Pistachios: Boron application for increased yields

• Research results in California have shown that foliar applications of Solubor^® have increased pistaschio yields.
• The best time for foliar application is from the late dormant to the early bud stages.
• Soil applications of boron are not as effective as foliar applications in supplying sufficient boron for flowering.

Brown, Ferguson, and Picchioni worked with 1,000 pistachio trees in California over a 4-year period to investigate the role of boron (B) nutrition and review current boron recommendations. Cumulative 3-year yields of pistachio per tree from foliar and soil-applied boron are given in the table shown here. Their results show greater yields were definitely obtained with foliar application of Solubor. The best application rate shown in this research was 5 lbs of Solubor in 100 gallons of water. The best time to use a foliar application was from the late dormant to early bud stages of development.

Soil-applied boron at 2 to 8 ounces per tree affected yields sometimes. Soil-applied boron results were not as consistent, nor as dependable as a foliar application.

Pistachio yield was only one measurement that Brown, Ferguson and Picchioni made on trees. They documented several influences of foliar-applied boron at the critical late dormant to early bud stages. Boron increased pollen viability, fruit set, and leaf boron concentrations, but decreased blanking percentage. All of these measurements lend support to applying 5 pounds of Solubor/100 gallons of water per tree at the right time.