Bi-directional nitrogen transfer between legume and non-legume plants
van Kessel, C.
Non-N2-fixing crops inter-cropped with legumes may benefit through transfer of symbiotically fixed N from the legume crop. The pattern of N transfer by mechanisms non dependent on decomposition of plant tissues was studied in a greenhouse. In addition, a study accessed the effect of inter-cropped alfalfa (Medicago sativa L.) on meadow bromegrass (Bromus riparius Rhem.) forage and N yield by a combination of N transfer mechanisms occurring under field . conditions. In the first study, shoot portions of one alfalfa or one bromegrass plant (donor) were foliarly fed with N labelled ammonium sulphate. No 15N from bromegrass was transferred to alfalfa, whereas 15N from alfalfa plants was transferred mainly to bromegrass plants. Transfer of 15N between plants of the same species was not significant in alfalfa and only detected in the nearest plant of bromegrass. The 15N content of the receptor plants showed that underground movement of N between plants occurred within 3 days. In the field study, swards of single bromegrass and alfalfa inter-cropped with bromegrass were seeded in rows 17. 8 cm apart. In the fell owing year individual rows of plants, adjacent to each other, on both sides of the edge between the different swards were harvested separately for dry matter (DM) and N yield. Results of bromegrass were related to distance from the nearest row of alfalfa. Forage yield gradually increased from 427 to 1230 kg ha-1 and N yield increased from 53 to 184 kg ha-1 as the distance between the bromegrass row and the alfalfa row decreased from 71.1 to 17. 8 cm. Yield of bromegrass located up to 35.6 cm from alfalfa was significantly increased, indicating transfer of N from alfalfa to bromegrass in agronomically relevant amounts.
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