Inoculated seeds of phasey bean (Macroptilium lathyroides cv. Murray) were sown in a sand
culture in a naturally-lit glasshouse, and imgated daily with nitrogen-Free nutrient solution. At early
flowering, the plants were either left uncut or cut at node 5 (high) or node 1 (low), retaining the
corresponding residual leaf areas of 74, 11 and Ocm 2 plant 1respectively. Following this initial cutting,
new shoots were individually harvested at the frequency of one, two, three, four or eight times
over a penriod of 56 days in Phase 1. Total dry weight of new shoots, seed yields and nitrogen concentrations
in the herbage were assessed. A II plants were allowed to regrow during the next 21-day
recovery period in Phase 2. Then, the root systems and plant tops were harvested. Nodulation,nitrogen fixation (total N) and regression analyses on s011Je plant parameters were computed. In Phase
1, cumulative yields of new shoots harvested following high or low-level cutting declined significantly
with increasing harvesting frequency, but yield reductions due to low-level cutting were detected only
under high harvesting frequencies. In Phase 2, recovery growth was always better following high than
low-level cutting, but unexpectedly, the various harvesting frequencies had no effect on recovery
growth following high cutting. After low-level cutting, high or low harvesting frequency reduced
recovery growth compared with moderately frequent defoliation (two harvests in 56 days), which
coincided with early flowering on the new top growth. Recovery growth had a positive linear correlation
(r = 0.98 ***) with nitrogen fixation, which was also linearly correlated with nodulation. These
results are briefly discussed with reference to the current concept that regrowth of nodulated forage
legumes is largely dependent on symbiotic nitrogen fixation
