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Section 2:Organic Manures

31

Introduction 33Farm Manures 33

Farm Waste Management Planning 33Nutrient content of manures 35Principles of nitrogen supply and losses 35

Allowing for the nutrient content of farm manures 37Cattle, pig, sheep or duck solid manures – Total and available nutrients 38Poultry manures – Total and available nutrients 40Cattle slurry and dirty water – Total and available nutrients 42Pig slurry – Total and available nutrients 45Using farm manures and fertilisers together (with examples) 47

Practical aspects of manure use 47Manure application 51

Sewage Sludges (Biosolids) 51Nutrient content of sludges 51Nitrogen supply from sludges 52

Sludges – Total and available nutrients 53Allowing for the nutrient content of sludges (with examples) 55Industrial wastes 56

33

INTRODUCTION

Organic manures applied to agricultural land may be produced on the farm (slurries, farmyard manures (FYM)and poultry manures) or supplied from other sources such as treated sewage sludges (commonly called biosolids)and some industrial ‘wastes’. These materials are valuable sources of organic matter and most major plantnutrients. Careful recycling to land allows their fertiliser value to be used for the benefit of crops and soil fertility.This will usually result in large savings in the use of inorganic fertilisers and at the same time reduce pollutionrisks.

Organic manures, particularly solid manures, add useful amounts of organic matter to soils, acting as soilconditioners and structural improvers. The water holding capacity, drought resistance and structural stability ofsoils can be increased, as well as the biological activity of soils. These improvements are most likely to be achievedwhere regular manure applications are made. Care should be taken during application not to cause soilcompaction, which may have a detrimental effect on crop growth and increase the risk of run-off.

Organic manures can present a considerable environmental risk if not handled carefully. Guidance on avoidingpollution is given in The Water Code (MAFF PB0587) and The Air Code (MAFF PB0618). A key guide is that thereshould be enough land available where manures can be applied to ensure that the amount of total nitrogen inorganic manures applied does not exceed 250 kg/ha/year. In some situations, lesser amounts may be appropriate.For example, care should also be taken to ensure that the amount of available nitrogen in organic manuresapplied to land does not exceed the amount of nitrogen recommended for the next crop. In some fields, it maybe necessary to limit organic manure applications in order to avoid excessive enrichment of soil P levels. In NitrateVulnerable Zones, it is mandatory to follow some sections of The Water Code as well as the practices detailed inthe NVZ Action Programme (Guidelines for Farmers in NVZs, MAFF PB3277) which includes some restrictions onthe use of organic manures (see page 27 for more details).

FARM MANURES

Farm Waste Management Planning

It is essential to plan the handling and use of manures on a farm. This will ensure that good use is made of thenutrient content of the manures and that the risks of causing environmental pollution are minimised. The WaterCode (MAFF PB0587) provides guidance on how to prepare a Farm Waste Management Plan. This plan will helpin deciding when, where and at what rate to apply solid manures, slurry and dirty water, thereby reducing therisks of causing water pollution and transfer of pathogens to water.

When planning manure management systems, information is needed on the quantity and nutrient content ofanimal manures produced on a farm. This depends on a number of factors, including the number and type oflivestock, the diet and feeding system, the volume of dirty water and rainwater entering storage facilities, and theamount of bedding used. Although the volume of manure to be managed will vary considerably with the amountof water introduced into the system (often doubling the volume of slurry to be handled), estimates of thequantities of excreta produced by livestock are a useful basis for planning purposes. The table on page 34 showsthe typical output of undiluted excreta and nutrients for the main livestock types. These estimated nutrientoutputs in excreta are less variable than output volumes, because they are not affected by dilution.

34

Estimated quantities of excreta and nutrients produced during thehousing period

Output during housing period

Undiluted

excreta

(t or m3)

Cattle

Dairy cow

Grower/fattenera

Grower/fattenera

Pigs

1 Maiden giltb

1 Sow + litterc

1 Weaner

1 Grower, dry meal

1 Bacon, meal fed

Poultry

1000 Laying hens

1000 Broilersd

1000 Turkeys (male)e

1000 Turkeys (female)e

1000 Ducksf

1 Adult eweg

1 Lambg

Type of livestock Body

weight

(kg)

Housing

period

(% of year)

Nitrogen

(N)

(kg)

Phosphate

(P205)

(kg)

Potash

(K20)

(kg)

550

500

400

90-130

130-225

7-18

18-35

35-105

2,200

2,200

13,500

6,500

3,400

65

35

50

25

66

100

100

90

90

90

97

76

80

80

85

8

8

9.61

2.91

6.21

2.61

4.01

0.41

0.91

1.51

41.61

17.61

46.61

22.61

90.61

0.13

0.03

48.5

15.5

31.5

13.5

19.5

3.0

6.1

10.5

660.5

495.5

1390.5

650.5

900.5

0.8

0.2

19.85

5.85

12.85

13.85

20.85

2.35

4.55

7.55

545.85

435.85

1225.85

575.85

900.85

0.25

0.05

48.4

15.4

31.4

10.4

16.4

1.8

3.6

6.0

360.4

290.4

810.4

380.4

630.4

0.4

0.1

a) Growing/fattening cattle:- ‘Occupancy’ is variable

b) Maiden gilts:- assumes all year round accommodation

c) Sows:- based on 2.3 lactations (23% of year) and dry period (77% of year)

d) Broilers:- output per 6.6 crops/year, 42 day cycle (76% occupancy)

e) Turkeys:- assumes 2.1 or 2.4 crops/year, for male and female birds

f) Ducks:- output based on 6 crops/year, 52 day cycle

g) Lowland sheep housed for 1 month at lambing.

