Tuesday, 11 July 2006

Effects of Intercropping and Organic Phosphate Application on Plant Growth, P Uptake and Microbial Community in Rhizosphere of P-Inefficient Wheat.

Dongmei Wang1, Petra Marschner2, and Zakaria Solaiman2. (1) School of Soil and Water Conservation, Beijing Forestry Univ, No 35 Qinghui Donglu, Haidian District, 100083, Beijing, China, (2) School of Earth and Environment Sciences, The Univ of Adelaide, DP 636, SA 5005, Adelaide, Australia

Many soils are poor in plant available P which may limit plant growth. P-efficient genotypes grow better at low P availability than P-inefficient genotypes. . Our previous studies showed that P efficiency was also related to changes in P availability and microbial community composition and activity in the rhizosphere. We tested the hypothesis that P-efficient plant genotypes (chickpea and wheat Goldmark) could improve P uptake and growth of the P-inefficient wheat genotype Janz by intercropping. A pot experiment was conducted in a glasshouse. The soil with low P availability from Mount Bold, SA was amended with 100 mg P kg-1 soil as phytate (C6H18O24P6) as an organic P source. The pots (20cm x14cmx12cm) were separated into two compartments to allow 3 different types of root interaction: no root barrier to allow complete interaction between the root systems, a 33-ÁM nylon mesh barrier to prevent direct root contact but permit exchange of exudates, nutrients and microorganisms, a solid root barrier to prevent rood interaction. The P-inefficient Janz was grown in combination with either P-efficient Goldmark or P-efficient chickpea. The plants were harvested after 9 weeks. The growth (whole plant dry weight) and P uptake of Janz intercropped with chickpea with no root barrier and mesh barrier were significantly greater than with the solid root barrier. Growth and P uptake of Janz intercropped with Goldmark were significantly greater with no root barrier than with the mesh barrier and solid root barrier. Growth and P uptake of P-efficient chickpea and P-efficient Goldmark intercropped with P-inefficient Janz were significantly greater with no root barrier than with the mesh barrier and solid root barrier. The results suggest that utilization of organic P by Janz were improved by intercropping with chickpea and Goldmark. The improved growth of the wheat Goldmark and chickpea without root barrier is probably due to the greater soil volume that was available compared to the treatments with a barrier. Microbial community composition assessed by Fatty Acid MethylEster (FAME) differed between genotypes and treatments indicating that the microbial communities in the rhizosphere of plants in intercropping systems interact.

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