Priority measures
for reducing nitrogen and phosphorus
losses from agriculture
and water protection
Prepared by:
Work package 3
Stefan Pietrzak, Institute of Technology and Life Sciences in Falenty (ITP),
Poland
October 2012
2
Content
Introduction ...................................................................................................................................................... 3
1. Promoting long-term grass cultivation of arable land ............................................................... 4
2. Vegetative cover in autumn and winter of arable land .............................................................. 5
3. Soil tillage management ......................................................................................................................... 6
3.1. Reducing soil tillage ......................................................................................................................... 6
3.2. Time-of the year effects .................................................................................................................. 7
4. Fertilisation management ..................................................................................................................... 8
4.1. Adapting the amounts of chemical and organic fertilisers applied ............................... 8
4.2. Calculating nutrient balances on farm and/or field level ................................................. 9
4.3. Avoiding the spreading of chemical fertilisers and manure during high-risk
periods ................................................................................................................................................ 10
4.4. No or reduced phosphorus fertiliser for high soil phosphorus fields or part
of fields .............................................................................................................................................. 11
5. Improved spreading technology for manure and chemical fertilisers .............................. 12
5.1. Site-specific dosage ....................................................................................................................... 12
5.2. Combi-drilling ................................................................................................................................. 13
5.3. Incorporation .................................................................................................................................. 14
5.4. Liquid manure ................................................................................................................................. 15
5.5. Solid manure .................................................................................................................................... 16
5.6. Manure spreading and ammonia emissions – general measures ............................... 17
6. Avoiding the application of chemical fertilisers and manure to high-risk areas .......... 19
7. Measures to optimise soil pH and improve soil structure ..................................................... 20
8. Adapted feeding ...................................................................................................................................... 21
8.1. Adopting phase feeding of livestock ....................................................................................... 21
8.2. Reducing dietary nitrogen and phosphorus intake .......................................................... 22
8.3. Phytase supplementation ........................................................................................................... 23
8.4. Wet feed and fermentation ........................................................................................................ 24
9. Reducing ammonia losses in animal houses ................................................................................ 25
10. Storage of manure ............................................................................................................................... 26
11. Constructed wetlands for nutrient reduction/retention ..................................................... 27
11.1. Sedimentation ponds .............................................................................................................. 27
11.2. Constructed wetlands ............................................................................................................. 28
12. Buffer zones along water areas and erosion-sensitive field areas .................................. 29
References ...................................................................................................................................................... 30
3
Introduction
Agriculture is the largest anthropogenic source of nutrients, introduced to the Baltic
Sea, which mainly contributes to its eutrophication. Eutrophication causes several adverse changes in the sea flora and fauna (is considered the most important environmental
problem of the Baltic Sea), and causes great social and economic losses. In order to counteract it, some efforts have been undertaken for many years – both common and on the
level of individual countries in the region – aimed at reducing the amount of nitrogen and
phosphorus compounds discharged to the Baltic Sea waters from agricultural sources. To
solve this problem, the international project Baltic COMPASS (Comprehensive Policy Actions and Investments in Sustainable Solutions in Agriculture in the Baltic Sea Region)
has been launched for the years 2009–2012. The project involved 22 partners from 9
countries in the Baltic Sea Region: Belarus, Denmark, Estonia, Finland, Latvia, Lithuania,
Germany, Poland and Sweden. It was designed as (panbaltic) regional platform where
participants and stakeholders can develop more efficient agro-environmental policies,
share innovations and best practices, create scientific scenarios and facilitate investments. Win-win solutions for agriculture and environment are fostered within the Baltic
Compass leading thus to more sustainable rural economies – in effect also friendly to the
Baltic Sea. Such solutions have been proposed, among others, by the team implementing
the third work package (WP3) of the Baltic Compass project called „Best Practice Utilization and Transfer”. Work package 3 has compiled a list of 25 prioritized measures [Description …] in 12 categories that can be used by farmers to reduce nitrogen and phosphorus leakage. They include i.a. the soil tillage management, fertilisation management and
improved spreading technology. Many of these measures are well known in BSRcountries but were not fully implemented (there is also a large variations as to what is
used among countries and within countries). The prioritized measures have been used by
the partners in the WP3 group to produce this brochure as a form of training material on
how to conduct environmental-friendly farming methods, for the authorities, organisations and farmers from the Baltic Sea countries. The dissemination and practical implementation of the knowledge contained here can significantly reduce nitrogen and phosphorus losses generated by agriculture in the Baltic Sea region and in this way contribute
to the improvement of water quality of this sea.
4
1. Promoting long-term grass cultivation on arable land
Nitrate, mg/l
An efficient way of reducing plant nutrient losses from arable land during the autumn
and winter is to keep the land under vegetative cover (green land) during this period,
particularly in areas with light soils and mild climate.
Both permanent and tem120
porary grasslands have the
100
potential to efficiently reduce
nutrient losses. Cultivation of
80
temporary grass or leg60
ume/grass crops in the crop
rotation can reduce nitrogen
40
and phosphorus leaching and
20
surface run-off losses, as well
as soil erosion, compared with
0
Arable
Mixed
Grass
only annual crops in the crop
rotation. Grasslands can be
Nitrate concentrations in leachate from fields within England
surface water NVZs, winter 2005/6; source: ADAS for Lord et al.
both extensively and inten(2006)
sively managed.
Low input grazing-based meat production is often practised on land where alternative land use is restricted and where the grazing may contribute to the maintenance of
high species diversity of the wild flora and fauna. The external nutrient inputs are generally small, as are the area stocking rates and productivity. Forage and grazing-based meat
or milk production can have a ten-fold higher nitrogen input, corresponding to the application of 200–400 kg nitrogen per hectare and year, and a high productivity.
Most of the beneficial environmental impacts of grasslands are highly site- and management-specific. Long-term continuity of grassland use is of importance, especially regarding the objectives related to biodiversity and the storage of soil carbon. Temporary
grassland contributes to environmental objectives such as soil and water protection, but
regular ploughing and conversion to arable crops might be crucial due to potential discharge of carbon and nitrogen, and is detrimental for biodiversity.
Temporary grassland [source: JTI – Swedish Institute
of Agricultural and Environmental Engineering]
Extensively managed grasslands [source:
JTI]
5
2. Vegetative cover in autumn and winter on arable land
Soil water nitrate, mg N/l
Annual winter crops, such as winter wheat or winter rape, can provide a vegetative
cover that actively takes up available nitrogen and phosphorus from the soil more efficiently than annual spring crops in a seasonal period with high precipitation and cool
climate.
200
Catch crops are fast-growing
Rye (5kg/ha lost)
crops that can be under-sown in the
Fallow (147 kg/ha lost)
175
main crop simultaneously or just af150
ter sowing of that main crop. When
the main crop is harvested, the catch
125
crop has an established root system
100
ready to take up nitrogen from the
soil during late summer and autumn.
75
Nitrogen that could otherwise have
50
been leached is then taken up and
incorporated into plant biomass. The
25
immobilised N will be released to the
0
soil again, in the moment of terminaOctNovDecJanFebMaApr96
96
96
97
97
97
97
tion of the catch crop growth e.g. by
Date
tillage. The catch crop is ploughed as
late as possible in autumn, or in
An example of overwinter nitrate concentrations under
bare soil plots and plots on which fodder rye was growspring. The selection of plant species
ing. This trial was set up directly after the incorporation
used as catch crop depends on cliof a grass/clover ley [HDRA]
matic and soil conditions.
