Nitrogen balance during production of 15N-labeled dairy cow compopsted manure on a practical scale
2005
Matsunami, H.(National Inst. of Livestock and Grassland Science, Tsukuba, Ibaraki (Japan)) | Hojito, M.
15N-labeled composted manure was produced using five adult dairy cows and 420 m(2) of grassland and the flow of 15N during the process was analyzed. Cows were fed 15N-labeled Dactylis gromerata 1st cut silage containing 6.2 atom% 15N. After 2 days, 15N concentration in their feces increased significantly, reaching 4.95 atom% 15N at the 10th day, and 15N concentration was almost stable after 8 days. Cows were subsequently fed 2nd cut silage containing 4.0 atom% 15N, resulting in a slight decrease in 15N concentration. However, 15N concentration remained high at approx. 3 atom% 15N, and decreased immediately after non 15N-labeled hay was fed upon completion of the 17-day procedure. Results of 15N concentration in urine were almost parallel with those for feces, although 15N concentration was significantly lower. In order to increase 15N concentration, feces and urine excreted when 15N concentration in the feces exceeded 3 atom% 15N were used for production of the compost. After dehydrating the feces to 68 kg kg(-1) water content and concentrating the urine in a heating oven at 80 deg C, the dried feces and concentrated urine were mixed and composted in an air sucking composter for 4 weeks. One hundred and forty seven kilograms of composted manure was obtained, containing 3.95 atom% 15N and 50 kg kg(-1) water. Uniformity of labeled 15N was determined by fraction separation through acid hydrolysis differing by acid concentration, and almost uniform homogeneity was confirmed. Satisfactory compost manure labeled 15N was obtained using this procedure. Relative N recovery ratio compared to the amount of N contained in the applied 15N labeled fertilizer was 23.6% in excreta, with the loss of 11.1% during drying and composting, and 10.6% N remained in the final composted manure.
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