Barley uptake of N deposited in the rhizosphere of associated field pea

Abstract

N deposited in the rhizosphere of a legume may contribute to the N-nutrition of an intercropped non-legume. The process of deposition and subsequent uptake by a neighbouring plant is often termed N-transfer. The N-transfer from field pea (Pisum sativum L.) to associated spring barley (Hordeum vulgare L.) was determined in three pot experiments using a direct split-root N-15-labelling technique. The donor (pea) and receiver (barley) plants were grown with their root systems either mixed within the same soil compartment or separated by a 20 mu m mesh bag. Pea-derived N was detected in barley after 4 weeks of growth, but in most associations <1% of total pea N was recovered in barley. N-transfer from barley to pea was not detected when barley was grown as the donor. The amount of pea-derived N in barley increased markedly with time, probably due to the accelerated turnover of root and nodule debris. Separating the root systems reduced the barley recovery of pea-derived N to about half the amount recovered in the association where root systems grew in the same compartment. The death of pea, caused by spraying with a herbicide, increased the amount of N recovered in barley, whereas shading the pea plant had no effect on the amount of pea-derived N taken up in barley. The N deposited up to 45 days of growth contributed <5% of the barley shoot N in most treatments. However, at 70 days, 19% of the N in barley was derived from pea. It is concluded that field pea rhizodeposition of N may be a significant source of N to intercropped barley, especially at low rates of N-fertilization