5. CONCLUSION
Significant changes of C, N, P content and stoichiometric ratio in
plants and soil began to appear after 7 years of alfalfa planting,
indicating that the 7th year was a turning point. The C:P and N:P ratios
of soil and alfalfa are positively correlated. The N:P ratio increased
with the growth age of alfalfa, and it exceeded 14 in 7, 9, and 10
years, indicating that the growth of alfalfa has been severely
restricted by P. Alfalfa responds to the increasing N:P ratio by
increasing underground biomass and decreasing aboveground biomass, while
it can improve the nutrient content and biological characteristics of
the soil at the meantime. Collectively, our research combines
stoichiometric characteristics with alfalfa cultivation, indicating that
after 7 years of cultivation, the growth of alfalfa has seriously
deteriorated, but it can significantly improve the soil fertility of Mu
Us Desert edge area.
ACKNOWLEDGMENTS
This research is jointly supported by the National Key Research and
Development Program of China (2017YFE0104500), the China Agriculture
Research System (CARS–34), Shaanxi Academy of Forestry Science and
Technology Innovation Program (SXLK2020-0204).
AUTHOR’S CONTRIBUTION
Professor Yang and Professor Xin carried out the conception and design
of the study, Zhouchang Yu, Yuanying Li and Ruirui Yan conducted the
entire experimental study, Wei Zhang, Yi Zhou, Zhiguo Xie and Zhouchang
Yu participated in the manuscript preparation and revision,Professor
Yang, Professor Xin and Zhiguo Xie provided financial support for the
study.