Nitrogen, potassium and calcium proportioning fertilization method for increasing sucrose content of pineapple fruit

Abstract

The application discloses a nitrogen-potassium-calcium ratio fertilization method for improving the sucrose content of pineapple fruits, and relates to the technical field of fruit tree cultivation.The specific steps of the method are as follows: firstly, the nitrogen-potassium-calcium ratio is adjusted according to the soil pH value; during the vegetative growth period, the compound nutrients are supplied regularly to cultivate strong plants; during the fruit swelling period, the same ratio of fertilizer is applied to directionally control the sucrose metabolic enzyme activity; the special fertilizer liquid is supplied to the leaves in batches to form the nutrient supply combining soil application with foliar spraying; finally, the sucrose content and enzyme activity are detected to verify the fertilization effect; according to the soil pH value and the root absorption efficiency, the base fertilizer is dynamically adjusted, the hindering of the acid-alkali imbalance to the root absorption is eliminated, and the material basis for sucrose accumulation is consolidated from the source; during the fruit swelling period, the nitrogen-potassium-calcium synergistic regulation is used to control the sucrose metabolic enzyme activity, the nutrient supply combining fast and slow is formed through foliar spraying, the root and leaf absorption channels are maximally utilized, finally, the effect is verified through harvesting and detection, and the stable improvement of the sucrose content of the fruits is realized.

Description

Technical Field

[0001] This invention relates to the field of fruit tree cultivation technology, specifically to a method for increasing the nitrogen, potassium, and calcium ratio of fertilization to improve sucrose production in pineapple fruits. Background Technology

[0002] Pineapple, a vital specialty fruit tree in my country's tropical and subtropical regions, boasts excellent taste and rich nutrition, resulting in consistently strong market demand. The sucrose content of the fruit is a core indicator for evaluating pineapple flavor, quality, commercial grade, and economic value. Mineral nutrient regulation is a crucial aspect of pineapple cultivation management. Nitrogen, potassium, and calcium are essential elements throughout the entire process of pineapple plant growth, photosynthetic product synthesis and transport, and fruit development and ripening, directly participating in plant physiological metabolism and the synthesis, decomposition, and storage of sucrose in the fruit. Furthermore, pineapple roots are highly sensitive to soil pH levels. Soil pH directly alters nutrient availability in the topsoil and root absorption capacity; pH ​​imbalances can lead to nutrient fixation and hindered absorption, thus inhibiting vigorous plant growth and fruit sugar accumulation. With the increasing scale and intensification of pineapple cultivation, the industry's requirements for standardized fruit quality are constantly rising, necessitating the development of a specialized fertilization technology system that adapts to soil conditions, matches growth patterns, and targets sucrose accumulation.

[0003] Traditional pineapple cultivation and fertilization methods often rely on planting experience, resulting in indiscriminate fertilization without considering soil pH characteristics or dynamically adjusting nitrogen, potassium, and calcium ratios based on actual soil conditions. This fails to create a suitable soil nutrient environment for root absorption. Fertilization does not differentiate nutrient supply according to key growth stages such as vegetative growth and fruit enlargement with sugar accumulation. The arbitrary ratios of elements ignore synergistic physiological effects, failing to effectively regulate the activity of key enzymes in sucrose metabolism, thus hindering sucrose decomposition and promoting sugar synthesis and storage. Furthermore, conventional fertilization often relies solely on soil application, neglecting foliar application for nutrient allocation, limiting nutrient absorption channels and resulting in low fertilizer utilization efficiency. The traditional method lacks quantitative assessment of nutrient absorption efficiency and metabolic enzyme activity, leading to inconsistent fertilization timing and volume, uneven plant growth, and insufficient photosynthetic product reserves. Ultimately, this results in low sucrose content and inconsistent fruit quality, severely hindering the development of high-quality pineapple cultivation. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for improving the nitrogen, potassium, and calcium ratio of fertilization in pineapple fruits. This method involves five steps of coordinated regulation: soil testing and application of base fertilizer, supplemental application for strengthening plants, topdressing for fruit expansion, foliar fertilization, and harvest verification. The nitrogen, potassium, and calcium ratio is dynamically adjusted based on soil pH, and a mathematical model of absorption efficiency is introduced to optimize fertilizer application. Topdressing with a matched base fertilizer ratio during the fruit expansion period synergistically regulates the activity of sucrose-metabolizing enzymes; foliar spraying of sugar alcohol-chelated calcium and potassium dihydrogen phosphate achieves complementarity between soil and foliar application. This method promotes sucrose synthesis and accumulation throughout the entire process, effectively improving fruit sweetness and quality.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for improving the nitrogen-potassium-calcium ratio of sucrose in pineapple fruits through fertilization, the specific steps of which are as follows:

[0006] S100, Soil testing and application of base fertilizer: Collect the pH value of the topsoil in the planting area, determine the nutrient ratio range based on the pH value, and complete the uniform distribution of nitrogen, potassium and calcium base fertilizers to create a soil basic nutrient environment suitable for pineapple root absorption.

[0007] S200, Strengthening Plants and Supplementing Nutrients: Relying on the established soil nutrient environment, compound nutrients are regularly supplemented throughout the pineapple's vegetative growth process. Based on the basic nutrients, robust plants are continuously cultivated, accumulating sufficient photosynthetic products that can be transported to the fruit.

[0008] S300, Precision Topdressing for Fruit Expansion: Relying on robust plants and stored photosynthetic products, apply nitrogen, potassium and calcium topdressing with the same ratio as base fertilizer during the concentrated accumulation stage of sucrose in the fruit, and directionally regulate the physiological activity of key enzymes in sucrose metabolism inside the fruit to promote the directional synthesis and storage of sugar.

[0009] S400, Foliar Fertilizer Application in Multiple Times: Based on the total amount of nutrients applied through soil fertilization, the proportion of soil application and foliar spraying of various nutrients is divided, and special fertilizer solution is sprayed during fixed growth periods to supplement the nutrients that can be absorbed by the plant leaves.

