A method for matching fertilization suitable for the growth of seedlings of ironwood

Abstract

The application belongs to the technical field of plant cultivation and fertilization, and relates to a matching fertilization method suitable for the growth of potted ironwood seedlings. The application provides a matching fertilization method suitable for the growth of potted ironwood seedlings, which comprises the following steps: mixing nitrogen fertilizer, phosphorus fertilizer and potassium fertilizer according to a mass ratio of 3-4:1-2:2-3, and then dissolving the mixture in distilled water to obtain a fertilizer solution; and applying the fertilizer solution to the cultivation substrate of the ironwood seedlings in batches. In the potting management of the ironwood seedlings, the mixed fertilizer is applied according to the scheme of nitrogen, phosphorus and potassium matching 3-4:1-2:2-3, which can help the overall healthy growth of hybrid ironwood seedlings.

Description

Technical Field

[0001] This invention pertains to plant cultivation and fertilization technology, and relates to a fertilization method with appropriate proportions suitable for the growth of potted Helleborus seedlings. Background Technology

[0002] Hellebores (Heliotropium indicum) have become increasingly popular as potted ornamental plants in the domestic flower market in recent years. Their long flowering period, unique flower shape, and good cold resistance have made them favored by many consumers. Currently, the commercial production of hellebores mainly relies on traditional horticultural experience, especially in the seedling stage. Fertilization management lacks standardized practices, often using general-purpose compound fertilizers or relying on experience to apply nitrogen fertilizer. This results in uneven seedling growth, with the number of leaves, stem divisions, and root development often falling short of expectations. For potted hellebores, the limited substrate capacity and weak nutrient buffering capacity make them more susceptible to fertilizer burn or nutrient deficiency if fertilized improperly, directly affecting the quality of the seedlings and the production cycle.

[0003] In plant nutrition research, the ratio of nitrogen, phosphorus, and potassium (NPK) is one of the key factors determining the effectiveness of fertilization. Different plants and different growth stages have significantly different requirements for the proportions of these three elements. Existing reports on fertilization of Helleborine (Heliotropium indicum) are scarce, and data available for reference in production is limited. Some growers refer to fertilization schemes for other Ranunculaceae flowers, but the actual results are inconsistent, easily leading to problems such as excessive vegetative growth and poor root development. Therefore, selecting a suitable NPK ratio scheme based on the growth characteristics of Helleborine seedlings has practical application value. Summary of the Invention

[0004] Currently, there are no known solutions specifically for the fertilization techniques of potted Helleborus seedlings. This invention systematically investigated the effects of different nitrogen, phosphorus, and potassium levels on the growth parameters, root indicators, photosynthetic characteristics, and leaf physiological and biochemical indicators of Helleborus seedlings, and selected the optimal ratio to provide technical support for the precise fertilization of Helleborus seedlings.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] On one hand, the present invention provides a fertilization method with a suitable ratio for the growth of potted Helleborus seedlings, comprising: Nitrogen fertilizer, phosphorus fertilizer and potassium fertilizer are mixed in a mass ratio of 3-4:1-2:2-3 and dissolved in distilled water to obtain fertilizer solution; the fertilizer solution is applied to the cultivation substrate of Helleborus seedlings in several applications.

[0007] Furthermore, the nitrogen fertilizer is urea, the phosphate fertilizer is superphosphate, and the potassium fertilizer is potassium sulfate.

[0008] Furthermore, the nitrogen content of the urea is 45-46%, the phosphorus content of the superphosphate is 16.5-17%, and the potassium content of the potassium sulfate is 52-53%.

[0009] Furthermore, the *Heliotropium indicum* seedlings are one-year-old hybrid *Heliotropium indicum* seedlings.

[0010] Furthermore, the *Heliotropium indicum* seedlings are one-year-old hybrid *Heliotropium indicum*. Helleborus × hybridus seedling.

[0011] Furthermore, the application is performed 4-5 times, with each application spaced 20-21 days apart.

[0012] Furthermore, the total amount of urea applied to each of the aforementioned Helleborus seedlings is 1-1.5g, the total amount of superphosphate applied is 0.91-1g, and the total amount of potassium sulfate applied is 0.58-0.6g.

[0013] Furthermore, the cultivation substrate is composed of peat and vermiculite mixed in a volume ratio of 1:1-1.2.

[0014] On the other hand, the present invention provides the application of the fertilization method of the present invention in improving the growth performance of potted hybrid Helleborine seedlings, wherein the growth performance includes plant height, number of tillers, number of leaves, root growth and biomass.

