EVAPORATIVE COOLING AND CYANAMIDE ON BUDBREAK AND MATURATION OF GRAPEVINE, CV. PERLETTE.

Chilling accumulation infuence dormancy of grapevines and determines budbreak. Under desert conditions, hydrogen cyanamide (H 2 CN 2 ) improve bud opening. To increase even further the quantity and uniformity of bud break, the effect of fall evap rative cooling (EC) alone or in combination with H 2 CN 2 (2.5%v/v was evaluated. Microsplinklers operated for 40 seconds at 10 min intervals from 10:00 h to 17:00 h, from 20 oct to 18 dec 1990. H 2 CN 2 was applied on 21 dec, one day after pruning. Cyanamide treated plants or with the chemical + EC, had 19% and 32% budbreak, respectively, by jan 15. Control or EC vines opened until feb 20, and reached 40% and 57% final values by mar 25. Therefore, cyanamide and EC acted sinergisti cally to open buds earlier and uniformily, although not on final budbreak. Harvest started may 8 with cyanamide + EC, five days earlier than cyanamide alone; by may 13, accumulated harvest was 39% and 13% respectively, and of 92% and 77% by may 28. Control vines with or without EC, were harvested early may to mid june.