3734 important questions on fertilizer and the environment

7/28/2019 3734 Important Questions on Fertilizer and the Environment

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Important questions on fertilizerand the environment

Qs


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ContentsPage

Introduction

Yara the global company 2

The role of fertilizers in: Feeding the world - the social dimension of sustainability 3

Making crop production competitive - the economic dimension of sustainability 4

Protecting the environment - the ecological dimension of sustainability 5

A Mineral fertilizers - Essential plant nutrients for sustainable food production 6

Q1 What is fertilizer? 7Q2 How and when were fertilizers invented? 8Q3 Why are mineral fertilizers necessary? 9Q4 How are fertilizers produced? 10Q5 Where do fertilizer raw materials originate? 12

Q6 How long will the natural deposits of raw materials for fertilizers last? 13Q7 Why manufacture soluble mineral fertilizers? Why not just grind up natural minerals? 14Q8 Why are manufactured fertilizers called mineral fertilizers and sometimes chemical fertilizers? 15Q9 Which nutrients are most needed? 16Q10 Why is adding sulphur to fertilizers more necessary now than previously? 17Q11 Organic fertilizers: Are they environmentally better or worse than mineral fertilizers? 18Q12 Can nature make up for nutrient deficiencies? 19Q13 What happens to nitrogen fertilizer? 20

B Fertilizer use in agriculture 21

Q14 Do fertilizers increase soil fertility (productivity)? 22

Q15 How are fertilizer application rates derived? 23Q16 How much fertilizer does a crop need? 24Q17 What constitutes balanced and timely applications of fertilizers? 25Q18 Does precision farming give any benefit to the farmer or the environment? 26Q19 Is the condition of fertilizer spreaders important? 26Q20 What is the effect of uneven spreading of fertilizers and how can it be minimised? 27Q21 How efficiently is fertilizer nitrogen used by crops? 28Q22 What is the efficiency of different forms of nitrogen in crop production? 29Q23 Do fertilizers acidify the soil? 30Q24 Does fertilizer use make plants susceptible to pests, disease and weed infestation? 31Q25 Do fertilizers cause soil compaction and/or erosion? 32Q26 Does fertilizer use contribute to drought problems in agriculture? 33

C Fertilizer Environmental impacts 34Q27 What environmental problems occur if application rates are well below recommended rates? 35Q28 What detrimental effects can excessive nitrogen application cause? 35Q29 Do fertilizers leach to ground water? 36Q30 Isnt there an increased risk of leaching when applying highly soluble nitrogen fertilizers? 37Q31 Do fertilizers give off ammonia, which is an atmospheric pollutant? 37Q32 What problems does ammonia volatilization cause? 38Q33 Is the economic optimum fertilizing intensity in conflict with environmental consideration? 39Q34 Do we gain or lose useful energy by using mineral fertilizers? 40Q35 How much energy (fossil fuel) does it take to make one kg of nitrogen fertilizer? 41Q36 Are fertilizers free of toxic substances and safe to handle? 42Q37 What is the companys policy regarding fertilizers and the wider environment? 43

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Yara

Yara - the global company

Yara is the worlds leading producer and supplier of mineral fertilizers providing farmersand growers with essential plant nutrients required for sustainable crop production.With more than 6,500 employees worldwide, Yara is operating from 50 countries,and with sales to more than 120 countries through an extensive marketing anddistribution network of more than 160 plants, terminals and warehouses, The rightproducts in the right place, at the right time are the keys to success in the internationalfertilizer industry.

Yara is the most international player in this industry.

The companys core business is the production and marketing of plant nutrients in theform of nitrogen fertilizers and complex NPK compound fertilizers, together with other

products to offer customers a balanced nutrient portfolio of mineral fertilizers. Theproduct range includes value added speciality fertilizers especially formulated forcash crops like fruit and vegetables where the contribution to quality and nutritionalcontent is equally important to yield. Agronomic competence and support is a uniqueand integral part of Yaras offer to growers, wherever they are in the world.

Fertilizers play an important role in harvesting energy and capturing CO2. Theystimulate plant growth, and the solar energy stored in the plants may be 5-10 timeshigher than the energy needed to make the fertilizer products. Furthermore, growingplants capture CO2 in their biomass. If this biomass is used as an energy source toreplace fossil fuel, fertilizer can help reduce global climate gas emissions. Optimumfertilizer input gives optimum yields and at the same time produces high amounts ofcrop residues, which contribute to organic matter in soil.

Mineral fertilizers are made from naturally occurring raw materials (nitrogen is extractedfrom the air and combined with natural gas to form ammonia, whilst phosphate andpotash are extracted from mined rock) containing nutrients which are transformed byindustrial processes into forms that are available to plants. Yara is committed to thefurther development of fertilizer products which meet high demands on quality,agronomic efficiency, safety and environmental care. Yaras operational proceduresand technical standards are continuously reviewed to match best industry practices.

The role of fertilizers is to supplement the natural supplies of nutrients so that thecrop can reach its full growing potential and produce optimum yields. On average, theuse of mineral fertilizers doubles the yield of crops in developed countries and increasesyields by 30 - 40% elsewhere. This brings four main benefits:

It generates food for the non-farming population

It makes farming profitable for the farmerIt reduces the cost of food production and increases its efficiencyIt minimises the land area needed for agriculture

In a world characterized by continuous population growth and limited availability ofnew land for farming and cultivation, soil productivity must be continuously increasedin order to satisfy the demand for food. Without the use of mineral fertilizers, a largeproportion of the worlds population would starve. A further benefit is reduced pressureon natural vegetation through increased production from cropped land.

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The role of fertilizers

The role of fertilizers in:

Feeding the world

- the social dimension of sustainability

Between 1950 - 1996 the world population increased from 2,000 million to 6,000million. If growth rates continue there will be 8,000 million by 2020. More than90% of this growth is expected to occur in developing countries.

Crop growth and yield are governed by climatic conditions and the availability of waterand plant nutrients. At harvest, nutrients are removed from the soil by the crop andthey need to be replaced. The nutrients in the soil reserves and from organic manuresare not sufficient, mineral fertilizers provide the additional input required for increasingcrop yields. Yield increase has followed the increase in world population and mustcontinue to do so if hunger is to be avoided.

Mineral fertilizers play a vital role in feeding the world. The rising food demandto feed the expanding population since the 1960s has been met from increasedfood production largely on existing agricultural land. This was made possiblefrom more use of mineral fertilizers combined with other developments, includingplant breeding, plant protection products, cultivation techniques and use ofirrigation.

Global trends in population growth, grain yield and origin of plant nutrients

Population,

1000million

Year

1950 1960 1970 1980 1990 2000 2010 2020

8

7

6

5

4

3

2

1

0

Actual data

Projected

- 4

- 3

- 2

- 1

- 0

Fertilizers

Manure

Soil reserves of nutrients

Population

Grainyield G

rainyieldt/ha

Source: Stapel (1982) with latest data added.

"Because synthetic nitrogen fertilizers provided about half of the nutrient inharvested crops, roughly 40% of the world's dietary protein supply in themid-1990's originated in the Harber-Bosch synthesis of ammonia."

(Abstract: Professor Vaclav Smil, University of Manitoba, Canada. 1999 Travis P Hignett Lecture, IFDC, AL, USA. IFDCReference: LS-2, October 1999.)

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Making crop production competitive

- the economic dimension of sustainability

Fertilizers maintain soil fertility and productivity through supplying/replacing essentialplant nutrients and therefore make a vital contribution to economic crop production.Cultivated soils do not usually contain sufficient amounts of plant nutrients for highand sustained crop yields. Harvesting crops removes nutrients and if they are notreplaced (through use of fertilizers) soil mining results, yields will diminish,crops will develop deficiency symptoms and in extreme cases, fail altogether.

The world's population is expanding, thus creating a need for increased food productionat affordable prices. Fertilizer use on an expanding scale is required for enhanced andeconomic agricultural productivity.

Fertilizers are necessary to support affordable and sustainable agriculture. Yarahas a range of fertilizer products to provide those nutrients in short supply. Optimal

fertilizer application with the correct balance of nutrients is required to ensurethe economic production of both high yielding and high quality crops.

The use of mineral fertilizers pays off

0 50 100 150 200 250 300

Fertilizer application, kg N/ha

1200

1000

800

600

400

200

100

0

The investment in nitrogenfertilizer is highly profitablefor growers

Net return is 7x theinvestment

Wheat yield response (monetary value)to N fertilizer rate

Source: Yield data: Long term trial (since 1 856), Broadbalk, Rothamsted, UK.

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The role of fertilizers


Protecting the environment- the ecological dimension of sustainability

Man has caused major changes to the land on planet earth. Most notably since the1850s.

