For farmers
Olive Tree Fertilizer: Organic or Chemical, When and How Much
Contents
Which olive tree fertilizer is the right one, and when should it go down? Olive trees are tough, but they do not produce from nothing. Every year, with the olives, the leaves and the pruned branches, a grove takes nitrogen, potassium and other elements from the soil that need to be replaced. The right fertilizer, at the right time and in the right amount, increases the crop, softens alternate bearing and directly affects the oil yield and quality. Below we explain what olive trees need, organic or chemical, when to apply it and how much.
In short
- Organic manure, well rotted, goes down in November–February, under the canopy.
- Nitrogen is given in two doses: late February–March and April, before flowering.
- Potassium goes down in autumn–winter; boron as a foliar spray before flowering.
- Rule of thumb: a mature, bearing olive tree needs about 0.5–1 kg of nitrogen (N) a year.
- Have the soil tested every 3–4 years instead of guessing.
What olive trees need
| Nutrient | Why it matters | Signs of deficiency |
|---|---|---|
| Nitrogen (N) | New shoot growth, flowers and fruit set | Pale, yellowish leaves, short shoots, few flowers |
| Potassium (K) | Fruit size, oil content, drought resistance | Scorched leaf tips and edges, small fruit |
| Phosphorus (P) | Roots and flowering; rarely lacking in old groves | Slow growth in young trees |
| Boron (B) | Fruit set after flowering | Flowers that drop, deformed fruit, dead shoot tips |
| Calcium and magnesium | Tissue structure and photosynthesis | Yellowing between the leaf veins (Mg), problems in acid soils |
Olive trees usually need more nitrogen and potassium than phosphorus, so compound fertilizers with a lower middle number suit most bearing groves.
Organic fertilizer for olive trees
Organic fertilizer feeds the tree slowly and, above all, improves the soil: it makes it looser, helps it hold water and feeds soil life. In groves on heavy soils that pack down after rain, as in parts of the Fier area, this effect is worth as much as the nutrients themselves.
- What: sheep, cow or chicken manure, only well rotted (at least 4–6 months); compost; chipped prunings.
- How much: roughly 20–40 kg of rotted manure per mature tree, every one to three years, depending on the soil.
- When: from November to February, so that the rains carry it into the soil before spring growth.
- How: spread it in a ring under the edge of the canopy, not against the trunk, and work it lightly into the soil.
- Green manure: legumes such as vetch or broad beans sown between the rows and worked in during spring add natural nitrogen.
Chicken manure is stronger than sheep or cow manure: use less of it and never fresh, because it burns the roots.
Chemical fertilizer for olive trees
Mineral fertilizers act quickly and allow precise doses, so they are useful when a tree needs a fast boost or when a soil test shows clear deficiencies.
- Nitrogen: ammonium nitrate (34.5% N) or urea (46% N), in two doses: late February–March and April. Do not give nitrogen in late summer or autumn, because it pushes soft shoots that are damaged by frost.
- NPK compounds (for example 20-10-10 or 15-15-15) are practical when nitrogen, phosphorus and potassium are all needed.
- Potassium: potassium sulphate in autumn–winter, especially after heavy crops.
How much fertilizer per olive tree?
The amounts depend on the tree's age, the expected crop, the soil and whether the grove is irrigated. As a guide for nitrogen:
| Tree age | Nitrogen (N) per year | Roughly as ammonium nitrate |
|---|---|---|
| 1–3 years | 100–200 g | 0.3–0.6 kg |
| 4–8 years | 300–500 g | 0.9–1.5 kg |
| Over 8 years, bearing | 500–1,000 g | 1.5–3 kg |
In light-crop years, or when the grove is not irrigated, stay at the lower end. Too much nitrogen does not bring more oil: it brings leaves, shoots and a tree that is more vulnerable to disease and to the olive fly.
Fertilizing olive trees in pots
A potted olive tree has little soil to draw on. Feed it with a slow-release, balanced fertilizer in spring and early summer, at the dose on the label, and stop feeding from late summer so that new growth can harden before winter.
Organic or chemical?
It is not an either-or choice. Organic fertilizer builds the soil over the years, while mineral fertilizer quickly corrects the season's shortfalls. Most groves do best with a combination: organic matter in winter and measured nitrogen in spring. Organic groves may only use certified organic and mineral inputs; more in certified organic olive oil.
Olive tree fertilizer calendar
| Period | What to do |
|---|---|
| November – February | Well-rotted organic manure; potassium and phosphorus if the soil test calls for them |
| Late February – March | First dose of nitrogen, together with pruning |
| April | Second dose of nitrogen; boron foliar spray before flowering |
| May – June | Fruit set; foliar feeding only if there are signs of deficiency |
| July | Leaf analysis (leaves from the middle of this year's shoots) |
| August – October | No nitrogen; irrigation as needed in irrigated groves |
How to apply fertilizer without wasting it
- Spread fertilizer under the edge of the canopy, where the feeding roots are, not against the trunk.
- Apply it to moist soil or before light rain, and work it in lightly with a cultivator or hoe.
- Split nitrogen into two doses: a single large dose is washed away by rain and can burn the roots.
- For young trees, spread it in a ring 30–50 cm from the trunk.
- For foliar sprays (boron, urea, potassium), follow the label doses and spray in the cool hours of the day.
Feeding and oil quality
A grove fed in a balanced way gives healthy fruit with more oil per kilo. Too much nitrogen, on the other hand, gives watery fruit, a lower yield and olives that are more vulnerable to the olive fly, which raises the acidity of the oil. That is why fertilizing goes hand in hand with olive tree pruning and with the control of olive tree diseases and pests. How much oil you will get in the end is explained in olive oil yield.
Frequently asked questions
When should olive trees be fertilized?
Organic manure goes down in winter (November–February). Nitrogen is given in two doses, in late February or March and in April, before flowering. Potassium is applied in autumn or winter.
How much fertilizer does a mature olive tree need?
As a guide, 1.5–3 kg of ammonium nitrate a year for a bearing tree, split into two doses. The exact amount depends on the soil, irrigation and crop; a soil test gives the most reliable answer.
What is the best fertilizer for olive trees?
There is no single best product. For most groves, well-rotted organic manure in winter combined with measured nitrogen in spring, adjusted to a soil test, gives the best results.
Is chicken manure good for olive trees?
Yes, if it is well rotted and used in moderate amounts, because it is very rich in nitrogen. Fresh chicken manure should never be put near the roots.
Do unirrigated olive trees need fertilizer?
Yes, but in smaller amounts and at the right time: nutrients are only taken up when the soil is moist, so winter and early-spring feeding matter even more.
Growing olives in the Fier area? After the harvest you can bring your olives to the Shkrela mill in Rreth Libofshë, where we buy whole olives and olive oil from local growers. Contact us for the season's terms.
