Soil contents and stoichiometry of carbon, nitrogen, and phosphorus in Finnish farmland and feedbacks on management patterns

The coupled cycles and interactions of soil carbon (C), nitrogen (N), and phosphorus (P) are fundamental for soil quality and soil organic matter (SOM) formation. Low C:N ratios through nitrogenous fertilizer addition may accelerate SOM cycling and promote C mineralization in soil, whereas P limitations may decline C storage by reducing plant and microbial biomass production. Deeper soil layers’ C-N-P stoichiometry has an important role in regulating SOM formation in subsoils. However, there is little information on soil C:N:P stoichiometry in deep soil layers of farmland. In this study, soil columns up to one meter were collected from 32 farms distributing across Finland with different soil texture and agricultural management history. The one-meter soil columns were cut into 10 cm deep slices and analyzed for the total organic carbon (TOC), total nitrogen (TN) by dry combustion method and total phosphorus (TP) contents by aqua regia digestion and ICP-OES method. Overall, the TOC, TN and TP contents all dropped sharply in 30-40 cm soil layers, but TP contents rose again in deep soil. The role of agricultural management practice (including crop rotation, crop cover, crop diversity and fertilization) on soil C:N:P stoichiometry as well as organic matter accumulation in the deep soil layers were explored. The preliminary results will be presented in the poster. The data deepens our understanding of soil C, N and P coupling and interaction related to soil C sequestration.