Nitrogen fertilizer application method for synergistically improving yield and quality of stevia rebaudiana

Abstract

The invention belongs to the technical field of fertilizers, and particularly relates to a nitrogen fertilizer application method for improving the yield and the quality of Stevia rebaudiana Bertoni. Through verification of experiments for many years of two varieties of stevia rebaudiana, the influence of the input proportion of nitrogen fertilizers (ammonium nitrogen and nitrate nitrogen) in different forms on the biomass and glycoside content of stevia rebaudiana is systematically explored, so that a nitrogen fertilizer application scheme for the optimal yield and quality of stevia rebaudiana is defined. Research results show that the biomass of the stevia rebaudiana leaves can be improved by increasing the ratio of the nitrate nitrogen fertilizer. Besides, the quality of the stevia rebaudiana leaves is determined by the content of stevioside in the leaves, the total stevioside content of the leaves can be effectively increased by increasing the input proportion of nitrate nitrogen, and the content can be optimal when the proportion of nitrate nitrogen to ammonium nitrogen is 3: 1. The test result also shows that the total accumulation amount of stevioside in the stevia rebaudiana leaves can be obviously increased by high nitrate nitrogen fertilizer input, and the economic benefit of stevia rebaudiana is promoted. Compared with the prior art, the method has the advantages that the yield of stevia rebaudiana and the stevioside accumulation amount of leaves can be synergistically increased, a high-yield and high-quality fertilization scheme is provided for planting of stevia rebaudiana, and a scientific basis and an innovative scheme are provided for production and research in related fields.

Description

Technical Field

[0001] The present invention belongs to Stevia ( Stevia rebaudiana Bertoni) cultivation technology, and specifically relates to a method for applying nitrogen fertilizer that can synergistically improve the yield and quality of stevia leaves. Background Art

[0002] Stevia is a special economic crop of the genus Stevia in the Asteraceae family. The steviol glycoside compounds rich in its leaves have the characteristics of "high sweetness and low calories", making it an ideal natural sweetener. In recent years, steviol glycosides have been widely used in the food and beverage industry to meet consumers' demand for low-calorie and sugar-free products. Therefore, steviol glycosides have extremely important medicinal and economic value. Increasing stevia yield and steviol glycoside content is of great significance to promoting the sustainable development of its industry.

[0003] In agricultural production, the rational application of nitrogen fertilizer is an important means to improve crop yield and quality. However, due to the lack of scientific fertilization guidance, agricultural growers often blindly apply nitrogen fertilizer, resulting in a year-on-year decline in stevia quality. At the same time, the trade-off between stevia yield and quality limits the demand for optimized nitrogen fertilizer application for high-yield and high-quality production of stevia. Therefore, exploring reasonable nitrogen fertilizer application methods is an important guarantee for increasing stevia yield and synergistically increasing leaf quality.

[0004] Nitrogen fertilizer management in agricultural production requires comprehensive consideration of the input of different forms of nitrogen fertilizers. Ammonium nitrogen and nitrate nitrogen are the two main inorganic nitrogen sources absorbed and utilized, and the input of nitrogen fertilizers in different forms will have a significant impact on crop yield and quality. At present, ammonium nitrogen fertilizers or amide nitrogen fertilizers are still the main ones used in stevia production, but research on the comprehensive effects of the ratio of ammonium nitrogen and nitrate nitrogen on stevia yield and quality is still relatively scarce, resulting in the failure to fully tap its potential for increasing yield and improving quality. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to provide a method for applying nitrogen fertilizer that can synergistically improve the yield and quality of stevia, and provide a scientific basis for the high-yield and high-quality cultivation of stevia.

[0006] To achieve the above purpose, the technical solution of the present invention is: on the basis of the traditional fertilization scheme based on ammonium nitrogen fertilizer, the input of nitrate nitrogen fertilizer is increased, and the input ratio of ammonium nitrogen to nitrate nitrogen is controlled to be 1:3, wherein ammonium nitrogen fertilizer accounts for 25% of the total nitrogen content and nitrate nitrogen fertilizer accounts for 75%.

[0007] As a further optimization of the above scheme, the ammonium nitrogen fertilizer is ammonium sulfate (nitrogen content ≥ 21%), and the nitrate nitrogen fertilizer is calcium nitrate (nitrogen content ≥ 13%).

[0008] As a further optimization of the above solution, the fertilizer is applied by soil application, and is applied respectively before the transplanting of stevia, 30 days after transplanting, and 60 days after transplanting, and the nitrogen fertilizer input ratios for the three times are 5:3:2.

[0009] As a further optimization of the above solution, the two fertilizers are evenly mixed before each application and then broadcast, and water is applied after each fertilization, and it is advisable that the surface is completely moist.

[0010] Compared with the prior art, the present invention has the following outstanding effects: it can effectively increase the total content and total accumulation of stevioside in stevia leaves while stabilizing or increasing the yield of stevia.

[0011] The present invention discloses a method for applying nitrogen fertilizer that can synergistically increase the yield and quality of stevia leaves. By adjusting the input ratio of different forms of nitrogen fertilizer during the growth process of stevia (controlling the ratio of nitrogen brought by nitrate nitrogen fertilizer to ammonium nitrogen fertilizer to be 3:1), the content and total accumulation of stevioside in stevia leaves can be effectively increased. Furthermore, it can improve the yield and economic benefits of stevia, providing a scientific basis for the high-yield and high-quality production of stevia, and having broad application value and promotion potential. Brief Description of the Drawings

[0012] Figure 1 It is a graph showing the influence results of different ratios of ammonium nitrogen fertilizer to nitrate nitrogen fertilizer on the leaf biomass of different varieties of stevia ('Shoutian No. 3' and 'Zhongshan No. 8') in the experiments in 2022 (A) and 2023 (B).

[0013] Figure 2 It is a graph showing the influence results of different ratios of ammonium nitrogen fertilizer to nitrate nitrogen fertilizer on the component content of stevioside in the leaves of different varieties of stevia ('Shoutian No. 3' and 'Zhongshan No. 8') in the experiments in 2022 (A) and 2023 (B).

[0014] Figure 3 It is a graph showing the influence results of different ratios of ammonium nitrogen fertilizer to nitrate nitrogen fertilizer on the total accumulation of stevioside in the leaves of different varieties of stevia ('Shoutian No. 3' and 'Zhongshan No. 8') in the experiments in 2022 (A) and 2023 (B).

[0015] Figure 4 It is a graph showing the influence of using machine learning technology to predict the influence of different ratios of ammonium nitrogen fertilizer to nitrate nitrogen fertilizer on the scores of different production traits of stevia (A) and the influence results of the comprehensive score.

[0016] Figure 5 It is a graph showing the influence results of the technology of the present invention (high nitrate nitrogen fertilizer) and high ammonium nitrogen fertilizer on the leaf biomass (A), leaf stevioside content (B), and accumulation amount (C) of stevia. Detailed Embodiments

[0017] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention and the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work belong to the scope of protection of the present invention.

[0018] Unless otherwise specified, the experimental methods used in the following embodiments are all conventional methods.

[0019] Unless otherwise specified, the materials, reagents, etc. used in the following embodiments can all be obtained from commercial channels.

[0020] Example 1 Effects of different forms of nitrogen fertilizers (ammonium nitrogen fertilizers and nitrate nitrogen fertilizers) on the leaf yield and quality of Stevia rebaudiana.

[0021] Experimental design.

[0022] This experiment was carried out as a pot experiment in the nursery of the Institute of Botany, Chinese Academy of Sciences, Jiangsu Province from June to September in 2022 and 2023.

[0023] The tested soil was taken from the cultivation land of the nursery of Nanjing Zhongshan Botanical Garden, and its basic physical and chemical properties are as follows: total carbon content 9.39 g / kg -1 , total nitrogen content 1.8711 g / kg -1 , available nitrogen content 70.34 mg / kg -1 , available phosphorus content 36.67 mg / kg -1 , available potassium content 117.64 mg / kg -1 .

[0024] This experiment adopted a two-factor design. The main factor was the ratio of different forms of nitrogen fertilizers (the ratios of ammonium nitrogen to nitrate nitrogen were 100:0, 75:25, 50:50, 25:75, 0:100), and the secondary factor was the Stevia rebaudiana variety ('Shoutian No. 3' and 'Zhongshan No. 8').

[0025] The flowerpots used for potting had an outer diameter of 25 cm and a height of 30 cm, and each pot was filled with 5.2 kg of soil.