Estimates for other livestock categories are given in the Managing Livestock Manures booklets.

35

Nutrient Content of Manures

For reliable fertiliser planning, it is important to know the nutrient content of manures applied to land. The tableson pages 38–46 give typical values of the total nutrient content of manures based on the analysis of a largenumber of samples.

Due to farm specific feeding and manure handling practices, manures produced at a particular livestock unit mayhave a nutrient content that is consistently different from the values given in the tables. It is therefore worthwhilehaving the nutrient content of representative manure samples determined by analysis. Rapid on-farm kits canreliably assess the ammonium-N content of slurries, but laboratory analysis is necessary for other determinations.The laboratory analyses should include dry matter (DM), total N, total phosphate (P2O5), total potash (K2O), totalsulphur (as SO3), total magnesium (as MgO) and ammonium-N (NH4-N). Additionally, nitrate-N should bemeasured for well composted FYM, and uric-acid N for poultry manures.

It is important that sampling is carried out carefully and that representative samples are provided for analysis (seeAppendix 6 for guidance on sampling). The optimum sampling frequency will vary depending on how manuresare managed on the farm, but at least two samples per year are often worthwhile, coinciding with the mainspreading periods. Hydrometers can be used to measure slurry dry matter content and, where dry matter varies,to estimate nutrient analyses by adjusting previous laboratory results.

Whether using typical values for the nutrient content of manures, or the results of analysis, the availability of thenutrients for crop uptake must be assessed before the fertiliser replacement value of a manure application can becalculated. Values for the availability of manure nutrients from different application timings and methods havebeen determined from detailed research studies.

Principles of Nitrogen Supply and Losses

Nitrogen is present in manures in different forms.• Readily available nitrogen (ammonium-N and uric acid-N) is the nitrogen that is potentially available for

rapid crop uptake. It is equivalent to fertiliser nitrogen. Slurries and poultry manures are ‘high’ in readilyavailable-N (40–60% of total N) compared with FYM which is ‘low’ in readily available-N (10–25% of total N)– see figure on page 36.

• Organic-N is the nitrogen contained in organic forms, most of which is not available in the first season afterapplication. This nitrogen will be slowly released and will become potentially available for crop uptake over aperiod of months to years.

• Crop available nitrogen is the readily available-N that remains available for crop uptake after accountingfor any losses of nitrogen. This also includes nitrogen released from organic-N forms.

There are two major nitrogen loss processes following land application – ammonia volatilisation and nitrateleaching. Ammonium-N can be volatilised to the atmosphere as ammonia gas following land application ofmanures. Following conversion to nitrate-N, further losses may occur through nitrate leaching and denitrification(gaseous loss as nitrous oxide and nitrogen under warm and wet soil conditions). To make optimum use of thenitrogen content, organic manures should be applied at times of maximum crop growth – generally during thelate winter/spring period.

Ammonia volatilisation

Around 40% of the readily available nitrogen content of manures is commonly lost following surface applicationto land. Ammonia loss and odour nuisance can be reduced by ensuring that manures are rapidly incorporatedinto soils (within 6 hours of application for slurries and 24 hours for solid manures). For slurries, injection or bandspreading are also effective. These practices will all increase the amount of nitrogen available for crop uptake.Ammonia losses are generally smaller from low dry matter slurries because they more rapidly infiltrate into thesoil. Higher dry matter slurries remain on the soil/crop surface for longer leading to greater losses. Losses are alsohigher when slurries are applied to dry soils under warm weather conditions.

36

Nitrate leaching

The amount of manure nitrogen leached following application to land is mainly related to the application rate,the readily available-N content and the amount of rainfall after application. As ammonium-N is rapidly convertedin the soil to nitrate-N, manure applications during the autumn or early winter period should be avoided, as thereis likely to be sufficient overwinter rainfall to wash a large proportion of this nitrate out of the soil before the cropcan use it. Delaying applications until late winter or spring will reduce nitrate leaching and increase utilisation ofmanure nitrogen. This is particularly important for manures with a high content of readily available-N. Addition ofa nitrification inhibitor to slurries can give small but inconsistent reductions in nitrate leaching from autumn andwinter slurry applications.

Typical Proportions of Different Forms of Nitrogen in Farm Manures

High available N manures

Ammonium–N

Uric acid–N

Organic–N

Pig slurry Cattle slurry

Broiler litter Layer manure

‘Old’ Cattle FYM ‘Fresh’ Cattle FYM

Low available N manures

Release from organic nitrogen

The organic nitrogen content of manures is released (mineralised) slowly over a period of months to years. Wherethis nitrogen is not taken up by the crop in the season following application, it may be lost by leaching during thefollowing winter period, or can accumulate in soil organic matter allowing further long-term savings in nitrogenfertiliser inputs.