[0010] S500 Harvest Quality Verification: Relying on the nutrient supply system formed by soil application combined with foliar spraying, the fruit is harvested after it has developed to maturity. The sucrose content and metabolic enzyme activity of the fruit are tested to determine the actual effectiveness of fertilization.

[0011] Furthermore, in the S100 method of soil testing and basal fertilizer application, the soil pH value is divided into three ranges to match the corresponding nutrient ratios. When the pH value is in the range of 4.5 to 5.0, the mass ratio of nitrogen, potassium oxide, and calcium oxide in the basal fertilizer is set to 1:(2.6 to 3.0):(0.9 to 1.1); when the pH value is in the range of 5.0 to 5.5, the mass ratio of nitrogen, potassium oxide, and calcium oxide in the basal fertilizer is set to 1:(2.9 to 3.3):(0.6 to 0.8); when the soil pH value is lower than 4.5, dolomite powder is added to the soil layer to adjust the soil pH to above 4.8. The dolomite powder is applied at a rate of 50 to 80 kg / mu for every 0.1 pH unit increase. The specific dosage is adjusted according to the soil buffer capacity. The dolomite powder is evenly spread on the soil surface 15 to 20 days before planting, and then tilled into the soil to a depth of 20 to 30 cm. The depth of the base fertilizer is increased to 1.0-1.3, and all nutrients are evenly mixed with the topsoil. By adjusting the proportion of calcium, the acidity of the soil is neutralized, eliminating the obstacles to root nutrient absorption caused by acid-base imbalance, and ensuring that the roots can steadily absorb various basic nutrients in the early stage of planting.

[0012] Furthermore, in S100, a quantitative mathematical expression for soil nutrient absorption is introduced into the soil testing and basal fertilizer application process. This formula is used to determine the actual absorption efficiency of nitrogen, potassium, and calcium under different pH conditions. In the formula, E is the comprehensive absorption efficiency index of nitrogen, potassium, and calcium by pineapple roots; P is the measured soil pH value; α is the pH influence coefficient, ranging from 0.12 to 0.18; N... s β represents the available nitrogen content in the soil; β is the nitrogen absorption coefficient, ranging from 0.21 to 0.27; K s γ represents the available potassium oxide content in the soil; γ is the potassium absorption coefficient, ranging from 0.30 to 0.36; C s δ represents the effective calcium oxide content in the soil; δ is the calcium absorption coefficient, ranging from 0.15 to 0.21. Based on the calculation results, the actual amount of various nutrients in the base fertilizer is finely adjusted to eliminate the nutrient absorption deviation caused by pH.

[0013] Furthermore, in the S200 and plant strengthening nutrient supply, the compound nutrient supply is applied by shallow trenching between rows, simultaneously with root irrigation. This is carried out throughout the entire process from the end of plant transplanting to the start of artificial flowering. The nitrogen, phosphorus, and potassium compound fertilizer is applied in three to four quantitative applications, with the weight of compound fertilizer applied per acre controlled at 20kg to 25kg per application. The fertilizer is applied in the empty soil between the plant rows. After the fertilizer is applied, the soil is promptly irrigated with clean water to promote the slow decomposition and release of nutrients from the nitrogen, phosphorus, and potassium compound fertilizer. This provides basic nutrients for the plant's vegetative growth and physiological activities such as leaf emergence and branch elongation, cultivating uniformly growing, photosynthetically efficient fruiting plants and reserving sufficient organic nutrients for subsequent fruit development and sugar synthesis.

[0014] Furthermore, in the S300 and precise topdressing for fruit expansion, nitrogen, potassium, and calcium topdressing is carried out by hole application. The fixed application period is selected as 60 to 75 days after the end of pineapple flowering. This period coincides with the rapid accumulation and development stage of sucrose inside the pineapple fruit. The nitrogen, potassium, and calcium ratio used in the topdressing is consistent with the ratio of S100 base fertilizer. Nitrogen is used to inhibit the activity of sucrose decomposing enzyme, potassium is used to activate the activity of sucrose phosphate synthase, and calcium is used to maintain the integrity of fruit pulp cell membranes. The three form a synergistic regulatory system to reduce sucrose decomposition and accelerate sucrose synthesis. The topdressing adopts the same solid form as the base fertilizer and is applied in the soil layer at a distance of 15 to 25 cm from the base of the plant and a depth of 10 to 20 cm.

[0015] Furthermore, the S300 stage, the precise topdressing stage for fruit expansion, employs a mathematical expression to regulate the activity of sucrose metabolic enzymes. This formula is used to calculate the overall change in the activity of sucrose-metabolizing enzymes after topdressing. In the formula, H is the relative value of the comprehensive sucrose metabolism activity after topdressing; H0 is the relative value of sucrose metabolism activity under natural conditions; μ is the activation coefficient of potassium on sucrose phosphate synthase, ranging from 0.35 to 0.40; K is the effective amount of potassium oxide applied; ν is the inhibition coefficient of nitrogen on sucrose-degrading enzyme activity, ranging from 0.25 to 0.30; N is the effective amount of nitrogen applied. The natural state refers to the conventional planting state without the application of the nitrogen, potassium, and calcium topdressing described in this invention. The effective amount refers to the amount of pure potassium oxide and pure nitrogen applied in the fertilizer. The formula, combined with the calculated values, locks in the actual amount of topdressing applied, accurately controlling the variation in the activity of the two key enzymes.

[0016] Furthermore, the S400 and foliar fertilizer application strictly define the overall allocation of the three core nutrients: 85% of the total nitrogen is applied through soil and 15% through foliar spraying; 70% of the total potassium oxide is applied through soil and 30% through foliar spraying; and 40% of the total calcium oxide is applied through soil in the form of water-soluble calcium fertilizers such as calcium nitrate and calcium chloride, and 60% is applied through foliar spraying in the form of sugar alcohol chelated calcium. The allocation is based on the nutrient absorption capacity of the plant's roots and leaves, avoiding the problem of uneven nutrient absorption caused by a single fertilization method, maximizing the use of both nutrient absorption pathways to complete nutrient replenishment. All allocation ratios remain constant throughout the process and do not change with the planting site environment.

