Distribution and utilization of nitrogen on moderately and heavily grazed temperate desert steppe using the N-15 tracing technique

文献类型： 外文期刊

第一作者： Jiao, Ting

作者： Jiao, Ting;Li, Yajuan;Zhao, Guiqin;Wu, Jianping;Zhao, Shengguo;Lei, Zhaomin;Wu, Jianping

作者机构：

关键词： N-15 tracing technique; Nitrogen fertilizer utilization rate; Distribution of nitrogen; Temperate desert steppe; Degenerate grassland

期刊名称：APPLIED SOIL ECOLOGY （ 影响因子：4.046； 五年影响因子：4.884 ）

ISSN： 0929-1393

年卷期： 2018 年 124 卷

页码：

收录情况： SCI

摘要： Due to overgrazing, grasslands in northern China have been severely degraded since 1980s. Grassland biomass and plant populations decreased dramatically. Application of fertilizer is a common technique for pasture management in many countries, however, it has not been widely used on China grasslands. Nitrogen (N) is an important productivity driver in grassland ecosystems, but its transportation, allocation and utilization in temperate desert steppe remained unclear. In this study, a sequential nitrogen addition experiment was conducted on a farm in southwestern Jingtai County, Gansu Province, in the transition zone between Loess Plateau and Tengger Desert. Two different grassland plots with moderate grazing (MG) and heavy grazing (HG) were fenced in 2008. N (NH4NO3) was applied at the rate of: 12.25 g N.m(-2), 24.5 g N.m(-2), 36.75 g N.m(-2) and 49 g N m(-2), respectively. To determine the amount and distribution of nitrogen applied to the grassland, the N-15 tracer technique was adopted. The results demonstrated that the recovery rates of N-15 ranged from 3.8% to 11.7% in the plants. The nitrogen recovery amount from both shoots and roots increased significantly (P < 0.05), while the recovery rate decreased gradually with increasing nitrogen application. The N-15 recovery from shoots under HG was much less than from MG. In one growing season, only 18.2%-8.0% of labeled N-15 was derived from fertilizer, so soil nitrogen is still the main source absorbed and utilized by plants. As much as 50.4%-84.4% labeled N-15 remained in soil, which was evenly distributed throughout 0-20 cm soil layer, and significantly increased with nitrogen application rates. The nitrogen remained in the top soil (0-10 cm) pool was much less than that of 10-20 cm layer (P < 0.05). The nitrogen loss amounts and rates were significantly different among N treatments, which indicated that there was an increasing trend in N loss with increasing N application rates. Loss/recovery analysis showed that 12.25 g N.m(-2) was the recommended application rate. This work is expected to provide the lowest risk/return ratio and produce both economic and environmental benefits for the degraded grassland in Gansu and analogus regions in China.

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