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IMPACT OF CLIMATE CHANGE ON WATER RESOURCES AND AGRICULTURAL PRODUCTIVITY BY REV. FR. PROF. MENSAH BONSU DEPARTMENT OF CROP AND SOIL SCIENCES FACULTY OF AGRICULTURE KNUST, KUMASI Outline of presentation • • • • What is climate change? Green house effect and climate change Sources of green house gases emissions Factors leading to potential vulnerability to climate change • Indicators of climate change • Climate change and water resources • Planning for future response to water resources and climate change • Climate change and its impact on agricultural productivity • Analysis of climate change impact on agriculture • Application of GCM in Ghana • Adaptations to climate change • Socio-economic factors and climate change What is climate change? A change in climate which is attributed directly or indirectly to human (anthropogenic) activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over a given or noticeable period of time. INTRODUCTION The green house effect and climate change • Estimates indicate that since 1991, the global atmosphere concentration of carbon dioxide has been increasing at a rate of about 1.8 parts per million or 0018% per year. • These trace gases in the atmosphere notably carbon dioxide, nitrous oxide and methane called “greenhouse gases” can absorb the heat radiated from the earth (i.e. Long wave radiation or infrared). • The greenhouse gases prevent the heat radiated from the earth from being escaped into space. INTRODUCTION The green house effect and climate change • Human activities have led to an increase in the concentration of these greenhouse gases in the lower atmosphere, resulting in anthropogenic greenhouse effect which is resulting in global warming and its attendant “climate change”. • The major greenhouse gases are carbon dioxide (CO2), Methane (CH4), Nitrous Oxide (N20), hydrofluorocarbons (H FCs). Perflurocarbons (PFCs) and Sulphur hexafluoride (SF6). Sources of Anthropogenic Greenhouse Gases Emissions The key sources of anthropogenic greenhouse gases emissions are: • The energy sector • Agricultural sector and • Waste management sector Sources of Anthropogenic Greenhouse Gases Emissions The Energy Sector • In the energy sector, greenhouse gases emissions emanate from fuel combustion through the energy, manufacturing and construction industries as well as vehicular emissions. • Other sources are through fugitive emissions from fuels in the form of solid fuels (e.g. coal and oil and natural gas). Sources of Anthropogenic Greenhouse Gases Emissions The Energy Sector • The industrial processes also contribute significantly to green house gases emissions such as: – mineral production – chemical industries – cement production – metal production – production and use of halocarbons and sulphur hexafluoride, and the production and use of solvents Sources of Anthropogenic Greenhouse Gases Emissions The Agricultural Sector The sources of emissions of greenhouse gases are: • Enteric fermentation of ruminants (CH4) • manure management (anaerobic decomposition) • rice cultivation (flooded rice fields) • mineralization in agricultural soils (CO2, N20) • use of nitrogenous fertilizers (N20) Sources of Anthropogenic Greenhouse Gases Emissions Waste Management • Sources of anthropogenic greenhouse gases emissions are through waste management. • Anaerobic as well as aerobic decomposition of wastes results in the emissions of carbon dioxide, methane and nitrous oxide (or other nitrogen oxides NOx). Indicators of climate change • High solar radiation intensities and global warming • Elevated air temperatures • Reduced rainfall amounts and occurrence of droughts • Unreliable and erratic rainfall events • Poor rainfall distribution • Extreme climate events – floods and storms • Hurricanes and tornadoes Factors Leading to potential vulnerability to climate change • Unsustainable use of natural resources • Lack of mitigation of greenhouse gas emissions in the industrial sector • Weak waste management systems and poor environmental sanitation • Imports of over-aged vehicles Climate change and Water Resources • • • • Sources of water resources natural precipitation groundwater resources freshwater rivers, streams, rivulets and lakes, dams and reservoirs and marine and estuarine water resources Natural precipitation is the key source of water that feeds all the other water resources. Therefore a decrease in rainfall due to climate change will deleteriously affect all the other water resources. Climate change and Water Resources Runoff • Runoff or overland flow is the major source of water feeding rives, streams, rivulets, dams, lakes and reservoirs. • It is estimated as amount of precipitation minus infiltration (i.e. the amount of precipitation that enters the soil). • The current low levels of water in dams indicate the sensitivity of reservoirs storage to variations in runoff due to climate change and drought. Climate change and Water Resources Groundwater Resource and Climate Change Groundwater is an important source of global water requirements for: • Domestic use • Agricultural use and • Industrial use Groundwater is recharged through: • Seepage from rainfall events • Seepage from dams and reservoirs, and • Seepage from rivers and lakes Climate change and Water Resources Marine and Estuarine Water Resources and Sea Level Rise due to climate change Table 1. Expected sea level rise in Ghana due to climate change Year Expected sea level rise (cm) 2020 2050 2080 5.8 16.5 34.5 Marine and Estuarine Water Resources and Sea Level Rise due to climate change Causes of sea level rise • Volumetric expansion of sea water due to rise in sea water temperature • Melting of polar ice due to rise in temperature • Melting of ice-bergs due to rise in temperature • Melting of mountain glaciers due to rise in temperature Marine and Estuarine Water Resources and Sea Level Rise due to climate change Effects of sea level rise • Accelerated coastal erosion. For example, the annual coastal erosion in the Keta area of Ghana is estimated to be 3m. • Inundation of low-lying coastal zones and • Increased tidal waves which favour further inland penetration of the sea water through internal lateral flow, which will increase salinisation of coastal aquifer and streams. Planning for the future response to water resources and climate change • Climate change must be factored into water-resource planning and policies for the future on a contingency basis. • A global climate change often results in linking of environmental factors that favour evaporative demand of the environment such as: • Increase in air temperature • Increase in net radiation • Decrease in atmospheric relative humidity, and increase in windiness In planning for the future response to water resources and climate change, the following factors must be considered: • A change in regional water resources must be considered holistically. • The dynamic nature of water resource management must be fully considered physically and socially. • Lessons from past development effects in connection with water resource management, especially past failures should be referred to and applied judiciously. • The approaches should consider current water problems in the context of political and cultural perspectives. Climate change and its impact on agricultural productivity The adverse effects of climate change on agricultural productivity are due to: • Increased temperatures (global warming) • Decreased rainfall Climate change and its impact on agricultural productivity Stresses due to these two climatic variables result in reduced crop yields because of the following reasons: • The plant tries to complete its life cycle more rapidly resulting in reduced storage of food product. • Heat stress and reduced water availability could result in the death of the plant. • Extreme climatic events such as storms and windiness can be devastating to plants through logging and flooding. Climate change and its impact on agricultural productivity • Higher temperatures increase the rate of water loss through evaporation and transpiration. • With high temperatures, nutrient release through organic matter decomposition is not synchronized with the time when the plants nutrient requirement