Around 10% of the total nitrogen content of manures may become available for the second crop followingapplication.

37

ALLOWING FOR THE NUTRIENT CONTENT OF FARM MANURES

Nitrogen

Estimates of the percentage of the total nitrogen content that is available for uptake by the next crop fromdifferent manure applications are given in the tables on pages 38–39 (cattle, pig, sheep or duck solid manures),pages 40–41 (poultry manures), pages 42–44 (cattle slurries and dirty water) and pages 45–46 (pig slurries).The values take account of differences in readily available-N and dry matter contents, the effects of applicationmethod and timing, soil type and autumn/winter rainfall following application. The footnotes should be used toadjust the values where appropriate.

Where more detailed field specific guidance on the fertiliser N value of manures is required, use of the MANNER(MANure Nitrogen Evaluation Routine) computerised decision support system is recommended. MANNER willpredict the fertiliser N value of field applied manures, taking into account the manure type, manure analysis data(total N, ammonium-N and uric acid-N), soil type, application timing and technique, ammonia-N and nitrate-Nlosses and mineralisation of organic-N.

Where there is uncertainty about the level of residual N present in the soil, for example, where manures havebeen applied regularly or at unknown application rates, sampling to measure soil mineral nitrogen (SMN) isrecommended (see page 13).

Phosphate,Potash,Magnesium and Sulphur

Manures are valuable sources of other nutrients as well as nitrogen, though not all of the total nutrient content isavailable for the next crop. Typical values for the total and available phosphate and potash contents of farmmanures are given in the tables between pages 39 and 46. Nutrients which are not immediately available willmostly become available over a period of years and will usually be accounted for when soil analysis is carried out.The availability of manure phosphate to the next crop grown (50-60%) is lower than from water solublephosphate fertilisers. However, around 90% of manure potash is in a soluble form and readily available for plantuptake.

Where crop responses to phosphate or potash are expected (soil Indices 0 or 1 for combinable crops andgrassland) or where responsive crops are grown (e.g. potatoes or vegetables), the available phosphate andpotash content of the manure should be used when calculating the nutrient contribution. Soils at Index 0 willparticularly benefit from manure applications. Where soil Indices are at the target level or above (usually Index 2or above, see page 18), the total phosphate and potash content of the manure should be used in nutrientbalance sheet calculations. For most arable crops, typical manure application rates can supply all of thephosphate and potash requirement. At soil P Index 3 or above, take care to ensure that total phosphate inputs donot exceed the amounts removed in crops during the rotation. This will avoid the soil P Index reaching anunnecessarily high level.

Manures also supply useful quantities of sulphur and magnesium, but there is only limited data on sulphuravailability for the next crop. For cattle slurry, 50% availability has been measured in the season followingapplication. However, as leaching of sulphate can occur over winter, it is best not to rely totally on the sulphursupply from autumn applied slurry.

38

Dry matter

%

Total Nitrogen

kg/t

Cattle farmyard manurea

Pig farmyard manurea

Sheep farmyard manurea

Duck manurea

25

25

25

25

6.0

7.0

6.0

6.5

CATTLE, PIG, SHEEP OR DUCK SOLID MANURES – TOTAL ANDAVAILABLE NUTRIENTS

Nitrogen – Typical total nitrogen content (fresh weight basis)

a) Values of nitrogen may be lower for FYM stored for long periods in the open.

To convert kg/t to units/ton, multiply by 2.

Duck manure is included here because its nitrogen availability is generally lower than that of other poultry manures.

Surface applied (i.e. not soil incorporated)

FYM

– freshc

– oldc

Soil incorporated 24 hours after applicationd

FYM

– fresh c

– old c

Autumna

(Aug – Oct, 350mm

rainfall to end March)

Wintera

(Nov – Jan, 200mm


Springa

(Feb – Apr)

Summera

use on

grassland

Sandy/

shallowbMedium/

heavybSandy/

shallowbMedium/

heavybAll soils All soils

5

5

5

5

10

10

10

10

10

10

15

10

15

10

20

15

20

15

25

20

ND

ND

N/A

N/A

N/A = Not applicable; ND = No data

a) The nitrogen availability estimates assume 350 mm of rainfall (after autumn application) and 200 mm (after winter application) up to the

end of soil drainage (usually end March). Where rainfall differs from these amounts, intermediate values of nitrogen availability should be

used. Reduce the values by half on medium/heavy soils where rainfall is much greater than 350 mm following autumn application (i.e. over

500 mm). For spring or summer applications, rainfall is not likely to cause movement of nitrogen to below crop rooting depth.

b) Sandy/shallow means light sand soils and shallow soils (see Appendix 1).

Medium/heavy means medium, deep fertile silt and deep clay soils. Use this category for organic and peaty soils.

c) Fresh FYM means manure which has not been stored prior to land application and has an estimated ammonium-N content of 25% of the

total N.

Old FYM means manure which has been stored for 3 months or more and has an estimated ammonium-N content of 10% of the total N.

d) The values assume incorporation by ploughing. Cultivation using discs or tines is likely to be less effective in minimising ammonia losses and

intermediate values of nitrogen availability should be used.

