Nutrients/Description: Difference between revisions
Jump to navigation
Jump to search
No edit summary |
No edit summary |
||
| Line 1: | Line 1: | ||
{{ComponentDescriptionTemplate | {{ComponentDescriptionTemplate | ||
|Status=On hold | |Status=On hold | ||
|Description=<h2> Wastewater nutrient model</h2> | |Reference=Bouwman et al., 2009; Bouwman et al., 2011; Van Drecht et al., 2009; Cleveland et al., 1999; Bouwman et al., 2013; | ||
Urban wastewater contains N and P emitted by households and industries that are connected to a sewage system, and households with sanitation but lacking a sewage connection. N discharges to surface water ( in kg per person per year) is calculated as follows (Van Drecht et al., 2009): | |Description=<h2> A. Wastewater nutrient model</h2> | ||
Urban wastewater contains N and P emitted by households and industries that are connected to a sewage system, and households with sanitation but lacking a sewage connection. N discharges to surface water ( in kg per person per year) is calculated as follows ([[Van Drecht et al., 2009]]): | |||
==Soil nutrient budget model== | {{FormulaAndTableTemplate|Formula1_N}} [[Formulaaaa*]] | ||
The soil budget approach (Bouwman et al., 2009; Bouwman et al., 2011) includes the N and P input and output for IMAGE grid cells. Soil N budgets are calculated for two production systems ( | |||
where is human N emissions (kg per person per year), D is the fraction of the total population that is connected to public sewerage systems (no dimension), and R N is the overall removal of N through wastewater treatment (no dimension). Total P emissions to surface water are calculated in a similar way, but also include estimates of P emissions to surface water resulting from the use of P-based dishwasher and laundry detergents. Nutrient removal by wastewater treatment R is based on the relative contribution of four classes of treatment (none, primary, secondary and tertiary treatment). D (calculated from the fraction of households with improved sanitation) and R (by treatment class) are scenario variables. | |||
==B. Soil nutrient budget model== | |||
The soil budget approach ([[Bouwman et al., 2009]]; [[Bouwman et al., 2011]]) includes the N and P input and output for IMAGE grid cells. Soil N budgets are calculated for two production systems (see figure on the right, B.), i.e. mixed and pastoral livestock production systems ([[Livestock]]). N input includes application of synthetic N fertiliser (Nfert) and animal manure (Nman), biological N fixation (Nfix), atmospheric N deposition (Ndep). Output includes N withdrawal from the field through crop harvesting, hay and grass cutting, and grass consumed by grazing animals (Nwithdr). The soil N budget (Nbudget) is calculated as follows: | |||
{{FormulaAndTableTemplate|Formula1_N}} [[Formulaaaa*]] | |||
For P the same approach is used, P input being animal manure and fertiliser. The soil nutrient budget ignores nutrient accumulation in soil organic matter in case of a positive budget (surplus), and soil organic matter decomposition and mineralisation. With no accumulation, a surplus represents a potential loss to the environment (for N this includes NH3 volatilisation ([[Emissions]]), denitrification, surface runoff and leaching; for P this is surface runoff). | |||
For a spatial allocation of the nutrient input to IMAGE grid cells, the crop groups in IMAGE (temperate cereals, rice, maize, tropical cereals, pulses, roots and tubers, oil crops, other crops, energy crops) and grass are aggregated to form five broad groups, including grass, wetland rice, leguminous crops, other upland crops and energy crops, within mixed and pastoral production systems. | For a spatial allocation of the nutrient input to IMAGE grid cells, the crop groups in IMAGE (temperate cereals, rice, maize, tropical cereals, pulses, roots and tubers, oil crops, other crops, energy crops) and grass are aggregated to form five broad groups, including grass, wetland rice, leguminous crops, other upland crops and energy crops, within mixed and pastoral production systems. | ||
===Fertiliser | ===Fertiliser=== | ||
