A review of all liquid manure spreading systems is made. The tank spreader can be mounted on axles and towed by a tractor or directly mounted on a truck frame. Those spreaders are of two kinds: Vacuum type that can load itself directly and need from 6 to 10 kW of power per cubic meter to operate (cost range from 1 200 to 2 400 CAN$ per cubic meter) and the conventional type that have to be filled from the top and use a rotary pump to empty itself. The conventional spreader needs from 6 to 9 kW per cubic meter to operate and costs from 800 to 1 500 CAN$ per cubic meter. Considering the cost, the conventional spreader is more interesting than the vacuum type. For manure spreading, different systems can be used: broadcast spreading, boom for spreading closer to the ground or boom using drop tubes, injection or incorporation systems. If a boom is used it is important that the flow rate be adjusted to the width of the application surface. Considering only the investment cost, the easy maintenance and use and the power needed, broadcast spreading is the most interesting system. However the application uniformity, the nutrient losses from volatilization and drift and the resulting odour emissions associated with broadcast spreading are the negative points compared to the use of boom spreading and also injection systems. Considering tank manure spreaders, considerations has to be put on the combination spreader/tractor for hydraulic power compatibility, total spreader tank vs. tractor weight and draw bar capacity, proper signs for the spreader and independent braking on the spreader if its total load exceeds the tractor weight. The number of axles or a track system on the spreader has also to be considered in order to lower the compaction induced by field traffic. Continuous application systems have to be considered for large farm that have to spread important volumes of manure. As manure can be pumped on relatively long distances the spreading capacity is generally increased by this technique compared to conventional manure hauling. The irrigation technology with rigid pipes and a reel will be used if manure is applied with an irrigation gun or a wide-span boom with or without dropping tubes. Rigid pipes and a flexible hose is used on equipment mounted on a tractor for boom spreading or injection. The flexible hose present an advantage as the system doesn’t have to follow specific trajectory for spreading however spreading in row crops is not possible which is not the case with the reel technology which used a more rigid pipe. When using a reel, transversal path ways have to be designed in order to move the reel and the boom between each passes. Hybrid systems can also be considered where manure hauling is done by trucks equipped with a tank or by pipes. The manure is then transferred to a temporary storage to feed an irrigation type spreading device or fill manure spreaders.
In order to select the appropriate spreading system for a given farm many aspects have to be considered such as the volume of manure to be spread, the time available for spreading, the soil propensity to compaction, the type of culture in the fields, the acceptable level of nuisances associated with spreading for a given farm, labor availability, the reliability of the system chosen, the accuracy of the application rate and also the uniformity in the rate applied considering lengthwise and widthwise sections of spreading.