1985 Volume 54 Issue 3 Pages 301-306
Bud breaking effects of a leaching solution containing 20% lime nitrogen (55% CaCN2) and cyanamide (H2CN2) applied to the surface of dormant buds of glasshouse grown vines and single-bud cuttings of ‘Kyoho’ grape were examined.
Treatment of intact vines with CaCN2 in December, January and February advanced bud break in the following spring by 16, 9, and 5 days, respectively. Treatment during the period of deep dormancy was most effective, in agreement with previous results. The effect of 3% H2CN2 given at the corresponding times was very similar to that of CaCN2, with bud break being advanced by 15, 7 and 4 days, respectively.
Treatment of the single-bud cuttings bedded in December with CaCN2 and 0.5 or 1% H2CN2 during the same month advanced the bud break by 2 to 4 days. The bud breaking effect on the cuttings was much smaller than on the intact vines. Furthermore, at concentrations of H2CN2 above 2%, buds of the cuttings died due to chemical injury. In cuttings, the effective concentration of H2CN2 was one-third to one-sixth of that in intact vines. This might be the result of shallower dormancy due to wound effects in the cuttings. In late February, when dormancy had been broken, chemical injury to the cuttings occurred even when treated with CaCN2 and 1% H2CN2.
These results indicate that H2CN2 has the same effect as CaCN2 on bud break of ‘Kyoho’ grape, which suggests that the bud breaking effect of lime nitrogen is mainly due to the active form of the cyanide ion (CN-), H2NCN being produced by partial hydrolysis of CaCN2.