Controlled-release fertilizer containing signal substance for promoting nitrogen transport in wheat root system and preparation method thereof

Abstract

The application discloses a controlled-release fertilizer containing signal substances for promoting nitrogen transport of wheat root systems and a preparation method thereof. The controlled-release fertilizer comprises an inner layer composite core and an outer layer enzyme response-ion crosslinking double-control membrane; the inner layer composite core material comprises urea, potassium dihydrogen phosphate, potassium sulfate, sophorolipid, trehalose-6-phosphate and bentonite; and the outer layer enzyme response-ion crosslinking double-control membrane comprises xanthan gum, gellan gum, soil enzyme response oligopeptide and calcium citrate. The application realizes the combination of functional components through the 'nutrient-signal composite core material', and realizes the matching of release behavior and crop physiological demand through the 'enzyme response-ion crosslinking controlled-release membrane'. The design solves the limitation that traditional controlled-release fertilizers can only delay nutrient release but cannot actively regulate crop physiological links, strengthens the absorption and internal transport capacity of wheat for nitrogen from the root source by protecting and accurately delivering signal substances, and significantly improves the nitrogen utilization rate to 50%-55%.

Description

Technical Field

[0001] This invention relates to the field of controlled-release fertilizer technology, specifically to a controlled-release fertilizer containing signaling substances that promotes nitrogen transport in wheat roots and its preparation method. Background Technology

[0002] Nitrogen is one of the most critical macronutrients for wheat growth and development. It directly affects biomass accumulation and plays a decisive role in grain yield and quality. Numerous studies have shown that wheat grain yield and protein content largely depend on the efficiency of nitrogen remobilization from vegetative organs such as leaves and stems to the grains during the later stages of growth. Especially during the grain-filling stage, nitrogen stored in vegetative organs is transported to the grains through internal redistribution pathways, providing an important nitrogen source for grain protein synthesis. Therefore, wheat nitrogen utilization depends not only on soil nitrogen supply levels but also on the physiological processes of nitrogen absorption, assimilation, and retransport within the crop. If the nitrogen supply rhythm does not match the needs of different wheat growth stages, it can easily lead to nitrogen excess in the early stages and nitrogen deficiency in the later stages, thus affecting grain-filling efficiency and protein accumulation levels.

[0003] To address this issue, controlled-release fertilizers are commonly used in agricultural production to regulate nitrogen supply. Traditional controlled-release fertilizer technology primarily involves coating fertilizer granules with physical or chemical barrier materials. These films often utilize slowly degrading synthetic polymers, allowing nutrients to be released into the soil environment at a slower rate, thus extending the fertilizer's effective period and improving fertilizer utilization. However, the release mechanism is passive and singular, achieving only a rough controlled release based on time or diffusion. It cannot respond to the crop's own physiological signals, resulting in a mismatch between the release curve and the actual nitrogen absorption and translocation requirements of wheat. Furthermore, it cannot actively intervene in the two key physiological processes of root absorption and grain assimilation. Existing controlled-release fertilizers often employ structures such as sulfur coating, resin coating, or polymer film coating. Their release mechanisms typically rely on water penetration, film swelling, or diffusion processes to achieve slow release over a time scale. These technologies can reduce nitrogen leaching and volatilization to some extent, improving nitrogen fertilizer utilization, and are therefore widely used in agricultural production. However, the release mechanisms of existing controlled-release fertilizers still have significant limitations. First, the membrane materials used are mostly slow-degrading synthetic polymers, which have limited environmental adaptability and may pose certain ecological risks if left in the soil. Second, the release behavior of existing controlled-release fertilizers mainly relies on passive diffusion or material degradation, and their release curves usually exhibit a single time-dependent characteristic, lacking the ability to respond to changes in crop growth stages, physiological states, and rhizosphere environment.

[0004] Furthermore, existing technologies typically focus only on the release of fertilizer into the soil, lacking a coordinated regulation of nitrogen absorption, translocation, and remobilization within the crop. Wheat grain protein accumulation depends not only on exogenous nitrogen absorbed by the roots but also on the efficiency of nitrogen remobilization in vegetative organs. Traditional controlled-release fertilizer technologies cannot respond to the crop's own physiological signals and struggle to actively regulate the two key physiological processes of root absorption and grain assimilation, thus hindering precise intervention in wheat yield and quality formation. Therefore, developing a controlled-release fertilizer containing signaling substances to promote nitrogen translocation in wheat roots, enabling precise nitrogen supply and translocation regulation during key crop growth stages, significantly promoting nitrogen absorption and translocation in wheat roots, and improving grain yield and nitrogen fertilizer utilization, has become a pressing technical problem in the field of agricultural fertilizers. Summary of the Invention

