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N2-fixation and residual effect of four legume species and four companion grass species

Rasmussen, J.; Søegaard, K. and Eriksen, J. (2012) N2-fixation and residual effect of four legume species and four companion grass species. European Journal of Agronomy, 36, pp. 66-74.

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Inclusion of forage legumes in low-input forage mixtures improves herbage production and soil fertility through addition of nitrogen (N) from N2-fixation. The impact of different grass–legume mixtures on the N contribution of the forage mixture has rarely been investigated under comparable soil and climatic conditions. We conducted a field experiment on a sandy soil at two nitrogen levels with seven twospecies forage mixtures: alfalfa, bird’s-foot trefoil, red clover, or white clover in mixture with perennial ryegrass, and white clover in mixture with meadow fescue, timothy, or hybrid ryegrass. We found high N2-
fixation of more than 300 kg N ha−1 from both red clover and alfalfa even when the two mixtures received 300 kg total-N ha−1 in cattle slurry. The addition of cattle slurry N fertilizer lowered N2-fixation for white clover and red clover as expected, but for bird’s-foot trefoil and alfalfa no changes in the proportion of N derived from N2-fixation was observed. We conclude that the competition for available soil N from perennial ryegrass in mixture was an important factor for the proportion of N in alfalfa, white clover, and bird’s-foot trefoil obtained from N2-fixation. White clover had a high proportion of N derived from
atmosphere for all companion grasses despite significant differences in white clover proportion. Although the perennial ryegrass–alfalfa mixture in the grass phase yielded more than twice the N from N2-fixation compared to white clover in the perennial ryegrass mixture, this did not in the following year lead to higher residual N effects of alfalfa. Both in terms of N yield in the grass phase and N yield in the subsequent spring barley red clover contributed most to the improvement of soil N fertility.

EPrint Type:Journal paper
Subjects: Crop husbandry > Crop combinations and interactions
Farming Systems > Farm nutrient management
Research affiliation: Denmark > DARCOF III (2005-2010) > ORGGRASS - Grass-clover in organic dairy farming
Deposited By: Eriksen, Professor Jørgen
ID Code:20635
Deposited On:26 Mar 2012 08:22
Last Modified:26 Apr 2013 08:58
Document Language:English
Refereed:Peer-reviewed and accepted

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