Fertiliser use is based on fertiliser use efficiency, representing the production in kilograms of dry matter per kilogram of fertiliser N (NUE) or P (PUE). NUE and PUE vary between countries because of differences in crop mix, their attainable yield potential, soil quality, amount and form of N and P application and management. For constructing scenarios on fertiliser use, data on the 1970–2005 period serve as a guide to distinguish countries with an input exceeding crop uptake (positive budget or surplus) from countries with a deficit. Generally, farmers in countries with a surplus are assumed to be increasingly efficient in the use of fertilisers (increasing NUE and PUE). In countries with nutrient deficits, an increase in crop yields is only possible under an increase in the nutrient input; initially this will cause NUE and PUE to decrease, which shows a decrease in soil nutrient depletion due to increased fertiliser use. | Fertiliser use is based on fertiliser use efficiency, representing the production in kilograms of dry matter per kilogram of fertiliser N (NUE) or P (PUE). NUE and PUE vary between countries because of differences in crop mix, their attainable yield potential, soil quality, amount and form of N and P application and management. For constructing scenarios on fertiliser use, data on the 1970–2005 period serve as a guide to distinguish countries with an input exceeding crop uptake (positive budget or surplus) from countries with a deficit. Generally, farmers in countries with a surplus are assumed to be increasingly efficient in the use of fertilisers (increasing NUE and PUE). In countries with nutrient deficits, an increase in crop yields is only possible under an increase in the nutrient input; initially this will cause NUE and PUE to decrease, which shows a decrease in soil nutrient depletion due to increased fertiliser use. | ||
===Manure | ===Manure=== | ||
Total manure production is computed from animal stocks and N and P excretion rates ( | Total manure production is computed from animal stocks and N and P excretion rates (see figure on the right, B.). IMAGE uses constant N and P excretion rates per head, for dairy and non-dairy cattle, buffaloes, sheep and goats, pigs, poultry, horses, asses, mules and camels. Constant excretion rates imply that the N and P generation per unit of product decreases under increased milk and meat production per animal. | ||
N and P in the manure for each animal category are spatially allocated to mixed and pastoral systems. Within each country and system, the manure is distributed over three manure management systems: (i) grazing; (ii) storage in animal housing and storage systems; and (iii) manure used outside the agricultural system as fuel or for other purposes. The amount of manure assigned to grazing is based on the fraction of grass in feed rations ( | N and P in the manure for each animal category are spatially allocated to mixed and pastoral systems. Within each country and system, the manure is distributed over three manure management systems: (i) grazing; (ii) storage in animal housing and storage systems; and (iii) manure used outside the agricultural system as fuel or for other purposes. The amount of manure assigned to grazing is based on the fraction of grass in feed rations (see figure on the right, B.). | ||
Stored animal manure available for application to cropland and grassland includes all stored and collected manure, excluding ammonia volatilisation from animal houses and storage systems. IMAGE assumes that, in industrialised countries, 50% of the available animal manure from storage systems is applied to arable land and the remainder to grassland. In most developing countries, manure spreading on croplands is 95% of the available manure and 5% to grassland, thus accounting for the lower economic importance of grass compared to crops in developing countries. For EU countries, maximum manure application rates of 170 to 250 kilograms N per hectare are used, reflecting existing regulations. | Stored animal manure available for application to cropland and grassland includes all stored and collected manure, excluding ammonia volatilisation from animal houses and storage systems. IMAGE assumes that, in industrialised countries, 50% of the available animal manure from storage systems is applied to arable land and the remainder to grassland. In most developing countries, manure spreading on croplands is 95% of the available manure and 5% to grassland, thus accounting for the lower economic importance of grass compared to crops in developing countries. For EU countries, maximum manure application rates of 170 to 250 kilograms N per hectare are used, reflecting existing regulations. | ||
===Biological N2 fixation | ===Biological N2 fixation=== | ||
