草地生态系统中家畜尿N转化研究

Study on turnover of livestock urine nitrogen in grassland ecosystem

系统总结了放牧家畜尿N转化过程中,尿N矿化和NH3挥发,尿N硝化和反硝化作用,及其影响因素和相互关系。家畜尿N矿化作用快、持续时间短,尿沉积加速N矿化;NH3挥发速度为裸地>草地,单播草地>混播草地;NH3挥发对尿N损失起主导作用。硝化作用在尿沉积1周后才开始明显,存在明显时滞特性;NO3--N淋洗主要发生于畜尿沉积当年,草地植物对春施尿N的利用率比秋施尿N高;NO3--N淋洗为奶牛>绵羊,三叶草草地>混播草地>禾草草地。尿斑构成草地尿N反硝化作用的主体,反硝化作用产生N2O和N2,是尿N损失的另一主要因素。尿N损失随排泄尿N量的增加而增加。

Nitrogen mineralization and N H3 volatilization,nitrification and denitrification, and their influencing factors and interrelations on grazing livestock urine nitrogen turnover in grassland ecosystems were summarized systematically in this paper. The rate of urine nitrogen mineralization is fast and is completed quickly,urine deposition can encourage urine nitrogen mineralization. NH3 volatilization loss is bare land 〉grassland,monoculture grassland 〉 mixed grassland,and N H3 volatilization plays an important role on loss of urine nitrogen. Urine nirtrogen nitrification becomes obvious after one week of livestock urine deposition,and exhibit a distinct time-delayed characteristics. NO3^- -N leaching occur mainly in the same year of livestock urine deposition, the urine nitrogern utilization rate of grassland vegetation of livestock urine deposition in spring is higher than that of urine deposition in autumn; and NO3^- -N leaching loss is cow〉sheep, clover grassland〉mixed grassland〉grass grassland. Animal urine patches consist of the main part of urine nitrogern denitrification, and urine nitrogern denitrification produce N2O and N2, which is another main factor of urine nitrogern loss. In addition, the urine nitrogern loss of grazing livestock increase with the excretion nitrogern increase.