Nitrogen-iron compound fertilizer, method for fertilizing crops

Abstract

The present disclosure provides a nitrogen-iron compound fertilizer, belonging to the technical field of crop fertilization, which is composed of nitrogen fertilizer and chelate iron fertilizer. The present disclosure also provides a method for crop fertilization, comprising: during the growth of crops, spraying the nitrogen-iron compound fertilizer in the form of an aqueous solution to the leaf surface of the crops, the spraying frequency being 2-3 times, and the interval time being 5-7 days, and the production management being normal crop planting field management, wherein the nitrogen-iron compound fertilizer is composed of nitrogen fertilizer and chelate iron fertilizer. By using the nitrogen-iron compound fertilizer and the method for crop fertilization provided by the present disclosure, the nitrogen-iron compound fertilizer is sprayed to the leaf surface of the crops during the growth of the crops, the tillering and the absorption and utilization of nitrogen and iron elements of the plants in the tillering stage are enhanced, thereby effectively improving the yield and nitrogen utilization rate of the crops. Among them, the response of the OsNLP4 overexpression rice to the spraying of the nitrogen-iron compound fertilizer on the leaf surface is stronger, and the yield and the nitrogen utilization rate are both significantly increased.

Description

Technical Field

[0001] This disclosure belongs to the field of crop fertilization technology, specifically relating to a nitrogen-iron compound fertilizer and a method for applying fertilizer to crops. Background Technology

[0002] Rice and wheat are important food crops, and their yields are crucial for addressing food crises and are also vital to the national economy. With population growth, decreasing arable land, and water scarcity, the contradiction between food supply and demand has intensified, making it imperative to increase rice and wheat production.

[0003] Applying chemical fertilizers is the primary measure for increasing rice and wheat yields. However, traditional fertilization methods are simplistic, and the pursuit of higher yields often leads to excessively large applications. Despite the significant annual increase in fertilizer use, grain production growth has been slow. Excessive fertilizer application results in soil fertilizer residue and acidification, with residual fertilizer flowing into rivers, lakes, and oceans, causing severe environmental pollution and ecological imbalance, and increasing farmers' production costs.

[0004] Therefore, developing a fertilizer and fertilization method for rice and wheat that can significantly increase yield while being efficient and low-cost, in order to achieve green and high yields of rice and wheat, is of great significance and has a promising application prospect. Summary of the Invention

[0005] In view of the above-mentioned technical problems, this disclosure provides a method for applying nitrogen-iron compound fertilizer to crops, in order to at least partially solve the above-mentioned technical problems.

[0006] The technical solution provided in this disclosure is as follows:

[0007] As one aspect of this disclosure, a nitrogen-iron compound fertilizer is provided, wherein the nitrogen-iron compound fertilizer is composed of nitrogen fertilizer and chelated iron fertilizer, wherein the concentration ratio of nitrogen fertilizer to chelated iron fertilizer is 83:1-1.5.

[0008] In one embodiment, the chelate iron fertilizer includes any one of the following: EDTA-Fe, EDDHA-Fe, DTPA-Fe, HEDTA-Fe, EDDHMA-Fe, EDDHSA-Fe, IDHA, EDDS-Fe;

[0009] Nitrogen fertilizers include any of the following: urea, ammonium nitrate, and calcium nitrate.

[0010] As another aspect of this disclosure, a method for fertilizing crops is provided, comprising:

[0011] During the growth of crops, nitrogen-iron compound fertilizer is made into an aqueous solution and sprayed on the leaves of the crops 2-3 times, with an interval of 5-7 days. Production management is the same as normal field management for crop planting. The nitrogen-iron compound fertilizer sprayed consists of nitrogen fertilizer and chelated iron fertilizer.

[0012] In one embodiment, the nitrogen-iron compound fertilizer aqueous solution sprayed onto the leaves of crops is a combination of nitrogen fertilizer aqueous solution and chelated iron fertilizer aqueous solution;

[0013] The concentration of the nitrogen fertilizer aqueous solution is 0.1-1.5%, and the concentration of the chelate iron fertilizer aqueous solution is 0.5-1.5 mM.

[0014] The total amount of nitrogen-iron compound fertilizer solution applied per spraying is 500-600 L / hm². 2 .

[0015] In one embodiment, the timing of foliar spraying of nitrogen-iron compound fertilizer solution onto crops includes the tillering stage;

[0016] The tillering stage includes: early tillering, middle tillering, and late tillering.

