AOBPreview published online on May 11, 2007
Annals of Botany, doi:10.1093/aob/mcm078
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Longevity of White Clover (Trifolium repens) Leaves, Stolons and Roots, and Consequences for Nitrogen Dynamics under Northern Temperate Climatic Conditions
1 Norwegian Institute for Agricultural and Environmental Research, Arable Crops Division, Apelsvoll, NO-2849 Kapp, Norway
2 Norwegian University of Life Sciences, Department of Plant and Environmental Sciences, PO Box 5003, NO-1432 Ås, Norway
* For correspondence. Present address: State Stende Cereal Breeding Institute, PO Dizstende, LV-3258, Talsi reg., Latvia. E-mail ievina.sturite{at}stendeselekcija.lv
Received: 2 November 2006 Returned for revision: 8 December 2006 Accepted: 5 March 2007
Background and Aims: White clover (Trifolium repens) is, due to nitrogen (N) fixation, important to the N dynamics of several northern temperate agroecosystems. This study aimed at monitoring growth and death of major white clover plant organs to assess their potential contribution to within-season N input and risk of off-season N losses.
Methods: White clover (‘Snowy’) was studied in a plot and root window experiment in southeast Norway (60°42'N, 10°51'E). Leaves, stolons and roots were tagged for lifespan measurement in harvested and unharvested stands during two experimental years. The availability of soil inorganic N was measured by plant root simulator (PRSTM) probes.
Key Results: The longevity of leaves and petioles ranged from 21 to 86 d (mean = 59 d), of main stolon sections from 111 to over 677 d (mean = 411 d) and of roots from 27 to 621 d (mean = 290 d). About 60 % of the leaves produced had turned over by the end of the growing season and another 30 % had died or disappeared by the subsequent spring. Harvesting reduced the longevity of stolons and increased plant fragmentation, but did not decrease leaf or root lifespan or increase soil N availability. From the plant organ turnover data, it was estimated that the gross N input to the soil–plant system from white clover in pure stand during two growing seasons corresponded to a 2·5-fold increase over the total N in harvestable shoots.
Conclusions: The short lifespan and poor over-wintering of leaves showed their potential importance as a nitrogen source in the soil–plant ecosystem but also their potential contribution to the risk of off-season N losses.
Key words: Harvesting, inorganic nitrogen, lifespan, leaves, main stolons, roots, Trifolium repens, turnover, white clover