is at its peak. • If climate change results in excessive rainfall, nutrient losses through leaching and erosion result in soil fertility decline. • Higher temperatures with moisture favour the germination of spores and spread of bacteria, fungi and nematodes. Climate change and its impact on agricultural productivity Impact of climate change on Animal Production Increased temperatures and animal physiology: • High temperatures accelerate metabolic processes requiring high oxygen consumption, which if not met can reach final stage resulting in death. • Higher surrounding temperatures could result intake of less food and more water and reduced gain-weight of the animal. Impact of climate change on Animal Production Increased temperatures and animal physiology: • At high temperatures proteins and nucleic acids are denatured and protein synthesis in the animal is drastically reduced. • High temperatures may change the membrane fluidity of the animal from gel phase to liquid crystalline phase leading to reduced performance and death. Analysis of Climate Change Impacts on Agriculture The analysis of future climate change impacts on agriculture demands multifaceted approaches involving: • The study of biophysical processes • Socioeconomic processes Analysis of Climate Change Impacts on Agriculture The approaches employed include: • Climate change Scenarios: These involve projections of what values climate parameters may assume in the future and how agriculture might fare in the new circumstances. This approach addresses the question: “What will agriculture be like in a given changed climate. In this approach, chain of causalities from the biophysical responses of crops and livestock at the farm level to socio-economic effects are constructed. Analysis of Climate Change Impacts on Agriculture There are different types of scenarios for the analysis of impacts of climate change on Agriculture. But the commonest ones are: • Global circulation models (GCMs) • Regional climate (Simulation) Models (Reg CMs) Application of GCM in Ghana • GCMs are normally used to generate future climatic parameters based on current climatic parameters of a specified period. The generated future climatic parameters are fed into a given Dynamic Crop Growth Model to generate future crop responses to the changed future climatic parameters. • This approach was used in Ghana to simulate the impact of climate change on maize and roots and tubers production. Application of GCM in Ghana Model simulation (GCMs) The GCMs used were the ‘Linked Model’ adopted from: • The Hardly Centre Model 2 (HADCM 2) • The U.K. Meteorological Office Transient Model (UKH 1) Application of GCM in Ghana Dynamic Crop Growth models: • Maize: IBSNAT Crop simulation models (DSSAT) (specifically CERES-Maize) was used • Cassava/Cocoyam: DSSATV4 (specifically) CROPSIM-Cassava/CROPGRO (ARGR 0980) were used Table 2. Expected average increase in temperature and decrease in rainfall Year Increase in Decrease in Temperature (⁰C) rainfall (%) 2020 0.6 2.8 2050 2.0 10.9 2080 3.9 18.6 Application of GCM in Ghana Simulated mean temperature and rainfall variations for all the agro-climatic zones of Ghana up to the year 2080 As temperature increased, rainfall also decreased systematically. Application of GCM in Ghana Using the 2020 data, average maize yield in Ghana would decrease by 7%. • National maize production in Ghana declined by 30% in 1982 due to drought. • Poor seed set in maize at temperatures above 38oC. Application of GCM in Ghana Table 3. Projected yield Reduction of Cassava and Cocoyam YEAR CASSAVA (%) COCOYAM (%) 2020 13 11.8 2050 23 29.6 2080 58 68 Adaptations of Agriculture and Water Resources to climate change • Altering the crops to be grown • Early maturing and drought tolerant crops may be grown Change the methods of cultivation Conservation tillage may be used instead of conventional tillage systems Increased use of irrigation in areas prone to drought • Altering timing of planting to make use of shifts in rainfall regimes • Integrated soil fertility management • Integrated pest and disease control measures Socio-Economic Factors