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Sealed lysimeters for the direct estimation of dinitrogen fixation by grain legume crops
Author(s) -
SIMS A. P.,
BARBER D. J.,
FOLKES B. F.,
WALLS D.
Publication year - 1986
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.1986.tb01573.x
Subject(s) - lysimeter , nitrogen fixation , sativum , legume , pisum , agronomy , nitrogen , environmental science , fertilizer , chemistry , soil science , horticulture , soil water , biology , organic chemistry
A new technique has been devised for the direct estimation of the contribution of N 2 ‐fixation to the total nitrogen of a legume crop. Sealed lysimeters and ancillary equipment are described by which it is possible to enclose in a gas‐tight system the roots of some of the plants within the crop, together with their associated core of soil. The normal soil atmosphere can then be replaced by one containing 15 N 2 , thus allowing, from the 15 N content of the resulting plants direct calculation of the N 2 ‐fixation. Regular monitoring is necessary to ensure that soil O 2 , CO 2 and moisture contents are maintained at normal field levels. The results indicate that the technique is capable of achieving its objectives and, provided the seedlings establish well initially, the resultant plants fully match the field average at final harvest. It has been possible to maintain the labelling of the soil atmosphere sufficiently constant to ensure that reliable and highly reproducible estimates of N 2 ‐fixation are obtained. Using Pisum sativum cv. Meteor at densities of 160 plants m −2 , fixation accounted for about 90% of the total nitrogen uptake. The limitations and merits of the method are compared with those of the 15 N‐fertilizer dilution method.