[0017] In one embodiment, the nitrogen-iron compound fertilizer aqueous solution is sprayed during the early tillering stage.

[0018] In one embodiment, the crop includes at least one of the following: rice and wheat.

[0019] In one embodiment, the rice variety includes at least one of the following: wild-type rice and genetically modified rice;

[0020] Wild-type rice includes: Japonica rice Zhonghua 11;

[0021] Genetically modified rice includes rice that overexpresses OsNLP4.

[0022] In one embodiment, a nitrogen-iron compound fertilizer solution is sprayed on the crop in the early tillering stage to promote tillering and increase crop yield and nitrogen utilization.

[0023] In one embodiment, a nitrogen-iron compound fertilizer solution was sprayed on OsNLP4-overexpressing rice in the early tillering stage to promote tillering, yield and nitrogen use efficiency, which increased crop yield and nitrogen use efficiency more than wild-type rice.

[0024] Based on the above technical solution, the nitrogen-iron compound fertilizer and crop fertilization method provided in this disclosure have at least one of the following beneficial effects:

[0025] (1) According to the embodiments of this disclosure, nitrogen-iron compound fertilizer composed of nitrogen fertilizer and chelated iron fertilizer is used. Compared with the compound fertilizers in the prior art that contain a variety of additives such as phosphorus, potassium and zinc in addition to nitrogen fertilizer and iron fertilizer, nitrogen-iron compound fertilizer is simpler in composition and lower in cost.

[0026] (2) According to the embodiments of this disclosure, the method of foliar spraying nitrogen-iron compound fertilizer is adopted to make the fertilizer application more uniform, especially for compound fertilizers containing iron trace elements.

[0027] (3) According to the embodiments of this disclosure, by determining the preferred time for applying nitrogen-iron compound fertilizer, the fertilizer formulation and the target crop to be sprayed, the yield and nitrogen utilization rate of crops with tillering characteristics can be significantly improved, providing theoretical support and technical guidance for improving the fertilization method of agricultural production, improving fertilizer utilization efficiency, and achieving green and high-yield crops.

[0028] (4) The crop fertilization method in this embodiment is simple to operate, has low fertilizer cost, has significant fertilization effect, is widely applicable to crops, and is easy to promote.

[0029] (5) In the embodiments of this disclosure, spraying nitrogen-iron compound fertilizer solution on the leaves of crops during the tillering stage can promote tillering of plants during the tillering stage, improve the absorption and utilization of nitrogen and iron elements, thereby effectively increasing crop yield and nitrogen utilization rate. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments.

[0031] In existing technologies, to achieve higher yields in crops such as rice and wheat, the approach is often to simply increase fertilizer application. However, with increased fertilizer application, crop yields have not significantly improved; instead, excessive fertilization has led to a series of environmental pollution problems and increased planting costs for farmers. Currently, one of the main reasons for this predicament is the lack of attention to the timing of fertilization and the proper ratio of fertilizer nutrients, resulting in low fertilizer utilization. Therefore, this disclosure provides a nitrogen-iron compound fertilizer and a method for crop fertilization. By optimizing fertilizer formulation, improving fertilization methods, application timing, and target organisms, this method significantly improves crop yield and nitrogen utilization.

[0032] According to embodiments of this disclosure, the nitrogen-iron compound fertilizer is composed of nitrogen fertilizer and chelated iron fertilizer, wherein the concentration ratio of nitrogen fertilizer to chelated iron fertilizer is 83:1-1.5.

[0033] Nitrogen fertilizers can include urea, ammonium nitrate, or calcium nitrate, or other nitrogen-containing compounds.

[0034] The choice of iron fertilizer includes soluble free iron salts or chelated iron. Among them, chelated iron is preferred because the iron ions in chelated iron are not easily precipitated, are easily absorbed by plant stems and leaves, have higher absorption efficiency, and have more stable fertilizer effect.

[0035] According to embodiments of this disclosure, the chelated iron fertilizer includes any one of EDTA-Fe, EDDHA-Fe, DTPA-Fe, HEDTA-Fe, EDDHMA-Fe, EDDHSA-Fe, IDHA, and EDDS-Fe. The nitrogen fertilizer includes any one of urea, ammonium nitrate, and calcium nitrate. It should be noted that the nitrogen fertilizer and chelated iron fertilizer are not limited to those listed.