[0017] Furthermore, in the S400 and foliar fertilizer application, the special fertilizer solution is a mixture of sugar alcohol chelated calcium and potassium dihydrogen phosphate. The mass-volume concentration of sugar alcohol chelated calcium is 0.4%–0.6%, and the mass-volume concentration of potassium dihydrogen phosphate is 0.5%–0.7%. It is sprayed once each at 60, 75, and 90 days after flowering. The spraying operation is carried out between 9:00 and 11:00 in the morning or between 16:00 and 18:00 in the afternoon. The prepared fertilizer solution is evenly sprayed on both sides of the plant leaves. The liquid nutrients are quickly absorbed through the pores of the leaf epidermis, which quickly replenishes the fast-acting nutrients required for fruit pulp development during the fruit enlargement stage. This, combined with the long-acting nutrient supply from the soil, forms a nutrient supply mode that combines fast and slow nutrient supply.

[0018] Furthermore, the S500 and harvest verification quality system relies on a complete nutrient supply system constructed by soil application combined with foliar spraying. After the pineapple fruits naturally develop to the physiological maturity stage, the centralized harvesting operation is completed. After harvesting, representative fruit samples are promptly extracted, and the total amount of sucrose accumulation and the proportion of soluble sugar components inside the fruit are measured in sequence. At the same time, the activities of two core sucrose metabolism key enzyme indicators, namely sucrose phosphate synthase activity and sucrose decomposition enzyme activity, are detected in the fruit tissue. By comparing the measured physiological and biochemical data with the standard reference range, the actual sugar-promoting effect is judged.

[0019] Compared with existing technologies, this method of fertilizing with a nitrogen-potassium-calcium ratio to increase sucrose in pineapple fruits has the following beneficial effects:

[0020] I. This invention dynamically adjusts the amount of base fertilizer applied by defining the nutrient ratio range of base fertilizer based on soil pH and combining it with a quantitative calculation method of root nutrient absorption efficiency. Simultaneously, for acidic soils, it employs a method of simultaneous soil improvement and nutrient adjustment to eliminate the obstacle of pH imbalance to root nutrient absorption, ensuring stable root uptake of various basic nutrients in the early stages of planting. Based on this, compound nutrients are supplemented in stages throughout the vegetative growth process using a combination of inter-row application and root irrigation, continuously supporting the plant's physiological activities such as leaf emergence and branch elongation. This cultivates uniformly growing plants with stable photosynthetic efficiency, providing sufficient organic nutrients for subsequent fruit development and sugar synthesis, thus solidifying the material basis for sucrose accumulation in the fruit from the source. This solves the problems of low nutrient utilization and uneven plant growth caused by the mismatch between nutrient supply and soil environment and plant growth stage in traditional fertilization methods.

[0021] II. This invention utilizes nitrogen, potassium, and calcium topdressing in the same ratio as basal fertilizer during the concentrated sucrose accumulation stage of the fruit. By leveraging the synergistic effect of these three nutrients, the physiological activity of key enzymes involved in sucrose metabolism within the fruit is targeted and regulated. Simultaneously, a quantitative calculation method for changes in sucrose metabolism enzyme activity precisely determines the amount of topdressing to be applied, reducing sucrose decomposition and accelerating sucrose synthesis. Furthermore, based on the absorption characteristics of different nutrients, the distribution ratio between soil application and foliar spraying is determined. Specialized fertilizer solutions are sprayed at fixed growth stages, forming a nutrient supply pattern that combines fast and slow application. This maximizes the utilization of both root and leaf nutrient absorption pathways, avoiding the uneven nutrient absorption caused by a single fertilization method. Finally, post-harvest testing of fruit sucrose content and metabolic enzyme activity forms a complete closed-loop verification of the implementation effectiveness, achieving a stable increase in fruit sucrose content and ensuring the practical application effect of the fertilization method.

[0022] Other advantages, objectives and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from an examination of the following, or may be learned from the practice of the invention. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0024] Figure 1 A framework diagram of a fertilization method to improve the nitrogen-potassium-calcium ratio of sucrose in pineapple fruit;

[0025] Figure 2 A flowchart of a method for applying nitrogen, potassium, and calcium in a balanced fertilizer ratio to increase sucrose in pineapple fruit;

[0026] Figure 3 This is a flowchart of the steps for applying foliar fertilizer in multiple applications according to the present invention. Detailed Implementation

[0027] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structure, features and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0028] Example 1:

[0029] This example was conducted in a pineapple planting plot with a soil pH of 4.7.

[0030] First, soil testing was conducted to determine the optimal application ratio of basal fertilizer. Based on the measured soil pH value, the mass ratio of nitrogen, potassium oxide, and calcium oxide in the basal fertilizer was determined to be 1:2.8:1.0. A quantitative mathematical expression for soil nutrient absorption was then introduced to calculate the comprehensive absorption efficiency index of nitrogen, potassium, and calcium by pineapple roots. The quantitative mathematical expression for soil nutrient absorption is as follows: In the formula, P is the measured soil pH value of 4.7, α is taken as 0.15, and N... s With a soil available nitrogen content of 68 mg / kg, β value of 0.24, and K... s The soil available potassium oxide content is 125 mg / kg, γ is taken as 0.33, and C s The soil's available calcium oxide content was 820 mg / kg, and the δ value was 0.18. The calculated comprehensive absorption efficiency index was 186.3. Based on the calculation results, the actual application rate of base fertilizer was slightly adjusted, determining that 12 kg of pure nitrogen, 33.6 kg of potassium oxide, and 12 kg of calcium oxide were applied per acre. All the nutrients were evenly mixed with the topsoil. By adjusting the calcium content, the acidity of the soil was neutralized, eliminating the obstacle to root nutrient absorption caused by acid-base imbalance, and ensuring that the roots could steadily absorb various basic nutrients in the early stage of planting.

