff, sediment, total nitrogen and total phosphorus into the Zhangjiafen stations. The results showed: The SWAT generally performs well and could accurately simulate monthly runoff, sediment, total nitrogen and total phosphorus yield with a Nash-Sutcliffe coefficient and a coefficient of determination of greater than 0.7 during calibration and validation. Three kinds of measures were obvious with reducing sediment, total nitrogen and total phosphorus in effect, conversion of farmland back to forests in whole watershed had the most effect on it.

Effects of urban and non-urban land cover on nitrogen and phosphorus runoff to Chesapeake Bay

Abstract The aim of this study was to determine the effects of catchment and riparian stream buffer-wide urban and non-urban land cover/land use (LC/LU) on total nitrogen (TN) and total phosphorus (TP) runoff to the Chesapeake Bay. The effects of the composition and configuration of LC/LU patches were explored in particular. A hybrid-statistical-process model, the SPAtially Referenced Regression On Watershed attributes (SPARROW), was calibrated with year 1997 watershed-wide, average annual TN and TP discharges to Chesapeake Bay. Two variables were predicted: (1) yield per unit watershed area and (2) mass delivered to the upper estuary. The 166,534 km 2 watershed was divided into 2339 catchments averaging 71 km 2 . LC/LU was described using 16 classes applied to both the catchments and also to riparian stream buffers alone. Seven distinct landscape metrics were evaluated. In all, 167 (TN) and 168 (TP) LC/LU class metric combinations were tested in each model calibration run. Runs were made with LC/LU in six fixed riparian buffer widths (31, 62, 125, 250, 500, and 1000 meters (m)) and entire catchments. The significance of the non-point source type (land cover, manure and fertilizer application, and atmospheric deposition) and factors affecting land-to-water delivery (physiographic province and natural or artificial land surfaces) was assessed. The model with a 31 m riparian stream buffer width accounted for the highest variance of mean annual TN ( r 2 = 0.9366) and TP ( r 2 = 0.7503) yield (mass for a specified time normalized by drainage area). TN and TP loadings (mass for a specified time) entering the Chesapeake Bay were estimated to be 1.449 × 10 8 and 5.367 × 10 6 kg/yr, respectively. Five of the 167 TN and three of the 168 TP landscape metrics were shown to be significant ( p -value ≤ 0.05) either for non-point sources or land-to-water delivery variables. This is the first demonstration of the significance of riparian LC/LU and landscape metrics on water quality simulation in a watershed as large as the Chesapeake Bay. Land cover metrics can therefore be expected to improve the precision of estimated TN and TP annual loadings to the Chesapeake Bay and may also suggest changes in land management that may be beneficial in control of nutrient runoff to the Chesapeake Bay and similar watersheds elsewhere.

Evaluation of Dandelion as a Potential Forage Species in Mixed‐Species Swards

Recent research has indicated that increasing species diversity of the pastures might improve sward productivity and stability. The present experiment evaluates the effect of dandelion (Taraxacum officinaleWeber) as a potential pasture species on the performance of a perennial ryegrass (Lolium perenneL.)–white clover (Trifolium repensL.) mixture in terms of total herbage yield, weed infestation, and nitrogen (N) yield in a replacement‐series experiment over three harvest years. The three species were grown in monocultures and in all possible binary and three‐species mixtures under two N fertilization levels (0 and 200 kg N ha−1). Herbage yield and N yield of the three‐species mixture were not significantly different from the ryegrass–white clover mixture over the 3 yr. The contribution of dandelion to the total herbage yield increased over years, which improved yield stability. A competition analysis, performed by calculating relative yield and relative yield total, indicated that ryegrass had a competitive advantage over white clover in fertilized and unfertilized swards, but over dandelion only when the sward was fertilized. Nitrogen application reduced the nonsown species yield in all mixtures, except that of white clover–dandelion. Our results indicate that dandelion might have the potential of contributing to herbage yield, nutritive value, and resistance to invasions of ryegrass–white clover pastures.