[0036] In the embodiments of this disclosure, the nitrogen-iron compound fertilizer composed of nitrogen fertilizer and chelated iron fertilizer is simpler in composition, lower in cost, and more environmentally friendly than the compound fertilizers of the prior art that contain additives such as phosphorus, potassium, and calcium in addition to nitrogen and iron.

[0037] According to embodiments of this disclosure, a method for spraying crops is provided, comprising:

[0038] During the growth of crops, nitrogen-iron compound fertilizer is made into an aqueous solution and sprayed on the leaves of the crops 2-3 times, with an interval of 5-7 days. Production management is the same as normal field management for crop planting. The nitrogen-iron compound fertilizer sprayed consists of nitrogen fertilizer and chelated iron fertilizer.

[0039] According to embodiments of this disclosure, the period during which nitrogen-iron compound fertilizer solution is sprayed onto the leaves of crops during the crop growth process is the tillering stage, wherein the tillering stage includes the early tillering stage, the middle tillering stage, and the late tillering stage, and more preferably the early tillering stage.

[0040] In the embodiments of this disclosure, spraying nitrogen-iron compound fertilizer onto the leaves of crops during the tillering stage can promote tillering, increase the number of tillers, and thus increase crop yield.

[0041] According to embodiments of this disclosure, the nitrogen-iron compound fertilizer aqueous solution sprayed onto the leaves of crops is composed of a nitrogen fertilizer aqueous solution and a chelated iron fertilizer aqueous solution.

[0042] According to the embodiments of this disclosure, the concentration of the nitrogen fertilizer aqueous solution is 0.1-1.5%, for example, the concentration of the urea aqueous solution is 0.1-1.5%, and can be selected as 0.1%, 0.5%, 1.0%, 1.5%, etc.; the concentration of the chelate iron fertilizer aqueous solution is 0.5-1.5 mM, for example, the concentration of the EDTA-Fe aqueous solution is 0.5-1.5 mM, and can be selected as 0.5 mM, 1.0 mM, 1.5 mM, etc.; the application rate of the nitrogen-iron compound fertilizer aqueous solution is 500-600 L / hm² per spray. 2 Among them, 500L / hm is optional. 2 550L / hm 2 600L / hm 2 wait.

[0043] In the embodiments of this disclosure, spraying nitrogen fertilizer solution or chelated iron fertilizer solution alone onto the leaves of crops during the tillering stage can promote tillering and improve the absorption of nitrogen and iron by the crops. Using a nitrogen-iron compound fertilizer solution composed of nitrogen fertilizer and chelated iron fertilizer solution simultaneously can further increase the number of tillers and improve crop yield and nitrogen use efficiency compared to spraying nitrogen fertilizer or chelated iron fertilizer solution alone.

[0044] According to embodiments of this disclosure, the sprayed crops include at least one of the following: rice and wheat, wherein the rice includes at least one of wild-type rice and transgenic rice. Wild-type rice includes Japonica rice Zhonghua 11. Transgenic rice includes rice overexpressing OsNLP4, and more preferably rice overexpressing OsNLP4 in the background of Japonica rice Zhonghua 11. It should be noted that the rice overexpressing OsNLP4 is obtained by referring to the method in the application of the rice nitrogen-efficient utilization gene OsNLP4 and its encoded protein in invention patent CN110272904A. It should be noted that the nitrogen and iron compound fertilizer and crop fertilization method provided in this disclosure are also applicable to other crops with tillering characteristics, and are not limited to the rice, wheat and their varieties exemplified in this disclosure. No further examples or limitations will be made regarding the types and varieties of crops here.

[0045] In the embodiments of this disclosure, rice itself contains the OsNLP4 gene. When nitrogen fertilizer or chelated iron fertilizer is applied alone, it can induce the OsNLP4 protein to migrate from the cytoplasm to the nucleus, transcribe and activate genes for tillering development, and promote rice tillering. Mixing nitrogen fertilizer and chelated iron fertilizer in a ratio of 83:1-1.5 can further enhance the induction of OsNLP4 protein into the nucleus, further promoting rice tillering. Therefore, using the method of this disclosure to spray nitrogen fertilizer or chelated iron fertilizer alone on wild-type rice (such as Japonica rice Zhonghua 11) during the tillering stage, as well as mixing nitrogen fertilizer and chelated iron fertilizer to form a nitrogen-iron compound fertilizer, can improve the yield and nitrogen use efficiency of Japonica rice Zhonghua 11. Among these methods, spraying nitrogen-iron compound fertilizer results in the greatest increase in yield. For transgenic rice, such as rice with OsNLP4 overexpression, which contains more OsNLP4 protein, the method disclosed herein can be used to spray nitrogen-iron compound fertilizer during the tillering stage to induce more OsNLP4 protein to enter the cell nucleus and promote rice tillering. This results in a more significant increase in yield and nitrogen use efficiency compared to ordinary rice (Japonica rice Zhonghua 11).

