Published online by Cambridge University Press: 27 March 2009
A model of a drying swath has been developed and used with 20-year long meteorological data sets from 32 sites in north-west Europe to provide an objective assessment of the influence of weather on field hay drying. The model considered the swath in terms of its bulk properties but incorporated the effects on swath drying of soil evaporation and stubble transpiration: delays in swath drying caused by interception of rain or dew were calculated explicitly.
A cutting season from May to September was assumed, and results given in terms of the number of daily cuts reaching various moisture contents in less than 10 days, and especially those reaching 25% (dry-weight basis) within 5 days so that dry-matter losses were relatively small, and immediate long-term storage was possible. Rainfall amounts on the faster-drying swaths were usually less than 1 mm. A large inter-annual variability in hay-drying prospects was demonstrated, even at sites with fairly good climates for drying on average. The most favourable conditions for field drying were shown to occur substantially earlier in the cutting season at maritime sites than at those with a more continental climate. Conditioning of the swath allowed more cuts to dry to a prescribed moisture content, but with the penalty of larger average rainfall on the swath, and consequent loss of quality.