Nitrogen – Percentage of total nitrogen available to next crop

%

Dry

matter

Total

Phosphate

Avail-

ability

Available

Phosphate

Total

Potash

Avail-

ability

Available

Potash

Total

Sulphur

Total

Magnesium

Sulphur

(as SO3)

Magnesium

(as MgO)

Phosphate (P2O5) Potash (K2O)a

kg/t % kg/t kg/t % kg/t kg/t kg/t%

39

Cattle farmyard manure

Pig farmyard manure

Sheep farmyard manure

Duck manure

Phosphate, potash, magnesium and sulphur (fresh weight basis)

25

25

25

25

3.5

7.0

2.0

5.5

60

60

60

60

2.1

4.2

1.2

3.3

8.0

5.0

3.0

7.5

90

90

90

90

7.2

4.5

2.7

6.8

1.8

1.8

ND

2.7

0.7

0.7

ND

1.2

ND = No data

a) Values of potash may be lower for FYM stored for long periods in the open.


Autumna

(Aug – Oct, 350mm


Wintera

(Nov – Jan, 200mm


Springa

(Feb – Apr)

Summera

use on

grassland

Sandy/

shallowbMedium/

heavybSandy/

shallowbMedium/


%

40

POULTRY MANURES - TOTAL AND AVAILABLE NUTRIENTS(Information for duck manure is given on page 38)


Dry matter Total Nitrogen

Layer manure

Broiler/turkey litter

%

30

60

kg/t

16

30


Percentage of total nitrogen available to next crop following POULTRYMANURE applications (% of total nitrogen)


Layer manure


Soil incorporated 24 hours after applicationc

Layer manure


10

10

10

10

20

20

25

25

15

15

20

20

30

25

40

40

35

30

50

45

N/A

N/A

N/A

N/A

N/A = Not applicable

a) The nitrogen availability estimates assume 350 mm of rainfall (after autumn application) and 200 mm (after winter application) up

to the end of soil drainage (usually end March). Where rainfall differs from these amounts, intermediate values of nitrogen

availability should be used. Reduce the values by half on medium/heavy soils where rainfall is much greater than 350 mm following

autumn application (i.e. over 500 mm). For spring or summer applications, rainfall is not likely to cause movement of nitrogen to

below crop rooting depth.



c) The values assume incorporation by ploughing. Cultivation using discs or tines is likely to be less effective in minimising ammonia

losses and intermediate values of nitrogen availability should be used.

Dry

matter

Total

Phosphate

Avail-

ability

Available

Phosphate

Total

Potash

Avail-

ability

Available

Potash

Total

Sulphur

Total

Magnesium

Sulphur

(as SO3)

Magnesium

(as MgO)

Phosphate (P2O5) Potash (K2O)

kg/t % kg/t kg/t % kg/t kg/t kg/t%

41

Layer manure



30

60

13

25

60

60

7.8

15

9

18

90

90

8.1

16

3.8

8.3

2.2

4.2


42

CATTLE SLURRY AND DIRTY WATER – TOTAL AND AVAILABLENUTRIENTS

Nitrogen – Typical total nutrient content (fresh weight basis)


Slurries/liquids

Dairy

Beef

Dirty water

Separated cattle slurries (liquid portion)

Strainer box

Weeping wall

Mechanical separator

%

2

6

10

2

6

10

<1

1.5

3

4

kg/m3

1.5

3.0

4.0

1.0

2.3

3.5

0.3

1.5

2.0

3.0

To convert kg/m3 to units/1000 gallons, multiply by 9.

Autumna

(Aug – Oct, 350mm


Wintera

(Nov – Jan, 200mm


Springa

(Feb – Apr)

Summera

use on

grassland

Sandy/

shallowbMedium/

heavybSandy/

shallowbMedium/


%

43

Percentage of total nitrogen available to next crop followingCATTLE SLURRY and DIRTY WATER applications (% of total nitrogen)


– 12% DM

– 16% DM

– 10% DM


– 12% DM

– 16% DM

– 10% DM

Deep injected (25-30cm)

– 12% DM

– 16% DM

– 10% DM

Dirty water (surface applied)

5

5

5

5

5

5

5

5

5

0

20

15

10

20

20

15

10

10

10

40

25

20

10

25

20

15

15

15

15

10

40

30

15

45

35

30

35

30

25

60

50

35

20

55

45

35

60

50

45

80

35

20

10

N/A

N/A

N/A

60

50

45

50








c) The values assume incorporation by ploughing. Cultivation using discs or tines is likely to be less effective in minimising ammonia.

Where slurry has been applied in spring or summer and incorporated more quickly than 6 hours, nitrogen availability should be

intermediate between the ‘soil incorporated’ and ‘deep injected’ figures. Where slurry has been applied in spring or summer using

shallow injection or band spreading methods, nitrogen availability will be intermediate between ‘surface applied’ and ‘deep

injected’.

For separated cattle slurry, use the values for 2% dry matter slurry.

