Abstract: To provide reference for formulating reasonable management measures in the dry farming area of Longzhong Loess Plateau, we explored the effects of no-tillage and straw mulching modes on carbon (C), nitrogen (N), and phosphorous (P) ecological stoichiometry in spring wheat and soil. Based on the long-term conservation tillage \[conventional tillage (T), notillage with no straw mulching (NT), conventional tillage with straw incorporation (TS), no-tillage with straw mulching (NTS)\] positioning experiment set in Mazichuan Village, Lijiabao Town, Anding District, we measured C, N, and P concentrations in different spring wheat organs (i.e., grain, leaf, straw) and soil in 2019. The results showed that compared with conventional tillage (T), conservation tillage treatments (NT, TS, and NTS) significantly increased soil C∶N and C∶P (P<0.01), but did not affect N∶P (P>0.05). The magnitude of C∶N and C∶P changes among different treatments was in the order of NTS>TS>NT>T. The order of C∶N for different organs of spring wheat was straw>leaf>grain, and the order of C∶P was grain>leaf>straw. Compared with T treatment, conservation tillage treatments significantly reduced leaf C∶N, straw C∶N and C∶P, whereas N∶P in each organ showed no variation among different treatments (P>0.05). The growth of spring wheat in this area was limited by N availability. The overall internal stability of C, N and P of spring wheat and the soil was P>N>C, the ratio internal stability was C∶N>C∶P>N∶P, and the internal stability of element ratio was stronger than that of each element. In short, NTS treatment is the most suitable farming measure for spring wheat growth and development in the dry farming area of the Longzhong Loess Plateau. The growth of spring wheat in this area is susceptible to N limitation. Nitrogen fertilizer application should be appropriately increased based on NTS treatment to ensure the growth of spring wheat.

Key words: tillage measure, spring wheat, soil, ecological stoichiometry, homeostasis.