Effects of N and P fertilization on the biomass and ecological stoichiometric characteristics of Agropyron michnoi in sandy grasslands

For effective management of sandy grasslands, it is important to determine whether adding P fertiliser is conducive to plant growth under global N deposition. We therefore carried out a field experiment in which N and P fertiliser was added to sandy grasslands. The results showed that, with increasing N addition (or N + P addition), the C, N and P concentrations in the leaves and roots and the above- and belowground biomass of plants increased significantly. The maximum per cent increases in the N and P concentrations in the leaves and roots and the total biomass under N + P addition were greater than those under N addition. When N deposition exceeded 15 g N m−2 a−1, the N + P treatments were greater than the N treatments in terms of their effects on N concentrations in the leaves and roots, on the above- and belowground biomass and on the RSR, with the exception of the leaf N concentrations under the addition of 15 g N m−2 a−1. Our results suggest that P fertiliser under N deposition may increase the self-regulatory adaptation of plants via the C:N, C:P and N:P stoichiometry of both the leaves and roots, increase plant biomass, and promote grassland restoration.