Data on biological N2 fixation by leguminous crops (pulses and soybeans) is obtained from the N in the harvested product (see nutrient withdrawal). Any change in the rate of biological N2 fixation by legumes is thus the result of the development of yields of pulses and soybeans. Apart from leguminous crops, IMAGE uses an annual rate of biological N2 fixation of 5 kilograms per hectare of N for non-leguminous crops and grass, and 25 kilograms N per hectare for wetland rice. N fixation rates in natural ecosystems were based on the low estimates for areal coverage by legumes from (Cleveland et al., 1999) as described by Bouwman et al. | Data on biological N2 fixation by leguminous crops (pulses and soybeans) is obtained from the N in the harvested product (see nutrient withdrawal). Any change in the rate of biological N2 fixation by legumes is thus the result of the development of yields of pulses and soybeans. Apart from leguminous crops, IMAGE uses an annual rate of biological N2 fixation of 5 kilograms per hectare of N for non-leguminous crops and grass, and 25 kilograms N per hectare for wetland rice. N fixation rates in natural ecosystems were based on the low estimates for areal coverage by legumes from ([[Cleveland et al., 1999]]) as described by [[Bouwman et al., 2013]]. | ||
===Atmospheric deposition | ===Atmospheric deposition=== | ||
Deposition rates for historical and future years are calculated by scaling the N deposition field for the year 2000 (obtained from atmospheric chemistry transport models), using emission inventories for the historical period and N gas emissions in the scenario considered. IMAGE ignores atmospheric P deposition. | Deposition rates for historical and future years are calculated by scaling the N deposition field for the year 2000 (obtained from atmospheric chemistry transport models), using emission inventories for the historical period and N gas emissions in the scenario considered. IMAGE ignores atmospheric P deposition. | ||
===Nutrient withdrawal | ===Nutrient withdrawal=== | ||
Withdrawal of N and P in harvested products is calculated from regional crop production from IMAGE and the N and P content for each crop, which is then aggregated to the broad crop categories (wetland rice, leguminous crops, upland crops and energy crops). IMAGE also accounts for the uptake by fodder crops. N withdrawal through grass consumption and harvest is assumed to amount to 60% of all N input (manure, fertiliser, deposition, N fixation), excluding NH3 volatilisation. P withdrawal through grazing or grass cutting is calculated as a fraction of 87.5% of fertiliser and manure P input. The remainder is assumed to be lost through surface runoff. For calculating spatially explicit nutrient withdrawal, a procedure is used to downscale regional crop production data from IMAGE to country estimates for nutrient withdrawal based on distributions in the year 2005. | Withdrawal of N and P in harvested products is calculated from regional crop production from IMAGE and the N and P content for each crop, which is then aggregated to the broad crop categories (wetland rice, leguminous crops, upland crops and energy crops). IMAGE also accounts for the uptake by fodder crops. N withdrawal through grass consumption and harvest is assumed to amount to 60% of all N input (manure, fertiliser, deposition, N fixation), excluding NH3 volatilisation. P withdrawal through grazing or grass cutting is calculated as a fraction of 87.5% of fertiliser and manure P input. The remainder is assumed to be lost through surface runoff. For calculating spatially explicit nutrient withdrawal, a procedure is used to downscale regional crop production data from IMAGE to country estimates for nutrient withdrawal based on distributions in the year 2005. | ||
== Nutrient environmental fate model== | == C. Nutrient environmental fate model== | ||
Nutrient losses from the plant-soil system to the soil-hydrological system are calculated from the nutrient budgets (Bouwman et al., 2013). For N, the budget is corrected for ammonia volatilisation from grazing animals and from manure spreading ( | Nutrient losses from the plant-soil system to the soil-hydrological system are calculated from the nutrient budgets ([[Bouwman et al., 2013]]). For N, the budget is corrected for ammonia volatilisation from grazing animals and from manure spreading ([[Emissions]]). Phosphorus not taken up by plants is generally bound to soil particles, with the only loss pathway being surface runoff. Nitrogen is much more mobile, and is transported via surface runoff and through soils, groundwater and riparian zones to surface water. | ||
===Soil denitrification=== | |||
===Soil denitrification | |||
