Algorithms for variable-rate application of manure

Baltic Forum for Innovative Technologies for Sustainable Manure Management

KNOWLEDGE REPORT

Algorithms for variable-rate application of manure

By Daniel Rückamp, Judith Schick, Silvia Haneklaus and Ewald Schnug

WP4 Standardisation of Manure Types with Focus on Phosphorus

October 2013

Baltic Manure WP4 Standardisation of Manure Types with Focus on Phosphorus

Algorithms for variable-rate application of manure By Daniel Rückamp, Judith Schick, Silvia Haneklaus and Ewald Schnug Julius Kühn-Institut, Federal Research Centre for Cultivated Plants (JKI), Institute for Crop and Soil Science

The project is partly financed European Regional Development Fund

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the

European

Union

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Preface An undesired surplus of nutrients in agricultural soils can be attributed among others to a uniform application of fertilisers as it does not address the small-scale variation of nutrients in soils. Site-specific fertilisation can reduce nutrient surpluses. The present report aims to introduce the legal framework of manure application in countries of the Baltic Sea region, to describe the advantages and disadvantages of fertilisation with manure in relation to mineral fertilisers, to give an overview about the nutrient composition and amount of slurry in relation to animal species and feeding regime, and to develop algorithms for the variablerate application of slurry. This report was compiled and edited by Daniel Rückamp, Judith Schick, Silvia Haneklaus and Ewald Schnug (WP4 leader, JKI). It is written as part of work package 4 “Standardisation of manure types with focus on Phosphorus” of the project “Baltic Forum for Innovative Technologies for Sustainable Manure Management” (Baltic Manure). The project aims at turning manure problems into business opportunities and is partly funded by the European Union European Regional Development Fund (Baltic Sea Region Programme 2007- 2013). The authors would like to thank Alar Astover (EMU, Estonia), Andras Baky (JTI, Sweden), Andreas Berk (FLI, Germany), Juha Grönroos (SYKE, Finland), Allan Kaasik (EMU, Estonia), Ksawery Kuligowski (POMCERT, Poland), Andrea Meyer (LWK Niedersachsen, Germany), Ulrich Meyer (FLI, Germany), Hanne Damgaard Poulsen (Aarhus University, Denmark), Lena Rodhe (JTI, Sweden), Jakub Skorupski (Green Federation GAJA, Poland), Annette Vibeke Vestergaard (Videncentret for Landbrug, Denmark), and Kari Ylivainio (MTT, Finland). They gave input to the legal standards, to the animal feeding, to the separation of slurry and to the manuscript in general.

October 2013 The authors

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Table of Contents 1

Introduction .............................................................................................................. 4

2

Legal framework for manure application ................................................................... 6

3

Advantages and disadvantages of mineral fertilisers and slurry................................ 11

4

Factors influencing the mineral composition of slurry .............................................. 13

5

Variable-rate slurry application ............................................................................... 24

6

5.1

Prerequisites ............................................................................................................... 24

5.2

Online-Measurement of manure composition .............................................................. 25

5.3

Strategies for manure production ................................................................................ 26

5.4

Additional application of mineral fertilisers .................................................................. 27

Algorithms for the variable-rate application of slurry ............................................... 28 6.1

Prerequisites ............................................................................................................... 28

6.2

Combined application of slurry and single-nutrient mineral fertiliser ............................ 28

6.3

Crop rotation ............................................................................................................... 40

7

Conclusions ............................................................................................................. 43

8

References .............................................................................................................. 44

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1

Introduction

Codes of Good Agricultural Practice imply the statuary law on management practices that can be adopted to minimise the risk of water, air and soil pollution (Schnug et al., 2011). Especially an undesired surplus of nitrogen (N) and phosphorus (P) on agricultural land as a result of an improper fertiliser use may lead to an increased nutrient discharge into water bodies. The nutrient surplus can be – among other factors – attributed to constant nutrient ratios of mineral multi-nutrient and organic fertilisers during the application. Usually, soil parameters and accordingly soil fertility vary naturally within one single field. Thus, a uniform application of fertilisers results in an imbalanced fertiliser application and consequently to unnecessary environmental impacts (Figure 1; Burrough, 1993; Haneklaus et al., 1998b; Haneklaus and Schnug, 2000).

Figure 1 Discrepancy between site-specific nutrient demand and uniform fertiliser rates (adapted from Schnug et al., 2011).

Usually, the balance of big livestock farms exhibits the highest nutrient surpluses (130-250 kg N ha-1, 90 kg P ha-1) (Haneklaus et al., 1998), which are caused by improper use of manure. Hence, manure is a major contributor to an increased nutrient input into the Baltic Sea region (BSR). Thus it may be concluded that a sustainable use of this valuable resource as an organic fertiliser is important for a balanced P supply of agricultural soils and for reducing nutrient losses to the Baltic Sea. Especially with view to phosphorus, manure handling needs special attention to ensure a careful use of this limited resource. A complementary strategy for the utilisation of manure, the maintenance of a sufficient soil nutrient status and the minimisation of environmental risks is necessary. A promising strategy is variable-rate application of fertilisers as the nutrient input matches exactly the nutrient demand. This concept considers the small-scale variability of soil and crop features

