With the slurry spreading season now open in two out of three zones, farmers should be getting their tanks tested to determine the nutrient content.
Slurry is a vital nutrient source on farms, and needs to be treated as such in order to obtain the best use of it on your farm.
Higher fertiliser prices in 2022 and 2023 saw a significant focus placed on the use of slurry on farms, and showed that grass can still be grown on farms with a reduction in chemical nitrogen (N).
The nutrient value can differ greatly from tank-to-tank and from farm-to-farm, depending on the system or how much water has gotten into the tank.
Along with soil sampling, this will give you a more accurate picture of the fields that require slurry and whether or not you can reduce the amount of chemical N being spread.
Slurry spreading
It is vital that slurry is being spread where it is needed, rather than where land is able to take it.
During this time of year, many farms can be under pressure from a storage point of view – but the risk of nitrate leaking is increased when it is spread on land that does not require it.
An important part of improving water quality and maintaining the nitrates derogation, is ensuring that nutrients are spread only where necessary.
The value of this slurry spread in the correct conditions, versus in back conditions, is significant at around €43/cow, according to Teagasc.
Spring and after silage harvesting is the time period in which land will benefit the most from spreading slurry.
Testing
There are two options for farmers that are looking to get their slurry tested. The first option, is to take a sample and send it off to the lab.
This is done by collecting about 1L of slurry and sending it to be tested. If you have a number of tanks, you can combine the samples.
The same labs that do soil testing will also test your slurry.
The second option is to buy a hydrometer, which means you can then test your own slurry on the farm.
A hydrometer works by determining the dry matter (DM) of the sample. The DM matter can then be used to determine the nutrient value
The test will determine the amount of N, phosphorus (P) and potassium (K) that the slurry contains, based on DM percentage.
DM
%N kg/m3
(units/1,000 gallons)P kg/m3
(units/1,000 gallons)K kg/m3
(units/1,000 gallons)2 0.4 (4) 0.21 (2) 1.4 (13) 4 0.7 (6) 0.35 (3) 2.3 (21) 6 1.0 (9) 0.5 (5) 3.5 (32) 7 1.1 (10) 0.6 (6) 4.0 (36)
Source: Teagasc
Once you know the contents of your slurry, you can determine how much N is going to be needed for silage ground where a combination of slurry and N will be used.