Topping of tobacco (Nicotiana tabacum L.) plants (removal of the inflorescence) is not practised in Cyprus. Two field experiments were carried out at Akhelia Station, in 1985 and 1986, to test whether topping increased the yield or improved leaf quality of flue-cured tobacco grown under different types of irrigation. In contrast to the results of other studies, topping when the corolla had appeared on half the flowers did not increase yield. Topping when the inflorescence was just clear of the leaves (21 leaves harvested from topped plants v. 32 leaves from untopped plants) increased fresh yield by 7·0% but dry matter yield by 18·0%. The effects of topping were more marked on the leaves reaped at the third and fourth harvests, which constituted 52% of the fresh yield or 60% of the dry matter yield. At these harvests, leaves from topped plants had a lower percentage of midrib material (18·5 v. 21·0%) than leaves from untopped plants but a higher dry matter content (19·2 v. 17·2%) and specific leaf weight (80·0 v. 56·0 g/m2). Leaves of the fourth harvest from topped plants (27% of the total fresh yield) contained appreciably more nicotine (1·34%) than leaves from untopped plants (0·40%) but had a similar content of reducing sugars (20%). Topping did not influence the N, P and K contents of the leaves.
Irrigation increased fresh yield from 12·0 t/ha (225 mm water) to 24·0 t/ha (450 mm water) and dry matter yield from 2·0 to 3·8 t/ha, respectively, in Expt 1.
As Cypriot tobacco growers are paid for fresh yield delivered to the curing plant, the marginal increase of fresh yield with topping will hardly cover the cost of the extra operations involved.