Saffron Growing Guide: Fertilization from Planting to Harvesting

Having a fertilization program for saffron helps in growing high-yield and high-quality saffron. In this article, we will discuss important tips for growing and fertilizing saffron using organic and mineral fertilizers.

What are the suitable fertilizers for saffron growing?

Saffron, known as “red gold,” is one of the most expensive and valuable spices in the world. This plant comes from flowers in the iris family and is grown in tropical and semi-tropical regions. Proper fertilization of saffron contributes to better growth and quality of the product. In this section, we will introduce different types of chemical and organic fertilizers suitable for saffron and explain the impact of each on growing saffron.

Chemical Fertilizers:

• Nitrogen Fertilizer: Nitrogen helps the leaves grow faster and increases the plant’s size. It also plays a role in producing chlorophyll, which is essential for photosynthesis.
• Phosphorus Fertilizer: Phosphorus strengthens the roots and improves flowering, helping the plant produce larger bulbs.
• Potassium Fertilizer: Potassium increases the plant’s resistance to environmental stress and improves the quality and color of the saffron flowers.
• Micronutrients (like Zinc and Iron): These elements help improve the plant’s metabolism, support nutrient production, and prevent diseases.

Organic Fertilizers:

• Compost: Compost improves soil structure and increases microbial activity, slowly releasing nutrients into the soil.
• Animal Manure (like cow or sheep manure): These fertilizers enhance soil quality and moisture while gradually providing nutrients.
• Green Manure: This involves using cover crops that are added to the soil, which helps increase nitrogen levels and improve soil structure.

Using a combination of chemical and organic fertilizers enhances the growth and quality of saffron. It’s important to consider the plant’s specific needs and the soil’s condition when choosing the type and amount of fertilizer.

Fertilization Program for Growing Saffron

Research indicates that growing saffron relies heavily—up to 70%—on soil conditions. The ideal soil for saffron should be light and rich in essential nutrients necessary for the plant’s growth. Saffron fertilization involves the use of both organic and chemical fertilizers. The quantity and timing of fertilization are tailored according to the geographical location and soil type. Therefore, the fertilization program must address the specific needs and deficiencies of the soil.

Generally, there are two types of fertilization for saffron cultivation:

1. Base Fertilization: This is done once at the time of planting saffron and is then renewed every two to three years.
2. Supplementary Fertilization: This involves several stages and needs to be repeated every year.

Fertilization Program for the Soil Before Saffron Planting

Before planting saffron, it is essential to use animal manure and phosphorus for fertilization. The animal manure added to the soil must be processed; using unprocessed manure can lead to fungal diseases and rot in saffron plants. The required amount of phosphorus is determined through soil testing and based on the specific needs of the soil.

Suitable types of animal manure for saffron fields include cow manure, sheep manure, and poultry manure. Cow manure is typically used to enhance soil texture and structure, improving nutrient absorption and creating better conditions for saffron bulbs to thrive. Sheep manure is rich in nitrogen, while poultry manure encourages vegetative growth. The best option for saffron fields is a blend of these animal manures.

Prior to planting saffron, you can determine the appropriate amount and type of animal manure based on soil analysis. In a standard field, approximately 30 to 50 tons of cow manure are needed per hectare of saffron. You can combine this with 7 tons of sheep manure and 3 tons of poultry manure. The exact mixture will depend on soil conditions and requirements, but typically, cow manure constitutes around 80% of the blend, while the remaining 20% comes from sheep and poultry manure.

The best time for base fertilization is in the summer, approximately one month before planting saffron.

Supplementary Fertilization Program for Saffron Growing

In supplementary fertilization, the amount and type of fertilizers are determined based on weather conditions, soil type, and the needs of the soil. To identify the soil’s needs and the levels of nutrients present, soil testing is necessary. Supplementary fertilization in saffron fields is done annually and involves several steps. Here, we will explain the steps of supplementary fertilization.

First Irrigation (Watering the Seedlings)

The first irrigation, known as “water for the seedlings,” takes place in late summer or early autumn. During this period, fertilizers are applied to strengthen the saffron bulbs. This fertilization helps the buds that have formed in the bulbs to grow fully. The fertilizers used at this stage include humic acid and NPK fertilizer. Humic acid helps saffron flowers emerge easily from the soil. The potassium needed during this stage is higher than the need for nitrogen and phosphorus; if necessary, potassium-containing fertilizers can also be used.

