Apricot Tree Fertilizer Requirements

First of all, before establishing your apricot orchard or applying any fertilization method, it is essential to perform a soil analysis in order to have more information concerning the soil characteristics and nutrient availability. No two fields are the same, nor can anyone advise you on fertilization methods without taking into account your field’s soil test data, leaf tissue analysis, and crop history. Contemporary commercial Apricot farming practices suggest that once a year (in summer – July, August), the grower should collect at least 100 leaves from Apricot trees and send them to the laboratory for a detailed analysis. If a deficiency is revealed (some essential chemical elements are below acceptable standards), the farmer may intervene directly to correct it (maybe through foliar fertilization). However, it is best to first consult your local licensed agronomist.

On average, an orchard requires per hectare:

• 140-180 kg (308-396 pounds) N (usually as ammonium nitrate)
• 70-120 kg (154-264 pounds) P₂O₅
• 120-180 kg (264-396 pounds) K₂O 

In these annual applications, many farmers choose to add some amounts of calcium (CaO as calcium nitrate) and Magnesium, around 200 and 40 kg per hectare, respectively. At the same time, micronutrients like Boron (B) and Zinc (Zn) can also be added. 

Applications are divided into 3 periods as follows:

1. Basal fertilization: This takes place late in winter by applying 2/3 of the total N needed per year, 1/2 of K₂O, and the entire amount or 2/3 of it of P₂O₅. In most cases, a complex fertilizer that combines all 3 elements (N-P-K) is used (for example, 20-5-10 fertilizer). This application aims to boost leaf growth and fruit set.
2. Top dressing is applied in mid-spring (and early summer) with 1/3 of N, 2/3 of K₂O, and the remaining 1/3 of P₂O₅. Potassium is key in this stage since it can boost fruit enlargement and weight.
3. Post-harvest fertilization is applied during late summer, providing: 1/6 of N (e.g., by using a 27-0-0 fertilizer). A small amount of phosphorus may also be included.

*In cases you have varieties sensitive to fruit cracking, 3 foliar applications with CaO 10% (necessary for fruit firmness) during fruit growing stages may be required. An extra application with copper (Cu) may also be beneficial. 

In apricot orchards with an established drip irrigation system, the farmers may choose to perform complementary fertilization (after the basal fertilization) with fertigations and divide the recommended amounts into more doses. This allows more precise control of apricots’ nutrition since the trees have different requirements during their different growing stages.

Before planting the young grafted apricots, many farmers choose to apply nitrogen-rich fertilizer or manure. In this case, it is important to avoid adding them too close to the young root systems, as they can be damaged. The farmer should avoid over-fertilization, especially with nitrogen, which can favor lush, vegetative growth (over-fruit formation) and increase disease susceptibility. Well-rotted manure or compost rich in potassium can be used as an alternative to chemical-synthetic fertilizers in organically cultivated apricot orchards. A common suggestion is adding 10 to 20 tons of well-rotted manure per hectare every one or two years.

However, these are just standard practices that should not be followed without doing your own research. Every field is different and has different needs. Checking the soil nutrients and pH is vital before applying any fertilization method. Leaf analysis is very important to diagnose and correct nutrient deficiencies in the Apricot tree after consulting an agronomist.

Most important Apricot tree Deficiencies

It is crucial to understand that a plant nutrient deficiency does not necessarily have the same soil deficiency as a cause. Nutrient deficiencies result from various environmental or cultural factors that lead to plant nutrient absorption disabilities. Thus, farmers should consider testing soil and foliage before applying any fertilizer solution to their plants.

• Nitrogen Deficiency

If our trees need more nitrogen, we will probably notice the older lower leaves turning yellow, combined with reduced growth rate and significantly lower fruit production. If the deficiency is severe, leaves may start to turn red.

• Iron Deficiency

Apricot trees that suffer from iron deficiency start to develop the characteristic symptom of interveinal chlorosis, combined with green nerves on their newly developed foliage.

• Zinc Deficiency

Symptoms of zinc deficiency include yellow spotted leaves; however, in this case, younger leaves are significantly smaller and closely emerged, and lateral leaf buds may not manage to grow.

• Boron Deficiency

Boron deficiency symptoms appear with chlorosis and deformations on younger leaves that finally die. In most cases, the tree will not manage to produce fruits.

Cover Crops in Apricot Orchards

Some producers, mainly in organic farming, choose to establish cover crops between tree lines in their orchards. This practice has multiple benefits. Cover crops can decrease the weed population and maintain soil structure by preventing erosion. At the same time, cover crops can retain soil moisture, decreasing evaporation and making more water available to the crops. 

Most producers prefer to sow grasses, such as wheat and barley, or plants of the Fabaceae family, like legumes and beans. Fabaceae plants offer a significant additional benefit since they can enrich the soil with nitrogen thanks to their symbiotic relationship with nitrogen-fixing bacteria. Grasses can be planted either during spring or in late summer. On the other hand, the proper time for sowing the Fabaceae is in the spring. Grass/legume mixtures are also preferred to obtain the benefits of both types of plants. Other species that have been successfully used as cover crops in an apricot orchard are the Phacelia tanacetifolia, Fagopyrum esculentum, Vicia villos, and Vicia pannonica. Based on experimental data, a mixture of V. pannonica (70%) and Triticale (30%) used as a cover crop of apricots was able to boost the apricot yield (higher fruit weight).

The cover crops can either be maintained in the field naturally (by letting the plants produce seeds or/and selecting perennial species) or resow yearly. In the second case, the farmer usually chooses to sow the legumes in early autumn and incorporate them into the ground (plowing) before they flower during spring. This plant material is used as green manure and enriches the soil with nitrogen making it accessible to the apricot trees. As an alternative for the farmers that want to apply limited tillage, they can cut the plants with a lawn mower or allow animal grazing within the orchard. 

However, every farmer should do his/her own research and small-scale testing before implementing any new practice into his/her orchard.

References

• https://extension.unh.edu/resource/fertilizing-fruit-trees
• https://extension.umaine.edu/fruit/growing-fruit-trees-in-maine/fertilization/
• https://extension.colostate.edu/topic-areas/yard-garden/fertilizing-fruit-trees-7-612/
• https://www.mdpi.com/2073-4395/8/8/150/pdf
• https://www.researchgate.net/publication/

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