Depending on soil conditions in
Poland the recommended crops are:
a) for weaker soils: yellow lupine,
serradella, phacelia and rye; b) for
medium soils: fodder pea (field pea),
sunflower, blue lupine, white mustard, radish, winter vetch; c) for fertile soils: edible beans and vetch,
rape and turnip rape. In the Scandinavian countries like Sweden and
Denmark grasses are often grown, for
example the perennial ryegrass (Lolium perenne L.) that is an effective
measure to reduce nitrogen leaching
in spring cereal crop production.
White mustard as stubble intercrop [photo: L. Zimny]
The benefits of growing the catch crops are the protection of soil surface and interception of surplus nutrients. Nitrate leaching is the smaller the longer the soil is covered
by vegetation. The effect of the catch crop on nitrogen leaching depends also on precipitation and drainage conditions, on the amount of available nitrogen in soil and on how successfully the catch crop may establish. Catch crops, apart from reducing nitrate leaching,
may also retain and recycle available P in the root zone, increase the amount of organic
matter in the soil and improve the soil structure.
It is relatively easy method to implement. It needs only buying and sowing the seeds,
and finishing the catch crop.
6
3. Soil tillage management
3.1. Reducing soil tillage
Organic matter content, %.
The traditional system of soil cultivation based on ploughing and other mechanical
treatments destroys the natural structure of soil, causes it’s over drying and accelerates
the mineralisation of organic matter. Organic matter losses after two decades of intensive
tillage may sometimes reach up 50%.
Reducing soil tillage can reduce
110
mineralisation of organic matter in soil
100
which contributes to the reduction of
90
nitrate leaching. In relation to tillage
80
system, two alternative systems can be
70
identified: a) conservation tillage
60
(ploughless); b) no tillage (direct seed50
ing).
Ploughless system (conservation
40
tillage,
simplified) is the mechanical
30
0
10
20
30
40
50
60
tillage of the soil surface without the
The number of years of intensive tillage
use of a plough (to a depth of 10–12
cm) or the tillage with deeper soil loosChanges in organic matter content [Smagacz, 2011
ening (up to 25 cm).
after Kinsella, 1995]
In this system the following equipment is used: cultivators with rigid legs (grubbers),
rotary or disc harrows, soil aggregates (used for complex grinding and loosening the soil).
These devices do not turn the soil, but strongly loosen and mix it. About 30% of crop
residues remain on the soil surface before sowing. For sowing seeds it is necessary to use
special drills, usually with disc tines.
No-tillage system is the sowing of seeds into the soil after harvest of previous crop
using special drills for direct seeding. The basic machines used in this system are drills of
different coulter construction, harrows, rotary cultivators, combined.
Cultivation agregate [photo: H. Zelenko]
Drill for direct seeding [photo: Hagenlocher]
It should be noted, that resignation from soil ploughing and using minimal or no cultivation systems also contributes to the lowering of phosphorus losses. Soil cultivation
with discs or tines, or using direct drill into stubbles (no-till) preserves organic matter in
soil and maintains its proper structure. Thanks to the improved infiltration and water
retention, total phosphorus concentrations in surface runoff are limited [Examples…].
7
3.2. Time of the year effects
Nitrate - N, kg/ha
Nitrogen, kg/ha
The time of soil tillage has a considerable impact on the process of nitrogen mineralisation in the soil and to some extent also on the amount of nitrate leached from the soil.
The process of N mineralisation is strongly influenced by soil temperature, moisture and
N balance under the previous crop. In temporary grassland, mineralisation process is
greater for grazed than for cut swards. It is also enhanced by increasing application of N
fertiliser or manure during the grass ley phase. Autumn cultivation, because of the warm
and moist soil conditions at this time and a lack of actively growing crop, stimulates the
process of mineralisation in the soil and increases the risk of nitrate loss. During the following winter period the accumulated nitrate is transported out of the soil profile by
drainage.
Autumn cultivation of land enhances the N mineralisation from
80
organic matter reserves at a time of
Early autumn ploughing
70
small nitrogen uptake by the crop
Spring ploughing
and increases the potential nitrate
60
leaching in the winter time. Land for
50
spring crops, ploughed in late autumn, is subjected to the winter frost
40
action and to wetting and drying cy30
cles to break down soil clods. Spring
cultivation is better than the autumn
20
one. It gives less opportunity for
10
leaching mineralised nitrogen. In
spring time bare soil is not exposed
0
to the harsh winter conditions.
August
September
November
December
April
Spring crops established soon after
Average soil mineral nitrogen content in the tillage
cultivation are able to take up nitrotreatments for each sampling occasion from yellow
ripeness [Stenberg et al., 1999, modified]
gen and provide surface cover.
Therefore arable land for spring crops and grasslands should be cultivated in spring
rather than in autumn. However, delaying primary tillage operations reduces grain yields
and causes the problems with perennial weeds, but a catch crop such as perennial ryegrass may reduce the problem. Ploughing in the autumn also allows early establishment
of the following spring crop as only secondary cultivations are required ahead of drilling.
150
On medium to heavy soils,
the delayed cultivations may
Early autumn ploughing
result in the spring crop being
Spring ploughing
drilled into a drying seedbed.
100
This may affect crop establishment and yield. Delaying
cultivation until the spring
may also have implications for
50
the control of some weeds.
There are also soil structural
implications associated with
cultivation during a wet
0
1993
1994
1995
1996
spring. For grassland, reseedYear
ing in spring is less reliable
Accumulated nitrate leaching (kg/ha) [Stenberg et al., 1999, modithan in autumn.
fied]
4. Fertilisation management
8
4.1. Adapting the amounts of chemical and organic fertilisers applied
Animal density is a measure of the number and type of animals kept in a farm in relation to the arable area available for spreading their manure (RAMIRAN, 2010). Animal
density is used as a tool to balance the amounts of nitrogen and phosphorus produced in
manure to available spreading area in the farm in order to avoid excess application of
nitrogen and phosphorus with manure.
Considering crop requirements for nitrogen and phosphorus in the fertilisation plan
is essential in order to avoid excessive application. The content of nitrogen and phosphorus in manure must be considered in the fertiliser plan in order to adjust the need for
chemical fertilisers and to avoid excessive application.
Sampling and analysing nitrogen and phosphorus in manure provides information on
their concentrations and the distribution of plant-available nitrogen (NH4-N + NH3-N) and
organic nitrogen. The effect of manure can then be valued in the fertilisation plan. Manure
characteristics can vary widely. Liquid manure is a general term that denotes any manure
from housed livestock that flows under gravity and can be pumped (RAMIRAN, 2010).
Liquid manure can have a high proportion of plant-available nitrogen in the total nitrogen
content. Solid manure is a general term that denotes any manure from housed livestock
with large amounts of bedding that does not flow under gravity, cannot be pumped but
can be stacked in a heap (RAMIRAN, 2010). Solid manure can have a high proportion of
organic nitrogen in the total nitrogen content.
Sampling and analysing nitrogen and phosphorus in arable soil provides information
on soil fertility concerning these nutrients, which should be considered in the fertilisation
plan in order to avoid excessive fertiliser applications or decline of soil fertility.
