The benefits of phosphorus fertilization of trees grown on salinized croplands in the lower reaches of Amu Darya, Uzbekistan

D. Djumaeva, J. P.A. Lamers, A. Khamzina, P. L.G. Vlek

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)


Afforestation of degraded croplands by planting N2-fixing trees in arid regions is highly recognized. However, fixation of atmospheric nitrogen gas (N2) by woody perennials is often limited on phosphorus (P) poor soils, while any factor limiting N nutrition inhibits tree growth. In a two-factorial field experiment, the effect of three P amendments was examined during 2006-2008 on N2 fixation, biomass production, and foliage feed quality of actinorhizal Elaeagnus angustifolia L. and leguminous Robinia pseudoacacia L. With the 15N natural abundance method, N2 fixation was quantified based on foliar and whole-tree sampling against three non-N2-fixing reference species: Gleditsia triacanthos L., Populus euphratica Oliv., and Ulmus pumila L. The P applications, in March 2006 and April 2007 only, included (i) high-P (90 kg P ha-1), (ii) low-P (45 kg P ha-1), and (iii) 0-P. After 3 years, the average proportion of N derived from atmosphere (Ndfa, %) increased from 78 % with 0-P to 87 % with high P when confounded over both N2-fixing species. With the used density of 5,714 trees ha-1, the total amount of N2 fixed (Ndfa, kg N ha-1) with high-P increased from 64 kg N ha-1 (year 1) to 807 kg N ha-1 (year 3) in E. angustifolia and from 9 kg N ha-1 (year 1) to 155 kg N ha-1 (year 3) in R. pseudoacacia. Total above-ground biomass increases were too variable to be significant. Leaf N content and therewith also leaf crude protein content, which is an indicator for feed quality, increased significantly (24 %) with high-P when compared to 0-P for E. angustifolia. Overall findings indicated the suitability of the two N2-fixing species for afforestating salt-affected croplands, low in soil P. With P-applications as low as 90 kg P ha-1, the production potential of E. angustifolia and R. pseudoacacia, including the supply of protein-rich feed, could be increased on salt-affected croplands.

Original languageEnglish
Pages (from-to)555-569
Number of pages15
JournalAgroforestry Systems
Issue number3
Publication statusPublished - 2013 Jun
Externally publishedYes

Bibliographical note

Funding Information:
Acknowledgments The German Ministry for Education and Research (BMBF) funded this study (0339970D). The financial support of the German Academic Exchange service (DAAD) to the first author is gratefully acknowledged. All authors are thankful for the support of the ZEF/UNESCO Landscape Restructuring Project in Uzbekistan. The authors thank Mrs. Margaret Jend for her English corrections. We thank the


  • Actinorhizal species
  • Afforestation
  • Central Asia
  • Elaeagnus angustifolia
  • Leguminous species
  • Robinia pseudoacacia

ASJC Scopus subject areas

  • Forestry
  • Agronomy and Crop Science


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