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on a single field and transforms this knowledge into algorithms for a variable-rate application. The small-scale spatial and temporal variation of nitrate in soils has been assessed by Haneklaus et al. (1998). The content of available nitrogen varies even over distances shorter than 30 m and between sampling dates. The nitrate contents range from 28 to 100 kg N ha-1 which resulted in variable-rates from 23 to 43 kg N ha-1. Algorithms for a variable-rate application of mineral multi-nutrient fertiliser have already been developed by Haneklaus and Schnug (2000). Algorithms for a site-specific input of manure and slurry are missing so far, but are crucial for a purely demand-driven input of nutrients. The site-specific fertilisation with manure is demanding as in contrast to manufactured mineral fertilisers manure is a heterogeneous product because dry matter content, elemental composition and pH vary considerably. Generally, variable-rate application requires some essential prerequisites. Firstly, the acquisition of information on the variability of some soil characteristics important for the nutrient availability has to be undertaken. Those parameters are on the one hand the actual available nutrient contents and on the other hand long-term stable features such as soil texture, organic matter content and geomorphology (Haneklaus and Schnug, 2000). Secondly, the composition and the short and long-term impact of the fertiliser on the nutrient availability have to be known for each application date. Additionally, techniques for the exact and just in time application are necessary. Such techniques will be discussed in this report. The aim of the presented report is 

to introduce the legal framework of manure application in the countries of the Baltic Sea region,



to describe the advantages and disadvantages of fertilisation with manure in relation to mineral fertilisers,



to give an overview about the nutrient composition and amount of slurry in relation e.g. to animal species and feeding regime, and



to develop algorithms for the variable-rate application of slurry.

The strategies presented in this report focus on slurry (liquid manure) and the environmentally relevant plant nutrients nitrogen and phosphorus. The presented data and algorithms are based on actual values and literature data.

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2

Legal framework for manure application

The legal situation for manure application in the countries of the Baltic Sea region is harmonised with directives of the European Union. Those directives were mostly transferred to national laws, where, in some cases, the general rules have been tightened. Most rules for manure application originate from one of the oldest EU environmental programs: the Council Directive of 12 December 1991 concerning the protection of waters against pollution caused by nitrates from agricultural sources (91/676/EEC, “Nitrate Directive”). In addition, also the Directive 2008/1/EC of the European Parliament and of the Council of 15 January 2008 concerning integrated pollution prevention and control (“IPPC Directive”) and the Directive 2000/60/EC of the European Parliament and of the Council establishing a framework for the Community action in the field of water policy (“Water Framework Directive”) have effects on manure application rules, for example on phosphorus losses. As a consequence of the Nitrate Directive, codes of good agricultural practice have been developed and have been implemented in national guidelines or even laws. Additionally, nitrate action programmes have to be developed by the member states. The oldest framework for protection of the Baltic Sea and preventive measures onshore is the Convention on the Protection of the Marine Environment of the Baltic Sea Area (Helsinki Convention). Table 1 and Table 2 summarise the legal standards for slurry application in the countries of the Baltic Sea region. The main differences between the countries are the area of the nitrate vulnerable zones, the maximum application amount following nitrogen or phosphorus and the regularly updated guidelines in Denmark. Several countries have declared the whole country as nitrate vulnerable; thus, the application rules are valid for the whole country. In Latvia, regulations apply for the entire country with stricter rules in nitrate vulnerable zones. In Sweden, most regulations are only valid in nitrate vulnerable zones and not the entire country. Most countries adopted the maximum value for manure application from the Nitrate Directive and fixed it at 170 kg N ha-1 a-1. Only 140 kg N ha-1 a-1 are allowed in Estonian NVZs and for pig manure in Demark. On the contrary, Sweden regulates the manure application by a phosphorus limit of 22 kg P ha -1 a-1, which also fulfils the requirements of the Nitrate Directive. Noteworthy is that mineral fertilisers can be applied in addition to manure whereby rates are not limited.

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Table 1 Legal frameworks for slurry application in countries of the Baltic Sea region. Country

Reference

Updates

Denmark

Vejledning om gødsknings- og harmoniregler (Guidelines on regulations of fertilising and harmony rules), 09.2012 Bekendtgørelse om erhvervsmæssigt dyrehold, husdyrgødning, ensilage m.v. (Order on commercial animal husbandry, manure and silage), 28.06.2012 Estonia Veeseadus (Water Act), 11.05.1994, last revision 21.12.2011 Finland Opas ympäristötuen ehtojen mukaiseen lannoitukseen 2007-2013 (Guide for fertilisation according to Agri-Environmental policy during 2007-2013), 04.2009 Germany Düngeverordnung (Fertilising Ordinance), 27.02.2007, last revision 24.02.2012 Latvia Noteikumi par ūdens un augsnes aizsardzību no lauksaimnieciskas darbības izraisītā piesārņojuma ar nitrātiem (Regulations regarding protection of water and soil from pollution with nitrates caused by agricultural sources), 18.12.2001, last revision 05.05.2009 Lithuania Lietuvos Respublikos Žemės Ūkio Ministro ir Lietuvos Respublikos Aplinkos Ministro: Dėl Vandenų apsaugos nuo taršos azoto junginiais iš žemės ūkio šaltinių reikalavimų patvirtinimo (On the approval of provisions for the protection of water from pollution caused by nitrogen compounds from agricultural sources of the Minister of Agriculture and the Minister of Environment of the Republic of Lithuania), 19.12.2001 Lietuvos Respublikos Žemės Ūkio Ministro: Dėl Geros ūkininkavimo praktikos reikalavimų (Codes of good agricultural practice of the Minister of Agriculture of the Republic of Lithuania), 16.07.2004, last revision 04.05.2006 Poland Ustawa o nawozach i nawozeniu (Fertiliser and Fertilisation Act), 10.07.2007 Rozporządzenie Ministra Rolnictwa i Rozwoju Wsi w sprawie szczegółowego sposobu stosowania nawozów oraz prowadzenia szkoleń z zakresu ich stosowania (Ministry of Agriculture Decree on application of fertilisers and education in fertilisation), 16.04.2008, last revision 25.06.2012 Ustawa Prawo wodne (Water Act), 18.07.2001, last revision 09.02.2012 Sweden Statens jordbruksverks föreskrifter och allmänna råd om miljöhänsyn i jordbruket vad avser växtnäring (Swedish Board of Agriculture rules on environmental concerns in agriculture as regards plant nutrients), 2004, last revision 22.06.2011

