The addition of potassium nitrate to rest-breaking chemicals in subtropical tree crops improved their efficacy by 20-30%.

Several experiments were conducted in southeast Queensland, Australia, to determine whether combinations of new rest-breaking chemicals could induce more uniform bud break and increase flowering of a range of low-chill temperate and subtropical species (low-chill stone fruit, i.e. nectarine cv Springbite, persimmon and custard apple).

The most successful rest-breaking chemicals were Armobreak (alkolated amine) and Waiken (mix of fatty acid esters), but only when combined with potassium nitrate, which greatly improved their efficacy by 20-30%. Potassium nitrate alone has a mild rest-breaking ability. In custard apple when sprayed together, Waiken (emulsified vegetable oil) 3% and potassium nitrate 5% resulted in statistically significantly greater number of laterals and flowers per meter main branch length than the control treatment or Waiken 3% alone on current season wood (Figure 1). Potassium nitrate has a synergistic effect with other dormancy- breaking substances, improving branching, flowering, fruit-set and early fruit maturation.

potassium nitrate tree crops

Figure 1. Effect of Waiken 3% and KNO3 5% sprays in custard apple on number of laterals and flowers per meter branch length on current season wood.

 

Author

George, A. P., R. H. Broadley, R. J.Nissen, and G. Ward. 2000. Effects of new rest-breaking chemicals on flowering, shoot production and yield of subtropical tree crops. Acta Horticulturae International Symposium on Tropical and Subtropical Fruits 575: 835-840.