ISSN:
1573-5036
Keywords:
Acetylene reduction
;
Lucerne
;
Medicago sativa
;
15N methodology
;
Nitrogen fixation
;
Quantitative estimation
;
Seasonal pattern
Source:
Springer Online Journal Archives 1860-2000
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Summary Lucerne is an important forage legume in the south and south-east of Sweden on well-drained soils. However, data is lacking on the apparent amount of nitrogen derived through N2 fixation by field-grown lucerne. This report provides basic information on the subject. The experiment was performed in a lucerne ley grown 40 km north of Uppsala. The input of nitrogen through fixation to the above-ground plant material of an established lucerne (Medicago sativa L.) ley was estimate by15N methodology during two successive years. The amount of fixed N was 242 kg N ha−1 in 1982 and 319 kg N ha−1 in 1983. The proportion of N derived from the atmosphere (%Ndfa) was 70% and 80% for the two years respectively. The first harvest in both years contained a lower proportion fixed N. Both N2 fixation and dry matter production were enhanced during the second year, particularly in the first harvest. The Ndfa was 61% in the first harvest in 1982, compared to 72% Ndfa during the same period in 1983. This demonstrates the strong influence of environment on both dry matter production and N2 fixation capacity of the lucerne. In addition anin situ acetylene reduction assay was used in 1982 to measure the seasonal distribution of the N2 fixation and in 1983 to study the effect of soil moisture on the N2 fixation process. The seasonal pattern showed great dependence on physiological development and harvest pattern of the lucerne ley. The maximum rate of N2 fixation occurred at the bud or early flower stage of growth and was followed by a rapid decline as flowering proceeded. After harvest the nitrogenase activity markedly decreased and remained low during at least two weeks until regrowth of new shoots began. Irrigation doubled the nitrogenase activity of the lucerne in late summer 1983, when soil moisture content in the top soil was near wilting point. No changes in nitrogenase activity did occur in response to watering earlier during the summer, when the soil matric potential was around −0.30 MPa.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02149828