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every year every second year unregularly regularly

unregularly unregularly

unregularly

unregularly

unregularly unregularly

unregularly unregularly

European

Union

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Table 2 Regulations for slurry application in countries of the Baltic Sea region defined by the legal frameworks listed in Table 1. The overview is restricted to slurry, application on arable land and without stating all legal exceptions. Some aspects of good agricultural practice like manure working into the soil and vegetation cover have not been considered. Country

NVZa

Maximum application total maximumb special rules

Animal density Application prohibited Winter time Water regime c -1 LU ha

• 140 kg N ha-1 a-1 (pigs) • 170 kg N ha-1 a-1 (cattle)

in certain areas, P is restricted by a maximum input level in the feeding ration

• ≤ 1.4 (pigs)

if > 100 kg N ≤ 2 ha-1 a-1, application in ≤ 1.5 (NVZ) two parts

% territory Denmark

100

Estonia

7.7

170 kg N ha-1 a-1 25 kg P ha-1 a-1 140 kg N ha-1 a-1 (NVZ)

Finland

100

170 kg N ha-1 a-1

• ≤ 1.7 (cattle)

harvest - 01.02. (winter oilseedrape and grass until 01.10.)

Other restrictions Excessive nutrients

on frozen, watersaturated, flooded or snowcovered soil

• buffer zone to open water bodies • regulations for sloping grounds • possible further restrictions (e.g. 0.7 x LU) in sensible groundwater-areas 01.11. - 31.03. on frozen, water• buffer zone to open saturated, water bodies flooded or snow• regulations for covered soil sloping grounds • advanced regulations for NVZ 15.10. - 15.04. if soil P exceeds 40- • buffer zone to open 50 mg dm-3 soil or 20 water bodies if not frozen or mg dm-3 peat • regulations for water-saturated: (highest P class, sloping grounds 15.11. - 01.04. depends on texture) if cattle manure is the only P source, application up to 20 t ha-1 even for high P classes are allowed Continued on next page

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Table 2 (continued) Germany

100

170 kg N ha-1 a-1

Latvia

13

170 kg N ha-1 a-1 (NVZ)

170 kg N ha-1 a-1 (including mineral N)

Lithuania 100

Poland

19

170 kg N ha-1 a-1 [25 kg P ha-1 a-1]

01.11. - 31.01.

on frozen, watersaturated, flooded or snowcovered soil

≤ 1.7 (NVZ)

15.11. - 01.03. (NVZ)

on frozen, watersaturated, flooded or snowcovered soil

≤ 1.7

01.12. - 31.03.

on frozen, watersaturated, flooded or snowcovered soil

01.12. - 28.02.

on frozen, watersaturated, flooded or snowcovered soil

• buffer zone to open water bodies • regulations for sloping grounds • Compensation fertilisation in autumn only for remaining straw • buffer zone to open water bodies • regulations for sloping grounds • advanced regulations for NVZ • buffer zone to open water bodies • regulations for sloping grounds • buffer zone to open water bodies • regulations for sloping grounds Continued on next page

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Table 2 (continued) Sweden

9

22 kg P ha-1 a-1

01.11. - 28.02. (NVZ) [170 kg N ha-1 a-1] 01.08. - 30.11. (NVZ) (Blekinge, Skåne, Halland (all within NVZ)): only on growing crops; special regulations for sowing crops a nitrate vulnerable zones according to the Nitrate Directive; b farm average; c livestock units

on frozen, watersaturated, flooded or snowcovered soil (NVZ)

• buffer zone to open water bodies (NVZ) • regulations for sloping grounds (NVZ) • if soil P exceeds P-AL class III, fertilisation equivalent only to plant removal