Detecting Temporal Change in Watershed Nutrient Yields

Meta-analyses reveal that nutrient yields tend to be higher for watersheds dominated by anthropogenic uses (e.g., urban, agriculture) and lower for watersheds dominated by natural vegetation. One implication of this pattern is that loss of natural vegetation will produce increases in watershed nutrient yields. Yet, the same meta-analyses also reveal that, absent land-cover change, watershed nutrient yields vary from one year to the next due to many exogenous factors. The interacting effects of land cover and exogenous factors suggest nutrient yields should be treated as distributions, and the effect of land-cover change should be examined by looking for significant changes in the distributions. We compiled nutrient yield distributions from published data. The published data included watersheds with homogeneous land cover that typically reported two or more years of annual nutrient yields for the same watershed. These data were used to construct statistical models, and the models were used to estimate changes in the nutrient yield distributions as a result of land-cover change. Land-cover changes were derived from the National Land Cover Database (NLCD). Total nitrogen (TN) yield distributions increased significantly for 35 of 1550 watersheds and decreased significantly for 51. Total phosphorus (TP) yield distributions increased significantly for 142 watersheds and decreased significantly for 17. The amount of land-cover change required to produce significant shifts in nutrient yield distributions was not constant. Small land-cover changes led to significant shifts in nutrient yield distributions when watersheds were dominated by natural vegetation, whereas much larger land-cover changes were needed to produce significant shifts when watersheds were dominated by urban or agriculture. We discuss our results in the context of the Clean Water Act.

Assessment of process control parameters in the biochemical methane potential of sunflower oil cake

Abstract A laboratory-scale study was conducted on the batch anaerobic digestion of sunflower oil cake (SuOC), solid waste derived from the extraction process of sunflower oil. A multi-reactor system was used to compare methane production from this waste at inoculum to substrate ratios (ISRs) of 3.0, 2.0, 1.5, 1.0, 0.8 and 0.5 (expressed as volatile solids (VS) basis). The tests were carried out at mesophilic temperature (35 °C) and run against a control of inoculum without substrate. The results obtained in the biochemical methane potential (BMP) tests showed that the ultimate methane yield (YM,ult) decreased considerably from 227±23 to 107±11 ml CH4 at standard temperature and pressure (STP) conditions g−1 VSadded when the ISR decreased from 3.0 to 0.5, showing a clear influence of the ISR on the methane yield coefficient. The biodegradability (BD) of the waste also decreased from 86% to 41% when the ISR varied from 3.0 to 0.5. A net total ammonia nitrogen (TAN) yield of 39.2 mg N g−1 VSadded was obtained, and this value was not influenced by the ISRs assayed, which demonstrated the appropriate operation of the hydrolytic–acidogenic stage of the overall digestion process. A clear imbalance of the methanogenic process was observed at the lowest ISRs studied (0.5 and 0.8) due to a considerable increase in CODs and TVFA in the digestates. The profile of VFA was also influenced by the ISR, typical of the proteinaceous substrates.

Effects of carbonized and dried chicken manures on the growth, yield, and N content of soybean

The present study was conducted to investigate the effects of nitrogen derived from dried or carbonized chicken manure on growth, nodulation, yield and N content of soybean. 15N labeled chicken manure used in this study was obtained from the droppings of chicken fed on hulled rice grown under field conditions and fertilized with 15N-labeled stable isotope ammonium sulphate and potassium nitrate fertilizers. Carbonized chicken manure was made by heat treatment in a muffle furnace in our laboratory. This study was conducted in pots filled with clay loam soil. Results from the study show that the application of carbonized chicken manure increased soybean seed yield by 23% and 43% for the 50 and 100 kg N ha−1 rates respectively. Dried chicken manure application increased soybean seed yield by 7% and 30% for the 50 and 100 kg N ha−1 rates respectively. There was no difference in the N manure yield of both manures when applied at the same rate. The percentage 15N recovery was 17.6% and 8.9% for carbonized chicken manure, 19.2% and 10.5% for dried chicken manure at 50 and 100 kg N ha−1 rates respectively at peak flowering stage of soybean growth. We found high total nitrogen yields of soybean at the rate of 100 kg N ha−1 for both manures. There was a positive relationship between number of nodules and seed yield of soybean. Total N content also showed positive relationship with number of nodules and seed yield of soybean. We supposed that the higher P content of carbonized chicken manure is responsible for the higher seed yield and nodule growth compared to dried chicken manure.

Dominance of organic nitrogen from headwater streams to large rivers across the conterminous United States

The frequency and magnitude of hypoxic areas in coastal waterbodies are increasing across the globe, partially in response to the increase in nitrogen delivery from the landscape (Diaz, 2001; Rabalais et al., 2002). Although studies of annual total nitrogen and nitrate yields have greatly improved understanding of the contaminant sources that contribute to riverine nitrogen loads (Alexander et al., 2000; Caraco and Cole, 1999), the emphasis of these studies on annual timescales and selected nitrogen forms is not sufficient to understand the factors that control the cycling, transport, and fate of reactive nitrogen. Here we use data from 850 river stations to calculate long‐term mean‐annual and interannual loads of organic, ammonia, and nitrate‐nitrite nitrogen suitable for spatial analysis. We find that organic nitrogen is the dominant nitrogen pool within rivers across most of the United States and is significant even in basins with high anthropogenic sources of nitrogen. Downstream organic nitrogen patterns illustrate that organic nitrogen is an abundant fraction of the nitrogen loads in all regions. Although the longitudinal patterns are not consistent across regions, these patterns are suggestive of cycling between ON and NO3− on seasonal timescales influenced by land use, stream morphology, and riparian connectivity with active floodplains. Future regional studies need to incorporate multinitrogen species at intraannual timescales, as well as stream characteristics beyond channel depth, to elucidate the roles of nitrogen sources and in‐stream transformations on the fate and reactivity of riverine nitrogen transported to coastal seas.

