Apple soil analysis #816966

Asked November 28, 2022, 12:52 AM EST

Greetings, I have both an eight year old Newton Pippen and an eight year old Granny Smith apple trees. I harvested apples and find that the apples have spots that appear to me to be bitter pit. There are more spots away from the stem and the spots increase after the apples have been picked. I do not taste the spots being bitter. There is only mild corky material under the spots. I do not think the spots are from stink bug attacks. I had the soil tested and the results are posted: Oregon State University Extension Douglas County Master Gardeners Soil Test Lab Results of Soil Analysis Client: November 12, 2022 Soil Texture: 47 % sand 40 % silt 13 % clay The approximate classification is: a loam soil. Humus: The humus concentration score was 0 This level is considered very low See comments on next page. pH: The pH of the sample was 8.0 SMP buffer value: not measured This soil is considered alkaline. Moderate range: 6 - 7 Nitrogen: The NO3-nitrogen level was 5 ppm, or 0.2 lbs/1000 sq. ft. This level is considered low. Moderate range: 40 - 99 ppm Phosphorus: The phosphorus level was 25 ppm, or 1.1 lbs/1000 sq. ft. This level is considered moderate. Moderate range: 20-40 ppm Potassium: The potassium level was 150 ppm, or 6.9 lbs/1000 sq. ft. This level is considered moderate. Moderate range: 150-250 ppm Calcium: The calcium level was 2800 ppm, or 128.6 lbs/1000 sq. ft. This level is considered high. Moderate range: 1000-2000 ppm Magnesium: The magnesium level was 5 ppm, or 0.2 lbs/1000 sq. ft. This level is considered low. Moderate range: 15-40 ppm 60-180 ppm I had planned to add lime because I read that a lack of calcium will cause bitter pit. However the soil test says I have high Calcium. I know a high pH prevents absorption of Calcium but my soil is only pH 8.0 so that is not high enough to prevent absorption. Can you tell me what fertilizer I should use on these trees? Thank you. Roger

Douglas County Oregon

Expert Response

Bitter pit is a physiological disorder resulting from calcium deficiency in the fruit. It can develop within the first month or two of cold storage as well as on the tree before harvest.
Low levels of calcium in the fruit are due to competition with shoots or high fruit load for calcium, which may be aggravated by weather conditions. Hot, dry weather in July or August tends to increase the incidence of bitter pit. Irregular irrigation may also increase bitter pit, however, summer deficit irrigation reduced size and bitter pit in 'Honeycrisp'. Heavy dormant-season pruning, overthinning, and excessive nitrogen fertilizer promote bitter pit. Injury to trunks, such as winter freezes, interferes with calcium movement. Bitter pit occurs most severely in years of light crops.
Cultivars very susceptible to bitter pit: Honeycrisp, Northern Spy, Gravenstein, Grimes Golden, and Baldwin. A cultivar moderately susceptible is Golden Delicious. Cultivars that are fairly resistant are Delicious, Gala, and Winesap. Rootstock can also influence the amount of bitter pit observed on the scion.

during irrigation season, avoid wide fluctuations in soil moisture

do not over-fertilize, as vigorously growing trees with over-sized fruit are more susceptible

do not over-prune in winter

do not over-thin in spring

keep trees at annual bearing through proper thinning and pollination practices

harvest at optimal timing because late harvested fruit is prone to bitter bit

calcium sprays (calcium chloride, calcium nitrate, STOP-IT, Nutri-Cal, Miracal, etc.) should be applied monthly throughout the growing season only if the above practices do not alleviate the problem

Here is a publication that will help:

chris Rusch Replied November 29, 2022, 7:09 PM EST

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