Lucas Rozendo de Lima Silva
Agricultural engineer – Federal Rural University of the Amazon (UFRA)
lucasrozendo@gmail.com
Harleson Sidney Almeida Monteiro
harleson.sa.monteiro@unesp.br
Sinara by N. Santana Brito
sinara.santana@unesp.br
Agricultural engineers and master’s students in Agronomy/Horticulture – UNESP
The use of slow-release fertilizers in carrot production represents an efficient strategy to optimize plant nutrition, providing benefits from both an agronomic and environmental point of view.
Slow nutrient release is a method that aims to gradually provide essential elements to plants throughout the growing cycle, more precisely aligning with their physiological needs.
By using slow-release fertilizers, such as those coated with polymers or controlled release, it is possible to minimize losses due to leaching, volatilization and fixation, common characteristics in conventional fertilizers.
This more precise control of nutrient release not only reduces input waste, but also contributes to environmental sustainability.
The carrot
In the specific context of carrots, the application of slow-release fertilizers can be adjusted to meet specific nutritional demands during different growth stages.
The gradual release of fundamental nutrients, such as nitrogen, phosphorus and potassium, promotes balanced crop development, resulting in healthier, more uniform roots with greater commercial quality.
In this sense, slow-release fertilizers are able to protect nutrients, especially nitrogen, in physical, chemical or biological ways, due to the soil, in general, having little available nitrogen in its composition, around 2-3%.
This happens mainly due to the low concentration of this nutrient in the rocks and minerals that give rise to the soil. In this context, slow release fertilizers (FLL) emerge as a good alternative for adding nitrogen to the soil, since their main function is to make nutrients available to plants over a longer period and in a controlled manner.
Types of FLL
One of the first FLL to be commercialized was urea formaldehyde, and its principle was to reduce the solubility of the nitrogen fraction of its composition. This product was a mixture of methylene urea with polymers of different chemical characteristics.
The release of nitrogen from this type of fertilizer depends on the microbiological decomposition of the polymer chain, therefore, factors such as PH, type of soil, humidity and temperature substantially influence the action of this FLL.
Another type is IBDU, formed by the reaction of isobutyraldehyde with urea, without the formation of polymers. Therefore, the release of nitrogen occurs depending, especially, on particle size, humidity, temperature and pH.
In addition to these two FLL, there is also CDU, which has similar characteristics to IBDU, however, with slower decomposition in acidic soils. Furthermore, there are coated fertilizers on the market, known as controlled release fertilizers (FLC).
However, unlike the slow-release ones, these are covered with various compounds, seeking to protect the conventional fertilizer granules. This method controls both the dissolution of the material and the release time of nutrients.
The urea (conventional fertilizer) in these fertilizers can be coated in three types: coated with elemental sulfur, with sulfur and polymers and with polymers only.
Technologies
Elemental sulfur coating was one of the first technologies that emerged to reduce the rate of urea dissolution in soil and volatilization losses. However, sometimes their granules had fissures that allowed water to enter, which solubilizes the urea, leaving only the coating in the soil.
These cracks caused two phenomena, which were characterized as a burst effect and a lock-off effect, the first being the early release of urea, and the second being the very late release of the nutrient.
Later, to try to correct the cracking errors of elemental sulfur, it was suggested to add a layer of polymers on top of the coated urea, thus creating fertilizers coated with elemental sulfur and polymers, or hybrid fertilizers, which represented an evolution in this field.
However, there were still cracks in its composition and, consequently, the burst effect and the lock-off effect. From another perspective, in a more technological and expensive way, fertilizers coated with just one or more layers of polymers appear.
Benefits
The benefits of using slow-release fertilizers in carrot production, when compared to the traditional method, are primarily due to the increased efficiency for the carrot, allowing a lower labor cost for the producer.
Around 40% of the costs in organic and conventional carrot production systems are dedicated to the workforce, generally paid for daily wages, necessary to care for the crop.
This cost reduction in this area is mainly based on the facilitated application of controlled-release fertilizers, which will only be applied once, in sufficient quantity to support the entire crop cycle in a homogeneous and balanced way.
Furthermore, the use of fertilizers with increased efficiency in carrots promotes improvements in the characteristics of the final product compared to the use of conventional fertilizers.
Among them, we can mention: increasing the size of the plant, both in height and diameter, and improving productivity and root length.
Therefore, the adoption of fertilizers with increased efficiency emerges as a promising strategy for carrot production, not only significantly reducing labor costs, but also optimizing the quality and yield of the harvest.
Homogeneous fertilization
The single, controlled application of these fertilizers provides homogeneous nutrition throughout the crop cycle, avoiding the complexities associated with conventional methods.
The benefits extend beyond saving resources, encompassing tangible improvements in plant characteristics and, therefore, in the quality of the final product, thus consolidating the effectiveness of this innovative approach to carrot production.
In practice
In studies on the use of phosphate FLL in carrots, an improvement in root height and dimension was observed for plants fed with FLL in comparison with other units fertilized with conventional fertilizer.
The experiment conducted by Adilson Pelá and co-authors was carried out on the experimental farm of the State University of Goiás, with soil characterized as a red-yellow latosol of medium texture.
For this specific work, the hybrid carrot cultivar “Juliana” was used in an experimental area manually planted with polymer-coated monoammonium phosphate and conventional monoammonium phosphate applied in the sowing furrow, to compare the results.
The first thinning was carried out 30 days after planting and with top dressing at 45 days.
The results obtained indicated potential for the use of controlled-release fertilizers in carrots, which, in addition to reducing the need for reapplication, also reduces environmental impacts related to common fertilization.
Studies demonstrate the potential of slow release fertilizers (FLL) in improving carrot productivity. However, its results, despite being valid and significant, are insufficient to establish standards for the culture in question.
Therefore, more work must be developed seeking to value fertilizers with increased efficiency.
Recommendations
Before making any recommendation, a soil analysis must be carried out on the property where the planting will be carried out so that the specific demands of the species are precisely met according to the physical and chemical conditions of the soil where it will be planted.
The carrot crop, as a species with a high demand for nutrition and rapid material formation, can be fertilized both minerally and organically. Furthermore, being part of the vegetable field, it responds positively, especially to organic fertilization.
Therefore, slow-release fertilizer options coated with materials of organic origin can, in addition to keeping inorganic elements in good condition, contribute to improving the physical, chemical and biological conditions of the soil.
READ TOO:
