Slurry Spreading – Methods of Application
The potential of slurry spreading in improving crop yields has been well established and the practice has brought farmers significant reductions in fertiliser costs. As a result, there has been a rapid development in different kinds of slurry spreading equipment, all providing slightly different ways of achieving effective application.
As well as supplying slurry applicators and associated machinery such slurry pumps we also have our own contracting business, carrying out slurry spreading for landowners in Norfolk, Suffolk and across East Anglia. As both equipment suppliers and contractors we are well placed to understand the many practical considerations involved in selecting the best methods for your land. Here we describe the most popular techniques and describe the type of equipment needed for each.
What Makes a Good Slurry Spreading Method?
There are several different factors to consider when comparing methods of slurry application:
Even application – This is by far the most important consideration, as it affects the crop or grass yield. Ideally, slurry needs to be applied evenly to the land, covering all areas where growth is required.
Speed and ease of application – It is desirable to minimise the amount of time taken to apply slurry, both in terms of manpower efficiency, but also to keep down fuel costs. So the more square metres that can be covered in one "pass" the better.
Controlled levels of nutrients – The aim should be to apply just enough slurry to achieve optimum fertilisation without applying more than necessary. Ideally, the chosen application method will be able to measure and monitor nutrient levels and the rate of flow during spreading.
Minimise damage – Passing through a crop with heavy machinery involves a risk of damage to the soil (through compaction) and to the crop. Minimising this damage through the use of lighter equipment and fewer passes, is desirable.
Grassland usable again as quickly as possible – Grassland which has had slurry applied to it cannot be used for grazing for a period of time as it poses a health risk to livestock. Time is needed to allow the slurry to be taken up by the soil or to be broken down by oxygen and sunlight. How much time is needed depends partly on environmental factors such as the time of year and levels of rainfall, and partly on how much has been applied – so it is better to apply the minimum necessary for fertilisation and if possible minimise direct contact with the grass itself.
Minimise ammonia emissions – As well as creating a lot of unpleasant odour, high ammonia emissions also indicate a loss of nitrogen, the key fertilising nutrient in slurry. As well as minimising ammonia loss during storage, it is preferable to use a slurry spreading technique which also minimises losses.
Minimise odours where possible – This can be an important factor for farmland close to residential populations. Since the key source of odour is ammonia, then choosing low loss application methods will also help to address this problem.
With these aims in mind, we can now compare the two main types of slurry spreading methods available:
Slurry is pumped along a pipeline from the store to the field and fed to a tractor mounted applicator which applies the slurry in various ways. The feed rate is controlled by the pump output, coupled with the forward speed of the applicator. Boom width can be as wide as 36 metres (though 24 metres and under is the norm), enabling large fields to be covered in just a few passes, which minimises damage to the crop and/or soil.
A large benefit of umbilical spreading is that slurry is constantly delivered to the field, unlike the tanker method which spends a larger proportion of time travelling between the store and the field.
Within the umbilical system there are slightly different types of spreading depending on the design of the boom and applicator nozzles. The three main types of umbilical applicator are Spread Nozzle Booms, Dribble Bars and Trailing Shoe. (Click the links for more information about how each of these work in detail.)
Spread nozzle booms, which are the most cost effective method, spray the slurry onto the crop usually from 2 or 3 spread nozzles depending on spread width. This method is becoming less popular because it can be wind dependent, and is also most likely to cause an odour problem.
Dribble Bars are the most common method of application. Most use a macerator to chop and distribute slurry evenly down individual pipes which cover the spread width at approximately 30cm intervals. This method gives a more accurate coverage, reduces odour and eliminates the problems caused by wind.
The Trailing Shoe applicator uses the shallow injection method and is mostly used on pasture. It works in the same way as the dribble bar, but uses a soil engaging element which parts the grass sward and dribbles the slurry directly onto the ground resulting in very little leaf contamination. Trailing shoe working width is normally between 5 and 8 metres.
In addition to supplying all the above types of umbilical applicator, we also supply Combination Bars which allow switching between Spread Nozzle and Dribble Bar application.
Slurry Spreading Norfolk, Suffolk and East Anglia – See our range of applicators here. Or view our video: