Foliar N/P ratio and nutrient limitation to vegetation growth on Keerqin sandy grassland of North-east China

Abstract

To examine whether the critical leaf N/P ratios (of 14, 16) are valid to test nutrient limitation in the context of semi-arid sandy grasslands, an experiment was conducted on a Keerqin sandy grassland in North-east China to investigate the responses of plant biomass and nutrient concentrations to fertilization. Plant biomass production and leaf nutrient concentrations were measured after five consecutive years of fertilization with N (20gNm-2year-1) and/or P (10g P2O5m-2year-1). Nitrogen fertilization increased the shoot biomass by twofold and consequently the shoot/root ratio, whereas P fertilization had little effect on either shoot biomass or shoot/root ratio. Leaf N/P ratio varied among species with an average of 5·6 in the control, while the mean leaf N/P ratio (7·5) under the N fertilization treatment remained below the threshold of 14. Our results suggest that the critical N/P ratio (14, 16) is not applicable as a test for nutrient limitations in the context of semi-arid, sandy grassland.