Emissions of N2O and NO from fertilized fields: summary of available measurement data

Information from 846 N2O emission measurements in agricultural fields and 99 measurements for NO emissions was summarized to assess the influence of various factors regulating emissions from mineral soils. The data indicate that there is a strong increase of both N2O and NO emissions accompanying N application rates, and soils with high organic-C content show higher emissions than less fertile soils. A fine soil texture, restricted drainage, and neutral to slightly acidic conditions favor N2O emission, while (though not significant) a good soil drainage, coarse texture, and neutral soil reaction favor NO emission. Fertilizer type and crop type are important factors for N2O but not for NO, while the fertilizer application mode has a significant influence on NO only. Regarding the measurements, longer measurement periods yield more of the fertilization effect on N2O and NO emissions, and intensive measurements (=1 per day) yield lower emissions than less intensive measurements (2–3 per week). The available data can be used to develop simple models based on the major regulating factors which describe the spatial variability of emissions of N2O and NO with less uncertainty than emission factor approaches based on country N inputs, as currently used in national emission inventories

Human alteration of the global nitrogen and phosphorus soil balances for the period 1970-2050

The Millennium Ecosystem Assessment scenarios for 2000 to 2050 describe contrasting future developments in agricultural land use under changing climate. Differences are related to the total crop and livestock production and the efficiency of nutrient use in agriculture. The scenarios with a reactive approach to environmental problems show increases in agricultural N and P soil balances in all developing countries. In the scenarios with a proactive attitude, N balances decrease and P balances show no change or a slight increase. In Europe and North America, the N balance will decline in all scenarios, most strongly in the environment-oriented scenarios; the P balance declines (proactive) or increases slowly (reactive approach). Even with rapidly increasing agricultural efficiency, the global N balance, ammonia, leaching and denitrification loss will not decrease from their current levels even in the most optimistic scenario. Soil P depletion seems to be a major problem in large parts of the global grassland are

Modelling global annual N2O and NO emissions from fertilized fields

Information from 846 N2O emission measurements in agricultural fields and 99 measurements for NO emissions was used to describe the influence of various factors regulating emissions from mineral soils in models for calculating global N2O and NO emissions. Only those factors having a significant influence on N2O and NO emissions were included in the models. For N2O these were (1) environmental factors (climate, soil organic C content, soil texture, drainage and soil pH); (2) management-related factors (N application rate per fertilizer type, type of crop, with major differences between grass, legumes and other annual crops); and (3) factors related to the measurements (length of measurement period and frequency of measurements). The most important controls on NO emission include the N application rate per fertilizer type, soil organic-C content and soil drainage. Calculated global annual N2O-N and NO-N emissions from fertilized agricultural fields amount to 2.8 and 1.6 Mtonne, respectively. The global mean fertilizer-induced emissions for N2O and NO amount to 0.9% and 0.7%, respectively, of the N applied. These overall results account for the spatial variability of the main N2O and NO emission controls on the landscape scal

Global nitrogen and phosphate in urban wastewater for the period 1970 to 2050

This paper presents estimates for global N and P emissions from sewage for the period 1970-2050 for the four Millennium Ecosystem Assessment scenarios. Using country-specific projections for population and economic growth, urbanization, development of sewage systems, and wastewater treatment installations, a rapid increase in global sewage emissions is predicted, from 6.4 Tg of N and 1.3 Tg of P per year in 2000 to 12.0-15.5 Tg of N and 2.4-3.1 Tg of P per year in 2050. While North America (strong increase), Oceania (moderate increase), Europe (decrease), and North Asia (decrease) show contrasting developments, in the developing countries, sewage N and P discharge will likely increase by a factor of 2.5 to 3.5 between 2000 and 2050. This is a combined effect of increasing population, urbanization, and development of sewage systems. Even in optimistic scenarios for the development of wastewater treatment systems, global N and P flows are not likely to declin

N:P:Si nutrient export ratios and ecological consequences in coastal seas evaluated by the ICEP approach