The Earths land area is 13 thousand million hectares which is 29% of the Earthssurface. Currently about 10% of all land is cultivated, with FAO projections suggestingonly small further expansion is possible. The reserves are mainly in Africa and LatinAmerica.

There are serious constraints on the use of the remaining reserves, such as lack ofwater, land quality, sparse population, preservation of forests and other environmentalconcerns.

Sustainable agriculture with more intensive use of the areas already employed forfood production will help to conserve the land reserves.

This can be achieved by improving the soils fertility through the judicious, and greater,use of fertilizers.

Mineral fertilizers play a vital role in conserving the land. Reducing the mineralnutrient input could mean that more virgin land would have to be ploughed up.In sustainable agriculture, the need for good quality food at affordable pricesshould be met with minimum adverse effects on the environment. Excessive ratesof fertilizer application are potentially environmentally harmful as well aseconomically wasteful. Applying fertilizer responsibly and according to good

farming practices can limit the risk of this occurring.

Transformation of land in the period 900 - 2000

1000 million haWater

14 Ice

13

Other land12

11

10

9 - Unexploitable forest

8

Primary forest7

6 Secondary forest

5 Natural grass

4

3 Grass

2

1 Crops

0 900 1700

1850 1950

World =44.8bha

Land = 13bha(29% ofworld area)

Freshwater= 3%(70% frozen)

1900 2000

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A Mineral fertilizers - Essential plantnutrients for sustainable food production

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A Mineral fertilizers - Essential plant nutrients for sustainable food production

Q1 What is fertilizer?Fertilizers are nutrients for plants, regardless of source.

Besides sunlight, carbon dioxide, oxygen and water, thirteen elements are consideredessential for plant growth. These are divided into:

Major nutrients - N, P, K (nitrogen, phosphorus, potassium).Secondary nutrients - Ca, Mg, S (calcium, magnesium, sulphur).Micro nutrients - Fe, Mn, B, Zn, Cu, Mo, Cl (iron, manganese, boron, zinc,copper, molybdenum, chlorine).

Some crops may benefit from other elements, e.g. Na (sodium) for sugar beet and

some tropical crops, and Si (silicon) for maize, grasses and particularly rice.

The primary and secondary nutrients are required in the largest amounts, althoughthere are large variations of requirement between crops. They are the constituentsof many plant components including proteins, nucleic acids and chlorophyll, and areessential for processes such as energy transfer, maintenance of internal pressure andenzyme function. Micronutrients are the vitamins of plants. They are not needed inlarge quantities but are necessary for plant health.

The components of mineral fertilizers are normal constituents of the soil in theinorganic form and are environmentally benign. In organic fertilizers the nutrients arepartly tied up in organic compounds that have to be mineralized to be available toplants.

Mineral fertilizers can supply the balance between the amount of nutrientsavailable from other sources like the soil, air or organic manures, and a cropsnutrition requirement.

Primary, secondary and micro-nutrients

PN K

Ca Mg S B Zn Fe Cu Mn Mo Cl

Primary nutrients

Secondary nutrients Micro-nutrients

H2O

CO2

O2

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Q2 How and when were fertilizers invented?

A Deficiency of any SingleNutrient is Enough to Limit Yield

JUSTUS VON LIEBIG1803 - 1873

Sodiu

m

Oxygen

Boron

Carbon

Dioxide

Soil Conditions& Other

Growth Factors

Water

Nitrogen

Phosphorus

Potassium

Calcium

Magnesium

Sulphur

IronC

hlorine

Yield

Warmth

Light

Yield

The law of the minimum illustrated bybarrel staves of varying lengthsrepresenting growth-controlling factors.

How plants take up nutrients

Manufactured fertilizers were introduced to European agriculture in the middleof the 19th century, after the discovery of the principles of plant nutrition.

In the 1830s, Justus von Liebig (1803-1873) discovered that minerals like nitrogen,phosphorus and potassium were plant nutrients. The scientist concluded that thesemineral plant nutrients originated from mineralized plant residues and other organicsoil material. It was concluded that a deficiency of any single nutrient was enoughto limit yield.

The value of fertilizers was demonstrated in the worlds first agricultural field trialsat Rothamsted in the UK. These trials continue to provide valuable information in

fertilizer efficiency, with the long term trial on the Broadbalk site in continuous existencesince 1856.

The history of fertilizer manufacture begins around 160 years ago. Some importantmilestones are:

1842 - J B Lawes produces superphosphate from rock phosphate at Rothamsted1905 - First production of synthetic nitrogen fertilizer at Notodden in Norway191 1 - Haber-Bosch process introduced to manufacture ammonia1927 - Nitrophosphate process developed in Norway

Yaras history goes back to 1905 when Norsk Hydro was established followingthe revolutionary invention of Birkeland & Eyde, utilizing Norways vast reserves

of hydroelectric power to capture nitrogen from the air.

Yara has responded to the global need for mineral fertilizers through developingfertilizer products and expert advice systems and services, which promote theresponsible use of the Companys products and support sustainable agriculturalproduction systems. Agronomic competence is a unique and integral part of Yarasoffering to growers of crops, wherever they are in the world.

S

Mg

Ca

K

P

N

plant residues

organicmatter

mineralization

plant residues are decomposed into minerals

manures

fertilizers

soil

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Q3 Why are mineral fertilizers necessary?Fertilizers maintain soil fertility/productivity through supplying/replacing essentialplant nutrients and therefore make a vital contribution to economic crop production.

Cultivated soils do not usually contain sufficient amounts of plant nutrients for highand sustained crop yields. Harvesting crops removes nutrients and if they are notreplaced (through use of fertilizers) soil mining results, yields will diminish, crops willdevelop deficiency symptoms and in extreme cases, fail altogether.The world's human population is increasing, demanding increased food productionfrom agricultural land, at affordable prices. Fertilizer use on an expanding scale isrequired for enhanced and economic agricultural productivity.

Fertilizers are necessary to support an affordable and sustainable agriculture.Yara has a balanced nutrient range of fertilizer products to provide those nutrientsin short supply. Optimal fertilizer application, with the correct balance of nutrientsis required to ensure the economic production of both high yielding and highquality crops.

The economic gains from applying mineral fertilizer

Treatment

No fertilizer 2.1 235 593 -358 282

Mineral fertilizer192 kg N/ha 9.3 1042 885** 157 95

* Assuming grain market price: 112 EUR/tonne (EU intervention price = 101 EUR/tonne)

** Cost increase due to intensive production including purchase of N fertilizer

Source: Winter wheat, long term trial, Broadbalk, Rothamsted (since 1856).Production cost: data from KTBL Germany.

The use of mineral fertilizers pays off

0 50 100 150 200 250 300

Fertilizer application, kg N/ha

1200

1000

800

600

400

200

100

0

The investment in nitrogenfertilizer is highly profitable

for growers

Net return is 7x theinvestment

Wheat yield response (monetary value)to N fertilizer rate

Source: Yield data: Long term trial (since 1 856), Broadbalk, Rothamsted, UK.

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Q4 How are fertilizers produced?

Fertilizer production routes

The production processes vary in accordance with the nutrients needed to beincluded in the fertilizer.

The components of finished fertilizer products are relatively simple chemicals, buthighly developed manufacturing technologies are employed in the production of highquality mineral fertilizers. There are various steps involved in their manufacture, fromthe raw materials, through intermediates, to the finished products.

Nitrogen (N) Fertilizers:The supply of nitrogen, determines a plants growth, vigour, colour and yield. Increasingthe nitrogen supply to a crop tends to increase the crops content of substances that

contain nitrogen such as proteins and vitamin B1.

The intermediate product in the case of nitrogen fertilizers is ammonia (NH3), whichis produced by combining nitrogen extracted from the air with hydrogen which isobtained from natural gas, or through the hydrocarbon steam reforming process.Approximately 85% of the ammonia plants in the EU use natural gas. Measures toimprove production processes have focused on reducing the amount of hydrocarbonfeedstock required to produce a tonne of ammonia.The further processing of ammonia produces straight N fertilizers such as urea,ammonium nitrate and calcium ammonium nitrate, as well as solutions of the abovefertilizers and ammonium sulphate. Ammonia is also the main intermediate for manymulti-nutrient fertilizers.

Phosphate (P) Fertilizers:

Phosphorus is required for good rooting and resistance to drought, for plant growthand development, for the ripening of seed and fruit and in the manufacture and useof sugars and complex carbohydrates. A good supply of phosphorus is essential in thefirst stages of a plants life and for early maturity.This nutrient is often described or declared as phosphate (P2O5) rather than phosphorus(P). This is just a convention and the terms can be used interchangeably but care needsto be taken with fertilizer recommendations, as 1 kg P is equivalent to 2.291 kg P2O5.