The fertiliser plan describes fertiliser recommendations based on the analysis of soil
and crop requirements. The plan also consists of the sustainable management tips and
advice on safe use of fertilisers for different crops. The fertiliser plan should be made for
each crop in each field before any nitrogen or phosphorus fertiliser is applied. The plan
should include [Guidance…, 2009]:
Analysis of nitrogen and phosphorus in the soil, which may be
available for crops during the
growing season;
Estimation of the optimum
amount of nitrogen and phosphorus, which should be used
during cultivation, taking into
account the supply of these
components from the soil;
Calculated amount of nitrogen
and phosphorus from any
planned use of organic fertiliser,
which may be available for crops
during the growing season;
Calculated amount of fertilisers
that should be delivered to the Preparation of fertiliser plans in farms are supported by
soil to meet the nutritional re- appropriate computer programmes [Plano...]
quirements of the crop.
9
4.2. Calculating nutrient balances on farm and/or field level
Calculating nitrogen and phosphorus balances on farm and/or field level is a performance tool and a policy tool for assessing the environmental impact. The tool can also
be used to monitor and evaluate the impacts of alternative manure and chemical fertiliser
management practices and technologies of nitrogen and phosphorus use in the farm.
When farm nitrogen and phosphorus balances can be linked to within-farm sources and
flows, there is a good possibility of identifying the weakest link and possible improvements for the farm. The tool can be used to assess the risk of ammonia losses from manure management and the risk of nitrogen leaching to water.
Nitrogen and phosphorus balance is calculated as the difference between the amount
of elements brought to the farm and removed from it (at the gate of the farm) or between
the input and output from agricultural land (on the surface of the field). The difference
represents the surplus of N and P.
Inputs
Outputs
Forage
Concentrations
Plant products
Animal products
Animals
Crop
Manure
Fertiliser
Seeds and planting material
Atmospheric deposition
Biological nitrogen fixation
Surplus
Soil
Schematic nutrient balance "at the farm’s gate" with selected nutrient circulation within the farm [from
Oenema, 1999, modified]
Inorganic
fertiliser
Manure
Biological
Nitrogen
Fixation
Atmospheric
deposition
Agricultural land
Harvested crop
production
Grass and
fodder crop
production
Organic
fertiliser
Seeds and
planting
material
Inputs
Surplus
Outputs
Balance "on the surface of the field" [OECD, 2001]
Results of the nitrogen and phosphorus balance can provide a background for practical proposals to reduce the environmental impact of agriculture and to improve farming
economy. The latter aspect results from the fact that more efficient use of nutrients
means lower costs of chemical fertilisers or feeds.
10
4.3. Avoiding the spreading of chemical fertilisers and manure during high-risk periods
The timing of chemical fertiliser and manure application is a key factor in achieving
high efficiency of nutrient use. Inappropriate timing is one of the most important sources
of large nitrogen leaching loads.
Fertilisers should not be used in times and conditions when the mineral nutrients,
especially nitrogen, are vulnerable to leaching to groundwater or to runoff to surface waters. This applies especially to the winter period but also to other periods, depending on
soil type, rainfall intensity and soil cover.
The winter period, depending on atmospheric precipitation and temperature, may be
characterised by a very different course of weather conditions from warm and humid to
dry and cold. The weather can vary widely and therefore fertilisers should not be applied
when the soil is frozen and covered with snow – even during a periodic warming.
In other periods, fertilisers should not be applied when the soil is not sown or plants are not
very advanced in their growth, and in the case of expected larger precipitations. This applies
primarily to the very light and light permeable soils, especially if they are very wet at the moment.
The figure below shows a representation of the interaction between N uptake by crop
and mineral N level in soil for arable crops. Nitrogen uptake is rapid in spring and summer periods. In case of correct estimation of fertiliser inputs, the concentrations of nitrate
are small by late summer. However, once the growth of plants slows and then stops (in
July for cereal crops) then the next amounts of nitrate created in results of natural soil
processes is no longer balanced by plant uptake, and thereby the concentrations of nitrate increase. If some or all of the nitrates present in soils are not taken up by plants they
will be leached during autumn [ADAS, 2007].
300
Crop N uptake
Soil Nmin
Crop senecence
Soil mineral N or N uptake, kg/ha .
250
Fertiliser
application
200
Crop harvest
150
Declines due to
crop uptake
Declines due to crop
uptake
Nmin Declines due to
leaching (& crop uptake)
Soil Nmin increases dou to
mineralisation of residues and soil
OM with minimal crop N uptake
100
Fertiliser
application
50
Criop established.
Some N uptake
Crop enters phase
of rapid N uptake
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Month
Exemplary nitrogen dynamics showing the risk of N leaching and the synchronicity between N supply from
the soil and N uptake by crop [ADAS, 2007]
11
4.4. No or reduced phosphorus fertiliser for high soil phosphorus fields or part of
fields
Runoff total dissolved P in runoff, mg/L
Phosphorus (P), because of its relatively large amounts required for plants growth, is
an essential element classified as a macronutrient. Appropriate P availability for plants
stimulates early plant growth and accelerates maturity. Despite the fact that P is needed
for plant growth, poor P management in soil may pose a risk to water quality. In fresh
waters the concentration of P is usually low enough to inhibit algal growth. In case of P
polluted lakes and rivers, excessive growth of algae is observed [Schierer at al. 2007].
There are three categories of P losses from agricultural lands: a) flash losses of soluble forms of phosphorus shortly after manure or fertiliser application, b) losses of soluble
phosphorus as a result of slow leaking or c) erosion processes [Wiederholt, Johnson
2005].
There is a positive relationship between the content of mobile forms of P in the upper
soil layer and their content in the water runoff. There is also strong evidence that the
concentration of soluble phosphorus in runoff increases linearly with increasing records
of soil test for phosphorus.
When the soil phospho2
rus increases beyond the
Loam
Silt Loam
agronomic optimum range,
1,5
y = 0,0022x + 0,143
there is a reasonably consistent pattern whereby phosphorus leaching increases
1
significantly.
y = 0,0007x + 0,143
Soil testing is the most
efficient
tool in phosphorus
0,5
management. Soil test reveals soil pH, the content of
0
phosphorus in soil and
0
100
200
300
400
500
600
identifies the recommended
Mehlich-3 soil test phosphorus, mg/kg
dose of phosphorus for the
Total dissolved P in runoff as a function of Mehlich-3 soil test phosgrowing crop.
phorus for different soils [Schierer at all., 2007, modified]
100,0
Relative crop yeld, %
However, phosphorus
leaching
shows a large spatial and temporal
variability and can
be influenced by
several factors interacting with each
other. It is, therefore, important to
consider
sitespecific factors in
order to identify
measures to reduce
phosphorus leaching.
