1. Please state project objectives and what work was done this quarter to address them:
Valencia fruit was harvested by the end of April in trial site 1.
Similar to the last year, 400 ppm of both Fertizink and Nuzink (treatments applied in October 2023, January 2024 and February 2024) increased yield as compared to control (180 Kg of fruit per 3 trees replicate as compared to 120 kg per three-tree replicate, 33% increase) with no significant differences between both compounds and by 17% as compared to trees treated on the same dates with Zn sulfate, that was incorporated as a grower standard control. Internal quality was not significantly affected this year. Additionally, the fruit juice and rinds have been digested for Zn content (analysis pending). We continued analyzing auxin content in fruit flavedo. After three applications of both compounds, NuZn and FertiZn, auxin increased as in last year by similar levels. Noticeably, trees this year are in worst shape, with very thin canopies, which may explain the lower yields, even though physiologically trees responded to the treatments by increasing endogenous auxin content. Next year study will be very important as we will have trees with better health, for instance trees that have received 2 years of OTC injections, these treatments could serve as a bridge for the gap year.
The greening severity was evaluated in trial site 2 (ridge) for both Valencia and Hamlins (400 ppm and 800 ppm Zn). In this site, we observed a dose dependent effect on the greening severity for both Hamlin and Valencia. Over 80% trees treated with 800 ppm of NuZn and FertiZn are rated as healthy compared to those treated with 400 ppm, the later rate displayed some symptoms of greening. Nevertheless, NuZn and FertiZn at these rates significantly increased the percentage of healthy rated trees compared to Zn sulfate. The greening evaluation correlates with the yield results. Valencia plot treated with NuZn and FertiZn (800 ppm), demonstrated a yield increase of 25% and 45%, respectively, compared to the untreated control and an increase of 8% and 25% compared to Zn sulfate.
Fruit and juice quality was assessed for Hamlin and Valencia (trial site 2) harvested in Fall 2023. FertiZn at 800ppm performed the best in terms of fruit size and weight in comparison to all other treatments including controls at both rates. None of the treatments have any significant impact on juice quality.
The raintfastness, Zn absorption and in planta mobility were evaluated using swingle liners. On average NuZn and FertiZn demonstrated a 20% and 130% increase of bound Zn, respectively, over Zn Sulfate. These findings correlate with the percentage of ion to insoluble Zn found in the formulations. A week after treatment, the Zn content in the plants was analyzed. It was found that FertiZn increased the Zn content in roots by 160% compared to Zn Sulfate. This might explain the reduction in greening severity and the impact on overall physiological response.
2. Please state what work is anticipated for next quarter:
In the next quarter, we will quantify the Zinc content in juice of fruit harvested trial site 1. Additionally, fruit shelf-life data will be analyzed to determine if the treatments possess other benefits. In year 3 trial, we will analyze Zn leaf residue on field samples. We will also communicate our research findings through peer-reviewed publications.
3. Please state budget status (underspend or overspend, and why):
on track