Soil acidifying treatments do not improve Honeycrisp apple fruit quality
In Washington State, the incidence of bitter pit in Honeycrisp apples can be greater than 75%. This has a significant negative effect on orchard profitability.
High soil pH has been implicated as a contributing factor in bitter pit development in arid apple growing regions.
We evaluated the effect of acidifying soil amendments on Honeycrisp apple quality and nutrient concentration during 2019 in eastern Washington State.
Soil amendments included sulfuric acid (93% H2SO4) at 25 (S25) and 50 (S50) mL tree‑1, phosphoric acid (78% H3PO4) at 25 (P25) and 50 (P50) mL tree‑1, citric acid (50% C6H8O7) at 50 (C50) and 100 (C100) g tree‑1, humic acid (12% C9H9NO6) at 100 (H100) and (H200) g tree‑1, fulvic acid (C14H12O8) at 100 (F100) and 200 (F200) g tree‑1, and an untreated control.
All treatments were applied on June 17, 2019 to four randomly selected blocks of five trees.
Samples collected 11 and 26 days after treatment showed that only S25 and S50 reduced soil pH, from 6.8 to below 5.0. Soil available iron (Fe) and manganese (Mn) were increased.
Soil calcium (Ca) availability was reduced by 57% with S25, while magnesium (Mg) availability increased by 30% with S50. Soil soluble salts were increased 2.7 times with S50 after 11 days and 2.2 and 1.9 times with S50 and S25, respectively, after 26 days, reaching toxic levels.
Similarly, S50 increased sulfur levels 5.7-fold.
The F100 treatment doubled soil nitrate and increased soil available copper (Cu) levels by 33%. Soil available phosphorous (P-Olsen) was increased 2.2, 3.0 and 5.2-fold with S25, P25 and P50 treatments, respectively.
However, differences in soil nutrient levels were not reflected in leaf tissue concentration.
Fruit dry matter was highest with P50 and P25 compared F100, while S25, P25 and H100 had 22, 22 and 19% increased phosphorous concentration.
All other nutrients were unaffected by the soil treatments.
Similarly, fruit weight, diameter and bitter pit incidence and severity were unaffected by the soil treatments.
In this one-year study, soil amendments affected soil chemical parameters but had little effect on fruit quality.
Sallato, B., Ragab, H. and Peters, R.T. (2023). Soil acidifying treatments do not improve Honeycrisp apple fruit quality. Acta Hortic. 1375, 343-350
DOI: 10.17660/ActaHortic.2023.1375.45
https://doi.org/10.17660/ActaHortic.2023.1375.45
DOI: 10.17660/ActaHortic.2023.1375.45
https://doi.org/10.17660/ActaHortic.2023.1375.45
root growth, calcium carbonate, drainage, potassium, salts
English
1375_45
343-350