These socio-economic factors should be tackled and resolved through government policy under changing climate conditions: • Farm land values and tenure arrangements • Crop produce market prices • Cost of irrigation • Cost of other inputs of production • Government subsidy • Improving the economic situation of farmers CONCLUSION Mitigation and adaptive measures are needed to offset any future impact of climate change on agriculture and water resources Estimation of Green House Gases Estimating methane emission from enteric fermentation Summary STEP 1 • Divide the livestock population into subgroups and characterize each subgroup. • To prevent bias, it is recommended to use three year averages of activity data if available. STEP 2 • Estimate emission factors for each subgroup in terms of kilograms of methane per animal per year. Estimating methan emission from enteric fermentation Summary STEP 3 • Multiply the subgroup emission factors by the subgroup populations to estimate subgroup emission. • Sum across the subgroups to estimate total emission. Enteric fermentation emission factors for Africa Livestock Emission factor (kg per head per year) Dairy cattle 36 Non-dairy cattle 25 Buffalo 55 Sheep 5 Goats 5 Camels 46 Horses 18 Mules/Asses 10 Swine 1 Poultry Not estimated Emissions from prescribed burning of savannas Background • The growth of vegetation in savannas is controlled by alternating wet and dry seasons. • Man-made and/or natural fires generally occur during the dry season. • Savannas are intentionally burned during the dry season primarily for agricultural purposes such as: ridding the grassland of weeds and pests promoting nutrient cycling: and Encouraging the growth of new grasses for animal grazing. Emissions from prescribed burning of savannas Emissions through savanna burning include: • CO2 – net CO2 released is assumed to be zero because of regrowth of vegetation between burning cycles. • Methane (CH4) • Carbon monoxide (CO) • Nitrous oxide (N2O) • Oxides of nitrogen (NOx), i.e. (NO and NO2) • Non-methane volatile organic compounds (NMVOCs) Emissions from prescribed burning of savannas Estimates of annual instantaneous gross release of carbon from savanna burning are uncertain because of lack of data on: • The above ground biomass density • The savanna areas burned annually • The fraction of above-ground biomass which actually burns, and • The fraction which oxidizes • The methodology takes these factors into account. Emissions from prescribed burning of savannas Calculations • First, it is necessary to estimate the total amount of carbon released to the atmosphere from savanna burning as these are needed to derive non- CO2 trace gas emissions. • It is recommended to use three-year averages of activity data • If data are not directly available, estimates can be derived as shown in Table 4.14 (IPCC Guidelines) Table 4.14 Default factors for regional savanna statistics (IPCC) Region Fraction of total savanna that is burned annually Above ground biomass density (t dm/ha) Fraction of biomass actually burned Fraction of above ground biomass that is living Tropical Africa 0.75 6.6 ± 1.6 Sahel zone 0.05 – 0.15 0.5 – 2.5 0.95 0.20 North Sudan zone 0.25 – 0.50 2 – 4 0.85 0.45 South Sudan zone 0.25 – 0.50 3 – 6 0.85 0.45 Guinea zone 0.60 – 0.80 4 – 8 0.9 – 1.0 0.55 Emissions from prescribed burning of savannas Step 1: Total carbon released from savanna burning. These data are required for each category • Total area of savanna; • Fraction of savanna area burned annually; • Average above-ground biomass density (tonnes dry matter/hectare) of savannas; • Fraction of above-ground biomass which actually burns; • Fraction of above-ground biomass that is living; • Fraction of living and of dead above-ground biomass oxidized; and • Fraction of carbon in living and dead biomass. Equations for calculations of estimates of total carbon released due to burning of savannas Equation 1: Area of savanna burned Annually (ha) = Total area of savanna (ha) x Fraction burned annually Equation 2: Biomass burned (t dm) = Area of savanna burned annually (ha) x above-ground biomass density (t dm(ha)) x