Trials have shown that phosphorus improves long-term storage characteristics, reducing bitter pit. However, care has to be taken as some forms of phosphate may contain cations that compete with calcium, which can increase bitter pit risks
Reducing Bitter Pit in Top Fruit
Bitter pit is a physiological disorder associated with low levels of calcium in the apple or pear tissue, which reduces fruit quality and marketability.
Symptoms are often seen in storage as deep brown/black lesions or spots varying from 2-10mm in diameter. Shallow small areas beneath the spots resemble small bruises.
A balanced crop nutrition is essential to ensure calcium does not compete with and is not restricted by other nutrients.
Crop Nutrition and Bitter Pit
Phosphorus
Potassium and Calcium
Potassium is one of the most important nutrients for a number of quality characteristics. Yet, it is important that potassium-concentrations are in balance with other nutrients, particularly calcium, as preferential uptake of potassium over calcium will significantly induce to greater incidence of bitter pit.
It is generally accepted that K:Ca ratio should be around 15 for fruit at 40-60g and no higher than 30 at harvest in order to reduce bitter pit problems
Soil supply is important, but this should be backed by fruit applied sprays targeted to get more calcium into the apples. The greater the number of sprays the better the fruit quality and it is important to continue spraying right through to harvest.
Boron
Boron spray programs also support calcium, reducing bitter pit and Jonathon spot in apples.
Magnesium
Care has to be taken since overuse of magnesium can restrict calcium uptake and increase the risk of bitter pit, as shown in studies with Jonagold apples in Poland.
Recommended Yara Fertilizers for Top Fruit
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YaraMila COMPLEX
12-4.8-14.9 + 8% S - Prilled NPK fertilizer which also contains magnesium and sulphur as well as micronutrients ideal for use on a wide range of arable and horticultural crops.
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YaraLiva TROPICOTE
15.5% N + 19% Ca - Granular calcium nitrate fertilizer for field application to a wide range of crops.
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YaraVita ZINTRAC 700
A fully formulated flowable liquid micronutrient fertilizer containing 700 g/l zinc for foliar application to prevent and treat zinc deficiency on a wide range of crops.
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YaraVita BORTRAC 150
A liquid micronutrient fertilizer containing 150 g/l boron for foliar application to provide additional boron or to treat boron deficiencies in a wide range of crops.
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YaraVita SENIPHOS
A liquid micronutrient fertilizer containing high concentrations of phosphate and calcium for foliar application to improve yield and quality in fruit and potatoes.
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YaraVita STOPIT
A liquid micronutrient fertilizer containing 160 g/l calcium for foliar application to control and reduce calcium related disorders in top fruit and other crops.
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YaraVita BUD BUILDER FL
A flowable liquid suspension fertilizer with nutrients and micronutrients including magnesium, zinc, nitrogen, boron and phosphate for foliar application to improve the flowering of top and soft fruit.