Foliar fertilizer application rates and recommendation for the sweet potato
- To exact determination and calculation the required amount of fertilizer application, it is recommended to conduct soil agrochemical analysis, taking into account the planned yield indicators
- We recommend to discuss nutritional special aspects with your regional manager
BBCH stages 13-19
Leaf Development
BBCH 31-39
Main stem elongation
BBCH 51-59
Inflorescence emergence
BBCH 71-79
Development of fruit
BBCH stages 13-19
Leaf Development
Leaf Development
This macro stage develops from the first true leaf and continues up to nine or more true leaves. First, the rudimentary stem nodes and internodes are established. The plant needs sufficient supplies of macronutrients such as phosphorus and potassium. When exposed to environmental and anthropogenic influences, amino acids are needed to eliminate them.
Leaves originate on the sides of the shoot tip. A local concentration of cell divisions marks the very beginning of the leaf; these cells then enlarge to form a nipple-shaped structure called a leaf support. The cells of the leaf support can be derived from the sheath or from the sheath and the hull. The support then becomes more and more flattened in the transverse plane due to laterally oriented cell divisions and subsequent expansion on both sides.
BBCH 31-39
Main stem elongation
Main stem elongation
To disclose in detail this macro stage, it is necessary to indicate that here occurs the formation of second-order growth cones, the formation of the available number of flowers in the inflorescence with the laying down of flower covering organs, the formation of anthers (microsporogenesis) and stigmas (megasporogenesis), the formation of a larger number of synchronously developed productive stems. There is intensive growth of organs in length, formation of ovules and pollen grains.
Applying nitrogen and phosphorus fertilizers can increase the number of flowers in an inflorescence. Although the structural organization of the vascular plant is relatively loose, the development of different parts is well coordinated. Control depends on the movement of chemicals, including nutrients and hormones. An example of correlation is shoot and root growth. The increase in the aerial part is accompanied by an increased need for water, minerals and mechanical support, which are satisfied by the coordinated growth of the root system. Several factors seem to be involved in control, as the shoot and the root affect each other mutually. The root depends on the shoot for organic nutrients, just as the shoot depends on the root for water and inorganic nutrients, and thus the flow of ordinary nutrients must play a role. However, more specific control can be provided by supplying the nutrients needed in very small quantities.
The root depends on the shoot for certain vitamins, and changes in supply reflecting the metabolic state of the above-ground parts can also affect root growth. In addition, hormonal factors affecting cell division pass upward from the root to the stem; although the exact role of hormones has not yet been established with certainty, they may be one of the ways in which the root system can influence the activity of the shoot apex. Secondary thickening control is another important example of growth correlation. As the size of the shoot system increases, the need for both greater mechanical support and enhanced transport of water, minerals, and elements is met by increased coverage of the stem through the activity of the vascular cambium. As a rule, the cambium of trees in temperate zones is most active in spring, when buds are budding and shoots are sprouting, creating a need for nutrients.
Cell division begins on each shoot and then spreads out from it. The terminal bud stimulates the cambium to divide rapidly through the action of two groups of plant hormones: auxins and gibberellins.
Inhibition of lateral buds, another example of a correlated growth reaction, illustrates a reaction opposite to that occurring when controlling cambial activity. Lateral buds are generally depressed, as axillary shoots grow slower or do not grow at all, while the terminal bud is active. This so-called apical dominance is responsible for the characteristic unit of trunk growth observed in many conifers and herbaceous plants, such as the mallow. Weaker dominance leads to a form with multiple branching. This fact that the lateral or axillary buds become more active when the terminal bud is removed is evidence of hormonal control. The flow of auxin from the shoot apex is partially responsible for the inhibition of axillary buds.
The nutritional status of the plant also plays a role, as verticillium dominance is strong when mineral supply and light are insufficient. Since the axillary buds are released from inhibition by treatment with substances that stimulate cell division, also called cytokinins, it has been suggested that these substances are also involved in the regulation of bud’s activity.
BBCH 51-59
Inflorescence emergence
Inflorescence emergence
In this macro stage, the processes of formation of all organs of the flower inflorescence are completed, the development of flowers from the rudiments up to their opening. The largest upper internode continues to grow. Compound fertilizers are applied with an emphasis on nitrogen and trace elements such as zinc.
In terms of development, a flower can be viewed as a determinate growth axis of a shoot, with lateral members occupying areas of the leaves that differentiate as floral organs – sepals, petals, stamens, and pistils. In the transition to flowering, the apex of the stem undergoes characteristic changes, the most noticeable of which is the shape of the apex area, which is related to the type of structure to be formed, whether a single flower, as in the tulip, or a bunch of flowers (inflorescences), as in the lilac.
