Carbon accumulation, nitrogen and phosphorus use efficiency of Sophora davidii seedlings in response to nitrogen supply and water stress

A greenhouse experiment was conducted to explore whether additional nitrogen (N) supply could enhance carbon (C) accumulation, and phosphorus (P) use efficiency (NUE_P) of Sophora davidii seedlings under dry conditions. Two-month-old seedlings were subjected to a completely randomized design with three water (80, 40 and 20% water field capacity (FC)) and three N supply (N0: 0, Nl: 92 and Nh: 184 mg N kg⁻¹ soil) regimes. Water stress decreased C, N and P accumulation, NUE_P, N and P uptake efficiency (NUtE_N and NUtE_P) regardless of N supply. The S. davidii seedlings exhibited strong responses to N supply, but the responses were not consistent with the various N supply levels. Nl increased C, N and P accumulation, and improved NUE_P, NUtE_N and NUtE_P in the same water treatment. In contrast, Nh did few or even depress effects on C, N and P accumulation, and NUE_P, although NUtE_N and NUtE_P increased with Nh in the same water treatment. Even so, NUE_N decreased with increase of N supply in the same water treatment. The results suggested that appropriate or low N supply should be recommended for S. davidii seedling establishment in dry environment by improving C accumulation and NUE_P.