80,0
Potential environmental
problems
60,0
40,0
20,0
0,0
Lov
Medium
High
Excessive
Soil test P
Relationship between the relative crop yield and the soil test P levels and
a range of potential environmental problems [Rehm et al., 2002]
12
5. Improved spreading technology for manure and chemical fertilisers
5.1. Site-specific dosage
In all fertiliser applications, the use of Global Positioning System (GPS) to determine
the current location of equipment on the earth’s surface can improve the possibilities for
controlled and proper distribution. GPS devices provide latitude and longitude information, and some can also calculate altitude. GPS in combination with steering aid systems
means that the fertiliser can be spread with a minimum of bare spots and overlaps. The
simpler version of the steering aid system is called guidance, where a ramp with a series
of LEDs shows whether the driver is located right on line, or whether the vehicle should
be steered to the right or left. Auto steer is an automated steering system where the driver
does not need to actively steer the vehicle except perhaps on curves or when turning.
[source: JTI]
[source: Agri Con GmbH]
Schematic use of the GPS for driving fertiliser application equipment
With the GPS it is also possible to reproduce various field properties and to use that
information for applying precise mineral fertilisation (fertilisation adjusted to soil richness in nutrients in a definite place of the field). To develop a plan for variable-rate fertiliser application in a particular field, the map-based method should include the following
steps:
systematic soil sampling and analysis for the field;
generation of the site-specific maps concerning the soil nutrient properties;
use of an algorithm developing a site-specific fertiliser application map;
use of the application map for controlling a variable-rate fertiliser applicator.
A positioning system
is used during the sampling and application
steps to continuously
know or record vehicle
location in the field. Application of the precise
fertilisation system allows for: a) decreasing
fertiliser consumption,
b) increasing the effectiveness of fertiliser use
by plants (due to their
better distribution in the
field), c) decreasing nutrient losses, d) improvAn illustration of a map-based system for varying crop input application
rates [Ess et al., 2001]
ing fertilisation profitability.
13
5.2. Combi-drilling
Combi-drilling involves placing seed and fertiliser in the soil using a single machine
in one work operation. A seed drill with normal distance between the seed coulters is
equipped with coulters for chemical fertiliser placed between alternate rows in front of
the seed coulters. The fertiliser coulters place the chemical fertiliser a few centimetres
deeper than the seeds.
Placing chemical fertiliser at this depth provides good conditions for germinating
seedlings to take up the added nutrients. In addition to time savings and better nutrient
use efficiency, combi-drilling reduces the competition for plant nutrients from weeds and
reduces the risk of nutrient surface runoff. Phosphorus in fertilisers binds quickly to soil
particles and is thus less exposed to leaching.
The recommended nitrogen dose for a particular yield level can be reduced by 10 kg
N/ha if combi-drilling is used. Leaching is probably reduced by 1–2 kg N/ha compared
with other fertilisation techniques.
Aggregate for the simultaneous sowing of seeds and fertilisers [Nilsson, Nilsson, 2005]
Coulter assembly in the aggregate for the simultaneous sowing of seeds and fertilisers [Nova Combi]
14
5.3. Incorporation
Incorporation of manure and chemical fertilisers can be achieved with equipment
such as plough, disc or tine cultivators, depending on soil type and soil conditions. Incorporation is usually performed in a separate work operation. The manure/mineral fertiliser must be completely incorporated into the soil to achieve maximum efficiency.
As regards liquid
manure, incorporation
should
take
place
quickly after spreading, as ammonia losses
begin immediately after
spreading.
To
achieve
worthwhile
abatement, incorporation is recommended
to be completed within
6 hours of spreading.
The most effective often considered method
of incorporation is to
bury completely the
liquid
manure
by Rapid slurry incorporation into the soil [Frandsen et al., 2011]
ploughing.
However, ploughing is a relatively slow operation. Therefore, in some circumstances,
the use of a tine or disc cultivator may be more effective because the slurry will remain
exposed on the surface for a shorter time. Injection of liquid manure (see section 5.4.)
plays the same role as incorporation.
Incorporation of solid manure applied on field surface is an efficient method of lowering ammonia emissions. The highest losses of ammonia take place within a few hours of
spreading. It is recommended, therefore, that incorporation should be done within 24
hours. For maximum reduction of losses the manure must be completely buried. It is often more difficult to achieve this with some solid manures (e.g. those containing large
amounts of straw) than with slurries. Ploughing is usually the most effective means of
incorporation. Other methods of incorporation, such as disc or tine cultivators, can be
also effective depending on the manure and soil characteristics. Incorporation is only
possible before crops are sown.
The spread fertiliser should be immediately incorporated into the soil through tillage
also to prevent the nutrients losses through runoff, erosion or volatilization and to retain
a greater proportion of applied nutrients for crop uptake. Thanks to incorporation, these
nutrients are mixed into the surface soil layer where roots are able to intercept them.
It is known that incorporation of manure prevents from the direct surface runoff of
solids and phosphorus. However, plots where manure was incorporated through tillage
show higher soil loss than untilled control plots. Therefore, it is recommended to incorporate in such a way as to maintain surface residues through such minimum tillage methods as knifing or injection.
15
5.4. Liquid manure
Liquid animal manure can be applied by a variety of methods including land surface
spreading, subsurface injection and spray irrigation.
The most effective method with respect to ammonia loss reduction during and following application is the direct injection of slurry or liquid manure into the soil or their
distribution with the use of band spreading technology
Direct injection can reduce nutrient emission through direct introduction of manure
beneath the soil surface. It decreases the manure exposition to air and increases its infiltration into the soil. In this system, liquid manure tankers may be used with three main
types of injectors:
shallow (or slot) injectors – cut narrow slots in the soil (usually 4–6 cm deep and 25–
30 cm apart) that are filled with liquid manure or slurry;
deep injectors – apply liquid manure or slurry to a depth of 12 – 30 cm in the soil with
the use of injector tines spaced about 50 cm apart;
arable injectors – are based on spring or rigid tine cultivators and are only intended to
be used on arable lands.
The injection of liquid manure means that the fertiliser is applied directly into the active soil layer, either in open or in closed slots. Manure is fully covered after injection by
closing the slots with press wheels or rollers fitted behind the injection tines. Closed-slot
injection is more efficient than open-slot in decreasing ammonia emissions. To obtain this
added benefit, soil type and conditions must allow effective closure of the slot.
Application of band spreaders can reduce nutrient emissions from slurry and liquid
manure through decreasing the manure exposition to the air and the flow of air over it.
Two main types of machines can be used in this system:
trailing hoses – slurry is discharged at ground level to grass or arable land by a series
of flexible hoses (the application between the rows of a growing crop is possible);
trailing shoes (or feet) – slurry is simply discharged by rigid pipes which end with
metal “shoes” designed to ride on the soil surface, separating the crop so that slurry is
applied directly to the soil surface.
As the liquid manure is distributed to trailing hoses/shoes via a ramp, good and uniform lateral distribution is achieved. The spread in the longitudinal direction can also be
kept at a constant level by means of the pumping equipment. Some newer spreaders are
also equipped with a control system that automatically adjusts the output to the driving
speed, which keeps the application rate at the desired level.
Manure spreader applicator for shallow injection of
liquid manure [photo: P. Nawalany]
Manure spreader with trailing hose system [photo: JTI]
16
5.5. Solid manure
Rate ton/ha
Solid and semi-solid manure, other types of organic fertilizers obtained from solid
manure subjected to separation or composting and other materials have highly variable
consistency and physical properties. For instance, composted manure usually has a finer
and more uniform particle size distribution than raw solid manure.