Dry

matter

Total

Phosphate

Avail-

ability

Available

Phosphate

Total

Potash

Avail-

ability

Available

Potash

Total

Sulphur

Total

Magnesium

Sulphur

(as SO3)

Magnesium

(as MgO)


kg/m3 % kg/m3 kg/m3 % kg/m3 kg/m3 kg/m3%

44

Slurries/liquids

Dairy

Beef

Dirty water

Separated cattle slurries (liquid portion)

Strainer box

Weeping wall

Mechanical separator


12

16

10

12

16

10

<1

11.5

13

14

0.6

1.2

2.0

0.6

1.2

2.0

Trace

0.3

0.5

1.2

50

50

50

50

50

50

50

50

50

50

0.3

0.6

1.0

0.3

0.6

1.0

Trace

0.15

0.25

0.6

2.0

3.5

5.0

1.5

2.7

3.8

0.3

2.2

3.0

3.5

190

190

190

190

190

190

100

190

190

190

1.8

3.2

4.5

1.4

2.4

3.4

0.3

2.0

2.7

3.2

0.4a

0.8a

1.1a

0.4a

0.8a

1.1a

ND

ND

ND

ND

0.4

0.7

1.0

0.4

0.7

1.0

ND

ND

ND

ND

ND = No data

a) 50% of the total sulphur is available to the next crop following spring application.



a) The nitrogen availability estimates assume 350 mm of rainfall (after autumn application) and 200 mm (after winter application) up to the

end of soil drainage (usually end March). Where rainfall differs from these amounts, intermediate values of nitrogen availability should

be used. Reduce the values by half on medium/heavy soils where rainfall is much greater than 350 mm following autumn application

(i.e. over 500 mm). For spring or summer applications, rainfall is not likely to cause movement of nitrogen to below crop rooting depth.



c) The values assume incorporation by ploughing. Cultivation using discs or tines is likely to be less effective in minimising ammonia losses.

Where slurry has been applied in spring or summer and incorporated more quickly than 6 hours, nitrogen availability should be inter-

mediate between the ‘soil incorporated after 6 hours’ and ‘deep injected’ figures. Where slurry has been applied in spring or summer using

shallow injection or band spreading methods, nitrogen availability will be intermediate between ‘surface applied’ and ‘deep injected’.

For separated pig slurry, use the values for 2% dry matter slurry.

Autumna

(Aug – Oct, 350mm


Wintera

(Nov – Jan, 200mm


Springa

(Feb – Apr)

Summera

use on

grassland

Sandy/

shallowbMedium/

heavybSandy/

shallowbMedium/


%


45

PIG SLURRY – TOTAL AND AVAILABLE NUTRIENTS


Pig slurry

%

2

4

6

kg/m3

3.0

4.0

5.0


Percentage of total nitrogen available to next crop following PIG SLURRYapplications (% of total nitrogen)


– 2% DM

– 4% DM

– 6% DM


– 2% DM

– 4% DM

– 6% DM

Deep injected (25-30cm)

– 2% DM

– 4% DM

– 6% DM

5

5

5

5

5

5

5

5

5

25

20

15

25

20

20

10

10

10

30

25

20

25

20

20

15

15

15

50

40

30

55

45

40

40

35

30

60

50

40

65

55

50

70

65

60

40

30

25

N/A

N/A

N/A

70

65

60

Dry

matter

Total

Phosphate

Avail-

ability

Available

Phosphate

Total

Potash

Avail-

ability

Available

Potash

Total

Sulphur

Total

Magnesium

Sulphur

(as SO3)

Magnesium

(as MgO)



46

Pig slurry


2

4

6

1.0

2.0

3.0

50

50

50

0.5

1.0

1.5

2.0

2.5

3.0

90

90

90

1.8

2.3

2.7

0.5

0.7

0.9

0.3

0.4

0.5


47

USING FARM MANURES AND FERTILISERS TOGETHER

A planned and integrated manure and fertiliser policy aims to utilise as much as possible of the nutrient contentof manures. Failure to adequately allow for these nutrients, particularly nitrogen, not only wastes money becauseof unnecessary fertiliser use but can reduce crop yields and quality – e.g. lodging in cereals, poor fermentation ingrass silage and low sugar levels in beet.

1 Calculate the quantity of available nutrients (equivalent to fertiliser) per tonne or m3 of each manure type thatis applied (see pages 37–46).

2 Identify the fields that are available and that will benefit most from the manure nutrients. This will need totake account of the accessibility and likely soil conditions in individual fields at the time of application, and theapplication equipment that is available. Crops with a high nitrogen demand should be targeted first. Fields atlow soil P or K Indices will benefit more than those at high Indices.

3 Plan the application rate for each field ensuring that no more than 250 kg/ha total manure nitrogen isapplied each year. Also take account of the phosphate content of manures to avoid excessive enrichmentof soil phosphorus levels. Make sure that the plans adhere to any other legal obligations such as the ActionProgramme in Nitrate Vulnerable Zones (see Guidelines for Farmers in NVZs, MAFF PB3277). As far aspossible, apply manures in the spring - this will make best use of the nitrogen content.

4 Aim for the manure application to supply no more than 50–60% of the total nitrogen requirement of thecrop, with inorganic fertiliser used to make up the difference. This approach will minimise the potentialimpact of variations in manure nitrogen supply on crop yields and quality.

5 Make sure the manure application equipment is well maintained and suitable for applying the manure in themost effective way, minimising losses of ammonia-N and soil or crop damage. The equipment should beroutinely calibrated for the type of manure being applied, using the guidelines contained in the ManagingLivestock Manures booklet 3.