Molecular beam measurements and Monte Carlo simulations of the kinetics of N2O decomposition on Rh(111) single-crystal surfaces

The kinetics of N2O decomposition on Rh(111) single-crystal surfaces were investigated both experimentally by isothermal molecular beam measurements and theoretically using a Monte Carlo algorithm. The present work was directed to the understanding of two unusual observations derived from our previous work on this system, namely, (1) the lower rates for N2O decomposition seen at higher reaction temperatures, and (2) the lower total nitrogen yields and final oxygen surface coverages that accompany that behavior. Experimentally, it was determined here that after the rhodium surface is rendered inactive by N2O decomposition at high (520 K) temperatures, significant activity is still possible at lower (350 K) temperatures. The Monte Carlo simulations explain these observations by assuming that the surface sites required for the activation of adsorbed N2O increase in size with increasing reaction temperature.

The fertilizing effect of compost and biogas residues from source separated household waste

In Sweden, deposition of organic waste will be prohibited in the year 2005. Instead, the waste will be either incinerated or source separated, processed (composted or anaerobically digested) and recycled back to arable land. In order to evaluate the biologically processed waste products as fertilizers, a field experiment was initiated in Sweden in the autumn of 1998. The main focus of the experiment was to compare compost (C) from source-separated domestic waste with biogas residues (BR) from source-separated domestic waste. Each fertilizer was applied in two combinations: in treatments C50 and BR50, 50 kg N/ha/year originates from the waste and 50 kg N/ha/year from mineral nitrogen fertilizer, while in C100 and BR100, the organic wastes were the only plant nutrient sources (100 kg N/ha/year). Mineral fertilizer (NPS100) and unamended were used as controls. Generally pure mineral fertilizers resulted in the highest yield, while control without nitrogen generated the lowest yield. A combination of organic fertilizer and mineral fertilizer resulted in higher yield compared with applying sole organic fertilizer. Total mineral N in the fertilizer was generally the best overall predictor/regressor for grain yield, total nitrogen yield and apparent bioavailable nitrogen. Application of biogas residue resulted in higher yield and grain quality than compost. The higher concentration of nitrogen in oats suggested that oats is a better choice when using compost as a fertilizer. In conclusion, compost and anaerobic biogas residues should not be used as sole fertilizers. Compost should be complemented with mineral N and the biogas residues with P. If compensation for the low content of mineral N in compost is made by a higher application rate, large amounts of heavy metals might be applied along with the compost.

NUTRIENT MASS BALANCE AND TRENDS, MOBILE RIVER BASIN, ALABAMA, GEORGIA, AND MISSISSIPPI1

ABSTRACT: A nutrient mass balance — accounting for nutrient inputs from atmospheric deposition, fertilizer, crop nitrogen fixation, and point source effluents; and nutrient outputs, including crop harvest and storage — was calculated for 18 subbasins in the Mobile River Basin, and trends (1970 to 1997) were evaluated as part of the U.S. Geological Survey National Water Quality Assessment (NAWQA) Program. Agricultural nonpoint nitrogen and phosphorus sources and urban nonpoint nitrogen sources are the most important factors associated with nutrients in this system. More than 30 percent of nitrogen yield in two basins and phosphorus yield in eight basins can be attributed to urban point source nutrient inputs. The total nitrogen yield (1.3 tons per square mile per year) for the Tombigbee River, which drains a greater percentage of agricultural (row crop) land use, was larger than the total nitrogen yield (0.99 tons per square mile per year) for the Alabama River. Decreasing trends of total nitrogen concentrations in the Tombigbee and Alabama Rivers indicate that a reduction occurred from 1975 to 1997 in the nitrogen contributions to Mobile Bay from the Mobile River. Nitrogen concentrations also decreased (1980 to 1995) in the Black Warrior River, one of the major tributaries to the Tombigbee River. Total phosphorus concentrations increased from 1970 to 1996 at three urban influenced sites on the Etowah River in Georgia. Multiple regression analysis indicates a distinct association between water quality in the streams of the Mobile River drainage basin and agricultural activities in the basin.