Manure spreaders should
45
ensure an even and accurate
40
distribution of each type of ma35
nure, both fresh and composted
30
Uniformity of application is
25
important in order to ensure
that plants will have good access
20
to nutrients across the whole
15
field. It is also essential for
10
minimising environmental risks.
5
Unfortunately, the application of
0
manure by many spreaders (es0,6 0,9 1,5 1,8 2,7 3,0 3,3 4,2 4,8 5,1 5,4
pecially by older models) is ofSwath, m
ten non-uniform: the rate of apSpread distribution from a single pass of a rear-discharge dry
plication is higher directly bemanure spreader (example). Notice the 18-foot swath width
hind the spreader than off to the
[Adaped from: Lorimor, 2000]
side of the spreader.
Even spreading of manure ensures that there will be no places on the field, which are
poorly or excessively covered with manure and, consequently, plants are over fertilised
or have deficiencies of nutrients. An even spreading of manure causes even intake of nutrients by plants, this prevents their leaching into the soil.
Solid manure may be spread only with manure spreaders that are in good working
order and are suited to spread the specific type of manure. The most important working
element determining the quality of a spreader is an adapter spreading the manure. In addition to the adapters with the axes set horizontally there are also elements with vertical
axes of the drum, whose number may be 2, 3 or 4. There are also one-drum spreaders
with a group of beaters and side ejection.
Manure spreaders at work [photo: Chatellier]
View of manure spreading with spreader equipped with
two vertical drums and shredding system [photo: P.
Nawalany]
17
5.6. Manure spreading and ammonia emissions – general measures
Most attempts to reduce ammonia losses from livestock production relates to the
land application of manure because this practice significantly contributes to the total
ammonia losses from agriculture. Ammonia losses resulting from the land application of
manure could reach 95 per cent of the total nitrogen-ammonium (N-NH4) content in manure.
Ammonia emitted to the atmosphere is rapidly removed from it; within the period
ranging from several hours to several days it returns to the surface in the form of dry or
wet precipitation. Dry deposition of ammonia is usually found near sources of its emission (within the range of about 1 km), while wet deposition can take place even at a distance of hundreds of kilometres from these sources.
Gas to particle
conversion
Atmospheric lifetime
1-3 hours
NH3
HNO3
H2SO4
Precipitation
scavenging
NH4+
aerosol
Lifetime
1-3 days
Dry deposition
Wet
deposition
NH3
BIOSPHERE
Behaviour of ammonia in the atmosphere [Tang et al., 2005]
The main mechanism for removing ammonia from the air is the reaction with sulphuric acid and nitric acid. These acids reacting with ammonia form ammonium salts,
ammonium sulphate (NH4)2SO4, and ammonium nitrate NH4NO3. As less volatile they
form molecules and reach the soil in the form of either dry or wet deposition. This deposition poses a serious threat to the environment by contributing to soil and water acidification and to eutrophication of aquatic and terrestrial ecosystems. Ammonia also accelerates the corrosion of metal structures and buildings and has a detrimental effect on human body. It has been estimated that in 2005 approximately 208,000 tons of nitrogen
were deposited into the Baltic Sea from the atmosphere [Bartnicki et al., 2007], which
constitutes about 25% of the total nitrogen discharged to the Baltic Sea from different
sources. Within the overall atmospheric N deposition, ammonia constituted 92,000 tons
(approx 44%), and the remaining was represented by nitrogen oxides [based on Bartnicki
et al., 2007].
Factors significantly affecting NH3 emissions after manure spreading include the soil
water content, air temperature, wind speed, manure type, dry matter content of manure,
total ammonia nitrogen in manure (TAN=NH3-N+NH4-N), application method and rate of
manure incorporation. Losses of NH3 may vary between 3 and 90% of the NH4-N applied
with manure.
18
The most effective strategy for reducing ammonia emissions during or after field application of manure is minimising the time of manure exposure on the ground surface.
The following best management practices for the reduction of ammonia volatilisation
after land application of manure are currently available:
direct injection of liquid manure into the soil – used injectors reduce ammonia emission by direct placing the manure under the soil surface, thus decreasing the manure
surface exposed to the air and increasing its infiltration into the soil,
band spreading of liquid manure on the soil surface but beneath the crop canopy using
drop hoses or trailing shoes (or feet) – the ammonia loss is reduced due to immediate
absorption of NH3 by plant leaves and roots; reduced surface of exposed slurry and
canopy modified microclimate disfavour ammonia volatilisation;
the incorporation of manure immediately after spreading – manure incorporation by
burying the majority of manure (by ploughing, harrowing or using cultivators) reduces
the losses of NH3 (proportionally to the depth of incorporation).
Practical considerations in the selection of ammonia abatement techniques for land
spreading manures [UNECE framework…]
Abatement technique
Reduction in emission
Restriction on applicability
Trailing hoses
10–50%
Field slope, size and shape. Not viscous
slurry. Width of tramlines for growing
cereal crops. Height of crop is a factor on
arable land.
Trailing shoe
40–70%
As above.
Shallow injection
open slot 50–70%;
closed slot 70–90%
As above. Not stony or very compacted
soils.
Deep injection (including
arable injectors)
70–90%
As above. Needs high powered tractor.
Incorporation into soil
20–90%
Land that
ploughed.
is
cultivated
preferably
In addition to the methods indicated above, the loss of ammonia from manure during
application may be reduced by:
selecting the appropriate application date – the emission of ammonia is largest on hot,
dry and windy days, so the use of fertilisers during cool, windless and humid days
helps reduce the emission;
diluting the slurry – diluted slurry infiltrates into the soil easier than the natural (due
to lower viscosity) – a drawback of this approach is that it greatly increases the volume
of distributed liquids (dilution of slurry with water can reduce ammonia losses by 44
to 91%);
mechanical fractionation of manure – separate application of liquid manure fraction
contributes to the reduction of ammonia emissions during application due to its easier
penetration into the soil (as in the case of diluted manure).
19
6. Avoiding the application of chemical fertilisers and manure to high-risk
areas
Examples of high risk areas on arable lands are those with a significant slope, with
flushes draining to a nearby watercourse, soils with cracks over field drains (troughs in
soil surface created by surface water to flow directly to groundwater), fields adjacent to
water, or fields with phosphorus content beyond the agronomic optimum range.
High-risk areas are the areas particularly exposed to high risk of rapid transport of solutes or suspended material to
watercourses. Wherever possible, the inputs of potential pollutants to these areas
should be avoided. The greatest P losses
are from eroded soil particles and by
leaching from soils rich in phosphorus. A
systematic application of chemical fertilisers and manure to these areas causes further increase in the surplus P content in
soil and increases its losses. Avoiding the
spreading of chemical fertilisers helps to
Soil erosion [photo: W. Schmidt]
prevent from the mobilisation and transfer
of pollutants from agricultural land to water, particularly in areas located close to
water courses (with a high degree of hydrological connectivity between the field
and watercourse). Avoiding the application of liquid manure to such areas reduces the danger of nutrients output with
overland flow or their flow directly to field
drainage system and further transport to
watercourses. The similar risk of losses of
soluble and suspended material exists
from solid manures. It will usually occur
Cracked soil [photo: Z. Kowalewski]
only after heavy rain following the manure
application.
Described method is most efficient in
preventing P losses, where the main way
of their transport is preferential flow and
surface run-off. Special attention should be
paid to excessive use of phosphorus fertilisation on fields with phosphorus content
Field adjacent to water [photo: P. Nawalany]
beyond the agronomic optimum range.