[0031] Select pineapple suckers with uniform growth for planting, with a plant spacing of 30 cm and a row spacing of 120 cm, planting 1850 plants per acre. Water thoroughly 7 days after planting to help the roots establish, and then keep the soil moist.

[0032] Next, nutrient supplementation will be provided to strengthen the plants. This will be carried out throughout the period from planting to the start of artificial flowering, with four applications of nitrogen, phosphorus, and potassium compound fertilizer. The fertilizer will be applied by digging shallow trenches between rows and simultaneously with root irrigation. The trenches should be 10 cm deep and dug in the open soil between rows, 30 cm from the base of the plant. The weight of compound fertilizer applied per acre per application is 22 kg. After the fertilizer is applied, the soil should be thoroughly watered to moisten it, promoting the slow decomposition and release of nutrients from the compound fertilizer. This will continuously provide basic nutrients for the plant's vegetative growth and physiological activities such as leaf emergence and branch elongation, cultivating uniformly growing, photosynthetically efficient fruit-bearing plants, and storing sufficient organic nutrients for subsequent fruit development and sugar synthesis. The four fertilizations will be carried out at 30, 60, 90, and 120 days after planting.

[0033] When the plant has grown to have more than 35 functional leaves, artificial flowering is performed. Flowering is induced by drenching the heart with a 40% ethephon solution diluted 500-1000 times, with 20-30 ml of solution per plant.

[0034] Then, precise topdressing is applied to promote fruit expansion. The application period is selected as 68 days after the pineapple flowering period, coinciding with the rapid accumulation and development of sucrose inside the pineapple fruit. The nitrogen, potassium, and calcium ratio used in the topdressing is consistent with that of the base fertilizer, i.e., a nitrogen, potassium oxide, and calcium oxide mass ratio of 1:2.8:1.0. It is applied using a hole application method: dig a hole 15 cm deep 20 cm away from the base of the plant, apply the fertilizer, and cover with soil. Apply 4 kg of pure nitrogen, 11.2 kg of potassium oxide, and 4 kg of calcium oxide per acre. Nitrogen inhibits the activity of sucrose-degrading enzymes, potassium activates the activity of sucrose phosphate synthase, and calcium maintains the integrity of the fruit pulp cell membranes. These three elements form a synergistic regulatory system, reducing sucrose decomposition and accelerating sucrose synthesis. The application method and soil layer location of the topdressing are maintained throughout the entire process.

[0035] The overall change in sucrose metabolism enzyme activity after topdressing was calculated using a mathematical expression for the regulation of sucrose metabolism enzyme activity. The mathematical expression for the regulation of sucrose metabolism enzyme activity is as follows: In the formula, H0 represents the relative value of sucrose metabolic activity under natural conditions (100), μ is 0.38, K is the effective amount of potassium oxide applied as topdressing (11.2 kg), ν is 0.28, and N is the effective amount of nitrogen applied as topdressing (4 kg). The calculated relative value of the comprehensive sucrose metabolic activity after topdressing is 131.4. By combining the expression with the calculated values, the actual amount of topdressing applied can be determined, and the variation range of the activities of the two key enzymes can be accurately controlled.

[0036] Foliar fertilizer was then applied in multiple applications. The overall allocation of the three core nutrient categories was strictly defined: 85% of the total nitrogen was applied through soil, and 15% through foliar spraying; 70% of the total potassium oxide was applied through soil, and 30% through foliar spraying; 40% of the total calcium oxide was applied through soil in the form of water-soluble calcium fertilizers such as calcium nitrate and calcium chloride, and 60% was applied through foliar spraying in the form of sugar alcohol chelated calcium. The allocation was based on the nutrient absorption capacity of the plant's roots and leaves, avoiding the problem of uneven nutrient absorption caused by a single fertilization method, and maximizing the use of both nutrient absorption pathways for nutrient replenishment. All allocation ratios remained fixed throughout the process and did not change with the environmental conditions of the planting site.

[0037] The special fertilizer solution is a mixture of sugar alcohol chelated calcium and potassium dihydrogen phosphate, with a mass-volume concentration of 0.5% for the sugar alcohol chelated calcium and 0.6% for the potassium dihydrogen phosphate. It is applied three times, 60, 75, and 90 days after flowering. Spraying should be done during periods of gentle daylight, specifically 9:00-11:00 AM or 4:00-6:00 PM. The prepared fertilizer solution is evenly sprayed onto both sides of the plant's leaves, allowing for rapid absorption of liquid nutrients through the leaf epidermal pores. This quickly replenishes the fast-acting nutrients needed for fruit development during the fruit enlargement stage, complementing the soil's long-acting nutrient supply to create a combined fast and slow nutrient delivery pattern. Figure 3 As shown.

[0038] Finally, quality is verified during harvesting. Harvesting is conducted centrally once the pineapple fruits have naturally reached physiological maturity. Physiological maturity is determined by the yellowing of the first one or two layers of small fruits at the base, moderate peel firmness, and the characteristic aroma of pineapple. Representative fruit samples are promptly collected after harvesting, and the total sucrose accumulation and the percentage of soluble sugars within the fruit are measured sequentially. Simultaneously, the activities of two key sucrose metabolism enzymes—sucrose phosphate synthase and sucrose degradase—are detected in the fruit tissue. The actual sugar-promoting effect is assessed by comparing the measured physiological and biochemical data with standard reference ranges. Figure 1 As shown.

[0039] Example 2:

[0040] This example was conducted in a pineapple planting plot with a soil pH of 5.2.

