Update 2012: Managing Pistachio Nutrition
|The overall goal of this research project is to develop an integrated nutrient management practices for pistachio trees across different ranges of environments in California. The specific objectives of our work with long term and large scale pistachio project are discussed below.|
Determine the degree to which leaf nutrient status varies across a range of representative orchards and environments and determine the degree to which nutrient status varies within the canopy and within the year. Goal: To refine leaf sampling techniques and develop early season sampling protocols.
Validate current critical values and determine if nutrient ratio analysis provides useful information to optimize fertility management. Goal: Refine current critical values and develop new methods of leaf sample interpretation
Develop a phenology and yield based nutrient model for Pistachio Goal: Determine how much and when nutrients should be applied.
Location of the Project
The project is located at four mature orchard sites located in Kings, Kern, Fresno and Madera Counties representing major growing regions in California. Orchards are planted to Kerman (female) on uniform rootstocks and under microsprinkler irrigation. Samples are taken at 54 sampling points uniformly distributed in a 10-acre block of trees in eachorchard. The experimental trees have been selected in a regular 5x5 grid system at four experimental sites.
Summary of Project Activities
- Leaf samples are being collected from non-fruiting branches at a tree-canopy height of 6 ft. from May through August and one month post-harvest.Fruit samples from each tree are being used to determine dry weight and Nitrogen (plus other major nutrients) accumulation in the fruit at harvest.
- Yield is being determined by individual tree harvest performed by shaking the individual tree and weighing by hand. Pistachio nuts are being graded and dry yields are determined.
- Trunk diameter has been determined in each tree.
- Tissue nutrient determination for samples for the major elements (N, P, K, S, Ca, Mg, B, Zn, Fe, Mn, and Cu) in all fruit and leaf samples are being processed by the DANR analytical laboratory at UC Davis.
The pistachio project has made significant progress toward achieving these goals and will utilize the 4th year (2012) of full season activity to verify and validate current results and models. An up to date summary of the accomplishments of ongoing project is presented in pistachio report (Reference: Pistachio report, 2011).
Variations in leaf nutrient status of the trees over the growing season, between sites and years have been used to establish field sampling methodology and develop an early season sampling protocol.
- We determined the number of samples needed to estimate the true mean of nutrients with 90% confidence (2009, 2010 and 2011). To effectively obtain the average nutrient concentration (N, P, K) of a single production area (or orchard) of average variability growers must collect leaves from at least 17 trees each spaced at least 25 yards apart. This sampling protocol is valid for orchards of average variability – if clear areas of differential tree behavior are known, these areas should be sampled and managed separately.
- Early season leaf sampling offers management advantages to growers allowing for in season adjustment. We have used three years (2009, 2010, and 2011) of data across four locations in California and have determined that May samples can be used effectively to predict July tissue values. New standards based upon this approach will be made available to testing labs and at the UC ANR Fruits and Nuts Website.
Comparison of leaf tissue value and yield of all experimental tree samples over four sites and two years has allowed us to estimate the validity of current critical values.
- Initial analysis (year 2011 pending completion) suggests that all CV’s presented in the current Pistachio production manual, with the exception of Mg, are adequate. Critical values of Mg should be lowered from the current 0.6% to 0.45%.
- Ongoing analysis suggests that the ratio of nutrients in the plant may have an important effect on plant response. In a subset of orchards strong evidence suggests that low Mg is compromising yield and that tissue K levels can exacerbate this deficiency. Further analysis of nutrient interactions is underway.
Leaf tissue analysis alone does not provide sufficient information to make fertilization decisions.
- Nutrient budget curves quantifying the time course of nutrient uptake and total plant demand were developed and will be further validated with subsequent year’s data
- Average nutrient removal per 1000 lb of harvested product has been calculated for all essential elements. Twenty eight (28) lbs of N, 25 lbs of K and 3 lbs of P is removed for each 1000 lbs of marketable yield.
- This information is valuable for estimating demand or replacing nutrient export and provides a baseline for all fertilization planning with the goal of growers to provide fertilization rates that replace nutrients removed in crop (fruits).
Ongoing Plans for 2012
For more information see the presentations and publications under Outreach