[0015] Furthermore, the application also includes enhancing the photosynthetic capacity, chlorophyll content, soluble protein content, and soluble sugar content of potted hybrid Helleborine seedlings.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Compared with the cultivation method of applying nitrogen fertilizer alone, the fertilization scheme of the present invention has obvious advantages. Applying nitrogen fertilizer, phosphorus fertilizer and potassium fertilizer according to the ratio of the present invention can effectively improve the growth status of one-year-old potted hybrid Helleborine seedlings, significantly improve the appearance growth indicators such as the number of stems and leaves, and promote root growth, increase the total root length and root surface area, and improve the problems of weak root development and uneven plant growth caused by applying nitrogen alone.

[0017] (2) After applying the fertilization scheme of the present invention, the photosynthetic capacity of seedlings is improved, and the content of chlorophyll, soluble sugar, soluble protein and other substances is also significantly increased, resulting in a better overall physiological state of the plant.

[0018] (3) The fertilization scheme of this invention clarifies the fertilizer ratio, single plant dosage, application interval and the whole cultivation process. It is simple to operate and the nutrient supply is in line with the growth characteristics of potted Helleborus seedlings. It can stably cultivate seedlings with excellent growth and is suitable for promotion and use in the large-scale cultivation of potted Helleborus. Attached Figure Description

[0019] Figure 1 The effects of different fertilization treatments on the growth of hybrid Helleborine seedlings after 100 days.

[0020] Figure 2 The effects of different fertilization treatments on the biomass of hybrid Helleborine seedlings are shown in Figure A; Figure B shows the effect of different fertilization treatments on the aboveground biomass of hybrid Helleborine seedlings. Different lowercase letters indicate the results of LSD multiple comparison tests. P The difference was significant at the <0.05 level.

[0021] Figure 3 The effect of different fertilization treatments on the chlorophyll content of hybrid Helleborine seedlings. Different lowercase letters indicate significant differences between treatments.

[0022] Figure 4 The effect of different fertilization treatments on the soluble protein content of hybrid Helleborine seedlings. Different lowercase letters indicate significant differences between treatments.

[0023] Figure 5 The effect of different fertilization treatments on the soluble sugar content of hybrid iron chopsticks. Different lowercase letters indicate significant differences between treatments.

[0024] Figure 6 Principal component analysis was performed on seedling growth parameters and physiological indicators under different fertilization treatments. In the analysis, CH represents chlorophyll content; NS represents branch number; NL represents leaf number; SW represents aboveground biomass; RW represents underground biomass; RL represents root length; RSA represents root surface area; SS represents soluble sugar; SP represents soluble protein; PN represents net photosynthetic rate; GS represents stomatal conductance; CI represents intercellular CO2 concentration; and TR represents transpiration rate. Detailed Implementation

[0025] The technical solution of the present invention will be described below with reference to embodiments. However, the present invention is not limited to the following embodiments. Unless otherwise specified, the experimental methods and detection methods described in each embodiment are conventional methods; unless otherwise specified, the reagents and materials are all commercially available.

[0026] Example 1: Materials and Methods 1.1 Test Materials and Site Select one-year-old hybrid helleborine seedlings ( Helleborus × hybridus The experimental material was a hybrid Helleborine seedling belonging to the genus Helleborine ( ). HelleborusThis is a hybrid of *Heliotropium indicum*. The plant height ranges from 11.5-12 cm, with 16-18 leaves. Seedlings are vigorous and similar in size. The cultivation substrate used was the peat moss:vermiculite (volume ratio 1:1), which performed well in the previous experiment. Seedlings were planted in polyethylene square pots with a diameter of 10 cm, a depth of 8 cm, and a total volume of 0.5 L. The volume of substrate in each pot was kept consistent. Before potting, the substrate was sterilized by mixing carbendazim at a ratio of 1 g:1 L. Urea (45% nitrogen content) was used as nitrogen fertilizer, purchased from Stanley Agricultural Group Co., Ltd., and superphosphate (16.5% phosphorus content) was used as phosphorus fertilizer. Potassium sulfate (52% potassium content) was also provided by Hebei Syngenta Agricultural Technology Co., Ltd. Peat moss was purchased from Pindstrup, Denmark; vermiculite was purchased from Tai'an Hetai Agricultural Technology Co., Ltd.

[0027] The experimental site was a forest area on the campus of Northwest A&F University. The experiment on the effects of different fertilization ratios on potted Helleborine began in May and lasted for 100 days.