The Indicator for Coastal Eutrophication Potential (ICEP) for river nutrient export of nitrogen, phosphorus, and silica at the global scale was first calculated from available measurement data. Positive values of ICEP indicate an excess of nitrogen and phosphorus over silica and generally coincide with eutrophication. The sign of ICEP based on measured nutrient fluxes was in good agreement with the corresponding one calculated from the Global-NEWS models for more than 5000 watersheds in the world. Calculated ICEP for the year 2050 based on Global NEWS data for the four Millennium Ecosystem Assessment scenarios show increasing values particularly in developing countries. For further evaluation of the ICEP at the outlet of the rivers of the world based on measurements, there is a need for additional determination silica fluxes and concentrations, which are scarcely documented

Compilation of a global inventory of emissions of nitrous oxide

A global inventory with 1°x1° resolution was compiled of emissions of nitrous oxide (N 2 O) to the atmosphere, including emissions from soils under natural vegetation, fertilized agricultural land, grasslands and animal excreta, biomass burning, forest clearing, oceans, fossil fuel and biofuel combustion, and industrial sources.A simple global model of the production potential of N 2 O in soils under natural vegetation was developed to analyze the relative importance of five major controls on N 2 O production: (i) input of organic matter, (ii) soil fertility, (iii) soil moisture status, (iv) temperature; and (v) soil oxygen status. Indices for the controls were derived from global gridded (1° x 1° resolution) data bases of soil type and texture, normalized difference vegetation index (NDVI) and climate. The model explains close to 60% of the variability found in measurements reported at about30sites in six different ecosystems throughout the world. The model results confirm conclusions from earlier studies that the major natural source regions of N 2 O are in the tropics.Literature data on N 2 O flux measurements from agricultural fields show that the fertilizerinduced N 2 O emission is higher for measurements covering longer periods than for measurements which represent short periods. A method to estimate the total annual direct N 2 O emission from fertilized fields was based on measurements covering periods of one year: N 2 O-N emission = I kg N ha -1yr -1plus 1.25 ± 1% of the amount of fertilizer N applied (kg Nha -1yr -1). This relationship was used to compile a global 1° x 1° resolution inventory of emissions of N 2 Ofrom fertilized arable land.The inventory of N 2 O emission from animal excreta was based on estimates of nitrogen (N) excretion by various categories of domestic animals. The estimated global amount of N in animal excreta (-100 x 10 12g N yr -1) suggests that the associated N 2 O emission may be of the same order of magnitude as that caused by the use of synthetic N fertilizer (-80 x 10 12g N yr -1)To illustrate the difficulty to describe the cycling ofNin ecosystems,Nbudgets were compiled for a deforestation sequence in the Atlantic Zone of Costa Rica. After forest clearing an important part of the soil organicNis mineralized. Part of the nitrate formed by nitrification of the mineralizedNis lost via leaching, while most of theNloss occurs through denitrification. After a period of3to 5 years most of the easily decomposable material is lost, and denitrification and N 2 Ofluxes decrease with time to levels lower than in the undisturbed forest. The global estimate of enhanced soil N 2 Oemission from denitrification following tropical forest clearing, accounting for this decline of N 2 O fluxes along with ageing of the clearing, indicates that deforestation is an important global source.Global 10 x 1° resolution inventories were also compiled for N 2 Oemissions from fossil fuel and fuelwood combustion, and industrialN2Osources. For N 2 Oemissions from oceans and biomass burning, inventories