Fraction actually burned Equation 3: Carbon released from live biomass (tC) = Biomass burned (t dm) x Fraction that is live x Fraction oxidized x carbon content of live biomass (tC/t dm) Equations for calculations of estimates of total carbon released due to burning of savannas Equation 4: Carbon released from dead biomass (t C) = Biomass burned (t dm) x Fraction that is dead x Fraction oxidized x carbon content of dead biomass (tC/t dm) Equation 5: Total carbon released (t C) = carbon released from live material (t C) + carbon released from dead material (t C) Equations for calculations of estimates of total carbon released due to burning of savannas STEP 2: Once the carbon released from savanna burning has been estimated, the emissions of CH4, CO, N2O and NOx can be calculated using emission ratios. Default values are given in Table 4.15. CH4 Emissions = (carbon released) x (emission ratio) x 16/12 CO Emissions = (carbon released) x emission ratio x 28/12 N2O Emissions = (carbon released) x (N/C ratio) x (emission ratio) x 44/28 NOx (NO2) Emissions = (carbon released) x (N/C ratio) x (emission ratio) x (46/14) Table 4.15. Default Emission Ratios for Savanna Burning Calculations Compound CH4 CO N2O NOx Ratios 0.004 (0.002 – 0.006) 0.06 (0.04 – 0.08) 0.007 (0.005 – 0.009) 0.121 (0.094 – 0.148) Field Burning of Agricultural Residue 1. Calculations STEP 1: Total carbon released Data required to calculate the amount of carbon burned in agricultural residues are listed below: • Amount of crops produced with residues that are commonly burned; • Ratio of residue to crop product; • Fraction of residue burned; • Dry matter content of residue; • Fraction oxidized in burning, and • Carbon content of the residue Field Burning of Agricultural Residue Total carbon released (tonnes of carbon) = Ʃ annual production (t of biomass per year) x the ratio of residue to crop product (fraction) x the average dry matter fraction of residue (t of dry matter/ t of biomass) x the fraction actually burned in the field x the fraction oxidized x the carbon fraction (t of C/t of dm). STEP 2: Based on carbon released the emissions of CH4, CO, N2O and NOx can be calculated as follows: CH4 = carbon released x emission ratio x 16/12 CO = carbon released x emission ratio x 28/12 N2O = carbon released x (N/C ratio) x emission ratio x 44/28 NOx = carbon released x (N/C ratio) x 46/14 Table 4.16 Default factors for emission ratios for agricultural residues Compound CH4 CO N2O NOx Ratios 0.005 (0.003 – 0.007) 0.06 (0.04 – 0.08) 0.007 (0.005 – 0.009) 0.121 (0.094 – 0.148) Table 4.17 Selected Crop Residue Statistics Product Residue/Crop Dry matter product fraction Carbon fraction Nitrogen – Carbon (N-C) ratio Maize 1 0.30 – 0.50 0.4709 0.02 Rice 1.4 0.78 – 0.88 0.4144 0.014 Millet 1.4 0.016 Sorghum 1.4 0.02 Bean 2.1 Soybean 2.1 Groundnut 1 0.05 I. N2O emissions from manure management • This deals with N2O produced during the storage and treatment of manure before it is applied to land. • Manure collectively include both dung and urine produced by livestock. • Factors that influence emission of N2O from manure during storage and treatment are: the nitrogen and carbon content of manure the duration of the storage, and the type of treatment given to the manure. II. THE IPCC GUIDELINES The IPCC Guidelines method for estimating nitrous oxide (N2O) from manure management entails: • Multiplying the total N excretion (from all animal species/categories) in each type of manure management by an emission factor for the type of manure management system. N2O emission = N excretion x Emission factor III. METHODOLOGY • The animal population must first be divided into species/categories. • Collect population data from livestock population characterization. • Determine the annual average nitrogen excretion rate per head (Nex(T)) for each defined livestock species/category T; • Determine the fraction of total annual excretion for each livestock species/category T that is managed in each manure management system S (ms(Ts)) III. METHODOLOGY Determine the N2O emission factors (EF) for each manure management system S (EF3 (s)): • For