[0028] 1.2 Experimental Design The experiment employed an orthogonal experimental design. Based on the actual nutritional requirements of one-year-old hybrid Helleborine seedlings during their growth period, four levels of nitrogen fertilizer (N) were set, and two levels each of phosphorus fertilizer (P) and potassium fertilizer (K) were set. There was one unfertilized control group (CK0) and four nitrogen-only control groups (CK1-CK4), totaling 13 treatment groups. Each group consisted of 12 pots, for a total of 156 pots. Detailed experimental protocols are shown in Tables 1 and 2. When fertilizing, the fertilizer was dissolved in 50 mL of distilled water and then slowly injected into the pots using a syringe. The unfertilized control group only received 50 mL of distilled water. Fertilizer was applied according to the specified ratio, once every 20 days, for a total of four applications. After fertilization, the plants were observed for 40 days, and all indicators were measured at the end of the experiment. Seedlings were thoroughly watered after initial potting. Thereafter, watering was arranged flexibly according to weather conditions during the cultivation period, ideally completed before 10:00 AM daily. Except for the treatment conditions specified in the experiment, all other cultivation management measures remained consistent.

[0029] Table 1. Factor Level Table for Fertilizer Ratio Application Experiment

[0030] Table 2 Total fertilizer application amount for each treatment group in the nitrogen, phosphorus, and potassium fertilization experimental design

[0031] 1.3 Indicator Measurement and Methods Measure the seedling height, number of tillers, number of leaves, and root indicators: Record the number of tillers, number of leaves, and plant height of the previous stage when fertilizing every 20 days during the growing season. Continue to observe for 40 days after the last fertilization to obtain the final plant height, number of leaves, and number of tillers.

[0032] Methods for measuring plant height, number of leaves, number of tillers, and root indicators: During the growing season, the number of tillers, number of leaves, and plant height were measured every 20 days. Plant height was measured from the base of the plant to its highest point, with an accuracy of 0.01 cm. The number of leaves was calculated by counting the true leaves excluding the cotyledons of the *Heliotropium indicum* seedlings. After rinsing the seedling roots with distilled water, images were acquired using a root scanner (WinRHIZO, UK), and parameters such as total root length and root surface area were obtained using the accompanying analysis software.

[0033] The following methods were used to determine the photosynthetic parameters, fresh and dry weight, chlorophyll content, soluble sugar content, and soluble protein content of seedlings: On a sunny, windless morning, leaf gas exchange parameters were measured using a TARGAS-1 portable photosynthetic measurement system (PP Systems, UK). Net photosynthetic rate (Pn), transpiration rate (Tr), intercellular CO2 concentration (Ci), and stomatal conductance (Gs) were measured. Three seedlings were selected for each treatment, and three leaves from each seedling were measured.

[0034] Fresh and dry weight were determined at the time of seedling harvest. Three seedlings were randomly selected from each treatment group, washed to remove soil, drained, and the fresh weight of the aboveground and underground parts was measured separately. The samples after fresh weight measurement were blanched at 105℃ for 30 min, then dried at 80℃ to constant weight, cooled to room temperature, and weighed. Both fresh and dry weights were accurate to 0.01 g, and each treatment was repeated in triplicate.

[0035] At the end of the experiment, mature leaves were randomly collected from potted hybrid Helleborine seedlings in each treatment group. After rinsing with deionized water, the leaves were blotted dry with absorbent paper. Each 0.1g sample was accurately weighed and stored in an ultra-low temperature freezer (-80℃) for later use. Chlorophyll content was determined using the ethanol extraction method; soluble protein concentration was determined using the G-250 Coomassie Brilliant Blue method; and soluble sugar content was determined using the anthrone colorimetric method. Each treatment was performed in triplicate.

[0036] 1.4 Data Processing and Statistical Analysis Data processing and statistical analysis methods: Data statistics and analysis were performed using Excel 2020 and SPSS 26.0 software. SPSS 26.0 was used for one-way ANOVA and principal component analysis (PCA). The least significant difference (LSD) method was used for multiple comparisons. P <0.05 is considered significant. After data processing, Origin 2021 was used to plot the results.

[0037] Example 2 Results and Analysis 2.1 Effects of different nitrogen, phosphorus, and potassium fertilization schemes on growth parameters of hybrid Helleborine seedlings 2.1.1 Effects of different nitrogen, phosphorus, and potassium fertilization schemes on the plant height of hybrid Helleborine seedlings Table 3 records the plant height of hybrid Helleborine seedlings at each measurement during the nitrogen, phosphorus, and potassium fertilization experiment. As shown in Table 3, the plant height of hybrid Helleborine seedlings under different fertilization schemes gradually increased with the increase of cultivation time. At the second fertilization, i.e., 20 days after cultivation, the seedlings in the N3P1K2 treatment group had the highest plant height (12.51 cm). This phenomenon continued until the end of fertilization; at 100 days after cultivation, the plant height of N3P1K2 was still superior to other treatments (13.94 cm), and 1.88 cm higher than the CK0 control group. In the nitrogen-only treatment groups CK1, CK2, CK3, and CK4, plant height increased with increasing nitrogen fertilizer level. The seedlings under the CK4 fertilization scheme achieved the highest plant height (13.92 cm), while the plant height of CK1 was the lowest (12.99 cm), but this difference was not significant. P >0.05).