from the literature were used. The complete inventory of annual N 2 Oemissions including all sources, was compared with source estimates inferred from inversemodeling. The N 2 Oinventories are in general agreement with inverse modeling results. However, there are major uncertainties, particularly in the tropics. The comparison between the emission inventory and the source estimates from inverse modelling, resulted in improved understanding of some sources:- The oceanic N 2 Oemission may be higher than previous estimates; the 0°N-30°N latitudinal zone and the Antarctic ocean show much higher N 2 Ofluxes than the mean global oceanic flux.- Most of the N 2 Ofrom arable lands and grasslands including effects of synthetic fertilizers and animal excreta comes from the northern hemisphere. Inputs of Nto soils fromNdeposition and from Nfixation by leguminous crops are of the same order of magnitude as synthetic Nfertilizer use. Their associated N 2 Orelease may also be similar in magnitude.- Fossil-fuel combustion and industrial N 2 Osources are dominant in the 30°N-90°Nzone, while N 2 Ofrom fuelwood combustion is mainly produced in the 0°N-30°Nzone.- The major part of the N 2 Oemitted from coastal marine and fresh water systems probably stems from the northern hemisphere.Global monthly estimates of N 2 O emissions were used to prescribe a three-dimensional atmospheric transport model. The simulated northern hemispheric N 2 O surface concentration was -1 ppb higher than in the southern hemisphere. This is in general agreement with atmospheric observations. The modeled N 2 O concentrations over strong source regions in continental interiors were up to 5 ppb higher than those over oceans. Predicted concentrations for the northern hemisphere were somewhat higher in summer than in winter, in agreement with the seasonality of N 2 O emissions. However, the atmospheric N 2 O concentration measurements show no seasonal variation in the northern hemisphere. The small seasonality in modeled atmospheric N 2 O concentrations for the southern hemisphere is more consistent with measurements. Inconsistencies between predicted and observed atmospheric N 2 O concentrations may be caused by overestimation of the seasonality in the northern hemisphere. The global N 2 O inventory used does not account for soil N 2 O consumption in temperate N-limited ecosystems and observed episodic emissions in temperate ecosystems during winter, early spring and autumn. These potential errors and possible underestimation of N 2 O emissions from combustion in winter may exaggerate the simulated seasonal trends.Another possible reason for the inconsistencies found between predicted and measured N 2 O concentrations is that seasonal trends in atmospheric N 2 O concentrations remain unobserved, because of the remote location of most monitoring stations. In addition, the precision of N 2 O measurements is not adequate for resolving seasonal trends.The major part of the atmospheric N 2 O increase stems from sources related to human food production. A growing world population will inevitably lead to more food demand. Moreover, an increasing portion of the synthetic fertilizers is used to increase animal production. At present, close to 40% of the global cereal production and 25% of the production of root and tuber crops is fed to animals. An important global reduction of N 2 O emission associated with food production could be achieved by a shift-away from animal production, by more efficient agricultural use of N, and by advanced fertilization techniques.Solutions to reduce N 2 O emission from fossil fuel combustion include technical options (e.g. development of new catalysts) and energy saving. Several industrial and chemical processes generate N 2 O, but so far only the N 2 O production from nitric and adipic acid production have been quantified. The global N 2 O emission from adipic acid production is currently decreasing as the major producers have agreed to reduce N 2 O emissions