Denitrification is calculated as a fraction of the soil N budget surplus based on the effect of temperature and residence time of water and nitrate in the root zone, and effects of soil texture, soil drainage and soil organic carbon content. In the case of a soil budget deficit, IMAGE assumes no denitrification to occur. | Denitrification is calculated as a fraction of the soil N budget surplus based on the effect of temperature and residence time of water and nitrate in the root zone, and effects of soil texture, soil drainage and soil organic carbon content. In the case of a soil budget deficit, IMAGE assumes no denitrification to occur. | ||
===Soil N leaching | ===Soil N leaching=== | ||
In case of an N surplus in the soil budget, leaching is the complement of denitrification. | In case of an N surplus in the soil budget, leaching is the complement of denitrification. | ||
===Groundwater transport, surface runoff and denitrification.=== | ===Groundwater transport, surface runoff and denitrification.=== | ||
Two groundwater subsystems are distinguished. The shallow groundwater system represents interflow and surface runoff for the upper 5 metres of the saturated zone, with short travel times before the water enters local surface water at short distances or infiltrates the deep groundwater system. A deep system with a thickness of 50 metres is defined with generally long travel times draining to larger streams and rivers; deep groundwater is assumed to be absent in areas with non-permeable, consolidated rocks or in the presence of surface water. Denitrification during groundwater transport is based on the travel time and the half-life of nitrate. The half-life depends on the lithological class (1 year for schists and shales containing pyrite, 2 years for alluvial material, and 5 years for all other lithological classes). Flows of water and nitrate from shallow groundwater to riparian zones are assumed to be absent in areas with surface water bodies, where the flow is assumed to by-pass riparian zones flowing directly to streams or rivers. | Two groundwater subsystems are distinguished. The shallow groundwater system represents interflow and surface runoff for the upper 5 metres of the saturated zone, with short travel times before the water enters local surface water at short distances or infiltrates the deep groundwater system. A deep system with a thickness of 50 metres is defined with generally long travel times draining to larger streams and rivers; deep groundwater is assumed to be absent in areas with non-permeable, consolidated rocks or in the presence of surface water. Denitrification during groundwater transport is based on the travel time and the half-life of nitrate. The half-life depends on the lithological class (1 year for schists and shales containing pyrite, 2 years for alluvial material, and 5 years for all other lithological classes). Flows of water and nitrate from shallow groundwater to riparian zones are assumed to be absent in areas with surface water bodies, where the flow is assumed to by-pass riparian zones flowing directly to streams or rivers. | ||
===Denitrification in riparian areas | ===Denitrification in riparian areas=== | ||
The calculation of denitrification in riparian areas is similar to that in soils, but with two differences: | The calculation of denitrification in riparian areas is similar to that in soils, but with two differences: | ||
# a biologically active layer with a thickness of 0.3 metres is assumed, instead of 1 metre for other soils; | |||
# the approach includes the effect of pH on denitrification. | |||
===In-stream nutrient retention.=== | ===In-stream nutrient retention.=== | ||
The water that enters streams and rivers through surface runoff and discharges from groundwater and riparian zones is routed through stream and river channels, and passes through lakes, wetlands and reservoirs. The nutrient retention in each of these systems is calculated on the basis of the nutrient spiralling ecological concept, based on residence time and temperature. | The water that enters streams and rivers through surface runoff and discharges from groundwater and riparian zones is routed through stream and river channels, and passes through lakes, wetlands and reservoirs. The nutrient retention in each of these systems is calculated on the basis of the nutrient spiralling ecological concept, based on residence time and temperature. | ||
}} | }} | ||
Revision as of 12:21, 16 December 2013
Parts of Nutrients/Description
| Component is implemented in: |
| Components: |
| Related IMAGE components |
| Projects/Applications |
| Key publications |
| References |