[0038] After the experiment, the plant height of hybrid Helleborine seedlings grown under each fertilization formula, from highest to lowest, was: N3P1K2>CK4>N4P1K2>CK3>N1P2K2>N4P2K1>CK2>N2P1K1>N2P2K2>N1P1K1>CK1>N3P2K1>CK0. The plant height of seedlings in all fertilization groups was significantly higher than that in the CK0 control group (12.06 cm), although there was no significant difference between the fertilization treatment groups. P >0.05).

[0039] Table 3. Plant height of potted Helleborus seedlings under different fertilization treatments at various growth stages.

[0040] Note: Different letters in the same column of the table indicate significant differences between treatments. P <0.05); NS indicates no significant difference.

[0041] 2.1.2 Effects of different nitrogen, phosphorus, and potassium fertilization schemes on the number of tillers in hybrid Helleborine seedlings Tables 4 and 5 record the number of tillers of hybrid Helleborus seedlings at each measurement during the nitrogen, phosphorus, and potassium fertilization experiment. As shown in Tables 4 and 5, the number of tillers in potted Helleborus seedlings during the experiment was similar to the seedling height, increasing with the duration of cultivation. In the early stages of cultivation, specifically on days 20, 40, and 60, no significant differences were observed in the number of tillers among the groups.P >0.05). At the end of the 100th day of the experiment, the difference in the number of tillers between the groups was statistically significant ( P <0.05). On day 20 of cultivation, the N1P2K2 group had the highest number of tillers (5.44). On day 40, the situation was the same as on day 20, with the N1P2K2 group having 7.11 tillers. However, by day 60 of cultivation, the seedlings grown under the N3P1K2 fertilization formula had the highest number of tillers (7.67), and this number remained dominant by day 100 (11.00). Therefore, at the end of the experiment, the N3P1K2 group had the highest number of tillers, followed by the N1P2K2 group (9.89). Compared with other fertilization treatments, the hybrid Helleborus seedlings grown in the unfertilized control group CK0 grew the slowest and had the fewest tillers (4.89). The seedlings grown under the N3P1K2 and N1P2K2 fertilization schemes had significantly more tillers than the control group. Although the tillers of the other treatment groups were more than the control, the difference between them and the control group was not significant. Except for the control group, the seedlings in the CK1 group had the fewest stem divisions (6.22).

[0042] After 100 days of cultivation, a comparison was made among the treatment groups CK1, CK2, CK3, and CK4, which were fertilized only with nitrogen fertilizer. It was observed that the number of tillers in potted Helleborus seedlings increased with increasing nitrogen fertilizer levels, with CK4 having the highest number of tillers (7.33). Compared to the N4P1K2 and N4P2K1 groups, which received the same nitrogen fertilizer level, the N4P1K2 treatment group had a higher number of tillers (8.56) than the nitrogen-only CK4 group, while the N4P2K1 treatment group showed the opposite trend (6.89). In the other three nitrogen-only treatment groups, compared to those fertilized with a balanced NPK fertilizer at the same nitrogen level, the treatments fertilized with phosphorus and potassium fertilizers had a higher number of tillers than the nitrogen-only treatment groups.

[0043] Table 4. Number of stem divisions in potted Helleborus seedlings grown under different fertilization treatments at each growth stage.

[0044] Note: Different letters in the same column of the table indicate significant differences between treatments. P <0.05).

[0045] Table 5. Number of stem divisions in potted Helleborus seedlings grown under different fertilization treatments at each growth stage.

[0046] Note: Different letters in the same column of the table indicate significant differences between treatments. P <0.05); NS indicates no significant difference; This indicates significant differences between different treatment groups.

[0047] 2.1.3 Effects of different nitrogen, phosphorus, and potassium fertilization schemes on the number of leaves in hybrid Helleborine seedlings Table 6 shows that different nitrogen, phosphorus, and potassium fertilization treatments significantly affected the number of leaves in hybrid Helleborine seedlings. P <0.05). As the experiment progressed and the cultivation time increased, the number of leaves in the hybrid helleborine seedlings also increased. On the 20th day of cultivation, the fertilization treatment group with the most leaves was the N1P2K2 group (26.00), but at this time the difference between the groups was not significant. P >0.05). The differences were not significant on day 40 of cultivation, but at this time the N4P1K2 group had more leaves than other treatment groups (33.33), followed by the N1P2K2 fertilization treatment group (31.56). The differences between groups were statistically significant on day 60 of cultivation. P <0.05). At this point, the fertilization treatment group with the highest number of leaves was still the N4P1K2 group (41.78), followed by the N3P1K2 treatment group (33.33). However, at the observation period after the four fertilizations, i.e., the 100th day of cultivation, the seedlings grown under the N3P1K2 fertilization program had the most leaves (51.78).