Rock phosphate (27 - 38% P2O5) is the raw material source from which most typesof phosphate fertilizers are produced, with minor exceptions such as basic slag (12 18% P2O5), which is a by-product of steel production.

In its unprocessed state, rock phosphateis not suitable for direct application, asthe phosphorus it contains is insoluble at

soil pH above 6.5. To transform thephosphorus into a plant-available formand to obtain a more concentratedproduct, phosphate rock is processed usingsulphuric acid, phosphoric acid and/ornitric acid. Acidulation by means ofsulphuric acid produces either phosphoricacid, an intermediate product in theproduction of triple superphosphate (TSP),monoammonium phosphate (MAP),diammonium phosphate (DAP) andcomplex fertilizers, or singlesuperphosphate (SSP). Acidulation usingphosphoric acid produces TSP, and

acidulation using nitric acid produces NPslurries for use in the manufacture ofcomplex fertilizers.

Ammonia plant

Nitric acid plant

Nitrophosphate plant

Phosphoric acid plant

Sulphuric acid plant

Urea plant

Ammonium nitrate plant

Calcium nitrate plant

NPK fertilizer plant

Ammonium phosphate plant

Natural gasWater

Air

WaterAir

Rock

Rock

Sulphur

CO2

Superphosphate plant

H2PO

4H2SO4

HNO3

NH3

Salts of K, Mg, S

Rock

AN

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Yara Glomfjord - Emissions to Air

Every year all Yara sites publish an environmental map with emission figuresand performance relative to the environmental permits.

Nitric acid plants A and BNitric oxides (NOx): 0.28 tonne/dNitric Acid Plant A Nitric oxides (NOx): 0.15 tonne/dNitric Acid Plant B Nitric oxides (NOx): 0.13 tonne/d

Complex fertilizer plantNitrogen (N) 4.4 kg/hFluorides (F) 0.04 kg/hAmmonia (NH3) 16.2 kg/hSulphur dioxide (SO2) 0.14 kg/hFertilizer dust 21.4 kg/h

To water:Nitrogen (N) 1.88 t N/dPhosphorus (P) 0.13 t P/d

Potash (K) Fertilizers:Potassium controls water relations in plants and helps give plant cells their turgor orstiffness. This is important for crop quality and resistance to disease. Sufficientpotassium is also critical for vitamin and mineral content, for texture, firmness and

resistance to drought. It is particularly significant in plants that store large amountsof sugar and starch, like potatoes. It is also vital for the root nodule bacteria onlegumes which fix nitrogen from the air.This nutrient is often described or declared as potash (K2O) rather than potassium (K).Whilst just a convention, the terms can be used interchangeably but care needs tobe taken with fertilizer recommendations, as 1 kg K is equivalent to 1.205 kg K 2O.

Most potassium used in fertilizer production is taken from natural deposits of potassiumchloride. The mined material is crushed and purified by the removal of rock particlesand salt and then applied direct, or more usually incorporated in NPK fertilizers.Relatively small amounts of potassium sulphate also are used in fertilizers.

Multi-nutrient Fertilizers:Multi-nutrient fertilizers produced in the EU are either complex fertilizers (every particle

contains the same ratio of nutrients), or blends (made by mixing particles of differentmaterials). Typically, complex NPK fertilizers are manufactured by producing slurriesof ammonium phosphates, to which potassium salts are added prior to granulationor prilling. PK fertilizers, on the other hand, are generally produced as compounds bythe steam granulation of super phosphates (SSP or TSP) with potassium salts.

Yara has a balanced nutrient range of fertilizer products, which has been speciallydeveloped for the worlds major crops. The Company produces and marketscomplex NPKs, Nitrates (ammonium nitrate, calcium ammonium nitrate andcalcium nitrate), UAN, Urea, Ammonia and other differentiated and value addedspeciality fertilizers containing one or more micronutrients.

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Where do fertilizer raw materials

Q5 originate?Most are from natural sources like the air, and minerals mined from the earth.

The principal raw materials for fertilizer production are:

Air to provide nitrogen.Natural gas and oil to provide hydrogen and energy (for production of ammonia).Rock phosphate (natural minerals with largest known reserves in North Africa,South Africa, USA, China).Potassium salts (natural minerals with largest reserves in Canada, Russia, Belarus,Germany).Sulphur (for production of sulphuric acid used in the production of most phosphate

fertilizers (mainly from desulphurization/cleaning of oil and gas).

Extraction and processing of any raw materials can have environmental effects andproduction plants must comply with local regulations.

Mining of phosphate and potash minerals can cause landscape changes. Phosphaterock mines are often operated as opencast sites, with large amounts of waste rockgenerated and considerable landscape restoration is required to minimize the impact.

Some phosphate rock contains minor amounts of naturally occurring radioactiveelements, e.g. uranium. Special precautions may be necessary to provide safe storagefor mining wastes. Uranium has occasionally been a commercial by-product ofphosphate mining.

Potassium extraction can give brines as a by-product, which could cause pollution towater.

Sulphur is extracted from stack gases e.g. electric power plants burning fossil fuels.Much of this sulphur is utilized by the fertilizer industry. This helps to reduceenvironmental pollution from sulphur dioxide in gas emissions from industry.

Yara has participated in the development of the EuropeanFertilizer Manufacturers Associations (EFMA) Product

Product Stewardship (from mine to farm)Stewardship Programme to ensure that proper care istaken along the whole chain-from product developmentand purchase of raw materials, during production andstorage and in the distribution network. The Companyhas adopted and expanded on the requirements in its

own application of the principles, and works accordingto the highest standards, complying with legislationwith regard to health, occupational and public safety,environment and security. Best available technologiesare adopted.

Application &Farmer services

ProductStewardship

Marketing& Sales

Storage

Transportation Manufacturing

Sourcing ofmaterials

Packaging

Productdevelopment

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How long will the natural deposits of

Q6 raw materials for fertilizers last?Phosphorus and potassium are considered to be among the most abundant elementsin the earth's crust. Scarcity of fossil fuels as a raw material and for energy usein production is of concern.

Agriculture is a relatively minor user of energy, using less than 5% of total EU energy,with food processing, transport and preparation accounting for a further 10%.

There are known reserves of oil and natural gas for approximately 40 to 60 years.New deposits are found each year, but at some time in the future, scarcity may appear.When this happens other methods for fertilizer production will be needed, for examplethat based on hydro electric power discovered by Norsk Hydro in 1905.

Lifestyles in the developed world and rising demand from growing economies in China,South America and elsewhere, will affect the future price, and perhaps supply, of oiland gas. This will directly affect production of nitrogen fertilizers.

Phosphorus and potassium are considered to be among the most abundant elementsin the earth's crust. Easily available resources of phosphate are expected to last forabout 90 years, and it is likely with ongoing exploration activities, that more will bediscovered.The same is true for potassium reserves.

Raw materials for other plant nutrients are also available in sufficient amounts comparedwith agricultural needs. Boron is a possible exception.

Yara develops and manages the Companys activities to make efficient use ofenergy and raw materials. It works systematically to reduce emissions to air,water and the ground and to minimize waste and ensure the safe handling of theCompanys products.

European energy use

Industry, traffic, households, public services 85%

Food industry 10%

Agriculture production (inclusive mineral fertilizer production) 5%

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Why manufacture soluble mineralfertilizers?

Q7 Why not just grind up natural minerals?Manufacturing processes are necessary for the nutrients in fertilizers to be in a

form which is readily available to plants in the quantities required.

Nitrogen:The only naturally occurring source that contains nitrogen in a plant-available formis "Chile saltpeter" (sodium nitrate). This "mineral" in a purified form is used as fertilizer,but supplies are inadequate for world agriculture.

Phosphorus:Nutrients are only available to plants when dissolved in water. Most minerals containing

Plants need three main nutrients: phosphorus are so insoluble that they are ineffective as a phosphorus source though

Nitrogen, Phosphorus and Potassium some rock phosphates are sufficiently reactive for use on acidic soils. Even reactivephosphates are too insoluble where a rapid response (on soils with low phosphorusstatus) is needed. Fine grinding of these rock phosphates does not sufficiently improvetheir availability.

Potassium:Most potassium fertilizers contain a ground-up natural mineral, potassium chloride.With a few exceptions, other minerals containing potassium are so insoluble that theyare relatively ineffective as a nutrient source. Very high application rates would be

YIELD ANDIELD AND required, but even then the results would be unreliable.QUALITLITY

Production processes developed and used by Yara ensure nutrients are converted

Nitrogen, the main driver of yield into forms that can be taken up by plants.

Yara is a truly global fertilizer company with a presence in approximately 50countries around the world, and selling to more than 120 countries through anextensive marketing and distribution network consisting of more than 160 plants,terminals and warehouses.