Phosphorus adsorbed on soil particles is lost in result of sediment erosion from fields
in surface and in drain flow. The amount of P lost with the transported soil depends on
the soil P reserves. The higher is the soil P-saturation, the grater are the amounts of P lost
in soil solution. Balancing P inputs with crop intakes, abandonment of P application to
soils with high P reserves and the amount of P supplied in fertilisers (chemical and manure) should all be taken into account together. Because the decline of high soil P reserves is a slow and gradual process, the expected results can be observed in the longer
term (>10 years).
20
7. Measures to optimise soil pH and improve soil structure
Nutrients are best available to plants at soil pH of 6.5–7.2. Even with a slight soil
acidification below 6.5 the absorption of some nutrients, including nitrogen and phosphorus significantly decreases.
Low soil pH and anaerobic conditions block the nitrification process, cause the loss of
gas and affect the instability of nitrates and nitrites, which finally are leached or transformed into molecular nitrogen. This is the most important reason of nitrogen loss in the
soil [Vademecum…]. On the other hand, both phosphorus in soil and from fertilisers is
permanently fixed with iron (Fe) and aluminum (Al) and immobilised at too low pH.
Liming accelerates organic
matter decomposition and nitrification, which proceed most efficiently when the soil pH is
slightly acidic or neutral. By improving soil aeration, liming prevents from negative denitrification processes that lead to nitrogen losses. Moreover, liming contributes to a better nitrogen intake by plants in the ammonium
form. Regulation of soil pH to
slightly acidic – neutral is also
very important in terms of the
growth of nitrogen-fixing bacteria.
The increase of pH causes
the gradual release of available
phosphorus, thus increasing its
utilisation from fertilisers and
soil.
The availability of most nutrients is the best around pH 6.5
[picture: Viljavuuspalvelu Oy]
As a result of liming,
phosphorus intake increases in some plants, for
example 2–3 times in corn,
by about 60% in oats and
by about 10–20% in clover
[Hołubowicz-Kliza, 2006].
Better utilization of
nutrients by plants means
that the risk of their loss is
lower.
Spreading lime [photo: M. Robinson]
21
8. Adapted feeding
Importance of adapted feeding
Matching dietary intake to the requirements of livestock can substantially reduce nutrients in excreta. In livestock production systems, low nutrient utilization efficiencies are
inevitable, since only a small proportion of nutrients ingested are actually retained. This
varies with livestock species, but is approximately between 13 and 28% N for dairy cows,
between 5 and 13% N for sheep, and between 4 and 10% N for beef cattle. Actual values
also differ with age; for example, in pigs the proportion of N retained has been calculated
to vary from 18% in piglets to 47% in weaned pigs, the corresponding values for P being
14% and 39%, respectively. Reproductive status is also important: more N and P are retained in sows during lactation than in dry sows.
Rations for livestock are often formulated with large safety “margins” so that nutrients can exceed nutritional requirements by as much as 30–50%. While this may not affect animal performance, it can result in excess application of both major and trace elements to soils via manure. On mixed farms with a high degree of crop and livestock integration, this should be less likely than on specialist farms focused only on purchased
feeds and animal products.
Changing diet to reduce environmental impact has cost implications. Commercial
feeds are often based on least-cost formulation, which oversupplies nutrients because
cheaper raw materials often have a poorer balance of amino acids and a lower digestibility. On-farm mixing of rations from arable crops produced on farm as well as crop residues or outgrades returned from the vegetable production often form an important part
of livestock diets. However, these feed components also need careful management and
analysis of nutrient content and dietary value to improve NUE (nutrient use efficiency).
8.1. Adopting phase feeding of livestock
Livestock at different growth stages or stages of the reproductive cycle have different
optimum nutritional requirements. Greater division and grouping of livestock on the basis of their feed requirements allows more precise formulation of individual rations. This
increases the animal’s nutrient use efficiency and results in reduced excretion of nitrogen
and phosphorus in fresh animal faeces and urine.
In pig feeding the fattening period can be divided into consecutive sub-periods (feeding phases). In any of these periods the level of protein in feed is closely adapted to the
needs of the porker and decreases with the animal’s growth. In growing pigs the percentage of protein in the feed should be reduced together with their growth due to the decreasing animal demand for protein. At the same time, an addition of lysine should be
used to improve the quality of protein.
According to some studies, 4-phase fattening and supplementation of protein with lysine (primary limiting amino acid for pigs) can reduce nitrogen excretion by pigs up to
66% when the addition of lysine is 7%.
Reduction of nitrogen excretion by the use of phase feeding and improving the quality of
protein, in kg N per porker [Potkański 1997 after Krichgessner et al., 1994]
1-phase feeding
Specification
Nitrogen uptake
Retention of nitrogen
Nitrogen excretion
in %
5.0
6.30
2.29
4.01
100
4-phase feeding
Lysine in the protein,%
5.0
5.5
6.0
5.66
5.14
4.72
2.26
2.26
2.26
3.40
2.88
2.45
85
72
61
6.5
4.35
2.26
2.09
52
7.0
4.04
2.26
1.78
44
22
8.2. Reducing dietary nitrogen and phosphorus intake
Farm animals are often fed diets with higher than recommended contents of nitrogen
and phosphorus as a safeguard against the loss of production arising from a deficit of
these nutrients. Surplus intake of nitrogen and phosphorus is not utilised by the animal
and is excreted with faeces and urine, leading to higher nitrogen and phosphorus content
in the manure. The nitrogen surplus is excreted with urine as ammonia which increases
the risk of ammonia losses. Therefore, a proportional balancing of nutrients in feed is a
key factor to ensure animal health and production requirements and to minimise adverse
environmental impacts. To improve nutrient use efficiency, all purchased and homeproduced feed components need careful management and analysis of nutrient content
and dietary value.
Ration balancing has the potential to ensure animal health and production requirements while minimising adverse environmental impacts. One example concerning dairy
cows: the reduction in dietary P from 0.48% to 0.38% can result in 30–35% decline in
faecal P excretion without compromising milk production or reproductive performance.
1,50
Faecal P, %
1,20
0,90
y = 0,0106x - 0,219
R2 = 0,7414
0,60
0,30
0,00
60
70
80
90
100
110
120
130
140
P intake, g/d
Relationship between P intake and faecal P in lactating dairy cows [Wu et al., 2001]
A helpful tool for reducing nitrogen and phosphorus in the diet of animals, and for
reducing the amount of excreted components is computer feeding programmes. They
enable to balance and optimise the feed formulations for farmed animals according to
their living and productive needs.
23
8.3. Phytase supplementation
The base of pigs feeding is fodders of plant origin of different abundance and accessibility of phosphorus (in the range between 3 and 12 g/kg dry feed). Phosphorus is present in them in two forms: phytic (not absorbable) and non-phytic (absorbable). The biggest amounts of phytates are present in cereal grains (from 55 to 77%), oil seeds and
pulses. Monogastric animals (pigs and poultry) have no bacterial microflora and cannot
produce phytase by themselves. It makes that phosphorus fixed in the form of phytic
compounds is unavailable for them.