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3

Advantages and disadvantages of mineral fertilisers and slurry

Manure is a natural organic product, which has been used traditionally for fertilisation. Manure contains large amounts of organically-bound and medium-term plant-available nutrients, while the nutrients of partly or fully digested mineral fertilisers are immediately or on a short term basis plant-available. Differences exist for the availability of phosphorus in mineral fertilisers: for instance, phosphorus in triple phosphate is water soluble and thus instantly plant available, whereas phosphorus in rock phosphates is soluble only in strong acids so that P availability on agricultural soils is marginal at best in acid soils. The actual N and P utilisation efficiency of different manure types is summarised in Table 3. The data basis for the values provided is small and it is founded on studies in single countries; therefore, the standard values are different in the countries of the BSR. In general, 50-70% of the nitrogen is credited as available in the first year with slightly higher values for pig slurry (Table 3). Only Estonia and Latvia give values (40% and 35%, respectively) for the phosphorus availability in the first year (Table 3). Additionally, manure application takes effect also in following years. The not readily available nutrients will be mineralised with time. Experiments showed that manure fertilisation according to the nutrient offtake by plants did not alter the content of available phosphorus in soils (Schnug et al., 2003; Schick et al., 2012). Hence, there is a dynamic equilibrium between mobilisation of former applied phosphorus forms and newly applied stable phosphorus forms (Schnug et al., 2003) and phosphorus is considered as entirely plant available on a long-term application of manure (Sächsische Landesanstalt für Landwirtschaft, 2007; Schneider-Götz et al., 2011). However, the long-term effect is largest in the second year, but only Estonia and Latvia give explicit nutrient availabilities for the second year (Table 3). Latvia refers to 10% of total N and total P, while Estonia specifies 0% of total N and 20% of total P. Both do not distinguish between pig or cattle manure (Table 3). Furthermore, regular manure applications have long-term effects on nutrient supply. Periodic manure applications cause an accumulation of organic matter, which is visible in two times higher organic matter contents in soils fertilised with manure for 140 years compared to ones without fertilisation (Rothamsted Research, 2006). The organic matter content in soils is even higher (factors 1.2-3.2) after manure applications than after mineral fertiliser applications shown in many long-term experiments (22-141 years; Edmeades 2003). Therefore, higher nutrient recoveries can be assumed for application periods longer than five years than for single applications (Sächsische Landesanstalt für Landwirtschaft, 2007; Schneider-Götz et al., 2011). Denmark considers that after ten years of regular manure applications nitrogen availability will be higher for the year of application (Table 3). So far these results have not been implemented in national regulations for manure application. The project is partly financed European Regional Development Fund

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Table 3 Percentages of plant available nutrients in slurry for the year of application and subsequent years. The data according to the EU member states’ action programmes is taken from European Commission – Directorate General Environment, 2010. Country

Definition of available nutrient

Denmark fertiliser replacement value Estonia direct effect = crop utilisation Finland indirect indication: fertiliser replacement value Germany available nutrient Latvia fertiliser replacement value Lithuania available nutrient Poland fertiliser replacement value Sweden available nutrient

Part of action Nt programme Cattle st

1 year % no

Pt Pig

Cattle

long-term

st

1 year

long-term

70

10 a (indirecta)

75

no

50

50

no

-

0% 2nd year no

no no

50 50

no 10% 2nd year

no no

-b

-

60 (spring), no 50 (autumn)

Pig

1 year

long-term

1st year

long-term

10 a (indirect)

-

-

-

-

0% 2nd year no

40

20% 2nd year

40

20% 2nd year

-

-

-

-

60 50

no 10% 2nd year

35

10% 2nd year

35

10% 2nd year

-

-

-

-

-

-

60 (spring), 50 (autumn)

no

-

-

-

-

-

st

no

75% of yes 100% of yes residual residual NH4NH4-N after N after c spreading spreading a The residual fertiliser effect is already incorporated in the 1st year value; b only values for solid manure available; c The NH3 losses after spreading in spring are presumed to be 10% of NH4-N content for slurry (Swedish Board of Agriculture, 2010).

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4

Factors influencing the mineral composition of slurry

Several factors influence the mineral composition of slurry in the tanks. These imply animal type and weight, feedstuff quality and quantity, housing management, storage time and condition, and water content (Cordovil et al., 2012). Table 4 shows differences in the N and P content of slurry in relation to animal species and housing system. In general, slurry of cattle contains more solids and more N and has consequently a higher N:P ratio than pig slurry. The differences between the housing systems are only minor. Only tie-up housing of dairy cows and fattening bulls exhibit higher N:P ratios in manure than cubicle housing. By comparing dairy cows and fattening bulls, it can be stated that slurry of fattening bulls has higher solid percentages, while slurry of dairy cows contains less N and P (Table 4 & Table 5). Table 5 shows also the effect of different cattle races on slurry composition. However, the race has obviously no large influence on manure composition. Table 4 Variation of slurry composition depending on different housing systems for pigs and cattle. Data taken from Poulsen, 2012. The values have been calculated by using a large Danish dataset originated from farmers, feedstuff companies, and controlling authorities (Poulsen, personal communication). Housing system

Solids %

N kg t

P

N:P

-1

Fattening pigsa Partly slatted floor (25-50%) 06.6 4.96 1.16 4.3 Fully slatted floor 06.1 4.53 1.15 3.9 Draining + slatted floor (33 + 67%) 06.1 4.63 1.15 4.0 b Dairy cows Tie-up housing with floor grating 11.1 6.10 0.91 6.7 Cubicles with solid floor 09.3 5.22 0.83 6.3 Cubicles with slatted floor 09.3 5.33 0.83 6.4 Fattening bullsc Tie-up housing with floor grating 12.8 6.91 1.14 6.1 Cubicles with solid floor 12.3 7.10 1.30 5.5 Cubicles with slatted floor 12.3 7.31 1.30 5.6 a Fattening from 32 kg up to 107 kg (+75 kg); b Heavy races, 9265 kg milk animal-1 a-1, 3.38% proteins; c Heavy races, 6 months fattening, 220 kg growth.

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Table 5 Effect of cattle races on slurry composition. Data taken from Poulsen, 2012. The values have been calculated by using a large Danish dataset originated from farmers, feedstuff companies, and controlling authorities (Poulsen, personal communication). Race

Solids %

N kg t

P

N:P

-1

Dairy cows, cubicles with slatted floor Heavy racesa 09.3 5.33 0.83 b Jersey 09.3 5.45 0.88 Fattening bulls, cubicles with slatted floor Heavy racesc 12.3 7.31 1.30 d Jersey 12.7 7.60 1.34 a -1 -1 b -1 -1 9265 kg milk animal a , 3.38% proteins; 6584 kg milk animal a , 4.13% proteins; c fattening, 220 kg growth; d 6 months fattening, 183 kg growth.

