Phosphorus supply enhances the response of legumes to elevated CO2 (FACE) in a phosphorus-deficient vertisol
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Background & aims
Understanding the mechanism of how phosphorus (P) regulates the response of legumes to elevated CO2 (eCO2) is important for developing P management strategies to cope with increasing atmospheric CO2 concentration. This study aimed to explore this mechanism by investigating interactive effects of CO2 and P supply on root morphology, nodulation and soil P fractions in the rhizosphere.
A column experiment was conducted under ambient (350 ppm) (aCO2) and eCO2 (550 ppm) in a free air CO2 enrichment (FACE) system. Chickpea and field pea were grown in a P-deficient Vertisol with P addition of 0–16 mg P kg−1.
Increasing P supply increased plant growth and total P uptake with the increase being greater under eCO2 than under aCO2. Elevated CO2 increased root biomass and length, on average, by 16 % and 14 %, respectively. Nodule biomass increased by 46 % in response to eCO2 at 16 mg P kg−1, but was not affected by eCO2 at no P supply. Total P uptake was correlated with root length while N uptake correlated with nodule number and biomass regardless of CO2 level. Elevated CO2 increased the NaOH-extractable organic P by 92 % when 16 mg P kg−1 was applied.
The increase in P and N uptake and nodule number under eCO2 resulted from the increased biomass production, rather than from changes in specific root-absorbing capability or specific nodule function. Elevated CO2 appears to enhance P immobilization in the rhizosphere.
KeywordsFree air CO2 enrichment FACE N2 fixation Nodulation P acquisition P fractions Rhizosphere
We thank Dr. Clayton Butterly and anonymous reviewers for reviewing the manuscript. This research was supported by an Australian Research Council Linkage Project (LP100200757), and utilised the SOILFACE facilities at DPI Horsham which were developed with funding by the Victorian Department of Primary Industries (VDPI), the University of Melbourne (UM), the Grains Research and Development Corporation (GRDC), the Federal Department of Agriculture, Fisheries and Forestry (DAFF) and the Australian Greenhouse Office (AGO).
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