Yara International unique global presence and infrastructure

46

15

18

Major Plants

Office 22

No. of plants/terminals/warehouses

On the ground in 50 countries, sales to more than120 countries, more than 160 infrastructure points.

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Why are manufactured fertilizers calledmineral fertilizers and sometimes

Q8 chemical fertilizers?Mineral fertilizers is the best descriptive name, as they are manufactured fromminerals.

Mineral fertilizers contain plant nutrients that occur naturally in the soil, in a concentratedform. For more detailed information, please refer to the answers to previous Questions,1-7. Fertilizers that are manufactured are sometimes called mineral, artificial,inorganic, industrial or chemical. Of these, mineral is the best description as thisdescribes the source. The other terms can be applied to a wide range of material,for example, all nutrients, regardless of source, are inorganic when taken up by plants.Sludge and often organic waste used as fertilizer can be called artificial, industrialor chemical.

Yara produces mineral fertilizers to high quality standards, which means:

Nutrients are available to crops.Fertilizer can be spread evenly and accurately.Production processes minimise energy use and emissions.

Nitrogen content in 1 tonne of fertilizer

400

350

300

kg/T

200

100

50

Mineral Cattlefertilizer (AN) manure

Fertilizer requirement to apply 100 kg

of nitrogen per ha

24

20

18

T/ha

12

6

0.286

0 Mineral Cattle

fertilizer (AN) manure

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Q9 Which nutrients are most needed?Nitrogen, followed by phosphorus and potash.

Generally, the limiting nutrient is the most needed one because it limits the uptakeof other nutrients and directly or indirectly, crop yield.The industrial production of mineral fertilizers makes it possible to correct for thesedeficiencies, and thus maintain soil fertility through balanced fertilization.

On a global scale, nitrogen is the most needed nutrient followed by phosphorus andpotassium. Owing to previous imbalanced fertilization with focus on nitrogen needs,deficiencies in phosphate and potash still occur in some parts of the world, e.g. partsof Asia. Phosphate and potash deficiencies also frequently develop in systems that

have been under organic farming for some years.Sulphur and zinc deficiencies are also quite common worldwide.

Yara has a balanced nutrient range of fertilizer products, which has been speciallydeveloped for the major crops in the world.The Company is the most diversified nitrogen fertilizer company in the world,producing and marketing complex NPKs, Nitrates (ammonium nitrate, calciumammonium nitrate and calcium nitrate), UAN, urea, ammonia and otherdifferentiated products with additional plant nutrients.

Nitrogen, the most important nutrient

Potassium (K)

Phosphorus (P)

Nitrogen (N)

Phosphorus in the soil

Source: IFA statistics season 2003/2004.

17%

24%

59%

Total 145.6 millionnutrient tonnes production

Slowlydegradable

organic P

Easilydegradableorganic P

Fast

Non-labile Pin apatites andsoil minerals

Fertilizer P

Soil solutionSlow

Slow

Labile P bonds

to minerals

Plant residues,manures

Mineralizationsoil microbes

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Without and with sulphur.

Why is adding sulphur to fertilizers more

Q10 necessary now than previously?There are various reasons:

Phosphate fertilizers are now more concentrated and thus their sulphur contenthas been reduced.

Rain used to provide enough sulphur to prevent sulphur deficiencies in WesternEuropean crops but the significant reduction in industrial sulphur dioxideemissions has decreased the rate of sulphur deposition from rain.

Sulphur deficiency may have gone unnoticed or been confused with nitrogendeficiency.

Sulphur demanding crops e.g. oilseed rape, are now more commonly grown.

Yields are higher than previously, hence more nutrients, including sulphur, areremoved from the system.

Sulphur deficiencies are now causing yield reductions in some regions and in somecrops, necessitating sulphur to be included in fertilizers.

There are four main sources of sulphur for crops:

The soil organic matter.The air.Organic manures.

Mineral fertilizers.

Mineral fertilizers can effectively be applied to balance any deficiency from othersources to meet crop need.

Yara has carried out extensive field trials investigating the response to appliedsulphur on a wide range of crops, soil types and climatic conditions. The Companys

fertilizer recommendation systems take account of all sources of sulphur, andformulations increasingly contain this element to meet the rising crop requirements.

Oilseed Rape often responds to sulphur.

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Organic fertilizers:Are they environmentally better or worse

Q11 than mineral fertilizers?Both organic and mineral fertilizers have their place in sustainable agriculture.

Manures and crop residues are by-products in agriculture that contain valuable cropnutrients and should be used wherever available and taken into account when makingfertilizer recommendations.

Manures table

Source % dry matter Nutrients, % of dry matter

Cattle manuresN P K

SlurryFYM

Sewage sludge

Chemical treatment (Fe/Al)

Biological treatment

Town refuse

Compost

922

20 - 40

17 - 20

70

4.62.6

0.5 - 3

0.8 - 5

1.17

0.80.8

0.2 - 3

0.1 - 1

0.25

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Origin and quantity of ammoniaemissions to air in Western Europe

Sewage sludge - sometimes called bio solids - is available for application to land buthas a low and varying nutrient content, and it may contain undesirable components(e.g. heavy metals). The phosphorous availability from chemically treated sludge islow, hence processes are under development to recover the phosphorous and makeit more plant available. The use of sewage sludge requires careful consideration ofthe quality and the variability of the product. Some countries, e.g. Switzerland, havebanned the spreading of sewage sludge on agricultural land. Others like Germany arecurrently developing strong quality regulations for unwanted components. Some crop

Animal husbandry Mineral fertilizer protocols like EUREPGAP do not allow the application of bio solid products.Manure spreading 32% Application 12.5%Grazing 8% Production 0.5% Yara fertilizer recommendation programmes routinely take account of, and giveManure storage 34% Leaf emission

guidance on how to combine mineral fertilizers with organic manures for balancedfrom crop 5%plant nutrition.Miscellaneous 8%

Source: ECETOC Technical Report No. 62Ammonia Emissions to Air in Western Europe.

Can nature make up for nutrientQ12 deficiencies?

Not in current intensive agriculture.

If a deficiency problem has occurred, the relevant nutrient or nutrients must be suppliedfor crops to thrive.

Deficiencies of nutrients indicate that the weathering of soil minerals or the releaseof nutrients from organic matter is too slow to sustain a high-yielding crop. In lowproductive shifting agriculture, minerals are made available to subsequent cropsthrough burning and weathering of soil minerals during a previous break from cropping.

Where soil or crop analysis shows deficiencies, mineral fertilizers fortified with oneor several of the nutrient elements listed in Question 1 can be applied to address thesymptoms and correct the deficiency.

Yara has over many years established an extensive and active presence in worldagriculture. Communication and practical interpretation of the results of theCompanys extensive Research & Development Programme has been a key aim,

and has resulted in the production of advisory tools and expert programs whichgive fertilizer recommendations for most crops, and special tools for nitrogenrecommendations. The Plant Master series of brochures cover the major growingaspects of the important crops in the world, and are a key part of communicationwith farmers and growers.

Lack of one or more nutrients reduce yield and quality

P shortage (left).Photo: P Seward, Yara.

K shortage (right).Photo: Kali and Salz, Germany.

S shortage (right).Photo: Rothamsted exp. station.

Mg shortage (right).Photo: D. D. Warncke, APS Press.

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Q13 What happens to nitrogen fertilizer?So long as it is applied to meet crop requirement and in accordance with good

farming practice, with locally derived rates and timing, it will be largely takenup by the plant. It is then present in agricultural outputs, grains, fruit, vegetables,milk, meat, and eggs.

The soil nitrogen cycle explains the nitrogen pathways.Nitrogen fertilizers dissolve in soil water and release ammonium-N and nitrate N,both of which are taken up by crops.

Of the fertilizer nitrogen applied:

Much is taken up by the plant.Some is used by soil microbes and incorporated in the soils pool of organic matter(called microbial nitrogen immobilization).The remainder is at risk of loss through leaching and gaseous products (ammonia,nitrogen oxides and di-nitrogen) The amounts are variable depending on the quantity,time and type of nitrogen fertilizer applied, as well as the environmental conditionsof soil and climate.

Yara has an extensive R & D programme to improve fertilizer N use and tominimise risks of nutrient loss from the soil.

The soil nitrogen cycle

Nitrogen in air (N2)

Nitrous oxide(N2O)

Soluble nitrogen

Insoluble nitrogen

Agricultural output: grain,roots, vegetables,fruits

Ammoniavolatilization

NitrogenFertilizer

milk, meat, eggs, etc.

Manure

Insoluble nitrogen,mainly in organic

matter.

