Kura Clover Early Growth Is Comparable to That of White Clover When Not Nitrogen Limited

ABSTRACT

Kura clover (Trifolium ambiguum M.B.) is a forage legume whose use is currently restricted by establishment difficulties. In this study, we evaluated the effects of rhizobial strain selection and nitrogen (N)-supply on early growth of Kura clover. There were eight treatments in total: non-inoculated, non-N-fertilized Kura clover; Kura clover fertilized or not with N-fertilizer and inoculated with either a commercial rhizobial strain (UMR6015) or a new rhizobial strain (CT1-2); non-inoculated, non-N-fertilized white clover (Trifolium repens L.); and white clover inoculated with rhizobial strain UMR6906 fertilized or not with N-fertilizer. Plants were collected every two weeks starting on the fourth week after seeding for a total of four harvests. Total dry matter (TDM), foliage DM (FDM), and root DM (RDM), plant height, and leaf and nodule number were recorded at each sampling; percent N, total N, and leaf area were determined 10 weeks after seeding. All inoculated Kura clover plants supplied with inorganic N produced similar TDM and FDM, but greater RDM than similarly treated white clover. Kura clover inoculated with CT1-2 also produced TDM and FDM similar to that of inoculated non-N-fertilized white clover, which was not the case with UMR6015. Kura clover produced significantly fewer leaves than white clover; however, it had greater individual leaf weight. Kura clover plants inoculated with UMR6015 produced 140% more nodules than those inoculated with CT1-2 or than white clover; however, most were small and ineffective. Total N content of non-N-fertilized Kura clover plants inoculated with CT1-2 was 70% greater than those inoculated with UMR6015, and similar to that of inoculated non-N-fertilized white clover plants, suggesting similar N₂ fixation levels. Results demonstrate that the use of UMR6015 may not maximize Kura clover early growth in N-limited environments. If not N-limited, Kura clover early FDM and TDM accumulation is comparable to that of white clover.

Keyword:

• forage
• Kura clover
• nodulation
• rhizobia

ACKNOWLEDGMENTS

This research was supported by a grant awarded to Philippe Seguin by the Natural Sciences and Engineering Research Council of Canada (NSERC). Guillaume Laberge and Fazli Mobood also received scholarships from the Fonds pour la Formation de Chercheurs et l'Aide à la Recherche du Québec (FCAR) and the International Council for Canadian Studies (ICCS) under the Commonwealth Scholarship and Fellowship Program, respectively.