6.4 6.2 5.6 5.7 6 months

The difference of manure composition at different animal age stages is stated for pigs in Table 6. For cattle, there is no data available, because the calves do not produce slurry. Due to the requirements at different age stages, also the housing systems are different. The solid content as well as the N:P ratio increase by animal age. However, there are distinct differences for the nutrient composition of slurry at different ages. Caused by higher nutrient uptake by older and bigger pigs, the N and P contents are higher in slurry of fattening pigs than of weaners. The P content of slurry of sow with piglets is remarkably high. Table 6 Liquid pig manure composition at different growth stages. Data taken from Poulsen, 2012. The values have been calculated by using a large Danish dataset originated from farmers, feedstuff companies, and controlling authorities (Poulsen, personal communication). Age stage

Housing system

Solids %

N kg t

P

N:P

-1

Sow with 28.1 pigletsa Individual housing, partly slatted floor 4.5 3.85 2.89 1.3 b Weaner Two-climate housing, partly slatted floor 5.0 3.36 0.99 3.4 c Fattening pig Partly slatted floor (25-50%) 6.6 4.96 1.16 4.3 a b c per year, piglets up to 7.3 kg; from 7.3 kg up to 32 kg; Fattening from 32 kg up to 107 kg (+75 kg).

The water content of slurry makes it expensive to transport manure over long distances. At the same time, the mixture of solids and water causes bad flow behaviour and manure solids that can block the manure spreading machine. Segregation causes stratification of manure with different nutrient compositions at the top and the bottom of the tank (Table 7). Though solids sink to the bottom, the nutrient content

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is not necessarily higher at the bottom (Table 7). Cattle slurry contains also organic particles which tend to float (Derikx et al., 1997) Table 7 Concentrations of total dissolved solids, nitrogen and phosphorus at different depths for various manure storage places. Source and storage type

Replicates Depth

Cattle, manure reservoir

1

Dairy cow, manure lagoon

1

Pig, nursery barn, deep-pit

2

Solids Nta

Ptb

N:P

Source

00.61 00.11 00.12 09.94 10.07 07.89 00.90 01.00 02.50 04.30 04.20 01.60 01.20 03.10 00.94 00.76 00.59 00.38 00.06 00.39 00.08

03.0 13.6 05.8 03.4 03.5 03.3 05.0 04.6 02.4 01.8 01.6 03.1 03.9 01.9

Goncalves Junior et al., 2006

06.8 05.1

McLaughlin et al., 2012

top 00.4 00.76 00.15 0.5 00.4 00.95 00.19 1.5 00.4 01.21 00.43 bottom 01.1 03.32 03.42 a b total nitrogen; total phosphorus; c data derived from figures.

05.2 04.9 02.8 01.0

Lovanh et al., 2009

m

Pig, finishing barn, 2 deep-pit

Pig, hogs, concrete storage

8

Pig, manure lagoon

1

Pig, manure lagoon

1

0.0 0.7 1.3 top middle bottom 0.0 0.6 1.2 1.6 0.0 0.6 1.2 1.8 top middle bottom 0.0 1.0

%

06.0 04.9 09.4 02.8 03.0 08.0 11.0 07.2 04.0 03.0 05.8 03.2 02.9 02.5

kg t

-1

01.84 01.50 00.69 33.40 35.20 26.20 04.50 04.60 06.00 07.90 06.90 04.90 04.70 05.80

Nova Scotia Department of Agriculture, 2011 Ndegwa et al., 2002c

Ndegwa et al., 2002c

Campbell et al., 1997

Seasonal trends of manure composition have been reported (Figure 2 & Figure 3). DeRouchey et al. (2002) analysed several pig slurry lagoons. The N concentrations are higher in June than October (1.6 versus 1.2 kg N t-1 FM) (DeRouchey et al., 2002). The P concentrations are higher in June than December (0.29 versus 0.13 kg P t -1 FM) (DeRouchey et al., 2002). According to DeRouchey et al. (2002), the reasons for higher nutrient contents in summer are mixing by an elevated number of microorganisms and concentration effects by higher evaporation and less rain. Animal production phase and chemical stability of the slurry contribute to the seasonal trend, too. For instance, ammonia releases are affected by

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the surrounding temperature (Sommer, 1997). For a variable rate application of slurry it is either necessary to produce a homogenous mixture or to analyse the mineral composition in real-time.

Figure 2 Seasonal trends of nitrogen concentrations in US-American anaerobic pig manure lagoons.

Figure 3 Seasonal trends of phosphorus concentrations in US-American anaerobic pig manure lagoons.

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Another significant factor influencing the mineral composition of slurry is the feeding regime. Usually, feedstuff is administered at rates that warrant maximum live weight gain and which supply the livestock with all essential nutrients. For example, in Germany, the Gesellschaft für Ernährungsphysiologie (Society of Nutrition Physiology) publishes recommendations for the energy and nutrition supply, which is based on scientific studies. Though, guidelines and feeding practices vary from country to country. Table 8 and Table 9 present feed quantity, feed composition and ex-animal manure composition for pigs and cattle in various countries of the Baltic Sea region. These tables underline the differences of feed and manure quantity and composition between animals of different ages (see also Table 6). Differences in ex-animal manure composition between countries are related to different animal productivities and demand for feedstuff. In detail, the concentrations of N and P in pig slurry are higher in Sweden than in Denmark. The nutrient concentrations in dairy cow slurries are difficult to compare, because of differing milk production. The higher the milk production, the higher the nutrient concentration in the slurry. Figure 4 and Figure 5 summarise the variation ranges of nitrogen and phosphorus concentrations in pig and cattle slurries. These variation ranges are displayed for the effects of different feedings, races, animal ages, housing systems, seasons, and storage depths on manure composition. The values of the variation range for feeding effects are ex-animal ones whereas the other variation ranges are based on ex-housing or ex-storage values; consequently, a loss of nitrogen from ex-animal to storage is visible in Figure 4. Supposedly, the nitrogen is degassed during storage (e.g. Donham et al., 1977). Animal races and housing systems tend to have a low effect on the variation of the nitrogen and phosphorus content. In comparison, animal age and especially the storage depths have a high impact on the variation of N and P (Figure 4 & Figure 5). The effects of different feedings on slurry composition are animal specific: dairy cows show a high variation of nitrogen and pigs of phosphorus concentrations in slurry.

