Carlsson, Georg
(2005).
Input of nitrogen from N2 fixation to northern grasslands.
Diss. (sammanfattning/summary)
Umeå :
Sveriges lantbruksuniv.,
Acta Universitatis Agriculturae Sueciae, 1652-6880
; 2005:76
ISBN 91-576-6975-9
[Doctoral thesis]
![]() |
PDF
2MB |
Abstract
Forage legumes form N2-fixing symbioses with rhizobia and may thus make substantial contributions to the N pool in grasslands. However, to optimize their use as sources of N, it is important to elucidate the effects of management factors that influence their N2 fixation rates, and to develop convenient methods for measuring N2 fixation quickly and reliably. An analysis of published data on N2 fixation in the field showed that lucerne (Medicago sativa L.), red clover (Trifolium pratense L.), and white clover (T. repens L.) grown in mixtures with grasses derived most of their N from N2 fixation, irrespective of geographic location and management practices – and despite large inter-annual variations in legume dry matter yield (kg ha-1 year-1). Consequently, there were strong correlations between legume dry matter yield and amounts of N2 fixed (kg N ha-1 year-1), which can be used very simply to obtain estimates of N2 fixation in these legumes. In experimental grassland plots where the species richness of neighbouring vegetation was varied, alsike clover (T. hybridum L.), red clover, and white clover consistently derived at least half of their N from N2 fixation, measured by the 15N natural abundance (NA) method using three different reference plants. This method is sensitive to the degree of discrimination against 15N in the N2-fixing plant (B value) and the choice of reference plant. B values were therefore established for each of the three clover species in symbioses with different Scandinavian Rhizobium leguminosarum bv. trifolii genotypes. In red clover, reductions following cutting in the activity of the N2-fixing enzyme, nitrogenase, and the rate of shoot regrowth were dependent on the cutting height. The recovery in nitrogenase activity after cutting followed the rate of leaf area increment, which confirms the correlation between N2 fixation and growth found in field experiments. The results of the work underlying this thesis show that perennial forage legumes growing in grasslands are highly dependent on N2 fixation. Awareness of this should facilitate the development of resource-efficient management regimes for northern grasslands.
Authors/Creators: | Carlsson, Georg | ||||
---|---|---|---|---|---|
Title: | Input of nitrogen from N2 fixation to northern grasslands | ||||
Year of publishing : | September 2005 | ||||
Number: | 2005:76 | ||||
Number of Pages: | 50 | ||||
Papers/manuscripts: |
| ||||
Place of Publication: | Umeå | ||||
Associated Programs and Other Stakeholders: | Z - SLU - Libray > Odla mera | ||||
ISBN for printed version: | 91-576-6975-9 | ||||
ISSN: | 1652-6880 | ||||
Language: | English | ||||
Publication Type: | Doctoral thesis | ||||
Full Text Status: | Public | ||||
Agris subject categories.: | P Natural resources > P35 Soil fertility F Plant production > F01 Crop husbandry P Natural resources > P34 Soil biology | ||||
Subjects: | Not in use, please see Agris categories | ||||
Agrovoc terms: | nitrogen fixation, rhizobium, grasslands, soil fertility, medicago sativa, trifolium pratense, trifolium repens, trifolium hybridum, forage, feed legumes, plant production, models, sweden | ||||
Keywords: | Acetylene reduction activity, clover, cutting height, δ15N, forage, legume, methods, N2 fixation, perennial, Rhizobium, species richness | ||||
URN:NBN: | urn:nbn:se:slu:epsilon-721 | ||||
Permanent URL: | http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-721 | ||||
ID Code: | 895 | ||||
Department: | (NL, NJ) > Dept. of Agricultural Research for Northern Sweden (VH) > Dept. of Agricultural Research for Northern Sweden | ||||
Deposited By: | Georg Carlsson | ||||
Deposited On: | 02 Sep 2005 00:00 | ||||
Metadata Last Modified: | 21 Oct 2015 14:01 |
Repository Staff Only: item control page