Nitrateleaching

Denitrification

Soluble nitrogen:nitrate (NO3-)

ammonium (NH4+)

Nitrogenfixation

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B Fertilizer use in agriculture

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Do fertilizers increase soil fertility

Q14 (productivity)?Yes. Crops are mining the soil for nutrients; fertilizers replace those nutrientsand can maintain or increase soil fertility through plant residues building organicmatter in the soil.

Appropriate use of fertilizer contributes to good agricultural practice. Mineral fertilizerapplications can increase soil organic matter through higher levels of root mass andcrop residues.

However, incorrect agricultural practices may diminish soil fertility even where fertilizersare used:

Increased yields increase nutrient removal, and those nutrients must be replaced.If nitrogen only is supplied, the soil can be so depleted of other nutrients thatfertility and productivity suffers.Poor rotations, with little or no return of crop residues or manures can result inreduced soil organic matter content and soil fertility. Fertilizers do not cause suchchanges, but can mask soil deterioration for some time.Repeated use of acidifying fertilizers i.e. ammonium sulphate, can cause increasedsoil acidification if not corrected by lime. Crops have varying tolerances to the pHstatus of soils.

Positive effects on soil quality

SOILQUALITY

SOILQUALITY

Increase or maintain organic matter:

mineral fertilizers - increased yields

organic manures - organic content

crop residues left in the field

crop rotations including grass

conservation tillage

Stabilises aggregates:

liming

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How are fertilizer application rates

Q15 derived?By taking all the factors involved in the nutrient status of the site, and requirementof the crop, into account fertilizer rates can be calculated to balance the nutrientsupply to produce optimum yield.

kgN

/ha

N fertilizerdemand

N supplyfrom the soil

Fertilizer recommendations should meet the crop's demand forN demand

nutrients, which is dependent on:of the crop

Crop type, variety, quality and end use requirements.Nutrient supply from non fertilizer sources i.e. the soil, organicmanures etc.Previous fertilizer applications and cropping.

Local climatic conditions.

Fertilizer recommendations can be estimated from:

Local fertilizer experiments.Farmers experience.Soil and plant nutrient analysis.Research based expert programs.

Such information is combined to give estimates of the amounts of nutrients thatshould be applied to obtain the best economic result.There is always difficulty in estimating accurate optimum fertilizer rates because:

The amount of nutrient available from the soil is difficult to establish accurately.

The weather represents an unpredictable influence on the crop's need for nutrients.

Yara has developed advisory tools and expert programs, which give fertilizerrecommendations for most crops, and special tools for nitrogen fertilization (N-Tester and N-Sensor), which measure the nutrient demand directly from the plant.Fertilizer recommendations, tools and programmes are essential to increase theaccuracy of managing the nutrient supply to crops. The Plant Master series ofbrochures cover the major growing aspects of the worlds most important crops.

Mar Apr May Jun Jul AugFeb

The MCL3 soil sampler. Capable of penetrating the hardestsoil, its cylindric probe technology provides samples down to adepth of 120cm.

The Yara N-Sensor. The Yara N-Tester.

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Average nutrient content of various crops


Q16 How much fertilizer does a crop need?It depends on the crop in question, its management, place in the rotation and theexpected yield. The N-Sensor is able to detect areas of different nitrogen supplywithin one field and converts this information into a nitrogen application mapthat takes into account the different nitrogen demands of the crop.

Average nutrient content of various crops

Nutrient

Primary

NitrogenPhosphorus (P)

Potassium (K)

Secondary

Sulphur

Magnesium

Calcium

Nutrient removal (kg t-1 of produce as harvested)

Wheat

Grain

213.6

3

Grain

1.6

1.2

0.4

Rough rice, Philippines

Grain

14.62.6

3

Grain

0.6

1.0

0.1

Straw

90.6

28

Straw

0.4

1.6

3.2

Total

23.63.2

31

Total

1.0

2.6

3.3

Sugar beet, UK

Root

1.40.4

2.7

Root

0.3

0.3

0.6

Top

3.60.4

3.4

Top

0.65

0.4

1.2

Total

50.8

6.1

Total

0.9

0.7

1.8

Potato

Tubers

40.7

5

Tubers

0.4

0.4

0.1

(Items written in italics are commercial produce).

More fertilizer is needed if crop residues are removed, than if they remain in the fieldand are available to the following crop. For example, rice and wheat crops yielding2-8 t grain/ha absorb 50-190 kg N/ha, 6-22 kg P/ha and 65-250 kg K/ha. Thecontent in the grain amounts to 30-120 kg N, 4-16 kg P and 6-24 kg K per hectare,

hence, the total amount needed for each crop depends on whether the residues fromthe previous crop are left in the field.

Sensor map:

Without slurry

Cattle slurry

Pig slurry

N-Application map

Spectralindex

High

Low

N (kg N/ha)

100

90

80

70

60

50

40

Crops such as sugar beet and potatoes have a largerproportion of the nutrients in the crop residues, thus,their fate is important when considering the nutrientneeds for the following crops and should be taken intoaccount when fertilizer plans are made.

Yara fertilizer recommendation programs takeprevious cropping into account, as well as the otherrelevant site-specific factors e.g. variety, soil type,planting date etc. Fertilizer recommendations toolsand programs are essential for increasing the

accuracy of management of the nutrient supply tocrops and for providing a record, required by manycrop growing protocols. The Yara Plant Masterseries of brochures has been produced for mostmajor crops.

Winter Barley. N-Sensor measurement and N-application on the 25th of May 1999.Source: AgriCon, Germany.

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What constitutes balanced and timely

Q17 applications of fertilizers?Balanced fertilizer use implies that:

The different nutrients are supplied in the right proportions according to theplant's needs.

All nutrient sources available to the crop are taken into account, i.e. mineralfertilizers, farmyard manure, sewage sludge, crop residues etc.

The total supply of added nutrients from all sources is just sufficient to meetthe crops requirement, so that deficiencies are avoided and nutrient residuesin the soil after harvest are minimized.

Unbalanced fertilizer use, for example only applying nitrogen, can give yields belowthe optimum, increase the crop's susceptibility to insect and fungal damage, andreduce crop quality.Timely fertilizer use means to apply fertilizer at or just prior to the time the croprequires a rapid uptake of nutrients. This also minimises any environmental impactof fertilizers.Plant analysis can be used to determine the nutrient status of the crops and the righttiming of fertilizer application.Fertilizers should not be applied outside and towards the end of the growing season,or when heavy rain is expected.

Yara provides a wide range of fertilizer grades that enable the farmers to selectthe right balance of nutrients for their crops. Yara has developed advisory tools

and programs which give fertilizer recommendations and timing of applicationsfor most crops, with more specific tools for nitrogen recommendations.

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Does precision farming give any benefit

Q18 to the farmer or the environment?Yes, it benefits both.

Precision farming technology helps the farmer to apply the optimum amount offertilizer on each spot within a field. The accurate application of fertilizer accordingto the actual nutrient demand of the crop avoids over-fertilization as well as under-fertilization in a field. This variable rate fertilizer application results in higher yieldsand reduced losses to the environment as the applied fertilizer is utilized more efficientlycompared to a standard fertilizer application, which is uniform for the whole field.Standard application doesn't take into account the varying nutrient demand within thefield.

Yara has developed N-Sensor, a system for measuring crop nitrogen status as itvaries within a field and for adjusting fertilizer applications accordingly. Currently,the system has been developed for use with winter cereals, oilseed rape, maizeand potatoes.

Is the condition of fertilizer spreaders

Q19 important?Yes, because a poor spreader will not accurately spread fertilizer.

Spreader manufacturers have developed application machinery which can achievegood levels of spreading accuracy in field conditions so long as:

The machine is set up and adjusted for the type of fertilizer to be applied.The operator is proficient.The fertilizer quality (physical properties) is good and the product is free flowingto enable the machine to work efficiently.

Fertilizer spreaders must be well maintained and calibrated regularly by a trained

mechanic.

Yaras fertilizers have been developed to have consistently good spreadingcharacteristics of size, bulk density and hardness. The Company has a goodrelationship with the worlds leading manufacturers of fertilizer spreaders, andproduct is supplied to them, so that good spreading advice and guidance isavailable for farmers and growers.

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What is the effect of uneven spreadingof fertilizers and how can it be

Q20 minimised?

Uneven 1st N application with urea in

early spring (spreading width 36m)

Biomass index

low high

Biomass monitoring in May shows a clear stripedpattern with under-fertilized and over-fertilizedstripes in the field. The stripe pattern is due tobad spreadability of low density urea at 36mworking width. Low biomass is a good indicatorof a potential loss of yield.

Uneven spreading is costly to the farmer and is potentially harmful to theenvironment. It can be minimised by choosing a high quality fertilizer with goodspreading characteristics and using a well-maintained spreader to apply the

fertilizer.