[0026] The fertilization amount for the pot soil culture experiment was calculated according to the weight of 2250 t of the 15-cm plough layer soil per hectare and converted according to the weight of the pot soil. To avoid the influence of fertilization level and method on the experimental results, the nitrogen fertilizer application rate in this study was set at 300 kg / ha with reference to the previous experimental results. -1The nitrogen fertilizer operation mode adopts base fertilizer: branch fertilizer: pre-flowering fertilizer = 5:3:2. At the same time, a certain amount of dicyandiamide is added as a nitrification inhibitor each time nitrogen fertilizer is applied. Superphosphate is used as phosphorus fertilizer, and the application amount is 75 kg P2O5ha -1 , applied once as basal fertilizer; potassium chloride was used as potash fertilizer, with an application rate of 90 kg K2O ha -1 , respectively, as basal fertilizer and branch fertilizer at a ratio of 1:1. The fertilization schemes for different treatments are shown in Table 1, with 3 replicates for each treatment.

[0027] Table 1 Fertilization scheme for different forms of nitrogen fertilizer ratio test

[0028] In this experiment, the ammonium nitrogen fertilizer used was ammonium sulfate, and the nitrate nitrogen fertilizer used was calcium nitrate. Except for the different ratios of ammonium nitrogen fertilizer and nitrate nitrogen fertilizer, the other fertilization and management measures remained consistent to ensure the accuracy of the test results.

[0029] Test results.

[0030] like Figure 1 As shown in the figure, in the two-year pot experiment, the ratio of different forms of nitrogen fertilizer had no significant effect on the leaf biomass of the 'Shoutian No. 3' variety of stevia, but had a significant effect on the leaf biomass of the 'Zhongshan No. 8' stevia. Specifically, in 2022, when the ratio of ammonium nitrogen fertilizer to nitrate nitrogen fertilizer was 0:100, the leaf biomass of 'Zhongshan No. 8' stevia reached the highest value; and in 2023, the leaf biomass was the highest when the ratio of ammonium nitrogen fertilizer to nitrate nitrogen fertilizer was 25:75. In both years of the pot experiment, the leaf biomass of 'Zhongshan No. 8' stevia was the lowest when the ratio of ammonium nitrogen fertilizer to nitrate nitrogen fertilizer was 100:0.

[0031] like Figure 2 As shown in the results, the content of steviol glycosides in the leaves was significantly affected by the ratio of different forms of nitrogen fertilizers. Among them, the content of steviosides in the leaves of 'Zhongshan No. 8' stevia was not significantly affected in 2022, but the content of steviosides in the leaves of 'Shoutian No. 3' was the highest when the ratio of ammonium nitrogen to nitrate nitrogen was 50:50, followed by 25:75 and 0:100. In the 2023 trial, the content of steviol glycosides in the leaves of both varieties of stevia was affected by the form of nitrogen fertilizer, and the content of steviol glycosides was the highest when the ratio of ammonium nitrogen to nitrate nitrogen was 25:75.

[0032] like Figure 3For 'Shoutian No. 3' Stevia rebaudiana, the total accumulation of steviol glycosides in the leaves was not significantly affected by the form of nitrogen fertilizer, but the accumulation of steviol glycosides was the lowest when the ratio of ammonium nitrogen to nitrate nitrogen was 100:0. For 'Zhongshan No. 8' Stevia rebaudiana, the accumulation of steviol glycosides in the leaves was affected by the form of nitrogen fertilizer. Among them, in 2022, the accumulation was the highest when the ratio of ammonium nitrogen to nitrate nitrogen was 0:100, followed by the ratio of 25:75. In 2023, the total accumulation of steviol glycosides in the leaves was the highest when the ratio of ammonium nitrogen to nitrate nitrogen was 25:75, followed by the ratio of 50:50.

[0033] As Figure 4 shown, the score values of Stevia leaf biomass, steviol glycoside content and accumulation under different input ratios of ammonium nitrogen and nitrate nitrogen were predicted by machine learning methods. It was found that when the ratio of ammonium nitrogen to nitrate nitrogen was 25:75, the steviol glycoside content in the leaves and the total glycoside accumulation could reach the highest value. As Figure 4 shown, when the same weights were assigned to these three indicators to calculate the comprehensive score value, the results showed that when the ratio of ammonium nitrogen to nitrate nitrogen was 25:75, the comprehensive score was the highest.