[0046] The following specific embodiments further illustrate the nitrogen-iron compound fertilizer and crop fertilization method disclosed herein. It should be noted that the specific embodiments described below are merely illustrative examples, and the scope of protection of this disclosure is not limited thereto.

[0047] Unless otherwise specified, the methods used in the following examples are conventional methods, and the reagents used are commercially available reagents.

[0048] Materials and Methods

[0049] Experimental materials: Field trials were conducted using the japonica rice variety Zhonghua 11 (WT), the OsNLP4 gene knockout mutant (nlp4-1) under the background of the japonica rice variety Zhonghua 11, and the OsNLP4 overexpressing rice line (OE-9). The mutant nlp4-1 was obtained through CRISPR / Cas9-based gene editing technology, and the overexpressing line was obtained through Agrobacterium (EHA105) transformation and resistance screening (refer to Wu et al. (2021). Rice NIN-LIKE PROTEIN 4 plays a pivotal role in nitrogen use efficiency. Plant Biotechnology Journal 19, 448-461).

[0050] Example 1

[0051] The experiment in Example 1 was conducted from May to October 2021 to determine the optimal time for foliar application of iron fertilizer. The experiment was conducted at the rice planting base of Zhejiang University in Changxing County, Huzhou City, Zhejiang Province.

[0052] The experiment included two foliar application treatments: tillering and heading stages. Foliar application of 1 mM Fe(II)-EDTA served as a control, with water application as the standard. Each treatment involved 80 plants, with four biological replicates (4 x 80 plants). Spraying was conducted on a sunny afternoon, using a sprayer to evenly atomize droplets onto both sides of the rice leaves. Three applications were given, five days apart, with each application rate of 550 L / hm². 2 Field management followed normal production practices. Samples were taken at rice maturity to record tiller number, yield, and nitrogen use efficiency. The results of this experiment were analyzed for significance and correlation using SPSS 20.0. The LSD and Duncan methods in one-way ANOVA were used for significance analysis, with a significance level of 0.05.

[0053] The specific test results are shown in Table 1, following the test method described in Example 1.

[0054] Table 1. Effects of iron fertilizer application at different time periods on tiller number, yield, and nitrogen use efficiency in rice.

[0055]

[0056] Note: CK: control; letters a, b, c, d, e indicate significant differences, p < 0.05.

[0057] Table 1 shows that, during the tillering stage, foliar application of iron fertilizer to wild-type rice (japonica variety Zhonghua 11, WT) increased the number of tillers per plant by 9.5% compared to the control group (H2O, CK), significantly increased the yield per plant by 11%, and increased nitrogen use efficiency by 11.2%. The OsNLP4 gene knockout mutant (nlp4-1) was insensitive to foliar iron fertilizer application, with no significant increase in tiller number or yield. However, OsNLP4 overexpressing rice (OE-9) showed the greatest increase in tiller number, yield, and nitrogen use efficiency after iron fertilizer application, increasing by 23.3%, 36.3%, and 36.5%, respectively.

[0058] There were no significant differences in the effects of foliar spraying during the heading and tillering stages, but the effects of foliar iron fertilization were significantly different. In wild-type (WT) and overexpression rice (OE-9), foliar spraying of iron fertilization at the heading stage did not significantly change the number of tillers, yield, or nitrogen use efficiency compared to foliar spraying under the same conditions. This experiment indicates that the tillering stage is the key period for foliar spraying of iron fertilization to significantly increase rice yield and nitrogen use efficiency. In particular, the number of tillers increased significantly in OsNLP4 overexpression rice, thus effectively improving the yield and nitrogen use efficiency of OsNLP4 overexpression rice.