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Table 8 Feeding instructions for pigs in various countries of the Baltic Sea region. (Sources: Denmark: Poulsen, 2012; Finland: MTT Agrifood Research, 2012; Germany: GfE, 2006 & Berk, personal communication; Germany RAM: Meyer & Berk, personal communication; Latvia: Kārkliņš & Līpenīte, 2008; Sweden: STANK database & Baky, personal communication). Country

Animal age / animal productivity

Days

Weight Feed Start End kg

Metabolisable Feed content energy N P MJ d⁻¹

Uptake N P g animal⁻¹ d⁻¹

Digestibility Slurry ex-animal N P N P Mass -1 % kg t t a-1

Denmark Sows, 28.1 piglets a-1 028 24.0 g FU⁻¹ 6.3 g FU⁻¹ 1315.7 345.4 80 45 6.3 1.4 4.0 Weaner 007.3 032 26.3 g FU⁻¹ 6.4 g FU⁻¹ 4.9 1.4 0.1 Fattening pigs 032 107 25.3 g FU⁻¹ 5.5 g FU⁻¹ 6.0 1.3 0.5 -1 Finland Sows, 20 piglets a 7.9 FU d⁻¹ 73.7 22.4 g FU⁻¹ 3.0 g FU⁻¹ 0177.0 023.7 a Fattening pigs 025 055 1.6 FU d⁻¹ 14.9 24.0 g FU⁻¹ 2.7 g FU⁻¹ 0038.4 004.3 Fattening pigs 055 080 2.4 FU d⁻¹ 22.3 19.2 g FU⁻¹ 2.4 g FU⁻¹ 0046.1 005.8 Fattening pigs 080 120 3.0 FU d⁻¹ 27.9 18.4 g FU⁻¹ 1.9 g FU⁻¹ 0055.2 005.7 -1 Germany Sows, 20 piglets a 6.7 kg d⁻¹ 88.0 25.6 g kg⁻¹ 5.5 g kg⁻¹ 0170.7 036.7 >80 >50 025 Weaner 028 0.7 kg d⁻¹ 08.7 27.2 g kg⁻¹ 5.0 g kg⁻¹ 0017.7 003.3 >80 >50 028 Fattening pigs 028 040 2.5 kg d⁻¹ 32.5 25.6 g kg⁻¹ 5.0 g kg⁻¹ 0064.0 012.5 >80 >50 050 Fattening pigs 040 115 4.3 kg d⁻¹ 55.3 24.0 g kg⁻¹ 4.5 g kg⁻¹ 0102.0 019.1 >80 >50 055 Germany, Sows lactating 26.4 g kg⁻¹ 5.5 g kg⁻¹ >80 >50 b RAM Weaner 030 27.2 28.8 g kg⁻¹ 5.5 g kg⁻¹ >80 >50 feed Fattening pigs 27.2 g kg⁻¹ 5.5 g kg⁻¹ >80 >50 Fattening pigs 22.4 g kg⁻¹ 4.5 g kg⁻¹ >80 >50 Latvia Sows, 18 piglets a-1 25.9 g kg⁻¹ 5.1 g kg⁻¹ Fattening pigs 020 130 28.6 g kg⁻¹ 6.6 g kg⁻¹ Sweden Fattening pigs 7.0 2.5 0.5 a -1 -1 b feed units (Denmark: 12.6 MJ metabolisable energy kg , Finland: 9.3 MJ net energy kg ); Feed with reduced nitrogen and phosphorus contents. The given values are maximum values for such feed.

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Table 9 Feeding instructions for cattle in various countries of the Baltic Sea region. (Sources: Denmark: Poulsen, 2012; Finland: MTT Agrifood Research, 2012; Germany: Landwirtschaftskammer Schleswig-Holstein, 2012; Latvia: Kārkliņš & Līpenīte, 2008; Sweden: STANK database & Baky, personal communication). Country

Denmark

Finland

Germany

Animal age / animal productivity

Dairy cows, heavy race, 9265 l milk Dairy cows, Jersey, 6584 l milk Fattening bulls, heavy race Fattening bulls, Jersey Dairy cows, 40 kg milk d-1, 3% protein Growing cattle Growing cattle Growing cattle Growing cattle Growing cattle Growing cattle Dairy cows, 30 kg milk d-1, 4.0% fat, 3.4% protein Growing cattle Growing cattle Growing cattle Growing cattle Growing cattle

