Article Dans Une Revue Plant and Soil Année : 2007

Comparison of two 15N labelling methods for assessing nitrogen rhizodeposition of pea

Résumé

Two 15 N labelling methods for assessing net rhizodeposition of nitrogen (N) in pea crop (Pisum sativum L.) were compared in the greenhouse and in the field: the cotton-wick (CW) and the splitroot (SR) methods. Rhizodeposition is defined as the organic material lost from roots during their growth through the soil. CW is a method in which 15 N urea was supplied to the plant in pulses via a wick threaded through the stem. In SR, the root system was divided between a hydroponic labelling compartment (LC) containing the labelling nutrient solution (1 or 5 mM 15 NO 3 -15 NH 4 ) and a compartment filled with soil in which the amount of 15 N rhizodeposition was assessed. The percentage of N derived from rhizodeposition (%Ndfr), was used to calculate the amount of N rhizodeposition which was obtained from the ratio of atom % 15 N excess of the soil : atom % 15 N excess of the roots. Above ground parts in the field accumulated markedly more dry matter and N than in the greenhouse, regardless of the labelling method. 15 N enrichments of above ground parts were higher than those of roots recovered from the soil. Results indicated that amount of 15 N applied to plants were lower in SR than in CW. Additionally, LC roots of SR tended to retain large amounts of 15 N. As a consequence, atom % 15 N excess of roots was less than 1% in SR, whereas most values varied from 1% to 4% in CW. However, relationships between enrichments of the soil and of the roots were different in SR and CW. It was not possible to compare the Ndfr:root-N ratio between the two methods, but the ratio of Ndfr:plant-N was found to be 10% higher in SR than in CW. Finally, relative to total plant-N, the total contribution of below ground parts to the N pool of the soil reached 22-25% at maturity for the two methods. From our experiments, we could not conclude that one method is better than the other for estimating either net rhizodeposition of N or the contribution of a pea plant to the soil N pool. However, CW is easier to adapt and monitor under field conditions than SR.

Dates et versions

hal-05011539 , version 1 (07-04-2025)

Identifiants

Citer

Stéphanie Mahieu, Joëlle Fustec, Marie-Line Faure, Guénaëlle Corre-Hellou, Yves Crozat. Comparison of two 15N labelling methods for assessing nitrogen rhizodeposition of pea. Plant and Soil, 2007, 295 (1-2), pp.193-205. ⟨10.1007/s11104-007-9275-8⟩. ⟨hal-05011539⟩
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