[0041] First, soil testing was conducted to determine the appropriate base fertilizer application. Based on the measured soil pH value, the mass ratio of nitrogen, potassium oxide, and calcium oxide in the base fertilizer was determined to be 1:3.1:0.7. A mathematical expression for quantifying soil nutrient absorption was introduced to calculate the comprehensive absorption efficiency index of nitrogen, potassium, and calcium by pineapple roots. In the formula, P represents the measured soil pH value (5.2), α is 0.15, N represents the available nitrogen content (72 mg / kg), β is 0.24, K represents the available potassium oxide content (132 mg / kg), γ is 0.33, C represents the available calcium oxide content (950 mg / kg), and δ is 0.18. The calculated comprehensive absorption efficiency index was 198.7. Based on the calculation results, the actual application rate of base fertilizer was slightly adjusted, determining that 11 kg of pure nitrogen, 34.1 kg of potassium oxide, and 7.7 kg of calcium oxide were applied per acre. All the nutrients are evenly mixed with the topsoil. By adjusting the proportion of calcium, the acidity of the soil is neutralized, eliminating the obstacles to root nutrient absorption caused by acid-base imbalance, and ensuring that the roots can steadily absorb various basic nutrients in the early stage of planting.

[0042] Select pineapple suckers with uniform growth for planting, with a plant spacing of 30 cm and a row spacing of 120 cm, planting 1850 plants per acre. Water thoroughly 7 days after planting to help the roots establish, and then keep the soil moist.

[0043] Next, nutrient supplementation will be provided to strengthen the plants. This will be implemented throughout the period from planting to the start of artificial flowering, with three applications of nitrogen, phosphorus, and potassium compound fertilizer in measured amounts. The fertilizer will be applied by digging shallow trenches between rows and simultaneously irrigating the roots. The trenches should be 10 cm deep and dug in the open soil between rows, 30 cm from the base of the plant. The weight of compound fertilizer applied per acre per application is 24 kg. After the fertilizer is applied, the soil should be thoroughly watered to moisten it, promoting the slow decomposition and release of nutrients from the compound fertilizer. This will continuously provide basic nutrients for the plant's physiological growth activities, such as leaf emergence and branch elongation, cultivating uniformly growing, photosynthetically efficient fruit-bearing plants, and ensuring sufficient organic nutrients for subsequent fruit development and sugar synthesis. The three fertilizations will be carried out 40, 80, and 120 days after planting.

[0044] When the plant has grown to have more than 35 functional leaves, artificial flowering is performed. Flowering is induced by drenching the heart with a 40% ethephon solution diluted 500-1000 times, with 20-30 ml of solution per plant.

[0045] Then, precise topdressing is applied to promote fruit expansion. The application period is selected as 72 days after the pineapple flowering period, coinciding with the rapid accumulation of sucrose within the pineapple fruit. The nitrogen, potassium, and calcium ratio used in the topdressing is consistent with the basal fertilizer ratio, i.e., nitrogen, potassium oxide, and calcium oxide mass ratio of 1:3.1:0.7. It is applied using a hole application method: dig a 15 cm deep hole 20 cm away from the base of the plant, apply the fertilizer, and cover with soil. The application rate is 3.8 kg of pure nitrogen, 11.8 kg of potassium oxide, and 2.7 kg of calcium oxide per acre. Nitrogen inhibits the activity of sucrose-degrading enzymes, potassium activates the activity of sucrose phosphate synthase, and calcium maintains the integrity of fruit pulp cell membranes. These three elements form a synergistic regulatory system, reducing sucrose decomposition and accelerating sucrose synthesis. The application method and soil layer location of the topdressing are maintained throughout the entire process.

[0046] The overall change in sucrose metabolic enzyme activity after topdressing was calculated using a mathematical expression regulating sucrose metabolic enzyme activity. In the formula, H0 represents the relative value of sucrose metabolic activity under natural conditions (100), μ is 0.38, K is the effective amount of potassium oxide applied (11.8 kg), ν is 0.28, and N is the effective amount of nitrogen applied (3.8 kg). The calculated relative value of the comprehensive sucrose metabolic activity after topdressing was 134.2. By combining the calculated values ​​with the expression, the actual amount of topdressing applied was determined, allowing for precise control of the activity fluctuations of the two key enzymes.

[0047] Foliar fertilizer was then applied in multiple applications. The overall allocation of the three core nutrient categories was strictly defined: 85% of the total nitrogen was applied through soil, and 15% through foliar spraying; 70% of the total potassium oxide was applied through soil, and 30% through foliar spraying; 40% of the total calcium oxide was applied through soil in the form of water-soluble calcium fertilizers such as calcium nitrate and calcium chloride, and 60% was applied through foliar spraying in the form of sugar alcohol chelated calcium. The allocation was based on the nutrient absorption capacity of the plant's roots and leaves, avoiding the problem of uneven nutrient absorption caused by a single fertilization method, and maximizing the use of both nutrient absorption pathways for nutrient replenishment. All allocation ratios remained fixed throughout the process and did not change with the environmental conditions of the planting site.

[0048] The special fertilizer solution is a mixture of sugar alcohol chelated calcium and potassium dihydrogen phosphate, with a mass-volume concentration of 0.5% for the sugar alcohol chelated calcium and 0.6% for the potassium dihydrogen phosphate. It is applied three times, 60, 75, and 90 days after flowering. Spraying should be done during periods of gentle daylight, specifically between 9:00 AM and 11:00 AM or between 4:00 PM and 6:00 PM. The prepared fertilizer solution is evenly sprayed onto both sides of the plant's leaves, allowing for rapid absorption of liquid nutrients through the leaf epidermal pores. This quickly replenishes the fast-acting nutrients needed for fruit development during the fruit enlargement stage, complementing the soil's long-term nutrient supply to create a combined fast and slow nutrient delivery pattern.

[0049] Finally, quality is verified during harvesting. Harvesting is conducted centrally once the pineapple fruits have naturally reached physiological maturity. Physiological maturity is determined by the yellowing of the first one or two layers of small fruits at the base, moderate peel firmness, and the characteristic aroma of pineapple. Representative fruit samples are promptly collected after harvesting, and the total sucrose accumulation and the percentage of soluble sugars within the fruit are measured sequentially. Simultaneously, the activities of two key sucrose metabolism enzymes—sucrose phosphate synthase and sucrose degradase—are detected in the fruit tissue. The actual sugar-promoting effect is assessed by comparing the measured physiological and biochemical data with standard reference ranges. Figure 2 As shown.

