Elevated CO sub(2) induced rhizosphere effects on the decomposition and N recovery from crop residues

• Published in: Plant and soil 2016-11, Vol.408 (1-2), p.55-71
• Main Authors: Butterly, Clayton R, Wang, Xiaojuan, Armstrong, Roger D, Chen, Deli, Tang, Caixian
• Format: Article
• Language: English
• Subjects: Pisum sativum; Triticum aestivum
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1007/s11104-016-2911-4

Elevated atmospheric CO sub(2) (eCO sub(2)) can affect soil-plant systems via stimulating plant growth, rhizosphere activity and the decomposition of added (crop residues) or existing (priming) soil organic carbon (C). Increases in C inputs via root exudation, rhizodeposition and root turnover are likely to alter the decomposition of crop residues but will ultimately depend on the N content of the residues and the soil. Two soil column experiments were conducted under ambient CO sub(2) (aCO sub(2), 390 ppm) and eCO sub(2) (700 ppm) in a glasshouse using dual-labelled ( super(13)C/ super(15)N) residues of wheat (Triticum aestivum cv. Yitpi) and field pea (Pisum sativum L. cv. PBA Twilight). The effects of eCO sub(2) and soil N status on wheat rhizosphere activity and residue decomposition and also N recovery from crop residues with different N status (C/N ratio 19.4-115.4) by different plant treatments (wheat, wheat + 25 mg N kg super(-1) and field pea). Total belowground CO sub(2) efflux was enhanced under eCO sub(2) despite no increases in root biomass. Plants decreased residue decomposition, indicating a negative rhizosphere effect. For wheat, eCO sub(2) reduced the negative rhizosphere effect, resulting in greater rates of decomposition and recovery of N from field pea residues, but only when N fertiliser was added. For field pea, eCO sub(2) enhanced the negative rhizosphere effect resulting in lower decomposition rates and N recovery from field pea residue. The effect of eCO sub(2) on N utilisation varied with the type of residue, enhancing N utilisation of wheat but repressing that of field pea residues, which in turn could alter the amount of N supplied to subsequent crops. Furthermore, reduced decomposition of residues under eCO sub(2) may slow the formation of new soil C and have implications for long-term soil fertility.