Transcript Nutrient Value of Dairy Effluent David Armstrong AK Consultants

Nutrient Value of Dairy Effluent
David Armstrong
AK Consultants
Main nutrients
Main nutrients are:
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Nitrogen
Phosphorus
Potassium
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Organic Matter
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Quantity of nutrients
Detailed research in USA - very useful figures
on nutrient output of dairy cows, related to
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Concentrations in the feed
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Amount of feed consumed
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Proportion of dung and manure collected in
yards
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How the effluent is treated or stored
Dry matter excreted
Total manure dry matter production (in dung
and urine);
Approximately 35-40% of dry matter intake.
Cow producing 20 litres of milk:
Feed intake around 19 kg/DM:
Produces 7.5 kg DM as manure.
Nitrogen excreted
Cow producing 20 litres milk/day
Excretes about 400 grams N/day
Phosphorus excreted
Cow producing 20 litres milk/day
Excretes about 65 grams P/day
Potassium excreted
Cow producing 20 litres milk/day
Excretes about 184 grams K/day
Total excreted per Lactation
Nitrogen
Phosphorus
Potassium
Total, kg
101
17
46
Most is deposited in the paddock; amount depends on
the time in the paddock and yards.
Generally 10-15% in yards.
Total excreted per Lactation in yards
Total, kg
Nitrogen
Phosphorus
Potassium
101
17
46
Kg in the yards,
3 hrs/day
13
2
6
What happens to the nutrients
Nitrogen
 Phosphorus
 Potassium

What happens to Nitrogen
•
90% is in the liquid portion, 10% in the solids
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50% is present as ammonia – easily lost
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Organic forms, subject to changes:
Conversion to other organic forms
Mineralisation – to ammonium
Nitrification - to nitrite, then nitrate (needs oxygen)
Denitrification – to nitrous oxide then nitrogen
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20-40% of N available in short term, residual 3 years
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Nitrates easily leached (esp, urine patches)
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Generally, 50% of the N in effluent is lost
What happens to Phosphorus
•
Present in organic and inorganic forms

No losses from the effluent on treatment or
storage
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Leaching only on coarse sandy soils
What happens to Potassium
•
No losses from the effluent

Present in high levels in feeds (pasture 1.5% K)
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Retained in clayey soils; leached from sands
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Commonly high levels in paddocks close to the dairy
and effluent paddocks
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High levels – contribute to health problems:
Calcium deficiency – milk fever
Magnesium deficiency – grass tetany
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Potassium limits the rate of effluent application
Potassium sets the limit
•
Limit effluent to around a maximum of 100 kg/ha K
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General rule, 1 hectare per 20 cows
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Nutrient applications, at 1 ha/20 head
Cows producing 375 kg/ha MS
In yards 3 hours/day
Average pasture feed composition
No losses of Nitrogen
Total Kg/ha
Fertiliser Kg/ha
Nitrogen
252 N
548 kg Urea
Phosphorus
42 P
467 kg Super
Potassium
114 K
228 kg Muriate
Manure Solids
Solids separators, material 10-30% DM
 P & K levels low
 N levels variable, around 0.3% on wet
basis (3 kg N/wet tonne)
 Value $20-$40/t wet.
 90% of value is in the nitrogen

First pond sludges
N & P concentrations vary with depth in
the pond
Phosphorus
against depth
Kconcentration
more
uniform.
Nitrogen concentration against depth
50
100
150
200
250
0
0
0
0.5
0.5
1
1
1.5
1.5
2
2.5
Depth (m)
Depth (m)
0
2
2.5
3
3
3.5
3.5
4
4
4.5
4.5
500
1000
1500
2000
First pond sludges
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Dry matter, 6-8%
N up to 1,700 ppm (1.7 kg/t wet)
P 200 ppm (0.2 kg/t)
K 600 ppm (0.6 kg/t)
Value $4,100/ML ($4/1000 litres)
25 mm application (0.25 ML/ha) will apply:
425 kg/ha N
50 kg/ha P
150 kg/ha K
Recommend 25 mm maximum application
Most nutrient in organic forms, slow release
Economic value per head
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13% of excreted nutrients are in the yard
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Fertiliser equivalents (Urea, Super & Muriate).
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If no N loss, $35/head/lactation
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At 50% N loss, $27/head.
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Value from the water in the effluent;
at 50 L/head/day, value $5/hd.
Maximising nutrient response
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Apply the effluent nutrients when plants can respond:
when plants actively growing
warm & moist conditions
Victorian trial responses (3 years results)
Crop
Response (tDM/ML)
Turnips
2.7 – 8.9
Pasture – silage regrowth
1.4 – 2.5
Pasture response 9-16 kgDM/kg N applied
Highest response in the year of application,
but response lasts 3 years.
Risks of effluent application
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Nutrient accumulation in effluent paddocks –
SOIL TEST
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High levels – animal health problems
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Contamination of surface water – runoff
Avoid spreading in wet conditions
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Contamination of groundwater
More likely from ponds.
Avoid waterlogged sandy soils.
Important points
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Useful amounts of N, P & K in effluents, potentially
around $35/head/lactation.
Most value is the Nitrogen.
N losses commonly 50%, lost as ammonia.
Most nutrient value is in the liquid.
Suggested maximum application rate is 1 ha per 20
cows; applies 252 kg/ha N, 42 kg/ha P, 114 kg/ha K
(cows on yards 3 hrs/day)
Avoid excessive application rates; K problems.
Avoid applying to waterlogged soils.
SOIL TEST application paddocks.
Effluent Management
Code of Practice
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TDIA prepared, November 2009
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Expected to be gazetted soon
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Part of the licence conditions to operate
a dairy
Effluent Management
Code of Practice
Three requirements:
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No effluent to leave the farm
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Effluent management system in place
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Land application to be sustainable
Effluent Management Plans
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TDIA has developed a generic EMP.
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Development and implementation will help
to demonstrate compliance with the CoP.
Conclusions
A good effluent management system:
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Utilises the nutrient content of effluent, worth
$25-$35/head/year
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Avoids pollution of surface and groundwater, and
risks to animal health
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Compliant with the industry Code of Practice