Spring fertilization of winter crops is a crucial stage in the cultivation technology, as it ensures the rapid recovery of vegetation, active growth, and yield formation. After winter, winter crops often experience a nitrogen deficiency—a key element necessary for active tillering, shoot formation, and productive stem development.
Applying nitrogen fertilizers during this period stimulates tillering, promotes the formation of productive shoots, and establishes a high yield potential. At the same time, improper application or excessive doses of nitrogen can lead to negative consequences, including lodging of crops.
KEY ASPECTS OF SPRING FERTILIZATION
◻️ In years with early vegetation recovery, it is advisable not to rush fertilization and to reduce the amount of nitrogen on well-developed crops to avoid lodging.
◻️ The optimal nitrogen fertilizer for winter cereals is ammonium nitrate, which contains nitrogen in two forms: nitrate – quickly absorbed, providing immediate nutrition, and ammonium – gradually absorbed, ensuring prolonged nutrition.
◻️ If phosphorus-potassium fertilizers were not applied in autumn, nitroammophoska can be used, as it contains NPK in a readily soluble form.
◻️ Applying nitrate fertilizers on a snow cover is ineffective due to the risk of nitrogen leaching with meltwater, leading to significant losses.
Spring fertilization is not just “somehow applying nitrogen fertilizers,” but a strategically important process that requires a well-balanced approach, considering crop conditions and weather factors.
THE FOLLOWING WILL DESCRIBE THE KEY APPROACHES TO FERTILIZING WINTER CROPS WITH NITROGEN FERTILIZERS
Table 1. Average rates of essential nutrient usage for the formation of 1 ton of yield and by-products (straw for wheat and stems for rapeseed)
Considering the specified rates, we can calculate the total nitrogen fertilizer requirement for different yield potentials.
Table 2. Optimal parameters of winter wheat 🌾 and total nitrogen requirement depending on yield potential
Table 3. Optimal parameters of winter rapeseed 🌿 and total nitrogen requirement depending on yield potential
◻️ Ammonium nitrate or UAN-32 is often used for winter wheat due to the rapid availability of nitrogen.
◻️ Winter rapeseed requires fertilizers containing sulfur (such as ammonium sulfate or sulfoammophos) since this crop has an increased demand for this element.
Table 4. Main types of nitrogen fertilizers for spring fertilization of winter wheat and rapeseed
FEATURES OF WINTER WHEAT NUTRITION
◻️ Nitrogen Requirements.
Winter wheat has the highest nitrogen demand during the phases of spring tillering, heading, and grain filling. During this period, it is crucial to ensure access to nitrogen in an easily absorbable form.
◻️ Application Rates:
- First application (on frozen-thawed soil): 30–40% of the total nitrogen amount. It is recommended to use ammonium or ammonium-nitrate fertilizers (ammonium nitrate, urea-ammonium mixture).
- Second application (at the tillering phase): 30–40% of the total nitrogen amount.
- Third application (before stem elongation): 20–30%, depending on plant conditions.
◻️ Recommended Fertilizers:
- Ammonium nitrate (NH₄NO₃): A universal fertilizer that acts quickly due to the combination of ammonium and nitrate nitrogen forms.
- UAN-32 (urea-ammonium nitrate solution): Evenly distributed across the field, ensuring gradual nutrient availability.
- Ammonium sulfate ((NH₄)₂SO₄): Provides sulfur, enhancing nitrogen uptake efficiency.
FEATURES OF WINTER RAPESEED NUTRITION
◻️ Nitrogen Requirements.
Winter rapeseed requires a significant amount of nitrogen for the formation of vegetative mass and the development of generative organs. Nitrogen demand begins in autumn, but the peak occurs in spring.
◻️ Application Rates:
- First application (on frozen-thawed soil): 40–50% of the total nitrogen amount. This application ensures a rapid growth start after vegetation recovery.
- Second application (at the stem formation phase): 30–40%.
- Third application (at the budding phase): 10–20%, depending on crop conditions.
◻️ Recommended Fertilizers:
- Ammonium sulfate: Contains sulfur, which is essential for protein synthesis and improves seed quality.