[0050] Example 3:

[0051] This example was conducted in a pineapple planting plot with a soil pH of 4.3.

[0052] First, soil testing was conducted to determine the appropriate base fertilizer application. Since the soil pH was below 4.5, dolomite powder was added to the soil layer to adjust the pH to 4.8. Dolomite powder was applied at a rate of 65 kg / mu (approximately 0.1 acre) for every 0.1 pH unit increase. In this example, a 0.5 pH unit increase was required, therefore 325 kg / mu (approximately 0.067 hectares) of dolomite powder was applied. The specific dosage was adjusted according to the soil's buffering capacity. The dolomite powder was evenly spread on the soil surface 15-20 days before planting, and then tilled into the soil to a depth of 20-30 cm. Simultaneously, the calcium oxide content in the base fertilizer was adjusted to 1.2. The mass ratio of nitrogen, potassium oxide, and calcium oxide in the base fertilizer was determined to be 1:2.8:1.2.

[0053] A mathematical expression for quantifying soil nutrient absorption was introduced to calculate the comprehensive absorption efficiency index of nitrogen, potassium, and calcium by pineapple roots. In the formula, P represents the improved soil pH (4.8), α is 0.15, N is the available nitrogen content (65 mg / kg), β is 0.24, K is the available potassium oxide content (118 mg / kg), γ is 0.33, C is the available calcium oxide content (1250 mg / kg), and δ is 0.18. The calculated comprehensive absorption efficiency index was 192.5. Based on the calculation results, the actual application rate of base fertilizer was slightly adjusted, determining that 12.5 kg of pure nitrogen, 35 kg of potassium oxide, and 15 kg of calcium oxide were applied per acre. Dolomite powder and all the nutrients were evenly mixed with the topsoil. By adjusting the calcium content, the acidity of the soil was neutralized, eliminating the obstacle to root nutrient absorption caused by acid-base imbalance, ensuring that the roots could steadily absorb various basic nutrients in the early stages of planting.

[0054] Select pineapple suckers with uniform growth for planting, with a plant spacing of 30 cm and a row spacing of 120 cm, planting 1850 plants per acre. Water thoroughly 7 days after planting to help the roots establish, and then keep the soil moist.

[0055] Next, nutrient supplementation will be provided to strengthen the plants. This will be carried out throughout the period from planting to the start of artificial flowering, with four applications of nitrogen, phosphorus, and potassium compound fertilizer. The fertilizer will be applied by digging shallow trenches between rows and simultaneously with root irrigation. The trenches should be 10 cm deep and dug in the open soil between rows, 30 cm from the base of the plant. The weight of compound fertilizer applied per acre per application is 23 kg. After the fertilizer is applied, the soil should be thoroughly watered to moisten it, promoting the slow decomposition and release of nutrients from the compound fertilizer. This will continuously provide basic nutrients for the plant's physiological growth activities, such as leaf emergence and branch elongation, cultivating uniformly growing, photosynthetically efficient fruit-bearing plants, and ensuring sufficient organic nutrients for subsequent fruit development and sugar synthesis. The four fertilizations will be carried out at 30, 60, 90, and 120 days after planting.

[0056] When the plant has grown to have more than 35 functional leaves, artificial flowering is performed. Flowering is induced by drenching the heart with a 40% ethephon solution diluted 500-1000 times, with 20-30 ml of solution per plant.

[0057] Then, precise topdressing is applied to promote fruit expansion. The application period is selected as 65 days after the pineapple flowering period, coinciding with the rapid accumulation and development of sucrose inside the pineapple fruit. The nitrogen, potassium, and calcium ratio used in the topdressing is consistent with that of the basal fertilizer, i.e., a nitrogen, potassium oxide, and calcium oxide mass ratio of 1:2.8:1.2. It is applied using a hole application method: dig a 15 cm deep hole 20 cm away from the base of the plant, apply the fertilizer, and cover with soil. The application rate is 4.2 kg of pure nitrogen, 11.8 kg of potassium oxide, and 5.0 kg of calcium oxide per acre. Nitrogen inhibits the activity of sucrose-degrading enzymes, potassium activates the activity of sucrose phosphate synthase, and calcium maintains the integrity of the fruit pulp cell membranes. These three elements form a synergistic regulatory system, reducing sucrose decomposition and accelerating sucrose synthesis. The application method and soil layer location of the topdressing are maintained throughout the entire process.

[0058] The overall change in sucrose metabolic enzyme activity after topdressing was calculated using a mathematical expression regulating sucrose metabolic enzyme activity. In the formula, H0 represents the relative value of sucrose metabolic activity under natural conditions (100), μ is 0.38, K is the effective amount of potassium oxide applied (11.8 kg), ν is 0.28, and N is the effective amount of nitrogen applied (4.2 kg). The calculated relative value of the comprehensive sucrose metabolic activity after topdressing was 133.1. By combining the calculated values ​​with the expression, the actual amount of topdressing applied was determined, allowing for precise control of the activity fluctuations of the two key enzymes.

[0059] Foliar fertilizer was then applied in multiple applications. The overall allocation of the three core nutrient categories was strictly defined: 85% of the total nitrogen was applied through soil, and 15% through foliar spraying; 70% of the total potassium oxide was applied through soil, and 30% through foliar spraying; 40% of the total calcium oxide was applied through soil in the form of water-soluble calcium fertilizers such as calcium nitrate and calcium chloride, and 60% was applied through foliar spraying in the form of sugar alcohol chelated calcium. The allocation was based on the nutrient absorption capacity of the plant's roots and leaves, avoiding the problem of uneven nutrient absorption caused by a single fertilization method, and maximizing the use of both nutrient absorption pathways for nutrient replenishment. All allocation ratios remained fixed throughout the process and did not change with the environmental conditions of the planting site.