Second Irrigation (Watering after Harvest)

Fertilization during the “water after harvest” stage occurs after saffron has been harvested, in late autumn. After harvesting, saffron bulbs need to be prepared for multiplication, and essential nutrients are made available through fertilization. At this stage, an NPK fertilizer with high phosphorus content is used. Some farmers also utilize seaweed fertilizer, which strengthens the saffron bulbs and protects them from frost damage. Humic acid and micronutrients may also be applied at this stage, depending on the soil’s needs.

Saffron Foliar Application

The next step in the supplementary fertilization program for saffron is foliar application, which takes place in the winter. The fertilizers used during this stage aim to strengthen the saffron bulbs and increase the size of the saffron stigmas. Foliar application is carried out in 3 to 6 stages, depending on the soil conditions.

First Foliar Application: The first foliar application focuses on photosynthesis, requiring the leaf part of the saffron plant. One of the fertilizers used to prevent the leaves from turning yellow is iron fertilizer. Iron helps keep the saffron leaves green, supporting the photosynthesis process. Using nitrogen fertilizer also promotes leaf growth. This first application typically occurs in January.

Second Foliar Application: The second foliar application usually takes place in February. At this stage, fertilizers high in phosphorus are used. High phosphorus fertilizers help increase tuber formation and the production of new saffron bulbs. To prevent frost damage to small bulbs, amino acids can also be applied. Healthy saffron bulbs should be dark brown or gray, free of spots, cracks, or visible damage. They should be firm and smooth, while bulbs with dry or wilted shoots are of low quality and may not grow well.

Third Foliar Application: The third foliar application occurs in March or April. By this time, the multiplication of saffron bulbs is complete, and the focus is on strengthening the new bulbs. Therefore, this application aims to increase the size of the saffron bulbs. High potassium fertilizers are particularly beneficial for this purpose, as potassium helps increase cell division, leading to larger and heavier bulbs. Additionally, depending on the needs, macro and micronutrients, vitamins, and various plant growth hormones can be used during this stage.

Suitable Conditions for Saffron Planting

To ensure that the fertilization program has the greatest impact on saffron plants, several conditions must be met:

1. Soil History: The best soil for saffron planting is one that has never grown saffron before or has not been used for saffron cultivation for at least ten years.
2. Fertilization Stages: The saffron fertilization program generally includes three stages: solid fertilizers (animal and mineral), irrigation fertilizers, and foliar application. Foliar application is done in 3 to 6 stages, depending on the soil and plant needs, with each stage spaced 15 to 20 days apart.
3. Weather Conditions: Foliar application should be carried out on sunny days to ensure that the leaves properly absorb the nutrients.
4. Soil Type: Suitable soil for saffron should be light and well-drained, such as sandy or loamy soil. This type of soil allows water to drain well and prevents moisture buildup around the roots.
5. Soil pH: The ideal soil pH for saffron planting is between 6 and 8. Extremely acidic or alkaline soils can negatively affect saffron growth.
6. Salinity: Saffron is not a salt-tolerant plant. High salinity can harm the growth and yield of saffron plants, leading to wilting, stunted growth, and reduced flower and bulb production. Adding organic fertilizers can improve soil quality and reduce the negative effects of salinity.
7. Temperature: The ideal temperature for saffron growing is between 15 and 25 degrees Celsius. Temperatures above 30 degrees can harm the plant, while exposure to temperatures below 0 degrees can cause stress and potentially kill the plant.
8. Climate: Saffron prefers dry climates with low rainfall. Areas with little rainfall, especially during the growing season, provide the best conditions for saffron cultivation. Saffron requires direct sunlight, with at least 6 hours of sunlight per day being ideal.
9. Watering Needs: Saffron requires minimal watering. It is important to prevent water from pooling on the soil surface or around the roots, as this can lead to root rot and fungal diseases.
10. Quality Bulbs: Choosing high-quality saffron bulbs is crucial for successful cultivation. The bulbs significantly impact growth, yield, and the quality of the final product. Larger, heavier bulbs (weighing at least 15-20 grams) are more vigorous and can produce better flowers.
11. Weed Control: The best method for controlling weeds in saffron fields is manual weeding.