Characterization of nitrogen transfer from diverse red clover populations to companion bluegrass and impact on soil nitrogen dynamics under field conditions

R. M. M. S. Thilakarathna1, Y. A. Papadopoulos1*, A. V. Rodd3, S. A. E. Fillmore4, A. N. Gunawardena1 and B. Prithiviraj5


Research into the dynamics of nitrogen flow between legume and companion grasses may provide a management strategy for developing efficient cycling of nitrogen (N) and reduce losses of this essential nutrient in crop production systems.

In the current study the ability of two diverse red clover (Trifolium pratense L.) cultivars (‘AC Christie’ - diploid and ‘Tempus’ - tetraploid) to transfer fixed nitrogen and the impact of these cultivars on soil nitrogen dynamics were evaluated under field conditions. Plants from each cultivar were transplanted into an established bluegrass (Poa pratensis L.) stand in 2008. Samples were collected from three harvests during the 2009 growing season and nitrogen transfer from the red clover cultivars to companion bluegrass was measured using the isotope dilution technique and natural abundance methods. Soil samples and soil water samples were also collected to evaluate cultivar effects on soil N dynamics.

Both the red clover cultivars were shown to have high N fixing capacity across three harvests and more than 90% of the clover nitrogen was derived from biological N fixation. The proportions of bluegrass N derived from N transfer were 7, 11 and 26 % with respect to the first, second and third harvests. The soil N associated with the two red clover cultivar rhizospheres was different from each other during the growing season. In this field study the soil extractable nitrate concentration of the red clover rhizosphere was consistently higher than ammonium concentration. Soil nitrate content with ‘Tempus’ increased as the growing season progressed. Soil extractable nitrate of the ‘Tempus’ sward was higher than the ‘AC Christie’ stand in the top 15 cm of soil as well as at the 15-30 cm zone. The soil water nitrate content associated with the ‘AC Christie’ sward increased periodically but remained constant throughout the growing period for ‘Tempus’ which suggests that the dynamics of nitrogen cycling is distinctly different between the two cultivars. Therefore selection of appropriate legume-grass mixtures is important to increase N transfer while minimizing N leaching losses.


Proceedings of Plant Canada Conference. Saint Mary's University, Halifax, NS. July 17-21, 2011.

Author Locations and Affiliations

(1) Department of Biology, Dalhousie University, Halifax, NS, Canada B3H 4J1
(2) Agriculture and Agri-Food Canada, Nova Scotia Agricultural College, Truro, Nova Scotia, Canada B2N 5E3
(3) Agriculture and Agri-Food Canada, Charlottetown, Prince Edward Island, Canada CIA 4N6
(4) Agriculture and Agri-Food Canada, Kentville, Nova Scotia, Canada B4N 1J5
(5) Department of Environmental Sciences, Nova Scotia Agricultural College, Truro, Nova Scotia, Canada B2N 5E3

Posted May 2013