Crop Nutrient Status & Demand in Pistachio: Patrick Brown

Development of Leaf Sampling and Interpretation Methods for Pistachio and Development of a Nutrient Budget Approach to Fertilizer Management in Pistachio

Patrick Brown and Muhammad Ismail Siddiqui

The objectives of our work with pistachio are to improve the practice, use and utility of leaf sampling, develop a phenology and yield based nutrient model. The integration of these objectives will help to develop best management practices (BMP) for pistachio.  Improved sampling and monitoring strategies and yield determination and quantification of fruit N remobilized from fruit back to the tree provides a sound and flexible approach to ensure high productivity and good environmental stewardship. We expect to also refine current leaf CV’s and define sampling protocols.

Sampling

The project is located at four mature orchard sites located in Kings, Kern, Fresno and Madera Counties. 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 each orchard.

The following activities are performed in each of the four orchard sites:

• Leaf samples will be collected from non-fruiting branches at a tree-canopy height of 6 ft. from May through Sept and one month post-harvest
• Fruit samples from each tree wil be used to determine dry weight and Nitrogen accumulation in the fruit at harvest
• Yield will be determined by individual tree harvest performed by shaking the individual tree and weighing by hand. Pistachio nuts will be graded and dry yield determined.
• Trunk diameter will be determined in each tree
• Tissue 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 will be processed by the DANR analytical laboratory at UC Davis.

Additional sampling in 2011:

• Results from 2010 leaf analysis for the month of May suggest that leaf samples from fruiting branches have a better relationship with yield than samples from non-fruiting branches, and that leaves from the lower canopy have a better relationship with yield than leaves from the top of the branches for the month of May. To validate this finding, leaf samples will be collected in 2011 from the top and lower portions of the canopy as well as from the fruiting branches to assess the variation in leaf nutrient status within a single canopy.

• To quantify the effect of delaying harvest times on the amount of N remobilization from fruit back to the tree, traits that will be measured are N concentrations in fruit over the season and at different harvest times; and the amount of N accumulated and mobilized from different fruit parts over the season

Statistical Analysis

In these experiments we will use a combination of linear and non-linear statistical approaches using individual tree analyses. Effects of climate, location in the field and environment on patterns of nutrient uptake, in-field variability and nutrient budget will be determined by cross-site comparison.  Maps of nutrient status for each element will be used to estimate the distribution of nutrient concentration in the field.

The large pool of data that will be collected, will be analyzed using a variety of statistical and graphical approaches to estimate nutrient optimums  A model of nutrient demand for all essential elements will be developed. Linear regression models will be used to determine the relationship between yield and the leaf nutrient status of the different leaf position and fruiting branches. The effects of harvest times on N remobilization will be determined by analysis of variance. The goal is to improve the current model for pistachio fertilization and to provide growers with sampling and interpretation tools to better manage their crops.