Initial Results for Two Years (2009-10)
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 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 these preliminary results leaf, samples in 2011 will be collected 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.
Nutrient budget curves quantifying the time course of nutrient uptake and total plant demand were developed based on the initial data, and will be further validated in 2011. Figure 1 (below) shows the pattern of N, K and phosphorus (P) accumulation by pistachio fruits over the season (2009). Nutrient content at harvest is the product of dry yield multiplied by fruit nutrient concentration at harvest. Nutrient content over the growing season is the product of dry yield* fruit biomass accumulation* nutrient concentration at a given month.
We have developed a model that successfully predicted leaf N status of the trees in July as a function of leaf nitrogen and other nutrients in May using multiple linear regression models. Validation is required and will be provided in 2011.
Variability analysis and geostatistical methods allowed us to estimate the generalized sample numbers needed to determine the true mean of nutrients within the field. This number varies temporally and in relation to the nutrient of interest. Eleven nutrients were evaluated, including N, K and P.
Yield maps were generated for nutrient and yield variability in individual orchards. Pistachio yield variation in within a single year and site exceeded 50% and a negative relationship with tissue N was observed. Correlations of yield with individual and multiple plant nutrients have pistachio orchards.
In Figure 2 (below) A, B, C and D shows relationship of nutrient ratios with the final yield (2009). A and B represents PK ratios for the month of May and July and shows that P: K ratios account for 18% and 38% of the variation in the yield for the Kern and Madera sites respectively. C and D represent the relationship of N to S ratio with the yield for the month of May and July.