Costly to the farmer because only the areas receiving the optimum rate will give a fulleconomic return:

The areas over fertilized are unlikely to produce enough extra yield to cover thecost of the additional fertilizer.The areas under fertilized are unlikely to have reached their yield potential.

Harmful to the environment because parts of the field could receive excessive rateswhich depending on field conditions and soil type, could be at risk of leaching. Alsoharmful if uneven spreading means fertilizer enters a watercourse.

Evenness of spreading is measured by the coefficient of variation (CV%):

1-15% is considered acceptable in field conditions

Uneven spreading can lead to a loss of yield as shown on this graph:

Financial losses due to uneven spreading

0 10 20 30 40

50

40

30

20

10

0

Wheat

OSR

1st Cut

Coefficient of variation (CV%)

If you can see striping,loss in yield could be

costing:

11.0 euros/ha inwinter wheat.6.5 euros/ha insilage.7.0 euros/ha inoilseed rape.

Further financial lossescan occur if unevenspreading leads to a

loss of crop quality premium. For example, the loss of milling premium in winterwheat could be worth 187 euros/ha (calculated from 22 euros/tonne for an 8.5t/hacrop)

The spreading performance of a range of fertilizer products

EXTRAN

Prilled Urea

Yara Size-MatchedGranules

Non-size MatchedPrilled AN + Granules

Non-Size MatchedPrilled Urea + Granules

Coefficient of Variation (CV%)

Products

403010 20

Faintstriping

Clearstriping Spinning Disc

Pneumatic

Acceptable infield conditions

Very inaccuratespread pattern

Poor spreadpattern

Source: Yara R&D programme.Trials carried out by Silsoe Research Institute 1999.Spinning disc and pneumatic machines tested at 24 metres bout width in field conditions (max wind speed 10kmh-1).

Good quality describes fertilizers whichare free flowing, and size- matched, togive an even distribution from the spreader.A pneumatic spreader may have moretolerance than a spinning disc machinebut neither type of spreader is able tosignificantly improve the spreadingperformance of a poor quality fertilizer.

Yaras fertilizers have been developedto have consistently good spreadingcharacteristics of size, bulk density andhardness. Investment in understanding

financial implications of poor spreadingof fertilizers has been committed viathe Companys Research & DevelopmentProgramme.

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How efficiently is fertilizer nitrogen used

Q21 by crops?Nitrogen efficiency in arable crop production is high.

Experiments with labelled nitrogen in fertilizers applied to cereals show that commonly40 to 70% of the applied nitrogen is found in the crop.

Much of the remainder stays in the soil organic matter. On average 10 to 20% is notaccounted for. This amount is probably lost as leached nitrate (NO3-) or as gaseousemissions (nitrous oxide (N2O), nitrogen oxide (NO), nitrogen (N2) and ammonia (NH3).

The efficiency varies with crop, soil, climatic conditions, type of fertilizer used andthe application method. Urea applied on the soil surface can lose up to 50% of the

nitrogen by volatilization as ammonia. Excessive applications increase nitrogen lossesand reduce the nitrogen efficiency.

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What is the efficiency of different forms

Q22 of nitrogen in crop production?

Conversion of urea to nitrate

Nitrate fertilizers have generally been found to be the most efficient nitrogenfertilizers. Crops use nitrogen mainly in the nitrate form, but can to a lesserextent also take up the ammonium form.Organic nitrogen, urea and ammonium nitrogen are transformed to nitrate in daysor, at most, a few weeks by microbes in the soil.

Main reasons for the higher efficiency of nitrates are:

A quicker availability (ammonium is adsorbed onto soil minerals).No volatilization losses to the air.A lower uptake by soil microorganisms (ammonium is preferred).

The losses of nitrogen by volatilization after application of urea are in the range from0 to 50%, but difficult to predict. Ammonia tends to be lost from calcareous soil,especially where it is low in organic matter, warm and dry. Smaller losses can occurunder these circumstances where UAN (mixture of urea and ammonium nitrate insolution) is applied and even smaller losses where CAN or ammonium nitrate isapplied. The reduction in crop yield due to these losses is almost always less than10% and usually less than 2%. However, a 2% yield penalty is very significant to afarmer and it will always be best practice to use the more effective nitrogen sourcefor local circumstances. Some farmers tend to apply more than the recommendedrate of urea-based fertilizers as an insurance against poor efficiency. Nitrate basedfertilizers are more accurate, no extra nitrogen is required hence losses are minimized.

Nitrate leaching may occur when nitrogen is applied at low crop N-uptake, e.g. during

autumn and winter. In general, split N application with N rates adjusted to the cropdemand effectively minimises the risk of nitrate leaching.

For high N-input systems it might be difficult to find substantial yield differencesbetween ammonium nitrate / calcium ammonium nitrate and urea, but it is importantto note that even a 2.5% loss in yield can significantly reduce the farmer's profitability.

Yara is the most experienced nitrogenfertilizer company globally. TheCompany has carried out many fertilizer

field trials throughout the world tocompare the efficiency of different

fertilizer nitrogen sources. Although thetrial results are very variable with a

large seasonal effect, in most cases,the nitrate-based fertilizers have been

found to be generally more efficient andalso more reliable compared to urea orammonium-based fertilizers.

Hydrolysis Nitrification

UreaCO(NH2)2

NitrateNO3

NitrateNO2

AmmoniumNH4+

* In soils of pH


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Q23 Do fertilizers acidify the soil?Some do, some don't. Soils tend to acidify naturally but the rate of acidificationcan be affected by fertilizer use.

Fertilizers containing ammonium (NH4+) are usually acidifying. Hydrogen ions arereleased and so acidity is increased when ammonium N is oxidized by soil microorganisms to nitrate N. Also, ammonium can displace the basic cations calcium(Ca2+) and magnesium (Mg2+) from the soil which decreases pH. Ammonium sulphateis especially acidifying as all the nitrogen is in the ammonium form and the sulphatecan contribute to acidity. (Fertilizer use enhances crop growth, which, in itself, isacidifying.) In contrast calcium nitrate has a liming effect.

It is important to know the lime status of the soil and its pH status should be checkedat regular intervals. If the soil is prone to acidification lime should be applied asappropriate for the crop, soil and region.

Soil acidification from ammonium

Nitrate nutrition Ammonium nutrition

pH pH4.5 4.5

Plant root5.5 5.5

6.0 6.0

NO3-N maintains/increases NH4-N acidifiespH of the rhizosphere the rhizosphere

6.5 6.5

The amount of lime as calcium oxide (CaO) required to neutralize the acidgenerated from the application of 100 kg N with the fertilizer specified.

Lime demand in kg CaO per 100 kg N/applied on arable soil

>300 kg>100 kg > 48 kg >-80 kg

Ammonium sulphate Urea CAN CN

100 kg CN-N per ha is equivalent to an application of >80 kg CaO

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Does fertilizer make plants susceptible

Q24 to pests, disease and weed infestation?Fertilizers promote rapid growth, which is likely to give the crop a competitiveadvantage over some, but not all weeds. Rapid and lush growth can createsheltered and humid conditions within the crop, which could encourage somepests and diseases.

Healthy plants require an ample and balanced supply of nutrients to ward off andrepair attacks by insects and fungi. Appropriate supplies of potassium, calcium andmicronutrients are especially important for crop resistance to disease, while excessivenitrogen application can increase weed growth, diseases and pests.

To avoid such problems:

Correctly timed and balanced fertilizer rates should be applied according torecommendations based on plant and soil analyses.The development of nutrient deficiencies should be avoided.

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Do fertilizers cause soil compaction and/or

Q25 erosion?Not directly.

Soil compaction can be caused by heavy machinery used for soil preparation, seeding,weed control, pesticide application, and harvesting or fertilizer application. Fertilizersas such do not cause soil compaction. Calcium, which is the main component in limeand some fertilizers, enhances the formation of soil aggregates and counteractscompaction.

Soil erosion is mainly due to poor, short-term management practices e.g. ploughingof slopes and crop rotations that do not provide crop cover. Fertilizer use encouragesan abundant supply of roots and plant residues that build up the organic matter in the

soil to reduce the wind and rain erosion problem and aid the establishment of newvegetation on reclaimed land.

Lack of crop cover increases risk of soil erosion.

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Does fertilizer use contribute to drought

Q26 problems in agriculture?No. Fertilizer use contributes to more efficient use of the water available to thecrops.

It takes less water to produce one tonne of grain in high yielding agriculture than inmore extensive systems. A finite water supply would therefore be utilized best if thecrop were fertilized to the economic optimum, well protected against pests anddiseases and the appropriate variety is grown.