[0060] The special fertilizer solution is a mixture of sugar alcohol chelated calcium and potassium dihydrogen phosphate, with a mass-volume concentration of 0.5% for the sugar alcohol chelated calcium and 0.6% for the potassium dihydrogen phosphate. It is applied three times, 60, 75, and 90 days after flowering. Spraying should be done during periods of gentle daylight, specifically between 9:00 AM and 11:00 AM or between 4:00 PM and 6:00 PM. The prepared fertilizer solution is evenly sprayed onto both sides of the plant's leaves, allowing for rapid absorption of liquid nutrients through the leaf epidermal pores. This quickly replenishes the fast-acting nutrients needed for fruit development during the fruit enlargement stage, complementing the soil's long-term nutrient supply to create a combined fast and slow nutrient delivery pattern.

[0061] Finally, the quality is verified during harvesting. Pineapple fruits are harvested centrally after they have naturally developed to physiological maturity. Physiological maturity is determined by the basal layer of one to two small fruits turning yellow, moderate peel firmness, and the characteristic aroma of pineapple. Representative fruit samples are promptly collected after harvesting, and the total sucrose accumulation and the percentage of soluble sugars within the fruit are measured sequentially. Simultaneously, the activities of two key sucrose metabolism enzymes—sucrose phosphate synthase and sucrose degradase—are detected within the fruit tissue. The actual sugar-promoting effect is assessed by comparing the measured physiological and biochemical data with standard reference ranges.

[0062] Comparative example:

[0063] This comparative example uses traditional pineapple planting and fertilization methods and is conducted on a plot of land with the same soil conditions as Example 1.

[0064] Apply 50 kg of NPK compound fertilizer per acre as base fertilizer, spreading it evenly and then tilling it into the soil. Use the same pineapple suckers as in Example 1 for transplanting, and maintain the same planting density and field management practices as in Example 1.

[0065] During the vegetative growth stage of the plants, apply 30 kg of nitrogen, phosphorus and potassium compound fertilizer per acre twice, 60 days and 120 days after transplanting.

[0066] During the fruit enlargement stage, apply 40 kg of nitrogen, phosphorus, and potassium compound fertilizer and 20 kg of potassium chloride per acre, 60 days after the flowering is induced.

[0067] Do not apply foliar fertilizer.

[0068] Pineapple fruits were harvested centrally after reaching physiological maturity through natural development, following the same harvesting standards as in Example 1. Representative fruit samples were promptly collected after harvesting, and the total sucrose accumulation and the percentage of soluble sugars within the fruit were measured sequentially. Simultaneously, the activities of two key sucrose metabolism enzymes—sucrose phosphate synthase and sucrose degradase—were detected in the fruit tissue.

[0069] To more clearly compare the technical solutions and effects of the various embodiments of the present invention with those of the comparative examples, the key parameters and test results are summarized in the table below:

[0070]

[0071] The comparison results above show that the sucrose content in the fruits of the three embodiments using the method of the present invention was significantly higher than that of the comparative example, the activity of sucrose phosphate synthase was significantly increased, and the activity of sucrose decomposing enzyme was significantly decreased. This indicates that the present invention, through techniques such as adjusting nutrient ratios based on soil pH, precise fertilization in stages, and combining soil fertilization with foliar fertilization, can effectively regulate the sucrose metabolism process in pineapple fruits, promote sucrose synthesis and inhibit sucrose decomposition, thereby significantly increasing the sucrose content of the fruits. Different embodiments were adjusted accordingly for different soil pH conditions, and all achieved good results, demonstrating the wide applicability and stability of the method of the present invention.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for applying fertilizer with a nitrogen-potassium-calcium ratio to increase sucrose content in pineapple fruit, characterized in that, The specific steps of this method are as follows: S100, Soil testing and application of base fertilizer: Collect the pH value of the topsoil in the planting area, determine the nutrient ratio range based on the pH value, and complete the uniform distribution of nitrogen, potassium and calcium base fertilizers to create a soil basic nutrient environment suitable for pineapple root absorption. S200, Strengthening Plants and Supplementing Nutrients: Relying on the established soil nutrient environment, compound nutrients are regularly supplemented throughout the pineapple's vegetative growth process. Based on the basic nutrients, robust plants are continuously cultivated, accumulating sufficient photosynthetic products that can be transported to the fruit. S300, Precision Topdressing for Fruit Expansion: Relying on robust plants and stored photosynthetic products, apply nitrogen, potassium and calcium topdressing with the same ratio as base fertilizer during the concentrated accumulation stage of sucrose in the fruit, and directionally regulate the physiological activity of key enzymes in sucrose metabolism inside the fruit to promote the directional synthesis and storage of sugar. S400, Foliar Fertilizer Application in Multiple Times: Based on the total amount of nutrients applied through soil fertilization, the proportion of soil application and foliar spraying of various nutrients is divided, and special fertilizer solution is sprayed during fixed growth periods to supplement the nutrients that can be absorbed by the plant leaves. S500 Harvest Quality Verification: Relying on the nutrient supply system formed by soil application combined with foliar spraying, the fruit is harvested after it has developed to maturity. The sucrose content and metabolic enzyme activity of the fruit are tested to determine the actual effectiveness of fertilization.

2. The method for increasing the nitrogen-potassium-calcium ratio of fertilization to enhance sucrose production in pineapple fruit according to claim 1, characterized in that, In the S100 method of soil testing and basal fertilizer application, the soil pH value is divided into three fixed ranges to match the corresponding nutrient ratios. When the pH value is in the range of 4.5 to 5.0, the mass ratio of nitrogen, potassium oxide, and calcium oxide in the basal fertilizer is set to 1:(2.6 to 3.0):(0.9 to 1.1); when the pH value is in the range of 5.0 to 5.5, the mass ratio of nitrogen, potassium oxide, and calcium oxide in the basal fertilizer is set to 1:(2.9 to 3.3):(0.6 to 0.8); when the soil pH value is lower than 4.5, dolomite powder is added to the soil layer to adjust the soil pH to above 4.8, and the proportion of calcium oxide in the basal fertilizer is simultaneously increased to 1.0 to 1.

