Splash plate spreading of slurry onto the field may be quick and easy, but it may not be making the most of your natural fertiliser. Richard Bradley seeks out expert advice to find out more.
Universal across umbilical or tanker systems, the Splash plate offers quick and simple slurry application.
While many farmers see spreading slurry as a laborious task, it remains one of the cheapest ways to fertilise your fields.
ADAS principal soil specialist, John Williams explained to Farmers Guardian that applying liquid slurries and digestates is just like applying bagged fertilisers, so the same care and consideration for accurate application is needed.
Understanding your soils is crucial according to Mr Williams, who says if you do not know what the soil needs, how can you apply nutrients where they are needed the most.
Slurry stores need to be mixed well before spreading to ensure a homogeneous mix.
Likewise, Mr Williams says “Slurries vary in consistency so stores should be mixed well before spreading to ensure a homogenous mix, samples should also be analysed to make sure you know what is being applied to the fields.
“If you work out what organic nutrients have been spread, you should be able to reduce your bag (fertiliser) application, without reducing yields or quality.”
While the fertiliser manual RB209 gives a guide to the nutritional value of slurries, samples should still be taken as no two slurries are the same. RB209 also gives information on what a crop’s nutrient uptake is likely to be, depending on the time of year and application method, allowing you to work out how much slurry to apply.
A refresh of the manual is expected in May 2017 which will include figures for digestates from anaerobic digester plants.
"If you work out what organic nutrients have been spread, you should be able to reduce your bag application, without reducing yields or quality"
- JOHN WILLIAMS
The nitrogen (N) content of slurries can be broken into two parts, readily available N which is potentially available for quick uptake into the crop, and organic N which requires breaking down before uptake.
In dairy cow slurry of six per cent dry matter, often about 40-45 per cent of the total N is readily available and vulnerable to nitrogen volatilisation.
When volatilisation occurs up to 40 per cent of the readily available N is lost to the atmosphere as ammonium, within the first six hours of application, unless the liquid is incorporated into the soil.
With agriculture accounting for about 90 per cent of the EU’s ammonia emissions, it is important for farmers to take care with their slurries.
To find out what this means for farmers and contractors, we take a look at some of the most common techniques for applying slurries and digestates.
Since Jesus was in short pants, applying slurry has been done using a splash plate.
While working widths, spreading patterns and consistency can vary wildly depending on a raft of factors, a splash plate offers a quick and simple system to get slurry on the ground.
The simplicity continues when attaching and setting up a splash plate, with a pair of over-centred latches or a set of bolts securing the system in place.
Along with the issue of inaccuracy, is the fact that the crop is left plastered until the next decent rain shower. About 40 per cent of the readily available nitrogen, which can be quickly absorbed by the crop, will be lost to the atmosphere as ammonium within six hours of application unless it is incorporated into the soil, which is not what any farmer wants to do to their standing crop.
Seen as the next stage up in application technique, the dribble bar gives a far greater level of accuracy over a splash plate and offers a 30 per cent reduced level of nitrogen volatilisation.
As liquid arrives at the dribble bar, a macerator is used to chop, mix and push the liquid down the outlet pipes, which are equally spaced over the machine’s working width. The liquid is then placed in thin strips, covering less of the crop leaf, meaning that grazing animals can be put into the field sooner. This method of applying slurry also means accurate application is possible from tramlines in arable crops.
Commonly used in 12-24m working widths, a dribble bar can be big piece of kit, and if mounted to a tanker, rear linkage frames, additional hydraulic lines and often a heavier duty chassis are required to be able to cope with the extra weight, meaning they need to be specified from new.
Some manufacturers do offer basic retro-fit dribble bars for tankers, however, which do not require bracing or linkages.
The trailing shoe system has a lot of similarities with the dribble bar, and offers about 40 per cent reduced nitrogen volatilisation.
A macerator and equally spaced outlets are used, with small ‘boots’ on the end of each hose, which trail along the ground. As the liquid is applied directly onto the soil, less of the crop leaf is covered in liquid, so could offer a better compromise for farmers who want to graze or harvest in shorter windows.
If tanker mounted, a rear linkage is required to lift and lower the applicator at the end of each row, which would again require a strengthened chassis to withstand the additional weight.
Firing liquid straight into the ground with a disc injector offers reduced nitrogen volatilisation levels by up to 70 per cent compared to splash plate application. Crop leaf coverage is minimal, meaning that animals can be grazed almost immediately after application.
Similar to dribble bar and trailing shoe systems, disc injectors use a macerator to distribute liquid equally to the outlets, a boot then applies liquid directly into the slot created by a disc.
Disc injectors however are only suitable in the right place, at the right time and in the right weather; if the ground is too hard the injector will not cut into the ground, too soft and it will sink in too far.
Due to the power required to pull the injector and the pressure needed to make it cut into the ground, working widths are generally smaller and tankers require a much heavier-duty chassis and frame too.