HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Morris, D. R. Articles by Weaver, W. Search for Related Content PubMed Articles by Morris, D. R. Articles by Weaver, W. Agricola Articles by Morris, D. R. Articles by Weaver, W.

Mobilization of ¹⁵N from Soybean Leaves as Influenced by Rhizobial Strains¹

Nitrogen nutrition of soybeans [Glycine max (L.) Merr.] during pod development is important in determining seed yield. Soybeans utilize leaf N to meet the N needs of developing fruit which may reduce yield potential. A field experiment was undertaken using ¹⁵N to test the hypothesis that high N₂-fixing rhizobia would delay mobilization of N from leaves to developing pods. Three strains of Rhizobium japonicum, USDA strains 110, 31, and an ineffective mutant of strain 8-0, varying in N₂-fixation effectiveness were used as inoculum to determine their influence on the utilization and translocation of N during pod fill. Foliarly applied ¹⁵N urea was sprayed onto leaves five times prior to pod formation to label vegetative N. Total application of N was approximately 3 kg/ha. During the first 17 days of pod development approximately 25% of the incorporated ¹⁵N was mobilized to the pods regardless of the rhizobial strain. During the final stages of pod development, mobilization of labelled N continued at nearly a linear rate for all rhizobial treatments. for USDA strain 110, there was an insignificant net loss in leaf and petiole N during the first 17 days of pod development which indicated there was an exchange between N₂ recently fixed and N previously incorporated into leaves. The rate of N₂-fixation by both effective strains of rhizobia increased during pod development. Even though strain 110 fixed more total N than strain 31 the final seed yield for both treatments was similar due to differential partitioning of N. Future research is needed to elucidate the partitioning of N₂ fixed during pod development and to determine why the better N status of plants inoculated by strain 110 did not result in increased yields.

Key Words: Effective rhizobia • Glycine max • Ineffective rhizobia • Nitrogen nutrition • Pod filling • Rhizobium japonicum

² Research associate and professor, Soil and Crop Sciences Dep., Texas A&M Univ., College Station, TX 77843.

Received for publication November 8, 1982.