[0005] In view of the above-mentioned prior art, the purpose of this invention is to provide a controlled-release fertilizer containing signaling substances that promotes nitrogen transport in wheat roots and its preparation method. This invention aims to organically combine the absorption-promoting signal sophorolipid and the assimilation / transporting signal trehalose-6-phosphate (T6P) with nitrogen, phosphorus, and potassium nutrients through a core layer design of "signal-nutrient synergy" and a smart membrane layer design of "sensing-response." Furthermore, it utilizes a smart membrane material with enzyme-responsive properties to control their release, thereby precisely regulating the physiological processes of nitrogen absorption in wheat roots and subsequent transport to grains, ultimately achieving a unified approach to increased wheat yield, improved quality, and efficient nitrogen fertilizer utilization.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a controlled-release fertilizer containing a signaling substance that promotes nitrogen transport in wheat roots, comprising the following raw materials in parts by weight: The inner composite core material consists of 93-95 parts, and the outer enzyme-responsive-ion cross-linked dual-control membrane consists of 5-8 parts. The inner composite core material comprises the following raw materials in parts by weight: Urea 40-45 parts, potassium dihydrogen phosphate 20-25 parts, potassium sulfate 16-20 parts, sophorolipid 0.05-0.1 parts, trehalose-6-phosphate 0.1-0.2 parts, bentonite 8-10 parts; The outer enzyme-responsive-ion crosslinked dual-control membrane comprises the following raw materials in parts by weight: 2-3 parts xanthan gum, 3-4 parts gellan gum, 0.05-0.1 parts soil enzyme-responsive oligopeptide, and 0.5-1 parts calcium citrate.

[0007] Preferably, the gellan gum is a high-acyl gellan gum with a gel strength ≥ 600 g / cm³. 2 The amino acid sequence of the soil enzyme-responsive oligopeptide is Glu-Glu-Gly-Pro-Arg.

[0008] Preferably, the time (T) required for 90% cumulative release of nitrogen is... 90 The duration was 130 ± 3 days.

[0009] A second aspect of the present invention provides a method for preparing a controlled-release fertilizer containing a signaling substance that promotes nitrogen translocation in wheat roots, comprising the following steps: (1) Sophorolipid and trehalose-6-phosphate were dissolved in anhydrous ethanol to obtain a signal substance solution; the bentonite was sprayed into the signal substance solution while stirring, and then vacuum dried to constant weight to obtain a loaded signal carrier; (2) Urea, potassium dihydrogen phosphate and potassium sulfate are crushed and sieved respectively, added to the loaded signal carrier prepared in step (1), heated and mixed, then granulated and dried to obtain granular inner layer composite core material. (3) Add xanthan gum and gellan gum to hot water and stir until completely dissolved to form a homogeneous colloid; add soil enzyme-responsive oligopeptide to the homogeneous colloid and stir evenly to obtain a colloidal solution; ultrasonically disperse calcium citrate in deionized water, add the colloidal solution, emulsify under high-speed shear, and cool to obtain an enzyme-responsive-ion crosslinked membrane solution. (4) Preheat the inner composite core material; spray the enzyme-responsive-ion crosslinking membrane solution onto the surface of the inner composite core material in a mist, and intermittently pulse atomize and spray calcium chloride aqueous solution. After spraying, continue fluidized drying and cool to obtain controlled-release fertilizer containing signaling substances that promote nitrogen transport in wheat roots.

[0010] Preferably, in step (1), the concentration of the signal substance solution is 5 wt%; the bentonite is bentonite dried at 120°C; and the vacuum drying temperature is 40°C.

[0011] Preferably, in step (2), the heating and mixing temperature is 60-65℃; the granulation is roller extrusion granulation, the roller temperature is 60-65℃ and the roller pressure is 10-15 MPa; the drying is drying in hot air at 50-55℃ for 1 hour.

[0012] Preferably, in step (3), the hot water is deionized water at 60-70℃; the high-speed shearing speed is 15000-20000 rpm; the emulsification time is 20-30 min; and the cooling temperature is 40-45℃.

[0013] Preferably, in step (4), the preheating temperature is 45-50℃; the mist spraying control inlet temperature is 60-65℃ and the air volume is 200-250m³ / h. 3 / h; the concentration of the calcium chloride aqueous solution is 1.5wt%; the intermittent pulse atomization spray is 3 seconds of spray followed by 12 seconds of pause.

