Nitrogen-15 labeling and nitrogen transformation in silage maize-cattle manure system
青贮玉米-牛粪尿体系的15N标记及氮素转化研究

15N tracer technique has been used in N cycling and utilization for livestock manure.The abundance and amount of 15N in different manure components and N forms affect whether 15N fate is consistent with all manure N.The purpose of this article is to better understand the characteristics of 15N transformation in silage maize-cattle manure system and distribution in cattle feces and urine by using 15N tracer technique.First,a sand culturing experiment was conducted by watering improved Hoagland nutrient solution with 15N labeled ammonium sulfate(AS,60 atom% 15N) to cultivate 15N labeled maize("Nongda-108").Then,15N labeled maize was mixed with unlabeled maize at a ratio of 55︰45,according to their amount of nitrogen,to get mixed 15N forage.Finally,a 2-years-old cattle starved for 2 days was fed on the mixed 15N forage for 4 days and starved 2 days again.During the 6 days,cattle feces and urine were collected and measured separately.The results showed that 15N abundance was 48.024% in labeled maize,26.579% in mixed silages,and 8.044% in cattle manure.In addition,26.3% of AS 15N was discovered in maize,36.0% of silage 15N was discovered in cattle manure.In all the manure N collected,fecal N,urine N,fecal ammonium N and urine ammonium N accounted for 70.25%,29.75%,5.44% and 0.03%,their 15N abundance were 9.223%,5.261%,6.505% and 5.419%,respectively.In 15N labeled manure of cattle fed on 15N labeled silage in a short period,the abundance of 15N in cattle urine and feces,and in different N forms were different.The 15N abundance of urine was lower than that of feces,and 15N abundance of mineral and easy-mineralized nitrogen was lower than that of hardly mineralized nitrogen.