6 Following application, use the tables in this section or the MANNER computer programme to calculate theamount of crop available nitrogen supplied from each manure application in each field. Use the tables in thisbook to calculate the amount of phosphate, potash, sulphur and magnesium applied.

7 Calculate the nutrient requirement of the crop, then deduct the nutrients supplied from manures. This willgive the balance that needs to be supplied as inorganic fertiliser (see examples 1 and 2 below).

Practical Aspects of Manure Use

➤ Manures are commonly applied to arable stubbles in the autumn prior to drilling winter cereals and oilseedrape. But to make best use of manure nitrogen and to minimise nitrate leaching losses, manures should, ifpossible, be applied in spring. Band spreaders and other equipment are now available that allow accurateslurry topdressing across full tramline widths without causing crop damage. An additional benefit of bandspreading is that ammonia emissions are reduced by 30–40% compared with conventional ‘splash-plate’surface application.

➤ Manure applications before spring sown crops (e.g. cereals, oilseed rape and root crops) should be madefrom January onwards to minimise nitrate leaching losses, particularly where high readily available N manuresare applied. Rapid soil incorporation will minimise ammonia losses.

➤ Manure applications to grassland are best made to fields intended for silage or hay production. Cattle slurryand FYM contain large amounts of potash relative to their readily available nitrogen and total phosphatecontents, and are ideally suited to this situation. Solid manure application rates should be carefully controlledto avoid the risk of sward damage and contamination of conserved grass with manure solids. This can

48

adversely affect silage quality. To encourage a low pH and good fermentation, grass cuts following solidmanure or late slurry applications should be wilted before ensiling, or an effective silage additive used. Tomake best use of slurry N, applications should be made in spring. Slurry and manure N applications in summerare likely to be less efficiently utilised because of higher ammonia losses. The use of band spreading orshallow injection (5–7 cm deep) methods will reduce ammonia-N losses and herbage contamination.

➤ Where slurry and solid manure applications are made to grazed grassland, the pasture should not be grazedfor at least 4 weeks following application, or until all visible signs of slurry solids have disappeared. This willminimise the risk of transferring disease to grazing livestock. Also, take care to ensure that the manure potashsupply does not increase the risk of grass staggers (hypomagnesaemia) in stock through reduced herbagemagnesium levels.

➤ Forage crops, particularly forage maize prior to drilling, provide an opportunity to apply manures in latespring. Manure application rates should be carefully controlled and where possible the manure should berapidly incorporated into the soil to minimise ammonia-N losses and odour emissions.

49

Example 1: Cattle Slurry for 1st Cut Silage

40 m3/ha of cattle slurry (6% dry matter) is broadcast in early spring before first-cut silage. The soil is at PIndex 2 and K Index 2-. Where the slurry is surface applied in the spring, allowing for the manure nutrientssaves up to £54/ha. This potential saving will be less following autumn or winter application or wheresoil P or K Indices are above maintenance levels.

1 Estimated total nutrients in slurry (kg/m3)

Analysis of representative sample or typical values

(see table on page 42)

2 Estimated available nutrients in slurry (kg/m3)

Nitrogen (see table on page 43)

Phosphate and potash (see table on page 44)

3 Nutrients supplied by slurry that are equivalent

to inorganic fertiliser (kg/ha)

40m3/ha supplies 120kg/ha total N and

40 kg/ha crop available N

Potential saving from manure use

4 Nutrient requirements for first-cut silage (kg/ha)

(see pages 153–155)

5 Inorganic fertiliser needed for the silage crop

(kg/ha)

Stage 4 minus Stage 3

Actual saving for next crop from manure use

6 Surplus manure nutrients for subsequent crops

that are equivalent to inorganic fertiliser (kg/ha)


Saving for subsequent crops from manure use

Nitrogen

(N)

Phosphate

(P2O5)

Potash

(K2O)

Financial

saving

£/ha

143.0

141.0a

140

120

180

NIL

41.2

40.6

48b

40c

NIL

48

143.5

143.1

140b

180c

NIL

160

£54/had

£40/ha

£14/ha

a) Nitrogen availability is 35% of total N (see table on page 43).

b) Total phosphate and potash content used in calculations to maintain soil Indices.

c) Nutrients required for spring application (soil P Index 2 and K Index 2–).

d) Saving for next crop plus value of surplus manure phosphate and potash which will contribute to the nutrient requirement of future

crops.

Assumed fertiliser costs: nitrogen 30p/kg; phosphate 30p/kg; potash 20p/kg

50

Example 2: Pig FYM for Winter Wheat

35 t/ha of pig FYM is applied in autumn to a clay soil before drilling winter wheat (8 t/ha grain yield, strawbaled). It is NOT rapidly incorporated. The soil is at P Index 2 and K Index 2-. Where the FYM is surfaceapplied in the autumn, allowing for the manure nutrients saves up to £116/ha. This potential saving willbe less where soil P or K Indices are above maintenance levels.