[0048] After the experiment, the number of leaves of hybrid Helleborus seedlings grown under each fertilization formula, from highest to lowest, was as follows: N3P1K2>N1P2K2>N4P1K2>N2P2K2>N3P2K1>N2P1K1>N1P1K1>CK2>CK4>CK3>CK1>N4P2K1>CK0. The number of leaves in each fertilization treatment group differed significantly and was higher than that in the CK0 control group. After the experiment, a comparison was made among the nitrogen-only treatment groups CK1, CK2, CK3, and CK4. It was found that the number of leaves in the potted Helleborus seedlings in group CK2 was greater than that in groups CK1, CK3, and CK4. Group CK2 had the highest number of seedling leaves (36.78), followed by group CK4 (35.44), group CK3 (34.44), and group CK1 (31.78). Compared to the nitrogen-only fertilization group and the NPK fertilization group with the same level of nitrogen, the seedlings grown under the N4P1K2 (44.56) fertilization regimen had more leaves than the CK4 group, while the seedlings grown under the N4P2K1 (29.78) fertilization regimen had fewer leaves than the CK4 group. Simultaneously, the seedlings grown under the N4P2K1 fertilization regimen also had fewer leaves than any of the nitrogen-only treatment groups. In the other three nitrogen-only treatment groups, compared to the NPK fertilization group with the same level of nitrogen, the Helleborus seedlings in the phosphorus and potassium fertilization treatment groups had more leaves than the nitrogen-only treatment groups, a situation similar to the number of stem divisions in potted Helleborus seedlings.

[0049] Table 6. Number of leaves in potted Helleborine seedlings at different growth stages under different fertilization treatments.

[0050] Note: Different letters in the same column of the table indicate significant differences between treatments. P <0.05); NS indicates no significant difference; This indicates significant differences between different treatment groups.

[0051] In conclusion, different fertilization formulas did indeed significantly affect the growth parameters of hybrid Helleborine seedlings, except for plant height. Figure 1 The experiment showed the growth status of seedlings under different fertilization treatments after the experiment, which also illustrates this phenomenon.

[0052] 2.1.4 Effects of different nitrogen, phosphorus, and potassium fertilization schemes on root growth of hybrid Helleborine seedlings Table 7 shows the root growth of hybrid Helleborine seedlings under different fertilization treatments. The root growth of seedlings under different fertilization schemes showed significant differences. P <0.05). As shown in Table 7, the total root length of the unfertilized control group CK0 was the shortest (137.32cm), while the total root length of the seedlings in the N4P2K1 group was the longest (473.87cm), and the difference between the two groups was significant.

[0053] The total root length of hybrid Helleborine seedlings grown under different fertilization formulas, from highest to lowest, was: N4P2K1>N3P2K1>N1P2K2>N3P1K2>N4P1K2>CK4>N2P2K2>CK3>N2P1K1>CK2>N1P1K1>CK1>CK0. Regarding root surface area, seedlings grown in the N4P2K1 treatment group achieved the largest root surface area (96.42 cm²). 2 In the unfertilized treatment group CK0, the seedlings still had the smallest root surface area (39.02 cm²). 2 ).

[0054] The root surface area of ​​hybrid Helleborine seedlings grown under various fertilization formulas, from largest to smallest, is as follows: N4P2K1>N4P1K2>N3P2K1>CK4>N1P2K2>N2P2K2>N3P1K2>N2P1K1>N1P1K1>CK2>CK1>CK0.

[0055] Comparing the seedling growth of the CK1, CK2, CK3, and CK4 treatment groups (which received only nitrogen fertilizer) revealed that CK4 achieved the highest values ​​in total root length and root surface area, indicating that root length and root surface area increased with increasing nitrogen fertilizer application. Regarding root system condition, compared to the nitrogen-phosphorus-potassium (NPK) fertilizer treatment group (which received the same level of nitrogen fertilizer), the treatment groups receiving both phosphorus and potassium fertilizers showed better root growth than the nitrogen-only treatment group.

[0056] Table 7. Effects of different fertilizer formulations on root growth of potted Helleborine seedlings

[0057] Note: Different letters in the same column of the table indicate significant differences between treatments. P <0.05).

