Nutrient Value of Dairy Effluent David Armstrong AK Consultants

Main nutrients Main nutrients are: Nitrogen Phosphorus Potassium Organic Matter

Quantity of nutrients Detailed research in USA - very useful figures on nutrient output of dairy cows, related to Concentrations in the feed Amount of feed consumed Proportion of dung and manure collected in yards 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 Total, kg Nitrogen101 Phosphorus17 Potassium46 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, kgKg in the yards, 3 hrs/day Nitrogen10113 Phosphorus172 Potassium466

What happens to the nutrients Nitrogen Phosphorus Potassium

What happens to Nitrogen 90% is in the liquid portion, 10% in the solids 50% is present as ammonia – easily lost 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 20-40% of N available in short term, residual 3 years Nitrates easily leached (esp, urine patches) 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 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) Retained in clayey soils; leached from sands Commonly high levels in paddocks close to the dairy and effluent paddocks High levels – contribute to health problems: Calcium deficiency – milk fever Magnesium deficiency – grass tetany Potassium limits the rate of effluent application

Potassium sets the limit Limit effluent to around a maximum of 100 kg/ha K General rule, 1 hectare per 20 cows 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/haFertiliser Kg/ha Nitrogen252 N548 kg Urea Phosphorus42 P467 kg Super Potassium114 K228 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 K more uniform.

First pond sludges 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 13% of excreted nutrients are in the yard Fertiliser equivalents (Urea, Super & Muriate). If no N loss, $35/head/lactation At 50% N loss, $27/head. Value from the water in the effluent; at 50 L/head/day, value $5/hd.

Maximising nutrient response Apply the effluent nutrients when plants can respond: when plants actively growing warm & moist conditions Victorian trial responses (3 years results) Pasture response 9-16 kgDM/kg N applied Highest response in the year of application, but response lasts 3 years. CropResponse (tDM/ML) Turnips2.7 – 8.9 Pasture – silage regrowth1.4 – 2.5

Risks of effluent application Nutrient accumulation in effluent paddocks – SOIL TEST High levels – animal health problems Contamination of surface water – runoff Avoid spreading in wet conditions Contamination of groundwater More likely from ponds. Avoid waterlogged sandy soils.

Important points 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 TDIA prepared, November 2009 Expected to be gazetted soon Part of the licence conditions to operate a dairy

Effluent Management Code of Practice Three requirements: No effluent to leave the farm Effluent management system in place Land application to be sustainable

Effluent Management Plans TDIA has developed a generic EMP. Development and implementation will help to demonstrate compliance with the CoP.

Conclusions A good effluent management system: Utilises the nutrient content of effluent, worth $25-$35/head/year Avoids pollution of surface and groundwater, and risks to animal health Compliant with the industry Code of Practice