- Department of Agricultural Biosystems and Technology, Swedish University of Agricultural Sciences
The thesis summerisees and discusses studies concerning factors influencing ammonia release in cow houses and factors influencing nitrogen surplus and nitrogen efficiency on dairy farms. The first investigation was carried out at the Animal Experimental Station at Anarp. The aims were to investigate if a lower content of crude protein in the diet for higli-yielding dairy cows will decrease the ammonia release from manure. The ammonia release was significantly decreased for cows fed with lower protein levels compared with high protein diets. The effects of manure-handling system, type of cow houses and feeding of dairy cows on ammonia release were studied in a field investigation. Results demonstrated a higher release of ammonia in free stall barns with liquid manure handling systems compared with tie stall barns with solid manure handling systems. There was a higher ammonia release from cow diets with a higher content of crude protein. A theoretical calculation or the nitrogen efficiency and nitrogen surplus at cow level and farm level was carried out. The assumptions for the calculations were for a farm located in central Skåne (south Sweden) with 50 dairy cows arid 50 hectares of arable land. The nitrogen efficiency at farm level was 28% on an average. Nitrogen surplus per hectare varied between 135 - 145 kg when the intensity was 8600 kg milk/ha. Nitrogen balances from conventional dairy farms situated in southern Sweden were investigated using the farm gate method. Neither nitrogen surplus per hectare nor nitrogen efficiency showed significant effects of the manure-handling system. The results showed that nitrogen efficiency was significantly improved by including sugar beet in the crop rotation and was negatively correlated with milk yield per hectare and nitrogen fertiliser per hectare. Analysis of dairy farms with balances from three consecutive years 1997, 1998 and 1999 showed that these dairy farms decreased their nitrogen surplus by 25 kg N/ha between 1997 and 1998. This decrease was not repeated in the following year. Input of N from artificial fertiliser decreased significantly from the first year.
farm gate balances; environment; ammonia emission; milk production; manure handling system; cow houses; crude protein
Acta Universitatis Agriculturae Sueciae. Agraria
2002, number: 333
Publisher: Swedish University of Agricultural Sciences
Animal and Dairy Science