Supplementation with synthetic phytase to pig feed reduces the need of addition of
mineral phosphate. Phytase increases the availability of phosphorus in the feed and allows total phosphorus content to be reduced without affecting productivity. With the addition of phytase, the phosphorus content of pig feed can be reduced by up to 30%.
Influence of phytase use on fattening pigs’ performance [Barowicz, 2012]
Specification
Phosphorus content in the feed, g
Daily gain, g
Feed utilisation, kg kg–1
Phosphorus digestibility, %
Calcium digestibility, %
kg–1
0
5.9
822
2.94
30.6
36.2
Phytase addition, FTU/kg*
0
250
500
3.9
3.9
3.9
973
891
916
3.08
2.82
2.81
27.4
46.6
50.2
41.2
52.8
50.0
1000
3.9
919
2.77
51.4
48.7
* FTU/kg – unit of active phytase, 1 FTU is the amount of enzyme which liberates 1 micromole of inorganic
phosphate per minute from sodium phytase
Thus, due to the use of not absorbable exogenous phytase in feeding pigs, phosphorus from feed of plant origin is largely used by animals, which contributes to the minimum supplementation of feeds with mineral phosphorus, or even its complete elimination. Such procedure can significantly reduce the amount of phosphorus in manure and
substantially reduce the problem of surface water pollution.
Reducing P excretion, %
45,0
40,0
35,0
30,0
25,0
20,0
15,0
10,0
5,0
0,0
piglets
fatteners
broilers
laying hens
turkeys
Species of animals
The reduction of phosphorus excretion by animals thanks to the use of phytase in the feed additive [based
on: Barowicz, 2012]
It should be noted that the addition of phytase to low protein diet increases the protein retention by about 17% while reducing nitrogen excretion into the environment by
22%.
24
8.4. Wet feed and fermentation
185
2,1
180
Daily gain, g
2,05
Daily gain
Feed utilisation
175
2
170
165
1,95
160
1,9
155
1,85
Feed utilisation, kg/kg
a)
150
1,8
145
140
1,75
wet
dry
Fedding system
316
1,7
Daily gain
Feed utilisation
314
1,69
312
310
1,68
308
1,67
306
304
Feed utilisation, kg/kg
b)
Daily gain, g
Wet feeding of pigs makes that
feed is better utilised by animals and
more nitrogen is retained in their
body, which reduces nitrogen release
to the environment. Moreover, wetting the pig feed some time before
feeding, activates endogenous phytase (endogenous phytase is an enzyme that increases the availability
of phosphorus bound in cereals) in
grains, thereby reducing or even
eliminating the need for mineral
phosphorus supplementation. This
means that pig production units with
wet feed systems should be able to
utilise feed with lower phosphorus
content than normally recommended.
It was found that wetting of cereal pellets for 2.5 hours before feeding causes the body excretes from a
few to several percent less phosphorus with faeces and urine. Fermentation of the feed can reduce the need
for mineral phosphate supplementation.
1,66
302
300
1,65
wet
dry
Feeding system
Influence of feeding system of piglets on fattening
results [on the basis: Milewska 2009 acc. to: Nielsen et al., 1983]; a) results for piglets weighing
between 9-16 kg; b) results for piglets weighing
between 8-20 kg
Fermentation occurs naturally in wet feed after some time. However, the fermentation process is difficult to manage and the method is still to be developed.
Feeding pigs with wet feed [JTI]
Installation for feeding with wet
feed [photo: Lipiński, 2012]
25
9. Reducing ammonia losses in animal houses
Emissions of ammonia from livestock buildings depend on the system of animal husbandry and the type of livestock. The highest emissions are present in pig and poultry
farms reaching up to 25% of nitrogen excreted in faeces. The amount and variation of
ammonia emissions from animal housing are determined by many factors, which also
interact with each other. Losses of ammonia in livestock buildings can be limited by:
1. Increased nitrogen use efficiency: Nitrogen contained in feed for animals fed above
their demands cannot be retained in their bodies, but is simply excreted in urine and
faeces. Optimising the feed composition and the diet of farm animals, both monogastric
and ruminant, means the reduction of nitrogen excretion in faeces. Because biochemical reactions decompose a lot of organic compounds to ammonia, emission of this
compound is mainly reduced as an effect of diet optimisation.
2. Reduction of the surface deposition of manure and the time of its exposure to open air:
In cowsheds and pigsties with bedding it is recommended to use a larger amount of
straw for bedding and to ensure rapid drainage of urine into the tank and to keep waterers and troughs in good condition to avoid water leakage. In litter-free buildings,
proper design of floor grates for quick runoff of manure and reduction of the exposed
surface of slurry in channels draining faeces to tanks contribute to the reduction of
ammonia losses.
3. Avoiding high temperature: Higher temperature in the livestock building results in
higher emissions of NH3. Therefore, the temperature should not be allowed to exceed
the optimum level.
4. Adapting the flow of air: the use of ventilation techniques that create low air velocities
around the places of storage of organic fertilisers. Air flow velocity over surfaces covered with manure should be minimised because the amount of ammonia released from
fertiliser increases with increased air circulation.
5. Adding chemical, mineral or microbial preparations to litter. The effect of these preparations consists in: a) fixation of ammonia in stable chemical compounds; b) development of microflora or alteration of physico-chemical properties of litter (drying and
reduction of litter pH), which in turn leads to a reduction of ammonia release.
6. The use of biofilters. Biofilters reduce the emissions of ammonia through the gas adsorption by organic media (adsorbents), such as straw, chaff, hay, bark of softwood
and hardwood.
Keeping livestock buildings and animals clean
reduces ammonia emissions [Sannö]
Biofilter [Sannö]
26
10. Storage of manure
Adequate collection and storage facilities provide the possibility to choose a time to
apply manure to fields when the crops can utilize N and P. Hence, fewer occasions when a
lack of capacity would force the farmer to spread manure at unsuitable times. Manure
storage must be of such a quality that it prevents N, P and manure losses. The main factors affecting ammonia losses from storage places are the manure properties (pH, dry
matter content), temperature and wind conditions, piling technology, storage time. Those
for liquid manure storage include: surface to volume ratio, crust formation and mixing
method. Ammonia losses can be sharply reduced if the air directly above the liquid manure storage is prevented from circulating. A method that efficiently reduces NH3 losses is
to cover the liquid manure stores with, for instance, a roof, a floating plastic cover or
a stable natural crust. If the liquid manure tank is filled underneath the cover, this can be
kept intact even during filling, which reduces the risk of NH3 losses.
a)
b)
c)
Stable natural crust
Floating plastic cover
Roof
Leaks
Vent
Method of NH3 loss reduction from stored slurry using: a) roof, b) floating plastic cover or c) stable natural
crust [from: Jacobson et al., 2001, modified]
Farmyard manure should be stored in tight manure pits with side walls of the discharge channel and a reservoir to collect leachates.
From storages with solid manure, especially if composting proceeds at high temperatures, NH3 losses could be high. Peat included in the bedding material will reduce NH3
losses during storage. Roofs on solid manure storages could be an effective measure to
reduce ammonia losses from solid manure. Additionally, a roof keeps rainwater away,
which could prevent nutrient leakage from the manure pad if it has insufficient or lacking
drainage leading to a collection pit.
