Farmers - utilise your slurry

Monday, 14 March 2011 14:36

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With fertiliser prices set to rise again and profit margins tightening on farms, we should all look at the slurry in our slatted tanks and manure pits as a fertiliser and not a waste. The way in how and when you spread you slurry determines whether you are spreading a waste or a fertiliser.
Cattle slurry can be used to replace some of the N, P and K fertiliser on the farm. Slurry typically contains 3.6kg N/ton, 0.6kgs P/ton and 4.3kgs K/ton.
In layman terms, 1,000 gallons is equivalent to one bag of 0-7-30 per acre with approximately 10 units of nitrogen per acre.
However, nitrogen utilisation depends on a number of factors, including weather conditions and time of year to maximise its value.

Traditionally slurry is applied to first cut silage ground after silage is cut. This is fine for the application of phorphorus and potassium nutrients, but is not the best time for nitrogen.
The contribution of nitrogen in this slurry to grass production is almost zero as N applied to silage stubble is lost by volatisation.
Likewise the N value of slurry applied in autumn is so low that the cost of application far exceeds the value of the slurry in nitrogen terms.
As 100 per cent of phosphorus and potassium is utilised by the grass plant in ideal conditions, the most we can hope for is 30 per cent use of nitrogen from slurry.

Drier, warmer weather in summer results in losses of up to 90 per cent of the available nitrogen within 24 hours of application.
This means the optimum time to apply your cattle slurry to maximise nitrogen use efficiency, as well as cost effectiveness of application, is in spring.
The three key opportunities to apply slurry in spring are: late January or early February to grazing ground which is to be grazed in late March and early April; just after first grazing in mid March, and late March to early April for first cut silage.

Research shows that the application of slurry in a planned way in spring can reduce the amount of nitrogen required by up to 30 per cent on drystock farms and 10 to 15 per cent on dairy farms.
A target of 70 per cent of slurry should be applied by mid April, with all applied by mid June. The use of a trailing shoe or band spreader to a lesser extent will reduce the loss of Nitrogen through volitisation, while the use of a trailing shoe reduces contamination.
Ideal weather conditions are cool, dull and calm weather, slightly misty, which provides optimal conditions for the utilisation of nitrogen in slurry.

The bottom line is 1,000 gallons of cattle slurry spread per acre in spring with correct weather conditions is equivalent to one bag of 0-7-30 and half a bag of CAN. In monetary terms, your four-bay single slatted tank full with 40,000 gallons is equivalent to €700 of 0-7-30 and €300 of nitrogen.
If you require any further information on the above or on any other agricultural issue, you can contact Michael or Barry at the IPI Centre, Breaffy Road, Castlebar, or phone them on (094) 9027300.