Nitrogen form but not elevated CO₂ alters plant phosphorus acquisition from sparingly soluble phosphorus sources.

摘要

Background and aims: Maintaining nutrient supply, including phosphorus (P), is critical to ensure the adaptation of cropping systems to future elevated CO₂ (eCO₂) environments. There is much speculation about the role of sparingly soluble sources to supply plants with P so we tested the hypothesis that eCO₂ increases plant's ability to utilise P from sparingly soluble sources via affecting rhizosphere properties. Methods: Chickpea and wheat were grown for 6 weeks in washed sand supplied with 40 mg P kg-1 as either readily soluble Ca(H₂PO₄)₂ or sparingly soluble AlPO₄ (Al-P), FePO₄ or hydroxyapatite (HAP). Half plants were exposed to eCO₂ (700 ppm) while the others to ambient CO₂ (380 ppm). Results: Elevated CO₂ increased biomass production of both species but did not influence P concentration in plants, rhizosphere pH or Olsen P. Among the sparingly soluble P sources, HAP resulted in the maximum biomass and total P uptake in wheat and chickpea with wheat acquiring more P. Supply of nitrate, as compared to urea, to wheat decreased the uptake of P from HAP but increased it from Al-P. Conclusion: Elevated CO₂ does not specifically affect plant access to P from sparingly soluble P sources. Urea facilitates P acquisition from HAP whereas nitrate facilitates it from Al-P.