青贮玉米-牛粪尿体系的15N标记及氮素转化研究

15N示踪技术已开始应用于畜禽粪便氮素循环与利用研究领域,而15N在畜禽粪便不同组分和不同形态氮素中的丰度与数量将直接影响到畜禽粪便15N示踪去向与氮素实际去向的一致性。为了解15N在畜禽粪便标记过程的转化特点和在标记粪尿的分布特征,本文首先采用改进的、含有15N标记硫酸铵(60 atom%15N)的Hoagland营养液砂培种植15N玉米,然后将15N玉米和普通玉米以55∶45的氮配比作为混合青贮饲料饲喂1头已空腹2 d的2龄黄牛,饲喂4 d后停喂2 d,收集全部牛粪尿并对其不同组分和形态氮素的15N丰度和数量进行分析。结果表明:标记玉米、混合青贮饲料、牛粪尿的15N丰度分别为48.024%、26.579%和8.044%;标记玉米对硫酸铵15N的回收率为26.3%,牛粪尿对标记玉米15N回收率为36.0%。在收集的牛粪尿氮中,牛粪全氮、牛尿全氮、牛粪铵态氮和牛尿铵态氮量分别占70.25%、29.75%、5.44%和0.03%,其15N丰度分别为9.223%、5.261%、6.505%和5.419%。在短期内通过饲喂黄牛15N青贮饲料制备的标记牛粪尿中,15N丰度在不同组分和形态氮素中的分布并不相同,牛尿氮的15N丰度低于牛粪氮,矿质态和易于矿化态氮的15N丰度低于不易矿化态氮。

Nitrogen-15 labeling and nitrogen transformation in silage maize-cattle manure system

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.