Manure pits with a tank to collect leachates [ITP-GCB
Tylicz]
A covered, solid manure storage reduces or
eliminates runoff [Hilborn, Johnson, 2006]
27
11. Constructed wetlands for nutrient reduction/retention
11.1. Sedimentation ponds
Small surface flow wetlands are designed primarily to retain phosphorus. This is
achieved by retaining eroded phosphorus bound to aggregates and particulate materials
in the runoff water by optimising the conditions for sedimentation processes.
Phosphorus and other
nutrients are reduced to
some extent due to biological and chemical decomposition and transformation
processes, as well as to plant
uptake.
Sedimentation
ponds are suitable for establishment in highly intensive
small-scale agricultural areas. The ponds are relatively
small,
representing
approximately 0.1–0.5% of the
runoff area. A sedimentation
pond can be constructed for
instance by widening a section of a ditch, slowing down
This sedimentation pond was established by widening a section of
the speed of the runoff water
a ditch. In the foreground, right after the inlet, is the deeper sediand hence increasing sedimentation basin [photo: S. Owenius]
mentation.
A sedimentation pond is often designed as a serial combination of: a) a sedimentation
basin with water depth of 1–1.5 m representing 20–30% of the total area of the sedimentation pond where the main sedimentation of larger particles takes place, followed by: b)
a wetland filter covered with typical wetland plants providing good conditions for sedimentation of smaller particles. Where the area is highly sloping, it is advisable to include
an overflow area followed by a second wetland filter prior to the outlet in order to further
improve the sedimentation efficiency.
According to a study conducted in Norway, sedimentation ponds retain 23 to 42%
phosphorus and 45 to 68% of the particles introduced to them in runoff (shape and structure of the catchment area have a large impact on the differences in the reduction efficiency between ponds).
Average retention of phosphorus and particles in four Norwegian sedimentation ponds
[Owenius, van der Nat for Braskerud and Hauge, 2008]
Pond
no
Pond
area, m2
Percent
of runoff
area
Retention of
phosphorus,
% of P-load
Specific retention
of phosphorus,
g/m2 year
Retention
of particles,
% of load
Specific retention of particles,
g/m2 year
1
2
3
4
900
345
870
840
0.06
0.07
0.08
0.38
42
27
23
42
51
58
37
46
66
45
62
68
83
89
36
22
The sediments accumulated in the sedimentation basin need to be removed on a regular
basis for maintenance.
28
11.2. Constructed wetlands
Large free water surface wetlands are designed and constructed primarily for removal of nutrients, e.g. nitrogen and phosphorus and other pollutants from runoff water
through sedimentation, biological and chemical transformation and degradation and
plant uptake. Constructed wetlands have additional benefits, i.e. improved biodiversity,
water storage capacity, resource recovery, irrigation possibilities and production of crop
biomass.
Example of constructed wetland in Haavisto in Finland [photo: S. Pietrzak]
Constructed wetlands are established, or re-established, to receive water from large
runoff areas in arable and agricultural lands. The runoff area should be covered by at
least 50% intensive agricultural land use, with the constructed wetland of an area approximately 0.5–4% of the total runoff area.
An important characteristic is the establishment of typical emerged and submerged
wetland vegetation. A constructed wetland provides heterogeneous water regimes and
environments. It is common to have a mixture of areas with (i) permanently high water
level, more or less covered with typical wetland vegetation and (ii) periodically waterlogged areas with low water level. The water regime can also vary over the year.
The capacity of nutrient reduction in wetlands is diverse, sometimes greatly, within
and between years depending on a number of factors. It is generally accepted that the
constructed wetlands retain 20 to 90% nitrogen and 25 to 100% of phosphorus introduced to them with runoff. Based on the current knowledge of and experience with constructed wetlands in intensive agricultural settings, plausible expected retention rates for
nitrogen and phosphorus are 250–500 kg N/ha/year and 5–10 kg P kg/ha/year, respectively [Owenius, van der Nat, 2008].
In Poland, as well as in Estonia, Latvia and Lithuania constructed wetlands are not
being built in order to retain nutrients flushed from fields because many natural wetlands
are preserved there.
Natural wetlands called "water little eye" in the West Pomeranian Region in Poland [photo: A. Brysiewicz]
29
12. Buffer zones along water areas and erosion-sensitive field areas
Buffer zones are uncultivated areas between fields and water courses, main ditches,
ponds, lakes or gulfs. Buffer zones should also be implemented in erosion-sensitive field
areas such as those around surface water wells or surrounding field areas with high
groundwater levels.
Buffer zones reduce the velocity of surface water runoff, mitigating losses of eroded
aggregates, soil particles, particulate phosphorus and other soil-borne pollutants. They
also decrease the risk from freshly spread manure and pesticides reaching the aquatic
environment. Buffer zones are an especially important measure in areas with erosion
problems. Moreover, they provide the conditions for biological and chemical transformation of pollutants and for plant uptake.
Grass buffer zone [photo: M. Śmietanka, D.
Śliwiński]
Complex buffer zone [photo: Z. Miatkowski]
Buffer zones comprise a permanent plant cover of dense grass or other vegetation.
Buffer zones are situated on former agricultural lands and have a width of 5–20 m. They
are not allowed to be cultivated, fertilised or sprayed with pesticides. The vegetation
should be kept dense and plants should be established if needed for maintenance.
Ability to reduce nutrients in buffer zones depends on: a) width of the zone; b) slope gradient; c) plant species composition, d) soil structure; e) area exposure; f) hydrological
conditions; g) meteorological conditions.
Nutrient retention efficiency of buffer zones depends on the type of plants. Grass
buffer strips are effective in removing sediments and sediment associated pollutants.
Grass buffers are much
Mean effectiveness of riparian buffers in removing nutri- less effective than forested
ents [Bastiene, Kirstukas, 2011]
buffers in removing nitroVegetation cover
Nitrogen removal Phosphorus removal gen, while wetlands retain
low amounts of phosphotype
effectiveness, %
effectiveness, %
rus. The combination of
Complex buffer
98.0 ± 1.3
95.0 ± 3.4
vegetation types (trees,
(trees, shrubs, grass)
shrubs and grasses) helps
Forest
90.0 ± 2.5
80.0 ± 8.3
maximize the efficiency
Forested wetland
85.0 ± 5.2
70.0 ± 9.8
and diversity of benefits
Shrubs
80.5 ± 10.2
73.7 ± 8.4
provided by the buffer
zones
(including
the
Grass
53.3 ± 8.7
61.5 ± 15.2
increase of ecosystem
Wetland
72.3 ± 11.9
50.0 ± 12.3
biodiversity).
30
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33
Baltic Compass
Baltic COMPASS promotes sustainable agriculture in the Baltic Sea region. The region’s
90 million inhabitants anticipate both high quality food produced in the region and a
healthy environment, including a cleaner Baltic Sea. Baltic Compass looks for innovative solutions needed for the future of the region and its agriculture, environment and
business.
Baltic Compass has a wide approach to the agri-environmental challenges, covering agricultural best practices, investment support and technologies, water assessment and
scenarios, and policy and governance issues.
Baltic Compass is financed by the European Union as a strategic project for its support to
investments and policy adaptation. The 22 partners represent national authorities, interest organizations, scientific institutes and innovation centres from the Baltic Sea Region countries. Baltic Compass is a three year project running until December 2012.
www.balticcompass.org