impact of climate change on water resources and agricultural productivity

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.

INTRODUCTIONThe 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


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).


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


The Agricultural SectorThe 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)


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.


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 ResourcesGroundwater Resource and Climate ChangeGroundwater 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

Marine and Estuarine Water Resources and Sea Level Rise due to climate change


Year Expected sea level rise (cm)

2020 5.8

2050 16.5

2080 34.5

Table 1. Expected sea level rise in Ghana 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


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


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.


• 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.


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

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.


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.

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 Temperature ( C)⁰

Decrease in rainfall (%)

2020 0.6 2.8

2050 2.0 10.9

2080 3.9 18.6

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.


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.


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

grownChange the methods of cultivationConservation tillage may be used instead of conventional

tillage systemsIncreased 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 FactorsThese 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

SummarySTEP 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

SummarySTEP 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 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)


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.


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


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

savannasEquation 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)


savannasEquation 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)


savannasSTEP 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 28/12N2O Emissions = (carbon released) x (N/C ratio) x (emission

ratio) x 44/28NOx (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 RatiosCH4 0.004 (0.002 – 0.006)

CO 0.06 (0.04 – 0.08)N2O 0.007 (0.005 – 0.009)

NOx 0.121 (0.094 – 0.148)

Field Burning of Agricultural Residue1. CalculationsSTEP 1: Total carbon releasedData 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 ResidueTotal 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 28/12N2O = 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 RatiosCH4 0.005 (0.003 – 0.007)

CO 0.06 (0.04 – 0.08)N2O 0.007 (0.005 – 0.009)

NOx 0.121 (0.094 – 0.148)

Table 4.17 Selected Crop Residue Statistics

Product Residue/Crop product

Dry matter 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 manurethe duration of the storage, andthe type of treatment given to the manure.

II. THE IPCC GUIDELINESThe 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. METHODOLOGYDetermine 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 systemT = 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


Anaerobic lagoon Manure residues in the 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

0.001

Open pits below animal confinements

Combined storage of dung and urine below animal confinement

0.001

Anaerobic Digester Dung and urine is anaerobically digested to produce CH4 gas for energy

0.001

Burned for fuel Dung is collected and dried in cakes and burned for heating or cooking

0.007

VI. DEFAULT EMISSION FACTORS FOR N2O FROM MANURE MANAGEMENT (JUDGEMENT BY EXPERT GROUP)


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 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)


Poultry manure without bedding

Manure is excreted in floor without bedding. Birds do not walk on waste

0.005

Aerobic treatment Dung/manure is collected as a liquid. The waste undergoes forced aeration, or is treated in aerobic ponds or wetland systems to provide nitrification and denitrification

0.02

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 AfricaType of animal Number of

animals(x 106)

N-excretion (kg N/animal/year)

Nex (T)

Non-dairy cattle 133198 40Dairy cattle 18734 60Poultry (E) 646000 0.6Sheep 179171 12Swine 12445 16Other animals (F) 162194 40

Table 4.14 Default adjustment factors when estimating N – excretion rates fro young animals

Animal species/category

Age range (years)

Adjustment factor

Non-Dairy cattle 0 – 1 0.3Non-Dairy cattle 1 – 2 0.6Dairy cattle 0 – 1 0.3Dairy cattle 1 – 2 0.6Poultry 0 – 0.25 0.5Sheep 0 – 1 0.5Swine 0 – 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 Wt (EF3)

PRP (EF3)

Used Fuel (EF3)

Other system (EF3)

Total N excreted (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 animals (F)

0.1 0.1 0.0 2.0 2.0 0.0 0.5 6.5

AL = Anaerobic lagoon LS = Liquid systems DS = Daily spreadSS + Dry wt = Solid storage and dry lot 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 RATESNex (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 VALUESTable 4.15. Default fraction N-intake retained by the animalAnimal 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.


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.


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.


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 N2OThe 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)


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 (1- Frac

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)


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 0.45 kg N/kg crop-N

Frac Fuel 0.0 kg N/kg N excreted

Frac GASF 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

Frac GRAZ Non-dairy cattle – 96; dairy cattle – 83; poultry – 81; sheep – 99; swine – 0; other animals - 99

Frac NCRBF 0.03 kg N/kg of dry biomass

Frac NCRO 0.015 kg N/kg of dry biomass

impact of climate change on water resources and agricultural productivity

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