3. All the nutrient ratios are uniformly mixed with the topsoil.

3. The method for increasing the nitrogen-potassium-calcium ratio of fertilization to enhance sucrose production in pineapple fruit according to claim 1, characterized in that, The S100 method, which incorporates a quantitative mathematical expression for soil nutrient absorption in soil testing and basal fertilizer application, is described. This formula is used to determine the actual absorption efficiency of nitrogen, potassium, and calcium under different pH conditions. In the formula, E is the comprehensive absorption efficiency index of nitrogen, potassium, and calcium by pineapple roots; P is the measured soil pH value; α is the pH influence coefficient, ranging from 0.12 to 0.18; N... s β represents the available nitrogen content in the soil; β is the nitrogen absorption coefficient, ranging from 0.21 to 0.27; K s γ represents the available potassium oxide content in the soil; γ is the potassium absorption coefficient, ranging from 0.30 to 0.36; C s δ represents the effective calcium oxide content in the soil; δ is the calcium absorption coefficient, ranging from 0.15 to 0.

21. Based on the calculation results, the actual amount of various nutrients in the base fertilizer is finely adjusted to eliminate the nutrient absorption deviation caused by pH.

4. The method for increasing the nitrogen-potassium-calcium ratio of fertilization to enhance sucrose production in pineapple fruit according to claim 1, characterized in that, In the S200 and plant growth nutrient supplementation, compound nutrients are applied by shallow trenching between rows and simultaneously with root irrigation. This is carried out throughout the entire process from the end of plant transplanting to the start of artificial flowering. The nitrogen, phosphorus, and potassium compound fertilizer is applied in three to four quantitative applications, with the weight of compound fertilizer applied per acre controlled at 20-25 kg per application. The fertilizer is applied in the empty soil between the plant rows. After the fertilizer is applied, the soil is promptly irrigated with clean water to continuously provide basic nutrients for the plant's vegetative growth and physiological activities, cultivating uniformly growing plants with stable photosynthetic efficiency.

5. The method for increasing the nitrogen-potassium-calcium ratio of fertilization to enhance sucrose production in pineapple fruit according to claim 1, characterized in that, In the S300 and precise topdressing for fruit expansion, nitrogen, potassium, and calcium topdressing is carried out by hole application. The fixed application period is selected as 60 to 75 days after the end of pineapple flowering. The fixed application period coincides with the rapid accumulation and development stage of sucrose inside the pineapple fruit. The nitrogen, potassium, and calcium ratio used in the topdressing is consistent with the ratio of S100 base fertilizer. Nitrogen is used to inhibit the activity of sucrose decomposing enzyme, potassium is used to activate the activity of sucrose phosphate synthase, and calcium is used to maintain the integrity of fruit pulp cell membranes. The three form a synergistic regulatory system, and the application form and soil layer location of the topdressing are not changed throughout the process.

6. The method for increasing the nitrogen-potassium-calcium ratio of fertilization to enhance sucrose production in pineapple fruit according to claim 1, characterized in that, The S300 and fruit expansion precision topdressing stages utilize mathematical expressions to regulate sucrose metabolism enzyme activity. The formula is used to calculate the overall change in the activity of sucrose metabolic enzymes after topdressing. In the formula, H is the relative value of the comprehensive sucrose metabolic activity after topdressing; H0 is the relative value of sucrose metabolic activity under natural conditions; μ is the activation coefficient of potassium on sucrose phosphate synthase, with a value of 0.35 to 0.40; K is the effective amount of potassium oxide applied; ν is the inhibition coefficient of nitrogen on sucrose decomposing enzyme activity, with a value of 0.25 to 0.30; and N is the effective amount of nitrogen applied.

7. The method for increasing the nitrogen-potassium-calcium ratio of fertilization to enhance sucrose production in pineapple fruit according to claim 1, characterized in that, The S400 and foliar fertilizer application strictly define the overall application and allocation of the three core nutrients. Specifically, 85% of the total nitrogen is applied through soil and 15% through foliar spraying; 70% of the total potassium oxide is applied through soil and 30% through foliar spraying; and 40% of the total calcium oxide is applied through soil in the form of other calcium fertilizers and 60% is applied through foliar spraying in the form of sugar alcohol chelated calcium. The allocation is based on the nutrient absorption capacity of the plant's roots and leaves, and all allocation ratios remain fixed throughout the process and do not change with the environment of the planting site.

8. The method for increasing the nitrogen-potassium-calcium ratio of fertilization to enhance sucrose production in pineapple fruit according to claim 1, characterized in that, In the S400 foliar fertilizer application, the special fertilizer solution is a mixture of sugar alcohol chelated calcium and potassium dihydrogen phosphate. The mass-volume concentration of sugar alcohol chelated calcium is 0.4% to 0.6%, and the mass-volume concentration of potassium dihydrogen phosphate is 0.5% to 0.7%. It is sprayed once each at 60 days, 75 days, and 90 days after flowering. The spraying operation is carried out during the period of gentle daylight. The prepared fertilizer solution is evenly sprayed on the upper and lower surfaces of the plant leaves. The liquid nutrients are quickly absorbed through the pores of the leaf epidermis, which quickly replenishes the fast-acting nutrients required for fruit pulp development during the fruit enlargement stage. This, combined with the long-acting nutrient supply from the soil, forms a nutrient supply mode that combines fast and slow nutrient supply.

9. The method for increasing the nitrogen-potassium-calcium ratio of sucrose in pineapple fruit according to claim 1, characterized in that, The S500 harvesting and quality verification system relies on a complete nutrient supply system constructed by combining soil application and foliar spraying. After the pineapple fruits naturally develop to the physiological maturity stage, the harvesting operation is completed in a unified manner. After harvesting, representative fruit samples are promptly extracted, and the total amount of sucrose accumulation and the proportion of soluble sugar components inside the fruit are measured in sequence. At the same time, the activities of two core sucrose metabolism key enzyme indicators, namely sucrose phosphate synthase activity and sucrose decomposition enzyme activity, are detected in the fruit tissue. By comparing the measured physiological and biochemical data with the standard reference range, the actual sugar-promoting effect is judged.

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