Update 2013: Managing Pistachio Nutrition Overview

Current Pistachio Industry Problems

 

At present, growers primarily use leaf tissue analysis to determine tree nutrient status and make fertilizer management decisions. Previous results of a survey of pistachio growers, and consultants in California, suggested that the existing leaf sampling protocol and comparison of the tissue results with the established standards does not provide sufficient guidance for nutrient management.
Concerns with leaf tissue testing include:

• A poor correlation between tissue nutrient concentration and soil nutrient availability
• A high degree of variability in tissue nutrient concentration in adequately fertilized crops within a single tree and within the same field.
• Additionally, the current practice of sampling late in the summer limits the grower’s ability to make in-season fertilizer adjustments.
• Another problem with the leaf sampling results is that these analyses do not provide information on the rate or timing of fertilizer application.

2013 Update | Findings | Model

 

Contribution of Current Project in Optimizing Fertilizer Use and Pistachio Yield

Substantial nutritional information was gathered under the pistachio nutrient optimization project entitled “Development of leaf sampling and interpretation methods for pistachio and the development of a nutrient budget approach to fertilizer management in pistachio”. This large scale project was conducted from 2009 to 2012 in four pistachio producing counties in California (Madera, Kern, Fresno and Kings Counties). In this study, we have assessed new and improved ways to assess the nutrient status of the trees to help pistachio growers manage their fertilizer applications with more precision.

Extensive leaf (4000) and fruit samples (4000) and yield data (>1000 trees) were collected at multiple times across four growing seasons and wide geographic locations to determine the degree of variability in tissue nutrient concentrations over time, space, and within tree canopies and to develop nutrient budget curves for major nutrients. Variations in leaf nutrient status of the trees over the growing seasons, between sites and years were used to refine the leaf sampling methodologies and to develop an early season sampling protocol. This early season sampling protocol offer management advantages to growers by providing information on which to base decisions about in-season fertilizer adjustments. Additionally, the large leaf data set was used to determine the mean nutrient status of the major nutrients in the field and to estimate the validity of current critical values of major nutrients in California.

Parallel to the development of improved leaf sampling protocols an analysis of the full suite of nutrients in the fruit combine with the yield data were used to develop nutrient budget curves for pistachio. The nutrient budget model as a management tool helps growers to optimize the time and rate of fertilizer application to match with the tree demand. The implementation of the improved leaf sampling strategies combine with the nutrient budget models is expected to help growers to better monitor and manage the nutrient status of their orchards and increase their profitability and environmental stewardship.