Days

Weight Start End kg

Feed kg d⁻¹

Metabolisable Feed content energy N MJ d⁻¹

P

Uptake N P g animal⁻¹ d⁻¹

Slurry ex-animal N P Mass -1 kg t t a-1

365

18.2

27.7 g FU⁻¹ a

4.3 g FU⁻¹

526.6

80.9

6.5

0.9

21.8

365

15.0

27.7 g FU⁻¹

4.3 g FU⁻¹

448.0

68.8

6.6

1.0

18.1

23.2 g FU⁻¹ 23.2 g FU⁻¹

4.2 g FU⁻¹ 4.2 g FU⁻¹

29.4 23.1 87.0

8.6 8.5

1.3 1.3

02.8 02.2

183 183 25.3

272.0

162.3 127.8 371.8

150 250 350 450 550 650 650

20.0

043.0 058.0 076.0 092.0 107.0 121.0 136.2

051.7 058.6 009.6 012.8 016.0 019.2 480.0

16.0 17.0 19.0 20.0 22.0 24.0 71.0

250 350 450 550 650

04.5 06.3 07.5 08.3 10.5

044.3 060.8 077.5 094.5 111.9

089.6 110.4 140.8 171.2 201.6

15.0 17.0 20.0 22.0 27.0 Continued on next page

650

650

100 150 250 350 450 550 650 150 250 350 450 550

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Table 9 (continued) Latvia

Dairy cows, 7000 kg milk 600 600 07.6 Fattening bulls 365 150 450 19.2 Sweden Dairy cow, 6000 l milk Dairy cow, 8000 l milk Dairy cow, 10000 l milk Dairy cow, 12000 l milk a feed units (Denmark: 12.6 MJ metabolisable energy kg-1, Finland: 9.3 MJ net energy kg-1).

19.1 g kg⁻¹ 23.7 g kg⁻¹

3.9 g kg⁻¹ 3.6 g kg⁻¹ 5.7 6.3 7.4 8.1

0.9 0.9 0.9 1.1

17.5 18.5 18.8 18.0

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Figure 4 Variation range of nitrogen contents in slurry of fattening pigs, bulls, and dairy cows depending on feeding (see Table 8 and Table 9), races (see Table 4), animal age (see Table 6), housing systems (see Table 4), season (see Figure 4, only data from DeRouchey et al., 2002), and storage depth (lagoon, deep-pit, and tank; see Table 7). The boxes give the minimum and maximum value and if more than two values are available also the median.

Figure 5 Variation range of phosphorus contents in slurry of fattening pigs, bulls, and dairy cows depending on feeding (see Table 8 and Table 9), races (see Table 4), animal age (see Table 6), housing systems (see Table 4), season (see Figure 5, only data from DeRouchey et al., 2002), and storage depth (lagoon, deep-pit, and tank; see Table 7). The boxes give the minimum and maximum value and if more than two values are available also the median.

The project is partly financed European Regional Development Fund

by

the

European

Union

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One putative problem for the use of manure is the existence of contaminants in manure. These can either be heavy metals like copper (from pig feed), or organic pollutants like veterinary medicals (Finck, 1992). Summarising the effects of different factors on mineral composition of slurry it can be stated that 

The N content in ex-housing slurry increases in the order pigs (median 4.6 kg N t-1 FM) < dairy cows (median 5.3 kg N t-1 FM) < bulls (median 7.1 kg N t-1 FM) by about 15% and 33%, respectively (Table 4). Thus, the N concentration varies with animal species by 153%.



The P content in ex-housing slurry increases in the order dairy cows (median 0.8 kg P t-1 FM) < pigs (1.2 kg P t-1 FM) < bulls (1.3 kg P t-1 FM) by about 39% and 13%, respectively (Table 4). Thus, the P concentration varies with animal species by 157%.



Animal race and housing system have only a low impact on ex-housing slurry composition (Table 4 & Table 5). The largest difference has the P concentration in slurries of heavy and Jersey dairy cows (6%).



N and P excretion increases with age from weaners (3.3 kg N t-1 FM and 1.0 kg P t-1 FM in ex-housing slurry) to fattening pigs (5.0 kg N t-1 FM and 1.2 kg P t-1 FM in ex-housing slurry) by about 48% and 17%, respectively (Table 6).



The effect of higher feeding supplements to pigs is visible in 17% higher N (7.0 kg N t-1 FM) and 92% higher P (2.5 kg P t-1 FM) concentrations in slurry from Sweden than in Danish slurry (6.0 kg N t-1 FM, 1.3 kg P t-1 FM) (Table 8).



The N and P contents have a broad range at different storage depths and varying storage systems. The N and P concentrations vary by 9191% (0.4-35.2 kg N t-1 FM) and by 17985% (0.1-10.1 kg P t-1 FM), respectively (Table 7).



Also the season has an influence on ex-storage slurry composition. The N and P concentrations vary by 142% (1.2-1.6 kg N t-1 FM) and by 219% (0.1-0.3 kg P t-1 FM), respectively (Figure 4 & Figure 5).

Usually, species, race, housing system and feeding regime are constant at each farm if the management does not change. Conn et al. (2007) found a high variation of slurry compositions between farms, but in general the composition of slurry of individual farms was consistent over time. The largest effects on slurry composition have the factors storage depth, the season and the animal age. However, the variation due to storage depth should be smaller than stated above, because the farmer uses only one type of storage and the

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Union

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slurry is often agitated in the storage tank. Seasonal variation affects the slurry composition most pronounced. In the warmer season (March-October), when slurry will be used, the pig slurry composition varies by 42% (N) and 35% (P). The effect of animal age on pig slurry composition is in the same order (N: 48%, P: 17%). A summation of those variations is difficult, because these are ex-housing and ex-storage values and ex-storage comprises exhousing effects. Ndegwa et al. (2002) studied the combined effect of pig age and storage depth on slurry composition: N varies by 76% and P by 378% (Table 7).