The area of cell division extends to the entire apex, and the end-cell RNA content increases. When a single flower emerges, lateral buds appear higher and higher on the sides of the apical dome, and the entire apex is absorbed in the process, after which apical growth ceases.
BBCH 71-79
Development of fruit
Development of fruit
In this macro stage, the growth and formation of the fruit and seeds occurs. It should be noted that the embryo and endosperm increase in size.
The size of the fruit and seeds and their length are typical of the variety and hybrid. It should be noted that it is possible to influence the mass and quality of the fruit and seeds by complex fertilizers, calcium and trace elements. The fruit is formed from the ovary of the pistil after fertilization and is a characteristic feature of a flowering plant. A sharp increase in ovary cell division is observed immediately after the pollination process. Then comes a phase such as cell stretching. The nature of growth is closely related to the type of fetus.
After pollination, cell division continues for some time. After pollination, cell division continues for some time. The fertilized egg, the endosperm and the developing seeds have a strong controlling influence on fruit growth. For example, underdeveloped seeds, for certain specific reasons, are a factor in premature fruit drop. If the seed development is not uniform, the consequence can be a deformed fruit.
Sweet potato (Ipomoea batatas) is a perennial herbaceous plant
belonging to the Convolvulaceae family, native to tropical America. It ranks among the world’s most widely cultivated food and feed crops, standing as the sixth most important food crop globally after rice, wheat, potatoes, and corn. With an annual global production exceeding 105 million metric tons, China accounts for over half of the total world output, producing 70,963,630 metric tons per year.
Despite its name, sweet potato is unrelated to the common potato. They differ in numerous aspects, including their biological origin, appearance, and nutritional properties. Sweet potato thrives in hot climates and warm soils, while common potato prefers cooler temperatures. Sweet potato is a tropical plant highly sensitive to cold, while common potato tolerates cooler conditions.
Sweet potato grows best in well-drained soils
with a pH between 4.5 and 7.0, ranging from light to medium texture. It can thrive at altitudes from sea level up to 2,500 meters. Sweet potato requires less labor and input compared to other crops like maize and can tolerate adverse growing conditions, such as drought periods and nutrient-poor soils.
Sweet potato’s nutrient requirements vary depending on its growth stage.
During the initial growth phase (BBCH 13-19), phosphorus and nitrogen are crucial. Phosphorus promotes root system development at early stages, ensuring adequate water and nutrient uptake. Nitrogen, on the other hand, is essential for amino acid synthesis, the building blocks of proteins. Proteins are necessary for creating new cells and tissues, including leaves. Sweet potato requires a significant amount of proteins during the initial growth phase for new cell formation.
Wonder Leaf Blue, with its N:P:K ratio of 10:53:10 + chelated Zn-2 (w/w%), serves as an ideal fertilizer for sweet potato during the foliage development stage. Wonder Leaf Blue not only enriches the plant with essential nutrients but also enhances its resistance to low temperatures, particularly crucial during the early growth stages.
Enriching sweet potato plants with manganese and zinc during the stem elongation phase (BBCH 31-39) is crucial for optimal growth.
Manganese plays a vital role in carbohydrate and lipid metabolism, providing energy and building blocks for new cells during stem elongation. Zinc, on the other hand, enhances antioxidant protection, enabling the plant to withstand stress factors like drought or high temperatures that could hinder stem growth.
We recommend using foliar fertilizers Wonder Leaf Mn 11, containing 11% chelated manganese, and Wonder Leaf Mono Zn 8, comprising 8% chelated zinc alongside other essential elements. The recommended application rate for both fertilizers is 1-2 l/ha.
Boron and amino acids play a significant role during the bud formation stage (BBCH 51-59) of sweet potato cultivation.
As the plant prepares for flowering and fruit development, boron promotes pollen tube growth, critical for successful fertilization and fruit set. Amino acids provide the necessary building blocks for protein and nucleic acid synthesis, influencing bud formation and development.
Wonder Leaf Blossom, containing 0.7% boron and 4% organic amino acids, is an ideal fertilizer for this growth phase. The recommended application rate is 4-5 l/ha.
During the fruit formation stage (BBCH 71-79)
high potassium supplementation is essential for sweet potato quality. Wonder Leaf Mono K 30, with its 30% potassium content, enhances fruit quality by improving their density, color, flavor, and storage life. It promotes healthy fruit development with good structure and reduces the risk of physiological disorders. Additionally, potassium contributes to increased fruit size and weight, boosting overall yield. This is attributed to improved water balance and efficient nutrient transport.
It is important to note that nutrient requirements may vary depending on the sweet potato variety
soil conditions, and other factors. Conducting a soil analysis is recommended to determine the precise nutrient needs for your specific sweet potato crop.
By adhering to these micronutrient fertilization guidelines, growers can cultivate healthy, productive sweet potato plants that produce high-quality tubers with enhanced yield and marketable characteristics.
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