A Slurry Spreader to Meet Farming Needs and Environmental Concerns

摘要

The splash plate slurry spreader is inexpensive and robust but it is not environmentally friendly. It releases most of the ammonia (NH3) in slurry, emits strong odours and distributes the remaining nutrients unevenly. The object of this report is to identify improvements to slurry spreaders that may eliminate these shortcomings.Several gases are released during and after slurry spreading. NH3 contributes to acidification of the environment and is emitted almost entirely from agriculture.Over 30% of European NH3 emissions come from slurry spreading.The Gothenberg agreement (UNECE, 1999) requires a reduction in national NH3 emission to 8% below 1990 levels. Emission of this gas from band, TF (trailing foot) and injector slurry spreaders is 40, 40 and 20% respectively of that from conventional splash plate machines. A switch to spreaders with lower emissions would provide sufficient reduction to satisfy the Gothenberg objective.Odour from livestock units gives rise to many complaints but there is little evidence that it is a health hazard. Emission of the vapours from slurry spreaders is in the order; (splash plate)>(band)> (TF and injector). Other gases (methane and nitrous oxide) are released primarily after injection.Infection of humans by slurry-borne organisms is not common. In general the differences between spreaders in regard to pathogens are not significant but this conclusion may not apply in all cases.Slurry nutrients amount to 40% of the N and 65% of the P required in agriculture. Several commercial and experimental methods exist to measure slurry nutrient content. Field application using a splash plate and vacuum tanker gives highly variable distribution. Any of the other spreaders reviewed here combined with a fixed displacement pump achieve more uniform application. Accurate spreading reduces the need for excess application so losses to water from soil are reduced. This conforms to the Water Framework Directive. Deep injection and incorporation can reduce loss of P from slurry but other spreading methods will not normally reduce the risk of P loss at spreading time.The proposed tanker consists of a closed tank with running gear fit for road and field conditions. A TF spreader is fitted at the back. The slurry is handled by a fixed displacement pump which fills the tank or empties it through the spreader. The pump must be protected from obstacles so an intake filter or chopper filter should be included. This slurry spreader would reduce emission of NH3 and odour and increase the recycling of slurry nutrients to crops. It is more expensive than splash plate machines but if widely adopted it could be an economical solution to the UNECE requirement to reduce NH3 emissions.Alternatives to improving spreaders exist. These include digesting slurry, and reducing emissions from livestock housing and slurry storage. With the exception of digestion these offer poor prospects of success especially in relation to odour reduction and exploitation of slurry nutrients. The cost of providing this equipment on Irish farms is likely to be between €200m and €800m and depends on the options chosen.