Nutrient Management Research Database

http://ucanr.edu/sites/Nutrient_Management_Solutions/files/212659.pdf

In this modern era of increasing concern over environmental stewardship, every fertilization event needs to be carefully evaluated and fully justified. Excess nutrients can easily escape from the orchard and become environmental pollutants or even remain in the orchard as soil contaminants. It is important to apply fertilizers only when they are needed for optimum production and to make sure they are not applied in excess. Having a method for assessing nutritional status of trees is a critical tool to help guide this process.

This paper summarizes the standard approach to nutrient sampling of fruit trees at the point of presentation - mid summer leaf analysis - and then presents a protocol for dormant shoot sampling as an alternative, as well as preliminary research on nutrient content and correlation with tree productivity and fruit quality.   

This paper suggests dormant shoot sampling as an alternative to mid-summer leaf sampling for evaluating nutrient status in peach and nectarine trees.  Results correlating nutrient concentrations of dormant shoots with productivity processes are presented.  A potential boron deficiency threshold of 12 to 15 ppm B is suggested.  Research presented here also found a strong correlation with dormant shoot P and a relationship with Zn, pointing towards deficiency thresholds of 0.12% P and 20 ppm Zn, as well as relationships between shoot P, fruit shape and premature fruit drop.  Dormant shoot Zn also correlated with spring leaf deficiency symptoms.