CONTRIBUTION AND TRANSFER OF NITROGEN FROM COVER CROPS TO RASPBERRY PLANT USING ISOTOPIC TECHNIQUES WITH ¹⁵N

The objective of this study was to determine the effect of a legume cover crop on raspberry production and to quantify the eventual nitrogen contribution from the legumes to raspberry plants.
The study was carried out in a 5 year-old organic orchard of raspberry cv.
Heritage.
Cover crop treatments were: a) white clover (Trifolium repens), b) a mixture of white clover and tall fescue (Festuca arundinacea) and c) a control without cover crop.
To estimate the nitrogen recovery by raspberry plants derived from the legume, a solution of ammonium sulfate 10% ¹⁵N atom excess (80 kg N ha^-1) was applied to raspberry plants growing with and without cover crops.
During the growing season in summer the ¹⁵N content (%¹⁵N atom excess) and total N was determined in leaves, stems and fruits, and the percentage of N derived from the legume in raspberry plant calculated.
Pastures of white clover and white clover + tall fescue produced high levels of biomass, 8.6 to 9.4 t DM ha^-1, with more than 3.3% of N. In soil mineral N content important differences were detected, with significant higher N content in the legume cover crop treatments.
Total raspberry biomass production was significantly higher (P≤ 0.05) when they grew for two years in association with a legume cover crop than when grown on bare soil.
On average 18–22% of the stem and leaf N content of raspberry plants growing with white clover cover crop derived from the legume.
Evaluations made at the end of raspberry plant growth cycle showed that recovered N in fruits was small (2.5 to 7.0%).

IX International Rubus and Ribes Symposium

C. Ovalle, M.I. González, J. Hirzel, I. Pino, A. del Pozo, S. Urquiaga

Rubus idaeus, Trifolium repens, legume pastures

https://doi.org/10.17660/ActaHortic.2008.777.71