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Rhizodeposition of nitrogen by red clover, white clover and ryegrass leys

Høgh-Jensen, Dr Henning and Schjoerring, Dr Jan K. (2001) Rhizodeposition of nitrogen by red clover, white clover and ryegrass leys. Soil Biology & Biochemistry, 33, pp. 439-448.

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Correct assessment of the rhizodeposition of N in grassland is essential for evaluation of the biological N2-fixation of legumes, for the total N balance of agro-ecosystems, and for the pre-cropping value of grasslands. Using a leaf-feeding technique by which plants were 15N labelled while growing in mezotrons in the field, the rhizodeposition of N by unfertilised red clover, white clover and perennial ryegrass growing in pure stands was shown to amount to 64, 71 and 9 g N m-2, respectively, over two complete growing seasons. The corresponding values for red clover and white clover growing in mixtures with ryegrass were 89 and 32 g N m-2, respectively. The rhizodeposited N compounds, including fine roots, constituted more than 80% of the total plant-derived N in the soil, and in all cases exceeded the amount of N present in stubble. In the mixtures of red clover-ryegrass and white clover-ryegrass and the pure stands of red clover, white clover and ryegrass, respectively, the rhizodeposition constituted a 1.05, 1.52, 1.26, 2.21 and 2.77 fold increase over the total shoot N harvested during the two production years. In pure stands and mixtures of clover, 84 and 92%, respectively, of this N derived from biological N2 fixation. It is concluded that rhizodeposition provides a very substantial input of N to legume-based grassland systems with great consequences for ecosystem N balance and turnover. Furthermore, the amount of atmospheric-derived N in the rhizodeposits may exceed that in the harvested shoots.

EPrint Type:Journal paper
Keywords:red clover, rhizodeposition, ryegrass, white clover, Pasture, nitrogen
Subjects: Soil > Nutrient turnover
Crop husbandry > Crop combinations and interactions
Crop husbandry > Production systems > Pasture and forage crops
Research affiliation: Denmark > DARCOF I (1996-2001) > I.2 Nitrogen fixation, recycling and leaching in organic cropping systems
Deposited By: Jensen, Dr Henning Høgh
ID Code:288
Deposited On:05 Dec 2002
Last Modified:12 Apr 2010 07:27
Document Language:English
Refereed:Peer-reviewed and accepted

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