1 Estimate total nutrients in FYM (kg/t)

Analysis of representative sample or typical values

(see table on page 38)

2 Estimate available nutrients in FYM (kg/t)



3 Nutrients supplied by FYM that are equivalent

to inorganic fertiliser (kg/ha)

35t/ha supplies 245kg/ha total N and

25 kg/ha crop available N

Potential saving from manure use

4 Nutrient requirements for winter wheat (kg/ha)

(see pages 78 and 86)

5 Inorganic fertiliser needed for the wheat crop

(kg/ha)


Actual saving for next crop from manure use

6 Surplus manure nutrients for subsequent crops

that are equivalent to inorganic fertiliser (kg/ha)


Saving for subsequent crops from manure use

Nitrogen

(N)

Phosphate

(P2O5)

Potash

(K2O)

Financial

saving

£/ha

147.0

140.7a

125

220

195

NIL

247.0

244.2

245b

270c

NIL

175

145.0

144.5

175b

195c

NIL

180

£116/had

£48/ha

£68/ha


b) Total phosphate and potash content used in calculations to maintain soil Indices.

c) Nutrients required for maintenance of soil reserves (soil P Index 2 and K Index 2–).

d) Saving for next crop plus value of surplus manure phosphate and potash which will contribute to the nutrient requirement of future

crops.

Assumed fertiliser costs: nitrogen 30 p/kg; phosphate 30p/kg; potash 20p/kg

51

Manure Application

It is important that manures are applied evenly and at known application rates. It is the incorrect setting of boutwidths and poor attention to machinery maintenance which are the most common causes of uneven applicationon farms. For both slurries and solid manures, the evenness of spreading is usually better with rear dischargespreaders than side discharge machines. Topdressing slurry to arable crops in spring can be carried out usingtankers or umbilical systems with boom applicators (fitted with nozzles or trailing-hoses) operating fromtramlines. The aim should be to apply all manure types evenly with a coefficient of variation (CV) of less than25%. This is achievable with many commonly used types of manure application equipment provided they arewell maintained and calibrated.

Application rates can be simply calculated from a knowledge of the capacity of the slurry tanker or solid manurespreader (by weighing both full and empty machines on a weighbridge), the number of loads applied per fieldand the field area. An accurate flow meter should be used to measure the slurry application rate of umbilical andirrigation systems.

Heavy Metals

Farm manures can also contain heavy metals which on certain soils, for example copper deficient soils, cancorrect a trace element deficiency. However, in the majority of situations, the accumulation of heavy metals in thesoil is the more important issue. Pig and poultry manures can contain elevated levels of zinc and copper, which inthe long-term (over 100 years), may lead to undesirably high soil levels. Where pig or poultry manures have beenapplied to land for a number of years and will continue to be applied, it is advisable to sample the soil periodicallyand carry out analysis for heavy metals.

SEWAGE SLUDGES (BIOSOLIDS)

Treated sludges (commonly called biosolids) are useful fertilisers and soil conditioners, which have undergoneprocesses to create a product suitable for beneficial use in agriculture.

Where sludges are applied to agricultural land the conditions of The Safe Sludge Matrix, The Sludge (Use inAgriculture) Regulations and The Code of Practice for Agricultural Use of Sewage Sludge must be followed. TheSafe Sludge Matrix provides the minimum standard for sustainable sludge recycling to agricultural land. Wheresludges are used on agricultural land, usage must be recorded and the soil tested by the sludge producer. Theseoperating requirements ensure that sludge applications to farmland are strictly controlled, that elevatedconcentrations of heavy metals do not accumulate in soils and crops, and that disease risks to humans andlivestock are minimised.

Nutrient Content of Sludges

Sludges are a valuable source of major plant nutrients and organic matter, which can be used by growers to meetcrop nutrient requirements and to maintain soil fertility (see example 3). Digested cake and digested liquidsludges are the products most commonly applied to farmland. In recent years there has been a marked increasein the production of lime stabilised, thermally dried and composted sludges. These sludges meet the requirementsof The Safe Sludge Matrix that all sludges applied to agricultural land growing food crops are treated.

Based on the analysis of a large number of samples, typical nutrient content data for the main sludge typesapplied to farmland are summarised in the table on page 53. However, the characteristics of these products canvary depending on the individual source and treatment process. Most sludge products are now supplied by WaterCompanies with specific nutrient content data and other information.

Around 50% of the total phosphate content of sludges is available to the next crop grown, with the remainderbecoming available over future seasons. However, the availability may be lower if the sludge has been tertiary

52

treated using iron and aluminium salts to enhance the removal of phosphorus from waste water. Sludges containonly small amounts of potash. Useful quantities of sulphur and magnesium are also applied which will help tomeet crop needs and contribute to the maintenance of soil reserves. Lime stabilised sludges also have value asliming materials (neutralising value commonly 10-20%).

Nitrogen Supply from Sludges

The same factors that affect the supply and losses of nitrogen from farm manures (ammonia volatilisation, nitrateleaching and organic N mineralisation) also apply to sludges (see page 35). The table on page 53 gives thepercentage of sludge total nitrogen that will be available for the next crop grown, in relation to product type,timing and application method, soil type and rainfall. Nitrogen will also be supplied to crops in the seasonsfollowing sludge application. Digested cake has been shown to supply around 10% of the total N applied in thesecond year and around 5% in the third year.