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European

Union

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5 5.1

Variable-rate slurry application Prerequisites

In the previous section, factors influencing the mineral composition of slurry, relevant parameters which cause variation of the mineral composition and water content of slurry were listed. The coefficient of variation (CV) was determined for mineral nutrients in slurry from different animals in extended surveys (e.g. Derikx et al., 1997; Sharpley and Moyer, 2000). The results of these studies showed similar results and the CV for total P varied between 21.0 and 75.8% in cattle slurry (Overcash et al., 1983 cited in Nath, 1992; Derikx et al., 1997; Salazar et al., 2007; Hjorth et al., 2010), 5.8 and 87.8% in pig slurry (Derikx et al., 1997; Sharpley and Moyer, 2000; Sánchez and González, 2005; Hjorth et al., 2010), and 21.0 and 75.8% in poultry slurry (Overcash et al., 1983 cited in Nath, 1992; Derikx et al., 1997). The reported CV vary over a wide range, but the lower CV are more regularly found in studies of temporal changes of slurry composition within a farm and not in studies with slurries from different farms. With view to variable rate application of slurry, the lower CV, especially of pig slurry, are suitable for an exact application of slurry as the range of variation is moderate. For instance, at a rate of 22 kg P ha-1 a-1, with pig slurry 21-23 kg P ha-1 a-1 would be applied (Sharpley and Moyer, 2000). In contrast, with dairy cow and laying hens slurry the amount of P would vary between 18-26 kg P ha-1 a-1 and 17-27 kg P ha-1 a-1, respectively (Derikx et al., 1997; Hjorth et al., 2010). In contrast, the application of slurries with a higher CV is unlikely to result in a match of P demand and P rate. For example, the amount of P in pig slurry can vary from 3 to 41 kg P ha-1 a-1 (Sánchez and González, 2005). Here, technological processing is required, for example by separating of slurry into solids and liquids together with homogenisation of the product (see section “Strategies for manure production”). Another important aspect of variable rate application of slurry is related to the legal framework for manure application (see section “Legal framework for manure application”). At the moment, application rates follow the N demand with rates of up to 170 kg N ha-1 a-1. This means that together with 170 kg N ha-1 a-1, on average 27 kg P ha-1 a-1 (dairy cow slurry: N:P ratio 6.4:1, Table 4), 43 kg P ha-1 a-1 (pig slurry: N:P ratio 4:1, Table 4) and 49 kg P ha-1 a-1 (poultry slurry: N:P ratio 3.5:1, Derikx et al., 1997) will be applied. With a view to a sustainable use of the finite resource P it will be necessary to base the maximum manure rate on the amount of P applied. This would mean that with 22 kg P ha -1 a-1, on an average 141, 88 and 77 kg N ha-1 a-1 would be applied with dairy cow, pig and poultry slurry. Such procedure would enforce the need for alternative uses and marketing of slurry.

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European

Union

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In the following sections, procedures for variable rate application of slurry have been summarized which assume a variation of the mineral content that does not conflict with original purpose of merging P demand and P rate. 5.2

Online-Measurement of manure composition

Slurry is a heterogeneous mixture, which composition varies over time and only if the range of variation is acceptable, variable rate input is recommended (see above). Still it is advisable to measure the manure composition before application in order to determine changes of nutrient loads. For variable-rate application, changes in the nutrient content of slurry are registered preferably on-line. Modern spreading machines automatically control slurry application on a volumetric basis so that nutrient output can be adjusted (Saeys et al., 2008). A relatively basic instrument for manure analysis is a hydrometer measuring the specific gravity of slurry. This is also called slurry meter (Tunney et al., 1985). Those hydrometers are calibrated to the solid concentration, which is in turn related to nutrient contents. Nutrient regressions have been presented e.g. by Piccinini & Bortone (1991) and Zhu et al. (2003). However, the slurry has to be mixed before measuring and the density measurements are restricted to a maximum solid content of 8% dry matter (DM) for pigs and of 6% DM for cattle, respectively (Tunney et al., 1985). Alternatively, the solid content can be measured ultrasonically (Scotford et al., 1998, Chien et al., 2000). This method can determine solid contents up to 40%, but an important disadvantage is that air bubbles distort the measurement. A similar method is to measure the electrical conductivity by electrodes and to correlate it with the nutrient content. This approach worked for N, but failed for P, as the P content correlates stronger with the content of solids (Provolo & Martinez-Suller 2007). To overcome this problem, electrodes for electrical conductivity could be linked with devices for measuring the solids (Scotford et al., 1998). A direct method for nutrient measurements is the use of ion-sensitive electrodes. Ready-touse ion-sensitive electrodes for N and K have been presented by the machinery company Wienhoff (Bawinkel, Germany). They stated the precision of the measurement with 90% (Wienhoff, 2010). Scotford et al. (1999) introduced the combined use of several sensors like ion-sensitive electrodes, pH electrode and electrical conductivity measurements. However, such expensive equipment is very rarely used by farmers. Infra-red spectroscopy has also the capability to determine all nutrients simultaneously. It is an indirect method, which uses near infra-red spectra and a calibration model to predict nutrient contents. Yet, only preliminary studies for the feasibility of infra-red spectroscopy for nutrient determination in slurry have been conducted (e.g. Millmier et al., 2000; The project is partly financed European Regional Development Fund

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Zimmermann et al., 2008). The machinery company Zunhammer (Traunreut, Germany) offers a slurry tanker with near infra-red sensor for the on-the-go measurement of N concentration (prediction error