Effects of Phosphorous Addition and Arbuscular Mycorrhizal Fungi Inoculation On Maize Photosynthesis and Growth in Reclaimed Soils of Mining Area.

Abstract�Improvement of soil fertility in the reclaimed lands of mining disturbed areas has been challenged with mostly the low bioavailability of soil indigenous phosphorus (P) as well as the unacceptable low use efficiency of fertilizer P applied. With the structural advantages and special physiological functions, abuscular mycorrhizal fungi (AMF) enhance plant P uptake, and thus inoculation of AMF may promote P utilization in the reclaimed soils of mining disturbed lands. The objective of this study was to evaluate the effects of AMF inoculation (i.e. AMF vs. no AMF inoculation, NAMF) on photosynthesis characteristics and growth of maize in a loess soil one year after reclamation in a coal-mining disturbed area. The soils were amended with fertilizer P at four rates, including 0,25,50 and 100 mg P kg^-1. AMF inoculation increased maize root AMF colonization by 263%, relative to the NAMF. AMF inoculation promoted AMF contribution to maize P uptake, with the contribution rates of 25% and 33% for above and belowground biomass, respectively. AMF inoculation increased leaf transpiration and net photosynthetic rates (mycorrhizal dependence was 5% and 11%, relative to the NAMF), regardless of the P rate. This was further evidenced by the decrease of intercellular CO₂ concentration caused by AMF inoculation, as compared with the NAMF. The enhancement of AMF on net photosynthetic rate was maximized at 0 P mg kg-1, but decreased with the increase in P rate. However, no AMF effects were found on leaf stomatal conductance. Consequently, compared with NAMF, AMF inoculation increased maize leaf area, stem diameter and dry weight of total biomass by 18,19,20 and 61%, respectively, as expressed in mycorrhizal contribution rate, with fertilizer P rates below or up to 50mg kg^-1, above which no AMF effect was observed. The results suggest that AMF inoculation poses potential for promotion of crop productivity, which can be beneficial to the restoration of vegetation in reclaimed soils that were heavily disturbed from coal mining.

Key Words: The Reclaimed Mining Area; Arbuscular Mycorrhiza Fungus; Growth of Maize; Photosynthesis