[0034] Example 2 Effects of high nitrate nitrogen fertilization on the growth and quality of Stevia rebaudiana.

[0035] This experiment was carried out as a pot experiment in the greenhouse of the Institute of Botany, Chinese Academy of Sciences in Jiangsu Province from June to August 2024.

[0036] The tested soil was taken from the nursery cultivation land of Nanjing Zhongshan Botanical Garden, and its basic physical and chemical properties were as follows: total carbon content 13.14 g kg -1 , total nitrogen content 2.211 g kg -1 , available nitrogen content 90.10 mg kg -1 , available phosphorus content 55.02 mg kg -1 , available potassium content 192.50 mg kg -1 .

[0037] This experiment adopted a two-factor design. The main factor was the ratio of different forms of nitrogen fertilizers (high nitrate nitrogen fertilizer treatment (ammonium nitrogen: nitrate nitrogen ratio of 25:75) and high ammonium nitrogen fertilizer treatment (ammonium nitrogen: nitrate nitrogen ratio of 75:25)), and the secondary factor was the Stevia rebaudiana variety ('Shoutian No. 3' and 'Zhongshan No. 8').

[0038] The pots used for potting had an outer diameter of 12 cm and a height of 9.5 cm. Each pot was filled with 5.2 kg of soil, and there were 5 replicates for each treatment. In this experiment, the ammonium nitrogen fertilizer used was ammonium sulfate, and the nitrate nitrogen fertilizer used was calcium nitrate. Except for the different ratios of ammonium nitrogen fertilizer and nitrate nitrogen fertilizer, the other fertilization and management measures were kept consistent.

[0039] The fertilization amount for pot soil cultivation is shown in Table 2 below, and the application method is the same as in Case 1.

[0040] Test results.

[0041] As Figure 5 shown in A, the leaf biomass was mainly affected by the Stevia variety, and the biomass of 'Zhongshan 8' was significantly higher than that of 'Shoutian 3'. In addition, although there was no statistically significant effect of the high nitrate nitrogen treatment on biomass compared with the high ammonium nitrogen treatment, the biomass value under the high nitrate nitrogen treatment showed a certain upward trend.

[0042] As Figure 5 shown in B, the stevioside content in the leaves was significantly affected by the nitrogen fertilizer form. Among the two Stevia varieties, the high nitrate nitrogen significantly increased the stevioside content in the leaves.

[0043] As Figure 5 shown in C, the total accumulation of stevioside in the leaves was significantly affected by the nitrogen fertilizer form. Among the two Stevia varieties, the high nitrate nitrogen significantly increased the total accumulation of stevioside in the leaves, further confirming the positive role of nitrate nitrogen in promoting the accumulation of stevioside.

[0044] The technical solution of the present invention is not limited to the limitations of the above specific embodiments. Any technical deformation made according to the technical solution of the present invention falls within the protection scope of the present invention.

Claims

1. A method for applying nitrogen fertilizer to improve the leaf yield and quality of Stevia rebaudiana, which is characterized in that, During the growth period of Stevia rebaudiana, nitrate nitrogen fertilizer and ammonium nitrogen fertilizer are mixed and applied at a ratio of 3:1 during the growth period of Stevia rebaudiana to significantly increase the leaf biomass and stevioside content of Stevia rebaudiana.

2. The method for applying nitrogen fertilizer according to claim 1, wherein: The nitrogen fertilizer is applied by combining ammonium nitrogen fertilizer and nitrate nitrogen fertilizer according to the ratio of nitrogen contained in ammonium nitrogen fertilizer and nitrate nitrogen fertilizer being 3:

1.

3. The nitrogen fertilizer application method according to claim 1, characterized in that: The ammonium nitrogen used is ammonium sulfate, and the nitrate nitrogen used is calcium nitrate.

4. The nitrogen fertilizer application method according to claim 1, characterized in that: The fertilizer used needs to be applied to the soil in three times during the growth process of Stevia rebaudiana, with the input ratios of base fertilizer, branching fertilizer and pre-flowering fertilizer being 50%, 30% and 20% respectively.

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