Soil Aggregate Size and Mycorrhizal Colonization Effect on Root Growth and Phosphorus Accumulation by Berseem Clover

Abstract

The effects of soil aggregate size and mycorrhizal colonization on phosphorus (P) accumulation and root growth of Berseem clover (Trifolium alexandrinum L.) were studied. Root length and dry weight decreased with increasing aggregate diameter. Colonization of clover plants by arbuscular mycorrhizae (Glomus intraradices Schenck and Smith) improved root growth and P accumulation in all aggregate‐size classes. Although total root length of either mycorrhizal or nonmycorrhizal plants decreased with increasing aggregate diameter, the length of living external hyphae was not affected by aggregate size. Thus, colonized root length was improved by 20% as soil aggregate diameter increased. Total P accumulation per plant decreased with increasing aggregate size. However, total P accumulation per unit root length improved as the size of soil aggregate increased. In our study, mycorrhizal colonization improved total P accumulation and root growth in soil with large aggregates and compensated, in part, for the effect of soil strength.

Keywords:

• Arbuscular mycorrhiza
• impeded roots
• P uptake
• Trifolium alexandrinum

ACKNOWLEDGMENTS

The authors thank Professor Sally Smith from the University of Adelaide for her constructive comments on the manuscript. Financial support for this research by the University of Shahid Chamran is gratefully acknowledged.