each manure management system type S, amount of nitrogen excretion (from all animal species/categories) in that system, to estimate N2O emissions from that manure management system. Then sum over all manure management systems. IV. EQUATION FOR CALCULATING N2O EMISSIONS FROM MANURE MANAGEMENT (N2O – N) (mm) = Ʃ(s) [(Ʃ(T) (N(T) x Nex (T) x MS(Ts) )) x EF3 (s) ] (N2O – N) (mm) = N2O – N emissions from manure management in the country (kg N2O – N/year) N(T) = number of head of livestock species/category T in the country Nex (T) = Animal average N extraction per head of species/category T in the country (kg N/animal/year) MS(Ts) = Fraction of total annual excretion for each livestock species/category T that is managed in manure management system (S) in the country. IV. EQUATION FOR CALCULATING N2O EMISSIONS FROM MANURE MANAGEMENT EF3 (s) = N2O emission factor for manure management system S in the country (kg N2O – N/kg N in manure management system (S). S = manure management system T = species/category of livestock • Conversion of N2O – N (mm) emission to N2O(mm) emissions N2O(mm) = (N2O – N) (mm) x 44/28 V. CHOICE OF EMISSION FACTORS • Accurate estimate will be obtained using country-specific emission factors. • If appropriate country-specific emission factors are unavailable, default emission factors are encouraged to be used. VI. DEFAULT EMISSION FACTORS FOR N2O FROM MANURE MANAGEMENT System Description EF3 (kg N2O – N/kg nitrogen excreted Pasture/range/Paddock Manure is deposited directly on soils by livestock (unmanaged) 0.02 Solid storage Dung and urine is collected and stored in bulk for a long time (months) before disposal 0.02 Dry lot Manure is allowed to dry until it is periodically removed. Upon removal the manure may be spread on fields 0.02 Liquid/slurry Combined storage of dung and urine in tanks 0.001 VI. DEFAULT EMISSION FACTORS FOR N2O FROM MANURE MANAGEMENT System Description EF3 (kg N2O – N/kg nitrogen excreted Anaerobic lagoon Manure residues in the 0.001 lagoon for periods from 30 days to over 200 days. The water from the lagoon may be recycled or used to irrigate and fertilize soils Open pits below animal confinements Combined storage of dung and urine below animal confinement Anaerobic Digester Dung and urine is 0.001 anaerobically digested to produce CH4 gas for energy Burned for fuel Dung is collected and dried 0.007 in cakes and burned for heating or cooking 0.001 VI. DEFAULT EMISSION FACTORS FOR N2O FROM MANURE MANAGEMENT (JUDGEMENT BY EXPERT GROUP) System Description Cattle and swine deep litter Cattle/swine dung and urine are excreted on stall floor. The accumulated waste is removed after a long time <1 month > 1 month EF3 (kg N2O – N/kg nitrogen excreted 0.005 0.02 Composting - intensive Dung and urine are collected and placed in a vessel or tunnel, there is forced aeration of the waste 0.02 Composting – extensive Dung and urine collected, stacked and regularly turned for aeration 0.02 Poultry manure with bedding Manure is excreted in floor with bedding. Birds walk on waste 0.02 VI. DEFAULT EMISSION FACTORS FOR N2O FROM MANURE MANAGEMENT (JUDGEMENT BY EXPERT GROUP) System Description EF3 (kg N2O – N/kg nitrogen excreted Poultry manure without bedding Manure is excreted in floor 0.005 without bedding. Birds do not walk on waste Aerobic treatment Dung/manure is collected 0.02 as a liquid. The waste undergoes forced aeration, or is treated in aerobic ponds or wetland systems to provide nitrification and denitrification VII. ACTIVITY DATA FOR ESTIMATING N2O EMISSIONS FROM MANURE MANAGEMENT SYSTEM The three main types of activity data required are: • Livestock population data • Nitrogen excretion data for each animal species/category, and • Manure management system usage data (i) Livestock population data (N(T)) • If default nitrogen excretion rates are used, a basic livestock population characterization is sufficient. • If calculated nitrogen excretion rates are used, an enhanced characterization must be performed. VII. ACTIVITY DATA FOR ESTIMATING N2O EMISSIONS FROM MANURE MANAGEMENT SYSTEM (ii) Annual average nitrogen excretion rates Nex (T) • Country-specific