Tougher NVZ regulations and sky-high fertiliser prices are boosting interest in alternatives to the traditional splash-plate method of slurry application. Nick Fone looks at the options.

Slurry, it seems, is finally turning from foe to friend. More and more farms are looking at new application equipment and techniques, both to gain more benefit from the nutrients in slurry and to meet ever-tougher nitrates directives.

Slurry is currently applied to farmland in different ways, the most common of which is by splash-plate. However, several studies show that this is not the most effective way to make best use of the nutrients in muck.

Research at the Agri-Food Biosciences Institute at Hillsborough in Northern Ireland showed that ammonia losses were cut by 60% when slurry was spread in bands with a dribble-bar applicator rather than simply surface spread. Even more strikingly, gaseous nitrogen losses were reduced to just 10% with a shallow injector.

Spiked injectors were equally effective but their relative complexity in comparison to a disc injector meant they were deemed impractical.

Not surprisingly, ammonia losses and odour issues mean that the use of splash-plate systems is becoming less popular. But deciding what to use instead can be difficult, since there is now a wide range off alternative – though not necessarily new – slurry application techniques that can be used with either tankers or umbilical systems.

Dribble bar

Dribble bar applicators consists of a boom mounted behind the tractor or tanker from which dangle a number of evenly spaced flexible pipes. Slurry travels down these to be deposited on the soil or crop surface.

These are very simple systems with few moving parts and are useful for spreading large quantities of slurry easily. However dribble bars don’t necessarily place the slurry on the soil surface which means that growing crops and grass can be contaminated or scorched by slurry. That’s less of a problem with young, growing crops, where the slurry will largely be deposited on bare soil.

Because there is no contact with the soil (unlike trailing shoe or injector applicators), no extra power, wearing parts or fuel is used to apply the slurry.

Trailing shoe (right) 

The trailing shoe system is mainly used for applying slurry to grassland. The “shoe”, a large number of which are mounted on toolbar behind the tractor or tanker, is pulled along the ground and parts the grass sward to allow slurry to be deposited on bare soil rather than on the plants themselves.

This results in very little contamination or scorch of the crop and grazing can resume much sooner. As the trailing shoes are pulled along the ground they do wear, with obvious implications on running costs.

Disc injector

The minimal disturbance disc injector is the most common type of slurry injector. A number of plain (i.e. not scalloped or angled) discs cut slots in the soil surface into which slurry is deposited.

This method of application leads to very little soil disturbance while depositing the slurry directly into the rooting zone, making it readily available to the roots of the growing crop.

It also means there is very little ammonia loss and the disc can help to aerate the soil, stimulating positive microbial activity.

Cultivator incorporators (below)

Disc-type cultivator incorporators use a disc cultivator such as the Amazone Catros to till the soil and incorporate slurry as it is applied. Often seen mounted on a linkage behind tankers on the Continent, it allows operators to cultivate and incorporate nutrients and organic matter in one-pass.

However, while slurry is applied below the surface, some will be left on the surface so ammonia loss will not be as low as when using an injector. Such equipment tends to be used with a tanker, rather than an umbilical system, which can lead to soil compaction.

Tine injectors

Tine injectors are not as common as other slurry applicators and use tines to rip channels in the soil into which slurry is dribbled via coulter pipes from the tanker or umbilical source. This method causes the most soil disturbance of all applicators and can only really be used on stubble or cultivated ground before a crop is established. However, it is a simple system with few working parts and can ensure that slurry is deposited at the right depth.

Spike wheel injector

The spike wheel is unusual and more suited to applying liquid fertiliser than slurry. It is used to apply material to grass, stubble and growing arable crops and consists of a row of wheels with hollow spikes around their circumference.

The wheels are mounted on an axle trailed or mounted behind the tractor or tanker. Slurry is pumped along the hollow axle and into each wheel, from where it is applied via the hollow spikes to the required depth in the soil.

By applying slurry below the soil surface contamination is kept to an absolute minimum, as is ammonia loss. However, such applicators are more prone to blockages and other problems due to the moving parts and seals which must be maintained to prevent leakage between the axle and wheels.

A fine macerator is essential in chopping organic material to keep the spike free from blockage and generally this system is better suited to dirty water applications rather than mainstream slurry spreading.

If you want to find out more about how NVZ regs will affect the way you store and apply slurry and see the latest muckspreaders and slurry application equipment in action, come to the new muck and slurry area at this year’s Grassland UK event at Shepton Mallet, Somerset on 7 May. See www.bathandwest.com for more details.