[0059] Example 2

[0060] The experiment in Example 2 was conducted from December 2021 to April 2022 to compare the effects of different concentrations of nitrogen-iron fertilizer application schemes on rice yield. The experiment site was the rice planting base of Anhui Academy of Agricultural Sciences in Lingshui County, Hainan Province.

[0061] Eight spraying treatments were administered, with 100 plants per treatment and four biological replicates (4 x 100 plants). The eight spraying formulations were: 0.5% urea (Formula 1), 1 mM Fe(II)EDTA (Formula 2), 0.5% urea + 1 mM Fe(II)-EDTA (Formula 3), 1.5 mM Fe(II)-EDTA (Formula 4), 0.5% urea + 1.5 mM Fe(II)-EDTA (Formula 5), ​​1% urea (Formula 6), 1% urea + 1 mM Fe(II)-EDTA (Formula 7), and 1% urea + 1.5 mM Fe(II)-EDTA (Formula 8). Water was used as the control group. Spraying was conducted at the tillering stage of rice development (based on the results of the first experiment), and the spraying and statistical methods were the same as in Example 1.

[0062] The specific experimental results following the method in Example 2 are shown in Table 2.

[0063] Table 2. Effects of spraying different formulations of nitrogen-iron compound fertilizer on tiller number, yield, and nitrogen use efficiency in rice.

[0064]

[0065] Note: CK: control; letters a, b, c, d, e, f, g indicate significant differences, p < 0.05.

[0066] Table 2 shows that the application of nitrogen-iron compound fertilizers of various concentrations all affected the tillering, yield, and nitrogen use efficiency of rice, and the degree of influence varied. When nitrogen fertilizer was applied alone to the leaves of wild-type rice (WT) during the tillering stage (formulas 1 and 6), the increase in tiller number, yield, and nitrogen use efficiency was not significant. Similar to the results of experiment (1), when iron fertilizer was applied alone to the leaves (formulas 2 and 4), the number of tillers, yield, and nitrogen use efficiency were significantly increased. The best effect was achieved when 0.5% urea + 1mM Fe(II)-EDTA compound fertilizer (formula 3) was applied to the leaves, with tiller number, yield, and nitrogen use efficiency significantly increasing by 11.6%, 13.1%, and 12.9% respectively compared to the control group (H2O). Foliar spraying of 0.5% urea + 1.5mM Fe(II)-EDTA compound fertilizer (formula five) showed a yield increase comparable to formula three (13.9%), but the spraying cost was higher. Increasing the urea concentration (1%) resulted in lower yield increases for nitrogen-iron compound fertilizers of different concentrations (formulas seven and eight) compared to formula three. When formula three was foliar sprayed, OsNLP4-overexpressing rice exhibited the greatest increase in tiller number, yield, and nitrogen use efficiency, significantly increasing by 39.3%, 42.3%, and 43.1% respectively compared to the control group. Therefore, the foliar spraying scheme using 0.5% urea + 1mM Fe(II)-EDTA compound fertilizer (the cost of spraying per acre, calculated based on analytical grade reagents, is approximately RMB 6.4) is most effective in increasing rice yield, especially for OsNLP4-overexpressing rice. The reason for these experimental results is that under conditions of nitrogen and iron balance within the plant, the OsNLP4 protein level in the cell nucleus is high, enhancing the transcriptional activation of key genes involved in tillering, thus leading to a significant increase in the number of rice tillers, yield, and nitrogen use efficiency. Conversely, when the external nitrogen fertilizer supply is too high and the iron fertilizer supply is too low, the OsNLP4 protein level in the cell nucleus is low, severely impacting rice growth and yield. Similarly, excessively high iron fertilizer content and excessively low nitrogen fertilizer content are also detrimental to rice growth.

[0067] Example 3

[0068] Materials and Methods

[0069] Experimental materials: Yangmai 13 wheat variety was selected for field trials.

[0070] Experimental method: The experiment was conducted from November 2021 to May 2022 to compare the effects of different concentrations of nitrogen-iron fertilizer application schemes on wheat yield. The experiment site was the planting base of Anhui Agricultural University in Hefei City, Anhui Province.

[0071] Eight spraying treatments were administered, with 200 plants per treatment and four biological replicates (4 x 200 plants). The eight spray formulations were: 0.5% urea (Formula 1), 1 mM Fe(III)-EDTA (Formula 2), 0.5% urea + 1 mM Fe(III)-EDTA (Formula 3), 1.5 mM Fe(III)-EDTA (Formula 4), 0.5% urea + 1.5 mM Fe(III)-EDTA (Formula 5), ​​1% urea (Formula 6), 1% urea + 1 mM Fe(III)-EDTA (Formula 7), and 1% urea + 1.5 mM Fe(III)-EDTA (Formula 8). Water was used as a control. Spraying was performed during the early tillering stage of wheat development. The spraying and statistical methods were the same as in Example 1.

[0072] The specific test results according to the test method in Example 3 are shown in Table 3.

[0073] Table 3. Effects of spraying different formulations of nitrogen-iron compound fertilizer on wheat tiller number, yield, and nitrogen use efficiency.

[0074]

[0075] Note: CK: control; letters a, b, and c indicate significant differences, p < 0.05.

[0076] Table 3 shows that, slightly different from the changes observed in rice, foliar application of nitrogen fertilizer alone during the tillering stage of wheat (formulas 1 and 6) did not significantly increase the number of tillers, but significantly increased yield and nitrogen use efficiency. However, foliar application of iron fertilizer alone (formulas 2 and 4) significantly increased the number of tillers, but did not significantly improve yield and nitrogen use efficiency. The best effect was achieved when foliar application of 0.5% urea + 1mM Fe(III)-EDTA compound fertilizer (formula 3), with tiller number, yield, and nitrogen use efficiency significantly increasing by 16.9%, 28.9%, and 29.6% respectively compared to the control group (H2O). This experiment demonstrates that foliar application of nitrogen-iron compound fertilizer during the tillering stage can significantly increase the number of tillers in wheat, thereby effectively increasing field yield and nitrogen use efficiency. The optimal application formula for nitrogen-iron compound fertilizer in wheat is 0.5% urea + 1mM Fe(III)-EDTA.

[0077] As can be seen from the embodiments of this disclosure, determining the preferred time, target organisms, and nitrogen-iron compound fertilizer ratio for foliar spraying of crops can significantly improve crop yield and nitrogen fertilizer utilization.

[0078] The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of this disclosure. It should be understood that the above descriptions are merely specific embodiments of this disclosure and are not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A nitrogen-iron compound fertilizer aqueous solution sprayed onto the leaves of crops during the tillering stage, wherein, The nitrogen-iron compound fertilizer aqueous solution is composed of a nitrogen fertilizer aqueous solution and a chelated iron fertilizer aqueous solution, wherein the concentration of the nitrogen fertilizer aqueous solution is 0.1-1.5% and the concentration of the chelated iron fertilizer aqueous solution is 0.5-1.5 mM; The chelate iron fertilizer is selected from EDTA-Fe.

2. The nitrogen-iron compound fertilizer aqueous solution according to claim 1, wherein, Nitrogen fertilizers include any of the following: Urea, ammonium nitrate, calcium nitrate.

3. A method for fertilizing crops, comprising: During the growth of crops, the nitrogen-iron compound fertilizer aqueous solution as described in any one of claims 1-2 is sprayed onto the leaves of the crops 2-3 times, with an interval of 5-7 days. Production management is carried out in accordance with normal field management for crop planting. The period during which the nitrogen-iron compound fertilizer aqueous solution is sprayed onto the leaves of the crops is the tillering stage.

4. The method according to claim 3, wherein, The total amount of nitrogen-iron compound fertilizer aqueous solution applied each time is 500-600 L / hm. 2 .

5. The method according to claim 3, wherein, The tillering stage includes: early tillering, middle tillering, and late tillering.

6. The method according to claim 5, wherein, The optimal time to spray a nitrogen-iron compound fertilizer solution is during the early tillering stage.

7. The method according to claim 3 or 5, wherein, The crops include at least one of the following: rice and wheat.

8. The method according to claim 7, wherein, Rice varieties include at least one of the following: Wild-type rice, genetically modified rice; The wild-type rice includes: Japonica rice Zhonghua 11; The genetically modified rice includes rice with OsNLP4 overexpression.

9. The method according to claim 8, wherein, Applying a nitrogen-iron compound fertilizer solution during the early tillering stage of the crop promotes tillering and increases crop yield and nitrogen utilization.

10. The method according to claim 9, wherein, Spraying the nitrogen-iron compound fertilizer solution on OsNLP4-overexpressing rice during the early tillering stage resulted in a more significant increase in tillering, yield, and nitrogen use efficiency compared to wild-type rice.

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