Cattle slurry, as a valuable source of N, P and K, should be applied on the fields that need it most and at the time of year that will give you the best response. All of the P and K in slurry is available to be utilised and fields that are low in both of these nutrients need to be targeted to receive slurry.
On a lot of farms, this will be the silage fields as this is where the feed that eventually produces the slurry comes from in the first place.The time of year that slurry is spread does not affect the availability or utilisation of P and K. This is not the case with N.
N in cattle slurry
Half of the nitrogen in cattle slurry is in an organic form and the other half is as ammonium, the very same form of nitrogen that is in purchased urea fertiliser.
It is the ammonium half that can replace bought-in bagged N. Similar to urea fertiliser, there are times of the year during which you can expect to get the maximum value of N from slurry and this is very much weather dependent.
Ideal conditions for getting the best nitrogen utilisation from cattle slurry are:
Overcast with very little sunshineSlight drizzle of rainLittle or no windWhere the weather conditions are only average, there is a 50% loss in utilisation rate and where the conditions are poor, ie a dry, sunny day with a strong breeze/wind, there is a further 25% loss in utilisation rate (Figure 1).
A good rule of thumb is that a day that is very good for drying clothes on a washing line is a bad day for spreading slurry if you want to get the maximum amount of N in it utilised.
In order to get the maximum value out of the N that is in cattle slurry, the majority of it should be spread in the spring when the weather conditions favour it most.
When weather conditions are suitable, apply 2,500 to 3,000 gallons of slurry to the paddocks/fields that will not be grazed for at least six weeks. Paddocks that have heavy covers of grass should not get slurry until immediately after they are grazed. When fields are grazed and closed for silage, apply between 2,500 and 3,000 gallons of cattle slurry per acre before applying any bagged N. Reduce the amount of bagged N spread by taking into account the units that have been supplied in this slurry.
There are three main advantages to using a trailing shoe slurry spreader in the spring compared with using a splash-plate spreader:
They widen the window of opportunity in getting slurry out on farms with heavier soils.They allow you to spread slurry on paddocks/fields with heavier covers of grass and still be able to graze them six weeks later, ie less contamination of grass.They increase the utilisation rate of the N that is available in slurry by up to 40%.
While there are advantages to using a trailing shoe spreader in comparison with more conventional spreaders, at their current cost they are still only justifiable in most cases on a contractor scale. Individual farmers should negotiate the best rate possible (per 1,000 gallons spread).
This article is an excerpt from Grazing Guide, which was published jointly by the Irish Farmers Journal and Teagasc.
Read more
To read the more of the 'Grazing Guide' click here.
Cattle slurry, as a valuable source of N, P and K, should be applied on the fields that need it most and at the time of year that will give you the best response. All of the P and K in slurry is available to be utilised and fields that are low in both of these nutrients need to be targeted to receive slurry.
On a lot of farms, this will be the silage fields as this is where the feed that eventually produces the slurry comes from in the first place.The time of year that slurry is spread does not affect the availability or utilisation of P and K. This is not the case with N.
N in cattle slurry
Half of the nitrogen in cattle slurry is in an organic form and the other half is as ammonium, the very same form of nitrogen that is in purchased urea fertiliser.
It is the ammonium half that can replace bought-in bagged N. Similar to urea fertiliser, there are times of the year during which you can expect to get the maximum value of N from slurry and this is very much weather dependent.
Ideal conditions for getting the best nitrogen utilisation from cattle slurry are:
Overcast with very little sunshineSlight drizzle of rainLittle or no windWhere the weather conditions are only average, there is a 50% loss in utilisation rate and where the conditions are poor, ie a dry, sunny day with a strong breeze/wind, there is a further 25% loss in utilisation rate (Figure 1).
A good rule of thumb is that a day that is very good for drying clothes on a washing line is a bad day for spreading slurry if you want to get the maximum amount of N in it utilised.
In order to get the maximum value out of the N that is in cattle slurry, the majority of it should be spread in the spring when the weather conditions favour it most.
When weather conditions are suitable, apply 2,500 to 3,000 gallons of slurry to the paddocks/fields that will not be grazed for at least six weeks. Paddocks that have heavy covers of grass should not get slurry until immediately after they are grazed. When fields are grazed and closed for silage, apply between 2,500 and 3,000 gallons of cattle slurry per acre before applying any bagged N. Reduce the amount of bagged N spread by taking into account the units that have been supplied in this slurry.
There are three main advantages to using a trailing shoe slurry spreader in the spring compared with using a splash-plate spreader:
They widen the window of opportunity in getting slurry out on farms with heavier soils.They allow you to spread slurry on paddocks/fields with heavier covers of grass and still be able to graze them six weeks later, ie less contamination of grass.They increase the utilisation rate of the N that is available in slurry by up to 40%.
While there are advantages to using a trailing shoe spreader in comparison with more conventional spreaders, at their current cost they are still only justifiable in most cases on a contractor scale. Individual farmers should negotiate the best rate possible (per 1,000 gallons spread).
This article is an excerpt from Grazing Guide, which was published jointly by the Irish Farmers Journal and Teagasc.
Read more
To read the more of the 'Grazing Guide' click here.
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