rates may be taken directly from documents on reports from agricultural industry and scientific literature; or • Derived from information on animal nitrogen intake and retention, or • IPCC default excretion rates should be used with defaults adjustment factors. • In order to adjust the values for young animals, it is a good practice to multiply the N-excretion rates by the default adjustment factors (Table 4.14). Table 4.20 Calculation of manure – N excretion and N2O emission factors for different animal waste management systems in Africa Type of animal Non-dairy cattle Dairy cattle Poultry (E) Sheep Swine Other animals (F) Number of animals (x 106) 133198 18734 646000 179171 12445 162194 N-excretion (kg N/animal/year) 40 60 0.6 12 16 40 Nex (T) Table 4.14 Default adjustment factors when estimating N – excretion rates fro young animals Animal Age range (years) species/category Non-Dairy cattle 0–1 Non-Dairy cattle 1–2 Dairy cattle 0–1 Dairy cattle 1–2 Poultry 0 – 0.25 Sheep 0–1 Swine 0 – 0.5 Adjustment factor 0.3 0.6 0.3 0.6 0.5 0.5 0.5 Table 4.20 Emission factors for AWMSs EF3 (% of manure N excreted that is lost as N2O) Type of animal AL (EF3) LS (EF3) DS (EF3) SS + Dry PRP Wt (EF3) (EF3) Used Fuel (EF3) Other Total N system excreted (EF3) (Tg N) Non-dairy cattle 0.1 0.1 0.0 2.0 2.0 0.0 0.5 5.3 Dairy cattle 0.1 0.1 0.0 2.0 2.0 0.0 0.5 1.1 Poultry (E) 0.1 0.1 0.0 2.0 2.0 0.0 0.5 0.4 Sheep 0.1 0.1 0.0 2.0 2.0 0.0 0.5 2.2 Swine 0.1 0.1 0.0 2.0 2.0 0.0 0.5 0.2 Other 0.1 animals (F) 0.1 0.0 2.0 2.0 0.0 0.5 6.5 AL = Anaerobic lagoon LS = Liquid systems SS + Dry wt = Solid storage and dry lot DS = Daily spread PRP = Pasture, Range, Paddock CALCULATION OF ANIMAL N EXCRETION RATES • The annual amount of N-excreted by each animal species/category depends on the total annual N intake and total annual N retention of the animal. • Annual N intake depends on: the annual amount of feed digested by the animal and the protein content of that feed • Total feed intake depends on the production level of the animal (e.g. growth rate, milk production, draft power). CALCULATION OF ANIMAL N EXCRETION RATES • Annual N retention (i.e. the fraction of N intake that is retained by the animal for the production of meat, milk and wool) is a measure of the animal’s efficiency of production of animal protein from feed protein. • N-intake and retention data for specific animal species/categories may be available from national statistics or from animal nutrition specialists ANIMAL N EXCRETION RATES Nex (T) = N intake (T) x (1 – N retention (T)) Where: Nex (T) = animal N excretion rates, kg N/animal/year N intake (T) = The annual N intake per head of animal of species/category T, kg N/animal/year N retention (T) = Fraction of annual N intake that is retained by animal of species/category T kg N retained/animal/year per kg N intake/animal/year DEFAULT N RETENTION VALUES Table 4.15. Default fraction N-intake retained by the animal Animal Category N retention (T) (kg N retained/animal/year per kg N intake/animal/year) Dairy Cattle 0.2 Non-Dairy Cattle 0.07 Buffalo 0.07 Sheep 0.10 Goats 0.10 Camels 0.07 Swine 0.3 Horses 0.07 Poultry 0.3 GREENHOUSE GAS EMISSIONS FROM AGRICULTURAL SOILS 1. Nitrous Oxide (N2O) Emissions Three sources of N2O distinguished are: • Direct emissions from agricultural soils • Direct soil emissions from animal production • N2O emissions indirectly induced by agricultural activities. GREENHOUSE GAS EMISSIONS FROM AGRICULTURAL SOILS 2. Anthropogenic input of N into agricultural systems include: • Synthetic fertilizer; • Nitrogen from animal wastes; • Nitrogen from increased biological N-fixation; • Nitrogen derived from cultivation of mineral and organic soils through enhanced organic matter mineralization. I. Direct N2O emissions from agricultural soils • Anthropogenic sources of N2O can be biogenic (e.g. enhanced N2O production by bacteria in fertilized fields) • Or abiogenic (e.g. formation during burning processes) Biogenic production of N2O in the soil results primarily from: • Nitrification process – the aerobic microbial oxidation of ammonium to nitrate; • Denitrification – anaerobic