An assessment of macerating mowers for zero effluent silage production

A weather-driven whole system model, previously used to study a range of ha y and silage conservation methods, practices and mechanization systems, has been further developed to represent the parameters of a silage system base d on macerating (severe conditioning) mowers. Parameters are based on field drying experiments with macerated grass. Weather-driven simulations have b een carried out to compare maceration systems with a number of conventional options for wilted silage, at 11 sites with contrasting weather in England , Scotland, Wales and Northern Ireland. Results are presented first in terms of the period required for wilting, se condly as losses and quantities of silage produced, and thirdly as gross va lue tin terms of cost of bought feedstuffs replaced), costs and net value o f silage produced. Results show that it is both technically feasible and po tentially economically viable to wilt macerated material to 30% dry matter content to avoid effluent production, whereas with conventional systems it is only feasible to wilt to 25% with the inevitable production of some effl uent. With maceration, over 60% of material can be harvested on the same da y as it is cut, so it does not remain in the field overnight, whereas this is not possible with conventional methods. It is also possible to reduce th e quantity of material rained on during field wilting to 1-4% at most sites , compared with around 25% for conventional material. These results are fou nd both for forage-harvested clamp silage on a large farm and for baled sil age on a small farm, and both with farmer-owned machinery and using contrac tors. Results also suggest potential advantages from technology to clear ma cerated material off the stubble with low dry matter loss, and to harvest m acerated material without chopping. If either of these two further technolo gies can be implemented, the macerating mower system will have an economic performance superior to that of a conventional system. (C) 2000 Silsoe Rese arch Institute.