The relation bewteen crop use of water and nutrients

In rainfed, dryland areas, moisture often is the most limiting factor for crop

yield, and it is a major challenge to adjust nutrient applications to the

moisture regime. Application rates are usually low; however, experience

indicates that judicious fertilizer use is one of the most important factors

in increasing and stabilizing yields of dryland crops. A fertilized crop yields

100-150% more than an unfertilized crop, but requires only 20-25%

additional moisture. Hence the rate of fertilizer application should be

decided on the basis of the water-storage capacity of the soil and the type

of crop to be grown.

Source: Singh, 1994; Carvalho and Bash (1996)

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C Fertilizer - Environmental impacts

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What environmental problems occurif application rates are well below

Q27 recommended rates?Constant cropping without replacing the removed nutrients reduces soil fertilityand can lead to soil erosion problems.

This situation is more likely to arise in less developed countries e.g. Africa. However,prolonged periods of nutrient removal in excess of input may severely reduce soilfertility and productivity in any farming system. Further, insufficient nutrient supplymay lead to a less dense plant cover, which increases the risk of soil erosion. Heavyerosion can remove fertile soil. Permanent plant cover is necessary on steeply slopingland to protect against erosion.

Land use is another environmental impact, which is often neglected. If

application rates are below recommended rates, yields usually decrease.This means an inefficient use of land, which has to be considered as ascarce resource. To produce the same amount of food, more land has tobe cultivated.

Yara has developed advisory tools and expert programs which givefertilizer recommendations and timing of applications for most crops,and special tools for nitrogen recommendations

What detrimental effects can excessiveQ28 nitrogen application cause?Poor economics, as well as crop quality problems and potential pollution to soil,water and air.

Human activity has doubled the amount To soils: unnecessary acidification.on N in the environment

To crops: lodging, enhanced susceptibility to diseases, quality problems.Natural N input is about 113 Mt N/yAnthropogenic N amounts to ca. 140 Mt N/y

To water: acidification, eutrophication and enhanced nitrate concentration that may- Agriculture is responsible for 80% of the lead to conflicts with the nitrate limit in drinking water.anthropogenic input (two thirds from mineralfertilizers, one third from increased growth oflegumes). To air: unnecessary emissions of ammonia (contributing to soil acidification and

eutrophication) and nitrous oxide (increasing the greenhouse gas content in the

withfertilizer

andcompost

withoutfertilizer

withfertilizer

andcompost

withoutfertilizer

Maize in Kenya (Photo from Dr. P. Seward) .

atmosphere).

To the farmer: excessive application is an expense with no benefit.

These problems are eliminated or minimised by careful fertilizer- planning and use.

Yara has developed advisory tools and expert programs which give fertilizerrecommendations and timing of applications for most crops, and special tools for

Legumes Natural nitrogen recommendations.Mineral fertilizer Fossil fuel

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Q29 Do fertilizers leach to ground water?Generally not.Most potential losses can be negated by adhering to good agriculturalpractice and following local fertilizer recommendation systems for optimum

Nitrate leaching is low, at or below rates and timing of applications to meet crop need.economic optimum N application

Yieldofwh

eatt/ha

leachingo

fN

9

8

7

6

5 4

3

2

1

0 0 50 100 150 200

- 90

- 80

- 70

- 60

- 50- 40

- 30

- 20

- 10

- 0

Economic optimum yield Fertilization kg N/ha Leaching kg N/ha

N applied kg/ha

Phosphorus, potassium, nitrogen as ammonium (NH4 +) andmicronutrients bind efficiently to soil particles, and leachinglosses are usually negligible. Most ammonium is graduallytransformed to nitrate (NO3-) by soil microbes. This naturalprocess goes on all the time except when the soil is frozen.

It is when nitrogen is in the nitrate form, (NO3-) that it is mostvulnerable to leaching as nitrate does not bind to soil particles,and moves in the soil water unless taken up by the plant rootsor soil microbes. Farmer practice can minimise the risk ofnitrate leaching by:

Avoiding nitrogen applications when heavy rain is expected-

Source: Yara R&D trials programme.

Source apportionment of phosphorusdischarges to Europes seas andpercentage reductions

North Sea80

1985

200070

000tonnesP/year

particularly in the spring.Planting winter crops or cover crops to take up post harvestnitrate residues.

Using local fertilizer recommendation systems for rates and timing so that theeconomic optimum rate of nitrogen is not exceeded.

Phosphorus does not readily leach, (except in exceptional circumstances, for exampleat very high soil phosphorus contents and following heavy rains that cause soil erosion).The principle routes of loss are not from fertilizer sources, but from soil surface runoff where winter applications of manures and slurry, have been applied particularlyto high risk fields. Notably, sloping land with potential for soil erosion, or riverbanksdamaged by livestock, which may also defecate directly into rivers.

When this occurs, lakes and rivers can become green and cloudy with enhanced algalgrowth and are referred to as eutrophic. This phenomenon causes the ecosystem todeteriorate, and can deleteriously affect fish populations.

Nutrient losses from agriculture to water may increase as a result of changes inagriculture, and where:

Fertilizer is not used at optimum rates but in excess of crop demand.More land is brought into cultivation.

60

50

40

30

20

10

0 Agriculture UWWT Industry Aquaculture

Urban wastewater treatment

Wetlands with the ability to absorb nutrients before they reach watercourses areBaltic Sea50 drained and converted to agricultural land.

Late 1980sArable and livestock farming are separated with the concentration of animal45 1995

000tonnesP/year farming in certain regions and arable farming in others.40

35

30

25

20

15

10

5 Sources:

North Sea progress report, 2002.0 Finnish Environment Institute, 2002.Agriculture UWWT Industry Aquaculture Black Sea Commission, 2002.

Urban waste Caspian Environment Programme (no date).water treatment European Environment Agency (EEA 2003).

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Is there an increased risk of leachingwhen applying highly soluble nitrogen

Q30 fertilizers?Nitrate leaching is low at or below If there is a balance between nitrogen applied and that removed in crops, the riskeconomic optimum N application, of leaching is not great.example for winter wheat.

It is important to apply the optimum rate according to good10

9

8

7

6

0 50 100

- 100

- 80

- 60

- 40

Grain yield

Soil nitrate at harvest(risk of leaching)

150 200 250 300

N rate (kg N/ha)

Soilnitrate

atharvest(kgN/ha)

agricultural practice. The risk of leaching is increased if excessivenitrogen is applied. The timing of nitrogen applications is alsoimportant and in many cases it is preferable to use splitapplications.

A high yielding cereal variety grown under favourable climaticconditions can yield up to ten tonnes per ha and take up

between 270 and 300 kg of nitrogen.Yieldt/ha

- 205

4 - - 0

Data from Baumgrtel et al.(1989).

Do fertilizers give off ammonia which isQ31 an atmospheric pollutant?Some do, others don't.Generally all ammonium-containing fertilizers have the potential for ammoniavolatilization, but urea and anhydrous ammonia have the highest potential.

Urea can lose up to 50% of nitrogen as ammonia (NH3) through chemical transformationsafter surface spreading. In Europe the average ammonia loss from urea is about 15%.Ammonium bicarbonate mainly used in China is unstable and emits substantialamounts of ammonia after application.NH3

NH4+Ammonium

NO3NitrateUrea

Urea hydrolysis Nitrification

Ammoniavolatilization

Manure

The soil conditions are also important. Nitrogen volatilization grows with increasingsoil pH. Ammonium-containing fertilizers (particularly ammonium sulphate anddiammonium phosphate) applied to calcareous soils may result in ammonia losses.

Nitrate-based fertilizers such as ammonium nitrate, calcium ammonium nitrate andcomplex fertilizers only lose a very low percentage of the nitrogen in this manner, andnitrate fertilizers e.g. calcium nitrate have no ammonia (NH3) emissions.

The dominant source of atmospheric ammonia is farm animals and their manures.Fertilizer use only contributesabout 10% of atmosphericEmission factors (NH3-N loss as % of total applied N)

Mean spring temperature

Fertilizer type > 13C 6 - 13C


39/45


What problems does ammonia

Q32 volatilization cause?Ammonia concentrations in the atmosphere are so low that they do not haveany direct toxic effects. Ammonia volatilization though, contributes to theacidification and eutrophication of land and water ecosystems, and plays a rolein the formation of fine dust.

Acidification results mainly from anthropogenic emissions of sulphur dioxide (SO2),nitrogen oxides (NOx) and ammonia (NH3) and is damaging acid-sensitive ecosystemsat a regional to continental level. In particular forests and fresh water lakes are sensitive

Share of different sources of ammonia to acidification. The consequences range from defoliation and reduced tree vitality toemissions in Europe declining fish stocks and decreasing biodiversity in lakes. NH3 is responsible for 31%

of the acidification effect in Europe, SO2 and NOx for 36% and 33%, respectively

(EEA, 2001). The gaseous NH3 emission returns back to the surface as dry or wetdeposition partly combined with SO2 as ammonium sulphate. While most of the drydepositions of ammonia take place nearby the emission site, compounds with nitricor sulphuric acid can be transported over distances of several thousand kilometres.