[0058] 2.1.5 Effects of different nitrogen, phosphorus, and potassium fertilization schemes on the biomass of hybrid Helleborine seedlings Depend on Figure 2 China A and Figure 2 As shown in B, there were significant differences in the fresh and dry weights of the aboveground and underground parts of the seedlings among different treatments. P <0.05). In Figure 2 In group A, the seedlings grown under the N3P1K2 fertilization formula had the highest aboveground fresh weight (14.79g), followed by the N1P2K2 treatment group (14.22g). The unfertilized control group CK0 had the lowest fresh weight (4.71g), showing a significant difference from other treatment groups, but not a significant difference from the CK1 treatment group (5.44g). The aboveground dry weight and fresh weight of the seedlings were similar. Figure 2 In group B, the seedlings grown under the N1P2K2 fertilization formula had the highest fresh weight of the underground parts (6.52g), followed by the N3P2K1 treatment group (5.86g) and the N3P1K2 treatment group (5.76g). The CK0 group had the lowest fresh weight of the underground parts (2.14g). The N4P1K2 treatment group (3.17g) and the CK1 treatment group (2.76g) had slightly higher fresh weights than CK0, but the difference was not significant. The dry weight of the underground parts was similar to the fresh weight.

[0059] Comparing the treatment groups CK1, CK2, CK3, and CK4, which only received nitrogen fertilizer, it was observed that the fresh and dry weight of both the aboveground and underground parts of seedlings increased with increasing nitrogen fertilizer application levels, but the differences between them were not significant. The fresh and dry weight of seedlings in the N1P2K2 group was significantly higher than that in the group receiving only the same level of nitrogen fertilizer. However, the fresh and dry weight of the aboveground parts of seedlings in the N4P2K1 group was significantly lower than that in the group receiving only the same level of nitrogen fertilizer. The fresh and dry weight of the underground parts of seedlings in the N4P1K2 treatment group was also significantly lower than that in the group receiving only the same level of nitrogen fertilizer.

[0060] 2.2 Effects of different nitrogen, phosphorus, and potassium fertilization schemes on photosynthetic indicators of hybrid Helleborine seedlings Table 8 shows the photosynthetic parameters of leaves of hybrid Helleborine seedlings under different nitrogen, phosphorus, and potassium (NPK) fertilization schemes. Different NPK fertilization treatments significantly improved the photosynthetic capacity of the hybrid Helleborine seedlings. In terms of net photosynthetic rate (Pn), the seedlings grown in the N1P2K2 fertilization treatment group had the highest Pn value (7.93 μmol CO2 / m³). 2 ·s), followed by the N3P1K2 group (7.89 μmol CO2 / m 2 Seedlings in both groups exhibited strong photosynthetic capacity. The unfertilized CK0 control group had the lowest Pn value (5.30 μmol CO2 / m³). 2 Except for group CK0, group CK4 had the lowest Pn value (5.54 μmol CO2 / m). 2 Regarding stomatal conductance (Gs), the seedlings of the N2P1K1 group showed the highest Gs value (172.58 mmol CO2 / m³). 2 The CK group had the lowest Gs value (103.86 mmol CO2 / m³). 2 ·s). In terms of transpiration rate (Tr), the N1P1K1 group had the highest Tr value (4.05 mmol H2O / m³). 2 ·s), followed by the N4P1K2 group (3.86mmol H2O / m 2 ·s) and N3P2K1 group (3.81mmol H2O / m 2 •s). The Ci value of intercellular CO2 concentration was the highest in CK0 (334.27 μmol / mol) and the lowest in the N3P1K2 treatment group (292.07 μmol / mol).

[0061] The treatment groups CK1, CK2, CK3, and CK4, which received only nitrogen fertilizer, were compared with CK0. The Pn values ​​of the CK1, CK2, CK3, and CK4 treatment groups were all higher than those of CK0, with the CK2 group having the highest Pn value (6.50 μmol CO2 / m³). 2 (·s) but the difference from CK0 was not significant. The Tr value of the CK4 group was the largest (3.63 mmol H2O / m 2 The Pn values ​​of the nitrogen-only fertilization group and the nitrogen-phosphorus-potassium (NPK) fertilization group were significantly different from those of the CK3 and CK2 groups. Compared with the nitrogen-only fertilization group and the NPK fertilization group, the Pn values ​​of the fertilization regimen containing all three elements (nitrogen, phosphorus, and potassium) were higher in the nitrogen-only fertilization group. Regarding Gs values, except for the N2P2K2 treatment group (112.32 mmol CO2 / m³), the Pn values ​​were significantly higher in the nitrogen-only fertilization group. 2 The CO2 / m³ concentration was lower than that of the CK2 group, which received the same level of nitrogen fertilizer (135.89 mmol CO2 / m³).2 Except for ·s), the other cases are similar to the Pn value. Finally, regarding the Ci value, except for the N4P2K1 group (332.58 μmol / mol), the Ci values ​​of the other nitrogen, phosphorus and potassium fertilizer ratio groups are similar to or lower than those of the CK group which was treated with the same level of nitrogen fertilizer.

[0062] Table 8 Effects of different fertilization treatments on photosynthetic parameters of hybrid Helleborine seedlings

[0063] Note: Different letters in the same column of the table indicate significant differences between treatments. P <0.05).

