Contribution from Stolons and Roots to Estimates of the Total Amount of N2Fixed by White Clover (Trifolium repensL.) |
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Authors: | JORGENSEN FINN VANMAN; LEDGARD STEWART F |
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Institution: | Plant Ecosystems and Nutrient Cycling, Plant Biology and Biogeochemistry Department, Risø National Laboratory, DK-4000, Roskilde, Denmark AgResearch, Ruakura Agricultural Research Centre, Private Bag 3123, Hamilton, New Zealand |
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Abstract: | Growth and N-accumulation rates in leaves, stolons and rootsof individual white clover plants were studied in three experimentsusing two methods. In a growth chamber experiment, the relativedifferences between tissues were found to be almost constantfor a wide range of clover plant sizes. The stolon dry matter(DM) production was 56% and the root DM production 40% of theDM production in leaves. The N yield of stolons was 30% whileN yield in roots was 34% of N yield in leaves. The effect ofN application on these relations was investigated in a glasshouseexperiment. Application of N reduced the root:shoot N ratiofrom 0.50 to 0.28, whereas the stolon+root:leaf N ratio (i.e.for abovevs.below cutting-height tissues) was only reduced from0.97 to 0.80. In a field trial with two contrasting N regimes,growth and N accumulation were measured on individual cloverplants. Dinitrogen fixation was estimated by15N isotope dilutionbased on analysis of leaves-only or by including stolons. Usingleaves-only did not affect the calculation of percentage ofclover N derived from N2fixation (% Ndfa) since the15N enrichmentwas found to be uniform in all parts of the clover. A correctionfactor of 1.7 to account for N in below cutting-height tissueis suggested when N2fixation in white clover is estimated byharvesting the leaves only.Copyright 1997 Annals of Botany Company Leaves; N accumulation; N2fixation; 15N isotope dilution; pastures; roots; root/shoot ratio; stolons; Trifolium repensL.; white clover |
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