N/A = Not applicable; ND = No data








c) The values assume incorporation by ploughing. Cultivation using discs or tines is likely to be less effective in minimising ammonia

losses. Where digested liquid sludge has been applied in spring or summer and incorporated more quickly than 6 hours, nitrogen

availability should be intermediate between the ‘soil incorporated’ and ‘deep injected’ figures.

Autumna

(Aug – Oct, 350mm


Wintera

(Nov – Jan, 200mm


Springa

(Feb – Apr)

Summera

use on

grassland

Sandy/

shallowbMedium/

heavybSandy/

shallowbMedium/


%

53

SLUDGES – TOTAL AND AVAILABLE NUTRIENTS



Digested liquid

Digested cake

Thermally dried

Lime stabilised

%

4

25

95

40

kg/m3

2.0

N/A

N/A

N/A

To convert kg/m3 to units/1000 gallons, multiply by 9. To convert kg/t to units/ton, multiply by 2.

Percentage of total nitrogen available to next crop following SLUDGEapplications (% of total nitrogen)


Digested liquid

Digested cake

Thermally dried

Lime stabilised


Digested liquid

Digested cake

Thermally dried

Lime stabilised

Deep injected (25–30cm)

Digested liquid

5

5

5

5

5

5

5

5

5

20

10

10

10

20

10

10

10

10

25

10

10

10

20

10

10

10

15

40

10

10

10

45

15

10

10

35

50

15

15

15

55

20

15

15

65

ND

ND

ND

ND

N/A

N/A

N/A

N/A

65

kg/t

N/A

7.5

35

6.0

Dry

matter

Total

Phosphate

Avail-

ability

Available

Phosphate

Total

Potash

Avail-

ability

Available

Potash

Total

Sulphur

Total

Magnesium

Sulphur

(as SO3)

Magnesium

(as MgO)



54


Digested liquid

Digested cake

Thermally dried

Lime stabilised

24

%

25

95

40

41.5

kg/t

49.0

45

48.0

50

%

50

50

50

20.75

kg/t

24.5

22

24.0

Trace

kg/t

Trace

Trace

Trace

N/A

%

N/A

N/A

N/A

Trace

kg/t

Trace

Trace

Trace

21.1

kg/t

26.0

25

28.0

0.3

kg/t

1.3

6.0

2.0




Allowing for the Nutrient Content of Sludges

The same principles apply as have been described on page 47 for farm manures.

Example 3: Digested Cake for Winter Wheat

30 t/ha of digested cake is applied in autumn before winter wheat (8 t/ha grain yield, straw baled), grownon a medium soil following a previous cereal crop. The sludge is rapidly incorporated. The soil is at PIndex 2 and K Index 2-. Where the digested cake is surface applied in the autumn, allowing for the sludge nutrients saves up to £87/ha. This potential saving will be less where soil P or K Indices are above maintenance levels.

55

1 Estimate total nutrients in digested cake (kg/t)

Analysis provided by biosolids supplier or

typical values (see table on page 53).

2 Estimate available nutrients in digested cake (kg/t)



3 Nutrients supplied by digested cake that are

equivalent to inorganic fertiliser (kg/ha)

30t/ha supplies 225kg/ha total nitrogen and

20 kg/ha of crop available N

Potential saving from sludge use

4 Nutrient requirements for winter wheat (kg/ha)

(see pages 78 and 86)

5 Inorganic fertiliser needed for the wheat crop (kg/ha)


Actual crop saving for next crop due to sludge use

6 Surplus manure phosphate for subsequent crops that

is equivalent to inorganic fertiliser (kg/ha)


Saving for subsequent crops due to sludge use

Nitrogen

(N)

Phosphate

(P2O5)

Potash

(K2O)

Financial

Saving

£/ha

147.5

140.7a

120

220

200

See note e

49.0

44.5

270b

70c

NIL

200

Trace

Trace

Trace

95c

95

Nil

£87/had

£27/ha

£60/ha


b) Total phosphate content used in calculations to maintain soil P Index.

c) Nutrients required for maintenance of soil reserves (soil P Index 2 and K Index 2–).

d) Saving for next crop plus value of surplus manure phosphate which will contribute to the nutrient requirement of future crops.

e) Some additional nitrogen will be available in the 2nd year (20 kg/ha) and 3rd year (10 kg/ha) after application – see page 52.

Assumed fertiliser costs: nitrogen 30p/kg; phosphate 30p/kg

56

Heavy Metals

Sludge products contain heavy metals but at lower concentrations than in the past. On certain soils, for examplecopper deficient soils, sludges can correct a trace element deficiency. However, in the majority of situations, long-term accumulation of heavy metals in the soil is the more important issue. For sludge additions, there is astatutory requirement to analyse topsoils for heavy metals before land spreading to ensure that concentrationsare below the maximum permissible soil levels. Limits for soil concentrations and the maximum permitted rates ofadditions of heavy metals are given in The Soil Code (MAFF PB0617) and The Code of Practice for Agricultural Useof Sewage Sludge.

INDUSTRIAL WASTES

Waste disposal is controlled by the Waste Management Licencing Regulations. These Regulations allow thespreading of some industrial wastes onto agricultural land, without licencing controls, providing certainconditions are met. The application of these wastes must be registered with the Environment Agency who willsupply advice on the Regulations and their interpretation. More detailed guidance is available in The Soil Code(MAFF PB0617).

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