- UAN-32 (urea-ammonium nitrate solution): Evenly distributed across the field, ensuring gradual nutrient availability.
- Ammonium nitrate: A fast-acting nitrogen source.
Why is it important to consider sulfur in the nutrition system? Sulfur is a key element in enhancing the efficiency of nitrogen fertilization. Sulfur deficiency leads to:
- Reduced amino acid synthesis.
- Impaired nitrogen uptake.
- Decreased yield and product quality.
Fertilizers containing sulfur (ammonium sulfate, UAN with sulfur) enhance nitrogen efficiency, especially in soils with low sulfur content.
Щодо складностей, які аграрії повинні враховувати у процесі весняного внесення добрив, то в основному це:
◻️ Low temperatures. If fertilizers are applied early, their uptake may not be optimal due to low root system activity.
◻️ Drought risk. If moisture is insufficient, granular fertilizers may not dissolve in time, affecting their efficiency.
◻️ Soil overwatering. Spring moisture can make mechanized fertilizer application with wheeled vehicles difficult.
◻️ Soil compaction. Applying granular fertilizers with heavy machinery negatively affects soil structure, especially in waterlogged areas of the field.
◻️ Inefficient fertilizer distribution. Using NDVI and similar multispectral indices allows for optimizing application rates.
If the first two factors are difficult for farmers to influence, issues related to overwatering, soil compaction, and efficient fertilizer distribution can be easily addressed with various types of agro-drones.
If the first two points are quite difficult for farmers to influence, then solving the issues of overwatering, soil compaction, and efficient fertilizer distribution can be easily addressed with various types of agro-drones.
The DJI AGRAS T50 agro-drone can apply almost any nitrogen fertilizer during the spring fertilization of winter wheat and rapeseed. It is capable of carrying up to 50 kg of liquid or solid fertilizers.
Nitrogen fertilization of winter wheat using a drone can be performed in three stages:
◻️ During the early spring tillering phase (on frozen-thawed soil).
BBCH 20–25 (regenerative)
◻️ At the stage of “completion of spring tillering – beginning of stem elongation.”
BBCH 27–32 (1st productive application)
◻️ From the appearance of the flag leaf to the beginning of heading.
BBCH 37–49 (2nd productive application)
Considering that:
◻️ To apply 50 kg of active nitrogen, 2–3 drone flights are required.
◻️ The application cost is $3–5 per hectare (more details in the article).
This results in a cost of $6 to $15 per hectare for a single nitrogen fertilization with a drone.
Is this a lot or not? – Let’s try to formulate an answer to this question.
Considering:
Application cost using wheeled machinery = $2–3 per hectare
- Crop damage during application
- Technological tracks with a depth of 50+ cm
- Uneven fertilizer distribution on field edges, corners, and due to terrain
- Loss of yield potential due to untimely application
Result: From $2/ha in costs to $500/ha in potential losses during a single nitrogen fertilization using wheeled machinery.
The author hopes that the reader has found the answer to the last question.
The DJI Mavic 3M agro-drone features a multispectral sensor and is designed for crop monitoring and field mapping for precision agriculture.
Key Features:
◻️ Cameras: 20 MP RGB camera, multispectral camera (4 channels: green, red, red edge, near-infrared)
◻️ Flight time: up to 43 minutes
◻️ Video transmission range: up to 15 km
◻️ Purpose: creating maps for variable-rate fertilizer and pesticide application
Using the DJI Mavic 3M to create variable-rate nitrogen application maps for winter crops allows for 10–30% fertilizer savings by accurately identifying different vegetation zones.
In this article, we will not continue to elaborate on various possible field scenarios or attempt to "push" the agro-drone topic to influence the reader. Instead, we will immediately acknowledge that wheeled machinery remains the universal backbone of key agricultural operations, and there is no way around it. However, we still hope that everyone will individually assess alternative innovative tools in the agricultural sector, considering their specific needs and capabilities. Agro-drones are just one of these solutions—and with that, we conclude this article.