microbial reduction of nitrate to nitrogen. • Nitrous oxide is a gaseous intermediate in the reaction sequences of both processes. GREENHOUSE GAS EMISSIONS FROM AGRICULTURAL SOILS 1.1 Anthropogenic input into agricultural systems include: • Synthetic fertilizer • Nitrogen from animal wastes • Nitrogen from biological N-fixation • Nitrogen derived from enhanced organic matter mineralization • N2O emitted directly in agricultural fields, animal confinements or pastoral systems or transported from agricultural systems into ground and surface waters through runoff, nitrogen leaching etc. GREENHOUSE GAS EMISSIONS FROM AGRICULTURAL SOILS 1.2 Direct N2O emissions from agricultural soils Anthropogenic sources of N2O can be: • Biogenic (e.g. N2O production by bacteria in fertilized fields) and • abiogenic (e.g. N2O formation during burning) Biogenic production of N2O in the soil results primarily from: • Nitrification – the aerobic microbial oxidation of ammonium to nitrate; and • Denitrification – the anaerobic microbial reduction of nitrate to nitrogen gas. • In both processes, Nitrous oxide is a gaseous intermediate in the reaction sequence. • These reactions are controlled by temperature, pH and soil moisture content. Summary of sources of N2O The following sources and sink of N2O can be distinguished: • Synthetic fertilizers; • Animal excreta nitrogen used as fertilizers; • Biological nitrogen fixation; • Crop residue and sewage sludge application; • Cultivation of high organic content soils; • Soil sink for N2O. 1.3 Methodology for estimating direct N2O emissions from agricultural fields The total direct annual N2O emission is: N2O direct [(FSN + FAW + FBN + FCR) x EF1] + FOS x EF2 N2O direct = direct emissions from agricultural soils in country (kgN/yr) FSN = synthetic nitrogen applied (kgN/yr) FAW = manure nitrogen used as fertilizer in country (kgN/yr) FBN = N fixed by N-fixing crops (kgN/yr) FCR = N in crop residues returned to the soil (kgN/yr) EF1= emission factor for direct soil emissions (kg N2O-N/kgN-input) FOS = area of cultivated organic soils within country EF2 = emission factor for organic soil mineralization due to cultivation (kg N2O-Nha/yr) 1.3 Methodology for estimating direct N2O emissions from agricultural fields FSN = N fert x (1-Frac GASF) FAW = (Nex x (1- Frac Fuel + Frac GRAZ + Frac GASM) FBN = 2 x CropBF + Frac NCRBF FCR = 2 x [Crop O x Frac NCRO + Crop BF x Frac NCRBF] x (1- Frac R) x (1Frac BURN) N fert = synthetic fertilizers used in country (kgN/yr) Frac GASF = fraction of synthetic fertilizer nitrogen applied to soils that volatilizes as NH3 and NOx (kg NH3 –N and NOx –N/kg of N input Nex = amount of nitrogen excreted by the livestock within a country (kgN/yr) Frac Fuel = fraction of livestock nitrogen excretion contained in excrements burned for fuel (kgN/kgN totally excreted) 1.3 Methodology for estimating direct N2O emissions from agricultural fields Frac GRAZ = fraction of livestock nitrogen excreted and deposited onto soil during grazing (kg N/kg N excreted) country estimate Frac GASM = fraction of livestock nitrogen excretion that volatilises as NH3 and NOx (kg NH3 –N and NOx –N/kg of N excreted) CropBF = seed yield of pulses + soybeans in country (kg dry biomass/yr) Frac NCRBF = fraction of nitrogen in N-fixing crop (kg N/kg of dry biomass) Crop O = production of all other (i.e. non-N fixing) crops in country (kg dry biomass/yr) Frac NCRO = fraction of nitrogen in non-fixing crop (kgN/kg of dry biomass) Frac R = fraction of crop residue that is removed from the field ad crop (kgN/kg crop-N) Frac BURN = fraction of crop residues that is burned rather than left on the field Table 4.19 Default values for parameters Frac BURN 0.25 (in developing countries (kg N/kg crop N) Frac R Frac Fuel Frac GASF 0.45 kg N/kg crop-N 0.0 kg N/kg N excreted 0.1 kg NH3 –N + NOx –N/kg of synthetic fertilizer N applied Frac GASM 0.2 kg NH3 –N + NOx –N/kg of N excreted by livestock Non-dairy cattle – 96; dairy cattle – 83; poultry – 81; sheep – 99; swine – 0; other animals - 99 Frac GRAZ Frac NCRBF Frac NCRO 0.03 kg N/kg of dry biomass 0.015 kg N/kg of dry biomass