Nutrient Management Research Database

http://ucanr.edu/sites/Nutrient_Management_Solutions/files/212767.pdf

The standard procedure for determining nutritional status of stone fruit trees was established many years ago. It involves taking a sample of mature leaves in June or July and analyzing for all macro and micro nutrients. Tables have been published indicating sufficiency ranges and deficiency thresholds (and sometimes toxicity levels) for each element. These tables were developed from leaves showing deficiency symptoms, from hydroponic experiments with small seedlings and from surveys of healthy and deficient orchards. For some nutrients, there has not been enough experience with deficiencies in the field to establish a threshold. Generally, these studies have not related the nutrient status of the tree to the different components of yield or fruit quality except in a qualitative way. Over the past 5 years we have developed a system for studying the nutrition of mature peach and nectarine trees in the field. We planted trees in 60 large sand tanks and have been differentially fertilizing them in order to obtain widely varying nutrient contents. The full details of the treatments and results have been presented elsewhere (Johnson et al., 2003) and will not be reported here. For the purpose of this paper only the average fruit weight data from 2002 and 2003 on Zee Lady peach and Grand Pearl nectarine will be used. This information, together with a rather obscure method of analyzing nutritional data, will be presented as evidence for changing the currently established deficiency thresholds.

This report presents a summary of nutrient management research conducted with mature Zee Lady peach and Grand Pearl nectarine trees planted in large sand tanks.  The trees were fertilized differentially to obtain wide variation in nutrient contents.  A boundary line analysis approach was used, in which for every nutrient level there is a theoretical maximum yield level.  Yields below that maximum would represent a loss of yield potential.

60 peach and 60 nectarine trees from 2002 and 2003 were assessed to give a total of 240 separate data points, and fruit weights were scaled to an relative fruit weight, where the largest fruit of the data set was given a value of 1.

Highlights of the results include:

• Boundary lines indicate that maximum potential fruit weight is decreased when leaf tissue boron levels fall below 25 to 27 ppm
• Deficiencythesholds (leaf tissue) for the following nutrients were also estimated:
  • Phosphorus - .12%
  • Copper - 5 ppm
  • Zinc - 10 ppm
  • Iron 60 ppm (based on May leaf sample)