Summer promotion of vegetative shoots to increase early flowering response of mango trees to ammonium nitrate sprays.
Medina-Urrutia V. M., Nuñez-Elisea R.
Author Affiliation: INIFAP - Tecomán, Apartado Postal 88, CP 28100 Tecomán, Mexico.
: 188-201
Abstract : During 1993-94, ammonium nitrate sprays applied in autumn were used to promote summer production of vegetative shoots, and to increase early flowering in 7-year-old trees of mango cultivars Haden and Tommy Atkins grown at Tecomán, Mexico. Haden and Tommy Atkins trees were treated in one of 4 ways: (1) terminal shoots pruned (PTS); (2) pruning plus a foliar paclobutrazol spray at 4000 ppm (PTS + PBZ); (3) GA3 spray at 25 ppm (GAS); or (4) non-treated control. Except for the controls, ammonium nitrate (2% aqueous solution) was sprayed on all trees on 15 and 30 November. PTS produced more summer vegetative shoots (1.38 shoots/terminal) than PTS + PBZ (1.21), GAS (0.94) or the controls (0.99). Haden and Tommy Atkins trees responded similarly to vegetative shoot-promoting treatments. Haden produced 68% of total flowering in January, whereas 70% of total flowering occurred in March for Tommy Atkins. Although early summer flushing was significantly promoted by pruning, early flowering was discouraged by rains during ammonium nitrate spraying in November. In another investigation, Haden trees were treated in one of 7 ways; (1) PTS; (2) PTS plus an application of soil drench at 7.5 g paclobutrazol/tree (PTS + PBZ); (3) PTS plus water stress; (4) elimination of the inflorescence axis (EIA); (5) PBZ soil drench alone; (6) ammonium nitrate spray only (ANS) (treatments 1-5 were also sprayed with ammonium nitrate); or (7) non-treated control. Trees subjected to PTS, PTS + PBZ or EIA had twice the number of vegetative shoots than controls. PTS and EIA increased early flowering by 16 and 51%, respectively, compared with ANS. The best early flowering response was obtained in Haden trees when a PBZ soil drench was applied alone or combined with summer pruning. The effects of the treatments on yield and fruit quality are discussed.