N:P ratio of the grass Bothriochloa ischaemum mixed with the legume Lespedeza davurica under varying water and fertilizer supplies
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Background and Aims
Plant growth and ecosystem processes in semiarid regions are limited by soil nutrient and water availability. Nitrogen (N) and phosphorus (P) status and the N:P ratio alterations among plant organs are critical in understanding the physiology and productivity of the grass-legume mixture system. This study aimed to identify the N and P distribution patterns and N:P stoichiometry of a local grass species mixed with a legume species under varying water and fertilizer supplies.
A C4 perennial herbaceous grass Bothriochloa ischaemum and a C3 perennial leguminous subshrub Lespedeza davurica were grown in a pot experiment with a randomized complete block design consisting of four fertilizations (non-NP, +N, +P and +NP fertilizers), three soil water regimes (80, 60 and 40 % of soil water field capacity, FC) and six planting ratios (2:10, 4:8, 6:6, 8:4, 10:2, and 12:0, grass:legume plants, respectively). Plants were assessed for biomass production, N and P concentration and N:P ratios in various organs 202 days after sowing (DAS).
For the grass species (B. ischaemum), N and P concentrations of leaf, stem and root were higher when mixed with the legume (L. davurica) compared to its monoculture, and with a trend to decrease as its mixture proportion increased. Supply with P fertilizer (+P) increased N and P concentrations of B. ischaemum regardless of mixture proportions and soil water regimes. In mixtures, N concentration was the highest in the root system followed by the leaf, and the least in the stem. There was no significant difference in N:P ratio of the stem and the root across the mixture proportions under +P and +NP treatments, and among all soil water regimes, either. Root N:P ratio was significantly lower under +P and +NP than that under non-NP or +N treatment regardless of mixture proportions and soil water regimes.
N and P capture and absorption in B. ischaemum were greatly improved when mixed with the legume species, L. davurica. The N and P concentrations in different organs were influenced by both fertilization and the mixture proportions. Application with combined N and P fertilizers enhanced N and P uptake in B. ischaemum. P fertilization should be considered when establishing artificial grassland using native species in the region.
KeywordsN:P ratio Fertilization Soil water content Mixture plantation Nutrient availability
This work was financially supported by National Science Foundation of China (41371509), Fundamental Research Funds for the Central Universities (ZD2013020) and Hundred Talents Program of the Chinese Academy of Sciences.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no competing interests.
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