Eutrophication can be defined as an undesired increase in biomass production inaquatic and terrestrial ecosystems caused by high nutrient inputs, which result in ashift in species composition. In surface waters eutrophication is particularly seriousbecause it can lead to algal blooms and the subsequent oxygen-consuming degradationprocesses, which may finally result in the death of fishes and other organisms.Manure storage 34%Ammonia emissions that deposit on water bodies and nitrate leaching are the mainGrazing 8%anthropogenic nitrogen inputs to water. Other important nutrient inputs to waterManure spreading 32%originate from waste water treatment plants and industry. However, land ecosystems

Mineral fertilizer may also suffer from nutrient enrichment. Naturally nutrient poor areas with great

Application 12.5% diversity of plant species (e.g. certain grassland communities) that receive additionalProduction 0.5% nitrogen from the atmosphere will deteriorate in terms of biodiversity.Leaf emission from crop 5%

There is increasing concern about negative health effects of particulate matter thatMiscellaneous 8% contributes to dust formation on a local to regional scale. Ammonia and sulphur

emissions are the main sources of fine dust with particles of less than 2.5 micrometersSource: ECETOC Technical Report No. 62Ammonia Emissions to Air in Western Europe. (PM2.5) in diameter. The main sources for bigger particles with a diameter up to 10

micrometers (PM10) are stationary combustion plants, industry and traffic (EEA,1998).

Nitrogen turnover in soils

Animal husbandry

volatilisation

NH3

N2

NH4

binding to clay minerals

Mineralisation

immobilisation

nitrificationNO3

leaching

NO + N2 + N2O

Plantdentrification

fixation

Organic N

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Is the economic optimum fertilizingintensity in conflict with environmental

Q33 consideration?No.

Life Cycle Assessment (LCA) studies of different application rates of nitrogen fertilizerhave shown that crop production at rates above the economic optimim N rate as wellas without applying N fertilizer causes the highest environmental damages.The economic optimum fertilizer rate shows only economic and social considerations.The economic fertilizing intensity is therefore preferable from a sustainability pointof view.

In the Yara authored, 2004 paper to the European Journal of Agronomy(vol 20, pp 247-264), entitled Environmental impact assessment of agricultural

production systems using the life cycle assessment methodology. The theoreticalconcept of a LCA method tailored to crop production. Yara scientists based atthe Hanninghof Research Centre have developed an LCA method specificallytailored to plant nutrients in arable crop production in Europe.

The scope of Life Cycle Assessment studies by Yara using European data

Inventory of

environmental impacts(per/t grain)

Emissions(NO3, NH3, N2O, CO2 etc)

and

Resources(Oil, gas, land etc)

Raw material extraction- Fossil fuels- Minerals

Production & transportation- Fertilizer- Pesticides- Machinery- Seeds

Arable farming- Tillage- Sowing- Plant nutrition- Plant protection- Harvest

= Wheat grain

Aggregation toeffects (per/t grain)

- Global warming- Acidification- Eutrophication- Land use- Energy consumption

EcoX value(per/t grain)

The role of fertilizers, at varying rates in terms of environmental impact

EcoX/t grain0.8 Eutrophication

(water and land)

Acidification0.6

0.4

0.2

0.0

Global warming

Land use

0 96 192 288

Kg N / ha

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Do we gain or lose useful energy by using

Q34 mineral fertilizers?We gain!

Agriculture produces energy in the form of food or feed for humans oranimals. Generally, the amount of energy stored in the harvested biomass ishigher than the energy required to produce the biomass. Fertilizers greatlyincrease this positive energy balance of agriculture, because the use ofnitrogen fertilizer enables crops to grow more biomass which in turn fixesadditional solar energy.

Fertilizer use consumes fossil fuels in order to produce food or feed, i.e. another formof energy that is not equivalent to what has been consumed. If agriculture produces

energy crops (like rape or maize) which are used to produce biodiesel or bioethanol,more fuel is produced than consumed - and optimum fertilizer supply enhances thispositive energy balance.

Capture of solar energy due to mineral fertilizers

GJ/ha140

120 Solar energy

+55

71

captured in extrabiomass produced

100

due to fertilizer use80

60

71Solar energy in

40 biomass producedwithout fertilizer use

20

0 Tillage etc- 7.5 - 7.5- 8 Fertilizer (170 kg N/ha)

GJ/hagrain

-20 zero N 170 kg N/ha

4.7 8.271.0 126.07.5 15.5

63.5 110.5

Date: Winter wheat field trials (Germany).Energy content: 15.4 GJ/t grain or straw

Fertilizers increase energy

Grain yield (t/ha)Energy yield (GJ/ha)Energy consumption (GJ/ha)Net energy yield (GJ/ha)

Energy is a central issue in agriculture. The very reason foragricultures existence is to supply energy to mankind. Itdoes this by converting foliar energy into biomass, which inturn supplies energy to human beings and animals in theform of food and feed. In fact, fertilizers can be considereda catalyst for capturing clean solar energy. Depending on thecrop and the yield, the plants can capture 5-10 times theamount of energy that is used in making and supplyingfertilizers. If the crop or crop residues are used for fuel, thiswill replace the use of fossil fuels and thus lead to an overall

reduction of the emission of CO2 climate gases. Also, organicmatter build-up in soils by the plant residues may lead tolong term capturing of CO2.

Conversion to biofuel

Soil organic build-up

Food and feedstuff

Plants for biofuel

Plant residues

5 - 10 energy unitsstored in plants due to the use of fertilizersSolar

energy

1 unit of energy for production anduse of fertilizers

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How much energy (fossil fuel) does it

Q35 take to make one kg of nitrogen fertilizer?Modern fertilizer plants utilize natural gas or other gases like propane or ethylene.In the most efficient plants it takes 0.6 kg of natural gas to make one kilo ofnitrogen as ammonia or ammonium nitrate, and 0.75 kg to make urea. This isequivalent to 0.8 and 0.93 kg respectively, of fuel oil. Most of the energyconsumption in the nitrogen fertilizer chain is during the production phase.

The energy efficiency in N fertilizer production has been significantly improved sincethe beginning of the 20th century. Modern fertilizer factories are close to the theoreticalminimum of energy consumption.

91%

Production

40 GJ/t N

2%

Logistics and transport

1 GJ/t N

7%

Application

3 GJ/t N

Reduced energy consumption

450

400

350

300

250

200

150

100

50

0

Birkeland-Eyde electric arc method

Theoretical minimum

Cyanamid method

Haber-Bosch synthesis

Steam reformingnatural gas

1910 1915 1930 1950 1960 1975 2000

GJ/tN

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What is the Companys policy regarding

Q37 fertilizers and the wider environment?Yara is committed to continuously improving and developing products, servicesand advice so that the companys fertilizer products actively:

Contribute to a sustainable agriculture.

Are responsibly used in line with best agricultural practice

Utilize best available technology in production

Meet best agricultural practice.

Comply with legislation.

The responsibility for how the product is actually used remains with the farmer.

Fertilizers are biologically active compounds, and as such, they can influence theenvironment. It is the Companys policy to reduce environmental impacts along theentire life cycle of a fertilizer, i.e. from production through to the use of our products.

Great improvements have been achieved in production technologies to minimiseenergy use and emissions.

Fertilizers correctly used are environmentally benign products. They are not poisonousto soil or water, and consist of naturally occurring plant nutrients that are necessaryfor maintaining soil fertility and securing adequate and sustainable food production.

The main environmental concerns arise through the irresponsible use of fertilizers.

The company promotes the responsible and correct use of fertilizers throughout thesupply chain, with adherence to good agricultural practices. The understanding of howour products behave in the environment is important to Yara, enabling avoidance ofrecommendations that could have unnecessary environmental effects. Investmentin R & D, adoption of novel technologies and the development of tools for optimalfertilizer use (taking full account of all nutrient sources) works to ensure minimalenvironmental impact.

The Company has for many years

Fertilizers, agriculture and sustainability published guidelines and has developedexpert systems for the end user whichproduce fertilizer recommendations likethe N-Tester and N-Sensor and Yara Plan.

The Company published a guidebook onenvironmental issues relating to fertilizeruse in 1990: (Agriculture and Fertilizers;private publisher), which was updated andextended in 1999 (Agriculture, Fertilizersand the Environment; CABI publishing).

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For further information please contact:

Yara International ASA

Bygdy all 2,

N-0202, Oslo, Norway

www.yara.com
http:///reader/full/www.yara.comhttp:///reader/full/www.yara.com

3734 important questions on fertilizer and the environment

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