[0064] 2.3 Effects of different nitrogen, phosphorus, and potassium fertilization schemes on chlorophyll content in hybrid Helleborine seedlings from Figure 3 It can be seen that different nitrogen, phosphorus and potassium fertilization ratios have a significant effect on the chlorophyll content in the leaves of hybrid Helleborine seedlings. P <0.05. The chlorophyll content of seedling leaves in the N3P1K2 fertilization treatment group was the highest (1.53 mg / g), followed by the N1P2K2 group (1.44 mg / g). The chlorophyll content of seedling leaves in all fertilization treatment groups was significantly different from that in the unfertilized control group CK0 (0.89 mg / g).

[0065] Comparing the nitrogen-only treatment groups (CK1, CK2, CK3, and CK4), the chlorophyll content of the CK4 treatment group (1.22 mg / g) and the CK3 treatment group (1.26 mg / g) was higher than that of the other groups, but the difference was not statistically significant. Comparing the nitrogen-only treatment groups with the NPK balanced treatment groups (N4P2K1, 1.05 mg / g), the chlorophyll content of the seedling leaves in the N3P2K1 treatment group was lower than that in the CK4 treatment group. The chlorophyll content of the seedling leaves in the N3P2K1 treatment group (1.19 mg / g) was lower than that in the CK3 treatment group. The chlorophyll content of the seedling leaves in the N2P2K2 treatment group (1.09 mg / g) was lower than that in the CK2 treatment group.

[0066] 2.4 Effects of different nitrogen, phosphorus, and potassium fertilization schemes on the soluble protein content of hybrid Hedyotis diffusa Different nitrogen, phosphorus, and potassium fertilization schemes have a significant effect on the soluble protein content of hybrid iron chopsticks. P <0.05). By Figure 4It was found that the seedlings grown in the N1P2K2 group had the highest soluble protein content in their leaves (8.54 mg / g), followed by the N4P1K2 group (8.06 mg / g). Both were significantly different from the control group CK0 (5.07 mg / g). Except for the CK0 treatment group, the seedlings grown in the CK1 group had the lowest soluble protein content in their leaves (5.89 mg / g), which was significantly different from the N1P2K2 treatment group.

[0067] In a comparison of treatment groups CK1, CK2, CK3, and CK4, which received only nitrogen fertilizer, the soluble protein content in seedling leaves increased with increasing nitrogen fertilizer application levels. Comparing the treatment groups receiving a balanced NPK fertilizer with the control group receiving the same level of nitrogen fertilizer, the N4P1K2 group (8.06 mg / g) had significantly higher soluble protein content in seedling leaves than the CK4 group (7.28 mg / g), while the N4P2K1 treatment group (6.18 mg / g) had lower content than the CK4 treatment group. The N3P2K1 treatment group (6.51 mg / g) also had lower soluble protein content in seedling leaves than the CK3 treatment group (6.80 mg / g). However, this phenomenon was not observed in the CK1 and CK2 groups, or in the NPK fertilizer formulations receiving the same level of nitrogen fertilizer.

[0068] 2.5 Effects of different nitrogen, phosphorus, and potassium fertilization schemes on the soluble sugar content of hybrid Helleborine seedlings The effects of different nitrogen, phosphorus, and potassium fertilization schemes on the soluble sugar content of hybrid Helleborus seedlings can be seen. Figure 5 The differences in soluble sugar content in the leaves of seedlings grown under different fertilizer formulations were statistically significant. P <0.05%. Among them, the seedling leaves of the N3P1K2 treatment group had the highest soluble sugar content (10.1%), followed by the N2P1K1 treatment group (9.4%) and the N1P2K2 treatment group (9.32%). Their contents were significantly higher than those of the unfertilized control group CK0 (7.69%).

[0069] Comparing the treatment groups CK1, CK2, CK3, and CK4, which only applied nitrogen fertilizer, it was found that the soluble sugar content in seedling leaves increased with increasing nitrogen fertilizer application level, but decreased in the CK4 group (7.83%). Comparing the treatment groups applying a balanced NPK fertilizer with the CK group applying the same level of nitrogen fertilizer, the N4P1K2 group (8.96%) had significantly higher soluble sugar content in seedling leaves than the CK4 group, while the N4P2K1 treatment group (7.76%) had lower content than the CK4 treatment group. This phenomenon was not observed in the CK1, CK2, and CK3 groups, or in the balanced NPK fertilizer formulations applying the same level of nitrogen fertilizer.

