Verdamping uit ligbodems van vrijloopstallen : oriënterende modelberekeningen = Water evaporation from bedding in dairy cattle freestall barns : model approach

Water evaporation from bedding in freestall dairy cattle houses was modeled. Calculated water evaporations from excreta in composting and non composting beddings were much lower in Holland than in Israel. A model approach to study the drying potential of bedding materials in freestall dairy cow barns under Dutch climate conditions was performed. Water evaporation from bedding in freestall dairy cattle houses was modeled. This was done as part of a feasibility study of freestall barns with different beddings under Dutch meteorological conditions. The beddings are made up of mixtures of soft composting, or non composting materials and animal excreta. Two available models on composting and drying were combined. The estimated water flux from urine and feces that is excreted on the bedding was integrated in the model approach. Model calculations were performed to compare the order of magnitude of evaporation from the bedding area under Dutch, Israeli and Minnesotan climate conditions and at 18 versus 9 m2 of bedding area per animal. Calculated water evaporations from excreta in composting and non composting beddings were much lower under Dutch weather conditions than under Israeli conditions. The calculated evaporation under cold Minnesotan winter conditions was lower and in hot Minnesotan summer was higher than under Dutch conditions. The calculated evaporation from a bedding that is composting was higher than from a non composting bedding. The calculated rate of composting was strongly dependent on the heat flux that results from conversion of organic matter and the heat loss from the bedding. The heat flux is strongly influenced by the air velocity above the bedding. High air velocities result in a large heat loss that may slow down or even inhibit the thermophylic composting process. The lower evaporation rate of inorganic beddings may be compensated to some extend by increasing the air velocity above the bedding. To keep the top layer of the bedding sufficiently dry it may also be searched for a bedding with a high fluid infiltrating capacity. By adding fresh bedding material or controlled drying of part of the bedding material outside the barn problems during adverse climate conditions may also be tackled. On farm pilot experiments with bedding materials and management are needed to test whether or not it is possible to keep the top layer of the bedding at an acceptable level of dryness under cold and moist Dutch weather conditions