Millennium Ecosystem Assessment Scenario drivers (1970-2050): Climate and hydrological alterations

This study was carried out to support and enhance a series of global studies assessing contemporary and future changes in nutrient export from watersheds (Global Nutrient Export from Watersheds (NEWS)). Because hydrography is one of the most important drivers in nutrient transport, it was essential to establish how climatic changes and direct human activities (primarily irrigation and reservoir operations) affect the hydrological cycle. Contemporary and future hydrography was established by applying a modified version of a global water balance and transport model (WBMplus) driven by present and future climate forcing, as described in the Millennium Ecosystem Assessment scenarios (1970-2050). WBMplus represents a major upgrade to previous WBM implementations by incorporating irrigational water uptake and reservoir operations in a single modeling framework. Contemporary simulations were carried out by using both observed climate forcings from the Climate Research Unit of East Anglia (CRU) data sets and from Global Circulation Model (GCM) simulations that are comparable to the future simulations from the same GCM forcings. Future trends in three key human activities (land use, irrigation, and reservoirs operation for hydropower) were taken from the Integrated Model to Assess the Global Environment (IMAGE). The reservoir operation required establishing a realistic distribution of future reservoirs since the IMAGE model provided only the hydropower potentials for the different future scenarios

N2O and NO emission from agricultural fields and soils under natural vegetation: summarizing available measurement data and modeling of global annual emissions

The number of published N2O and NO emissions measurements is increasing steadily, providing additional information about driving factors of these emissions and allowing an improvement of statistical N-emission models. We summarized information from 1008 N2O and 189 NO emission measurements for agricultural fields, and 207 N2O and 210 NO measurements for soils under natural vegetation. The factors that significantly influence agricultural N2O emissions were N application rate, crop type, fertilizer type, soil organic C content, soil pH and texture, and those for NO emissions include N application rate, soil N content and climate. Compared to an earlier analysis the 20% increase in the number of N2O measurements for agriculture did not yield more insight or reduced uncertainty, because the representation of environmental and management conditions in agro-ecosystems did not improve, while for NO emissions the additional measurements in agricultural systems did yield a considerable improvement. N2O emissions from soils under natural vegetation are significantly influenced by vegetation type, soil organic C content, soil pH, bulk density and drainage, while vegetation type and soil C content are major factors for NO emissions. Statistical models of these factors were used to calculate global annual emissions from fertilized cropland (3.3 Tg N2O-N and 1.4 Tg NO-N) and grassland (0.8 Tg N2O-N and 0.4 Tg NO-N). Global emissions were not calculated for soils under natural vegetation due to lack of data for many vegetation type

Past anthropogenic activities offset dissolved inorganic phosphorus retention in the Mississippi River basin

The rapid acceleration of anthropogenic phosphorus (P) loadings to watersheds has fuelled massive freshwater and coastal eutrophication and completely changed the global P cycle. Within watersheds, emitted P is transported downstream towards estuaries. Reservoirs can retain a significant proportion of this P. In the long term, this accumulated P can however be re-mobilized, a process lacking in current global P budgets. Here, we include P cycling in a coupled integrated assessment-hydrology-biogeochemistry framework with 0.5 by 0.5-degree spatial resolution and an annual time resolution, and apply it to the Mississippi River basin (MRB). We show that, while reservoirs have aided in the net retention of P, they serve as dissolved inorganic P (DIP) sources due to the transformation of legacy P in sediments. The increasing DIP sourcing in the MRB has been offsetting P retention in streams, especially towards the end of the twentieth century. Due to its bioavailability, DIP is the most likely form to trigger eutrophication. Although P inputs into the MRB have decreased since the 1970s, legacy effects are delaying positive outcomes of remediation measures.Industrial Ecolog

Coupling global models for hydrology and nutrient loading to simulate nitrogen and phosphorus retention in surface water - Description of IMAGE-GNM and analysis of performance

The Integrated Model to Assess the Global Environment–Global Nutrient Model (IMAGE–GNM) is a global distributed, spatially explicit model using hydrology as the basis for describing nitrogen (N) and phosphorus (P) delivery to surface water, transport and in-stream retention in rivers, lakes, wetlands and reservoirs. It is part of the integrated assessment model IMAGE, which studies the interaction between society and the environment over prolonged time periods. In the IMAGE–GNM model, grid cells receive water with dissolved and suspended N and P from upstream grid cells; inside grid cells, N and P are delivered to water bodies via diffuse sources (surface runoff, shallow and deep groundwater, riparian zones; litterfall in floodplains; atmospheric deposition) and point sources (wastewater); N and P retention in a water body is calculated on the basis of the residence time of the water and nutrient uptake velocity; subsequently, water and nutrients are transported to downstream grid cells. Differences between model results and observed concentrations for a range of global rivers are acceptable given the global scale of the uncalibrated model. Sensitivity analysis with data for the year 2000 showed that runoff is a major factor for N and P delivery, retention and river export. For both N and P, uptake velocity and all factors used to compute the subgrid in-stream retention are important for total in-stream retention and river export. Soil N budgets, wastewater and all factors determining litterfall in floodplains are important for N delivery to surface water. For P the factors that determine the P content of the soil (soil P content and bulk density) are important factors for delivery and river export.FWN – Publicaties zonder aanstelling Universiteit Leide