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Acta Prataculturae Sinica ›› 2025, Vol. 34 ›› Issue (5): 40-50.DOI: 10.11686/cyxb2024221

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Effect of phosphate-solubilizing bacteria and phosphorus on non-structural carbohydrate content and the carbon∶nitrogen∶phosphorus stoichiometry of alfalfa roots

Kong-qin WEI(), Ying-ying ZHANG, Jin-feng HUI, Chun-hui MA, Qian-bing ZHANG()   

  1. College of Animal Science & Technology,Shihezi University,Shihezi 832003,China
  • Received:2024-06-11 Revised:2024-07-15 Online:2025-05-20 Published:2025-03-20
  • Contact: Qian-bing ZHANG

Abstract:

The aim of this study was to determine the effects of phosphorus fertilizer applied with phosphate-solubilizing bacteria on the non-structural carbohydrate content and stoichiometric characteristics of alfalfa (Medicago sativa) roots. An experiment with a two-factor completely randomized design was established with two phosphorus (P2O5) fertilizer levels: 0 (P0) and 100 mg·kg-1 (P1); and four inoculation treatments: no inoculation (J0), single inoculation with Bacillus mucilaginosus (J1), single inoculation with Bacillus megaterium (J2) and mixed inoculation (J3), making a total of eight treatments. The root vigor, contents of soluble sugars, soluble protein, starch, and malondialdehyde, and the contents of carbon (C), nitrogen (N) and phosphorus (P) in the rhizosphere soil and roots of alfalfa were determined. Two-way ANOVA showed that phosphorus application and bacterial inoculation significantly affected the root vigor, the contents of malondialdehyde, soluble sugars, and starch in the roots, rhizosphere soil N∶P, and root C∶N, C∶P, and N∶P (P<0.05), but did not significantly affect the root soluble protein content (P>0.05). Further analyses showed that at the same level of phosphorus application, inoculation with phosphate-solubilizing bacteria increased alfalfa root vigor, soluble sugar content, and soluble protein content (except for J2P0 and J2P1); increased root starch content (except for J1P1); increased rhizosphere soil and root C, N, and P contents (except for root C in J2P1 and root N content in J1P0 and J2P0); and increased rhizosphere soil C∶P (except for J3P0) and N∶P; but reduced the rhizosphere soil C∶N and root malondialdehyde content (except for J1P1 and J2P1). Under the same inoculation treatment, phosphorus application increased root vigor and the contents of soluble sugars, soluble protein, and starch in the roots, increased rhizosphere soil C and P and root N and P contents, and decreased root C∶N, C∶P, N∶P, malondialdehyde content, and rhizosphere soil N∶P, compared with their respective values in the no-phosphorus control. On the basis of these comprehensive analyses, the treatments could be ranked, from the highest composite score to lowest, as follows: J3P1>J2P1>J1P1>J0P1>J3P0>J2P0>J1P0>J0P0. In conclusion, phosphorus application (100 mg·kg-1) and mixed inoculation with B. mucilaginosus and B. megaterium effectively increased the nutrient content of alfalfa rhizosphere soil and increased the accumulation of non-structural carbohydrates in alfalfa roots.

Key words: phosphate-solubilizing bacteria, phosphorus, alfalfa, non-structural carbohydrates, stoichiometry