Increasing Citrus Fruit Number
Citrus fruit number needs to be carefully managed and a strong supply of virtually all major and micronutrients is critical to fruit set and fruit number.
Application of fertilizer prior to flowering and then through to fruit set and early fruit fill is critical to maintain high numbers of fruit per tree.
Crop Nutrition and Fruit Number
Nitrogen
Around 80% of the nitrogen in fruit and leaves in mature trees originates from tree reserves rather than from fertilizer N applied in that growing season. Pre-bloom foliar sprays made in the winter can help increase yields in the following season by increasing fruit number.
Potassium
Use of potassium - either through foliar or soil application - results in higher fruit numbers and higher yields.
Calcium, as calcium nitrate helps boost fruit set and fruit number. Timing is critical, and significant fruit set improvement come from applications made immediately prior to and during flowering. Less than 30mg of calcium in the fruitlet at 5 weeks will lead to increased fruit drop.
Boron
Boron deficiency reduces calcium uptake and increases fruit drop. As a result, adequate boron is important to boost calcium uptake.
Fe, Mn, Zn and S
Micronutrient deficiencies due to poor supply of iron, manganese and zinc, restrict fruit set and fruit number. It is important to ensure the tree has sufficient levels of these nutrients to maintain strong growth through flowering and fruit set. Good sulfur supply can increase fruit set in lemons, minimizing fruit drop.