[0070] 2.6 Principal component analysis and comprehensive evaluation of different fertilizer formulations Principal component analysis (PCA) can perform dimensionality reduction and comprehensive evaluation on complex datasets, and achieve quantitative evaluation of multi-indicator systems by calculating a comprehensive score, ultimately yielding a comprehensive rating. To comprehensively evaluate the impact of different fertilization schemes on the growth of potted Helleborus seedlings, this embodiment organized relevant growth and physiological index data and used principal component analysis to comprehensively evaluate the growth performance of seedlings under each fertilization treatment. The results are shown in [Figure number missing]. Figure 6 This method transforms the original variables into a set of linearly independent composite variables, i.e., principal components. Principal component analysis revealed three principal components, with a cumulative variance contribution rate of 85.26%, which can comprehensively reflect most of the information contained in the original data. Under this analysis, the higher the composite score of the treatment group, the better the growth conditions of the seedlings under this fertilization treatment and the better the fertilization effect.

[0071] Seedling growth was comprehensively evaluated using a combined score (F) and a ranking (R), and the optimal fertilization treatment to promote seedling growth was selected based on this (Table 9). Analysis showed that the highest combined growth score index for seedlings under different fertilization schemes was N3P1K2 (5.84), followed by N1P2K2 (5.48). The unfertilized control group CK0 had the lowest combined score (-0.13) and was ranked last. Therefore, the optimal fertilization scheme for potted hybrid Helleborine seedlings is N3P1K2.

[0072] Table 9. Comprehensive Evaluation of Different Fertilizer Formulas

[0073] Note: F represents the overall score of each matrix component, and Rank is the ranking level of each treatment. Fn is the score of the matrix combination on the nth component (n=1, 2, 3, 4). The F value is obtained by multiplying each score by its corresponding weight and summing them.

[0074] The results of this invention's embodiments show that, compared to applying nitrogen fertilizer alone, nitrogen-phosphorus-potassium (NPK) fertilization effectively promotes a positive increase in growth parameters and physiological indicators of hybrid Helleborine seedlings, resulting in better growth. When the NPK ratio is 3:1:2, and urea, superphosphate, and potassium sulfate are applied four times at total amounts of 1g / plant, 0.91g / plant, and 0.58g / plant, respectively, it significantly increases the number of tillers, leaves, and roots, and promotes net photosynthetic rate. Simultaneously, the content of soluble sugars, chlorophyll, and soluble proteins in the leaves is also significantly increased. It is worth noting that hybrid Helleborine seedlings also have a certain threshold for the absorption of nitrogen, phosphorus, and potassium; excessive amounts can hinder normal physiological processes. It is recommended to apply mixed fertilizer with a NPK ratio of 3:1:2 during the potted management of Helleborine seedlings, which can help the hybrid Helleborine seedlings grow robustly overall.

[0075] It should be understood that the disclosed invention is not limited to the specific methods, schemes, and substances described, as these are all subject to variation. It should also be understood that the terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit the scope of the invention, which is limited only by the appended claims.

Claims

1. A fertilization method suitable for the growth of potted Helleborus seedlings, characterized in that, include: Nitrogen fertilizer, phosphorus fertilizer and potassium fertilizer are mixed in a mass ratio of 3-4:1-2:2-3 and then dissolved in distilled water to obtain fertilizer solution; The fertilizer solution was applied to the cultivation substrate of the Helleborus seedlings in several applications.

2. The method for applying fertilizer according to claim 1, characterized in that, The nitrogen fertilizer is urea, the phosphate fertilizer is superphosphate, and the potassium fertilizer is potassium sulfate.

3. The method for applying fertilizer according to claim 2, characterized in that, The urea has a nitrogen content of 45-46%, the superphosphate has a phosphorus content of 16.5-17%, and the potassium sulfate has a potassium content of 52-53%.

4. The method for applying fertilizer according to claim 1, characterized in that, The *Heliotropium indicum* seedlings are one-year-old hybrid *Heliotropium indicum* seedlings.

5. The method for applying fertilizer according to claim 4, characterized in that, The *Heliotropium indicum* seedlings are one-year-old hybrid *Heliotropium indicum*. Helleborus × hybridus seedling.

6. The method for applying fertilizer according to claim 1, characterized in that, The application is to be done 4-5 times, with an interval of 20-21 days between each application.

7. The method for applying fertilizer according to claim 2, characterized in that, The total amount of urea applied to each of the aforementioned Helleborus seedlings is 1-1.5g, the total amount of superphosphate applied is 0.91-1g, and the total amount of potassium sulfate applied is 0.58-0.6g.

8. The method for applying fertilizer according to claim 1, characterized in that, The cultivation substrate is composed of peat and vermiculite mixed in a volume ratio of 1:1-1.

2.

9. The application of the fertilization method according to any one of claims 1-8 in improving the growth performance of potted hybrid Helleborine seedlings, characterized in that, The growth performance includes plant height, number of tillers, number of leaves, root growth, and biomass.

10. The application according to claim 9, characterized in that, The application also includes enhancing the photosynthetic capacity, chlorophyll content, soluble protein content, and soluble sugar content of potted hybrid Helleborine seedlings.

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