[0014] A third aspect of the present invention provides the use of a controlled-release fertilizer containing a signaling substance that promotes nitrogen translocation in wheat roots in at least one of the following 1) to 3): 1) Increase wheat grain yield; 2) Activate the expression of nitrogen transporter genes in wheat roots; 3) Promote the efficient transport and accumulation of nitrogen in wheat grains.

[0015] Preferably, the wheat root nitrogen transporter genes include TaNRT2.1 and TaAMT1.1.

[0016] This controlled-release fertilizer is suitable for winter and spring wheat cultivation. A single basal application is recommended at a rate of 210 kg / hm² of pure nitrogen. It can be applied by sowing seeds simultaneously (fertilizer depth 8-10 cm, spacing from seed rows at least 5 cm). Field trials have shown that: Significantly increases wheat grain yield: Under the same nitrogen input, it increases yield by more than 18% compared to the conventional multi-application fertilization treatment; Increase grain protein content: Grain protein content can be increased to 10%-15%; Activation of nitrogen translocation in roots: The expression levels of genes such as TaNRT2.1 and TaAMT1.1 in wheat roots during the jointing stage were increased by 1-1.5 times compared with conventional fertilization treatment; It enhances the activity of flag leaf glutamine synthase (by 30%-40%), accelerating nitrogen assimilation; Optimize nitrogen allocation and utilization: Promote the efficient transfer of nitrogen to grains, and increase the agronomic utilization rate of nitrogen fertilizer from the conventional 30%-40% to 50%-55%, achieving synergistic effects of increased yield and efficiency.

[0017] The beneficial effects of this invention are: (1) This invention is the first to integrate two key signaling substances, sophorolipids and trehalose-6-phosphate (T6P), within the same fertilizer system. Sophorolipids target the root system and enhance nitrogen absorption at the source by specifically upregulating the expression of nitrogen transporter genes such as TaNRT2.1 and TaAMT1.1. T6P targets the aboveground parts and, as the carbon and nitrogen metabolism center, drives nitrogen assimilation and distribution to the grain by increasing the activity of key enzymes such as glutamine synthase. The two work synergistically at the two key nodes of "absorption" and "assimilation / transport", optimizing the entire metabolic flow of nitrogen from the root system to the grain and achieving dual physiological regulation of the nitrogen metabolism pathway.

[0018] (2) The membrane material of this invention uses gellan gum as the main film-forming agent. After gellan gum is compounded with xanthan gum, it can form a network with high mechanical strength and dense structure through calcium ion cross-linking. Its water resistance, swelling resistance and controlled release stability are significantly better than traditional polysaccharide membrane materials such as sodium alginate and carrageenan. At the same time, by introducing soil enzyme-responsive oligopeptides as "molecular switches", the membrane layer can specifically respond to the proteases in wheat root exudates, so as to achieve the purpose of membrane degradation being triggered by the crop's own physiological activities, and realize the intelligent response characteristics of the degradable membrane layer.

[0019] (3) By setting up an enzyme-responsive membrane, this invention directly links the release kinetics of nutrients and signaling substances with the physiological activity (protease secretion level) of wheat roots. When the crop enters the jointing to grain-filling stage where nitrogen demand is high, the enhanced root activity triggers the membrane to degrade more rapidly, thereby synchronizing the release rate with the fertilizer demand intensity and greatly improving the matching degree between fertilizer release and crop physiological needs.

[0020] (4) The present invention adopts a "one-step pulsed ion crosslinking coating" preparation process. The coating process achieves instantaneous in-situ solidification of the membrane liquid by pulsed spraying of crosslinking agent, replacing the traditional long-term hot air drying. The process is simple, the parameters are easy to control, which is conducive to large-scale stable production and reduces energy consumption and cost.

[0021] (5) The controlled-release fertilizer of the present invention, through the synergy of "precise signal regulation" and "synchronous nutrient supply", can not only significantly increase wheat grain yield (more than 18%) and protein content, but also improve nitrogen fertilizer utilization rate to 50%-55% by strengthening root absorption and grain assimilation capacity. In addition, all membrane material components are completely biodegradable and have no environmental residues, realizing the unity of increased yield and efficiency with green environmental protection, and the synergistic effect of agronomic and environmental benefits. Attached Figure Description

[0022] Figure 1 Wheat grain yield in each treatment group; Figure 2 Protein content of wheat grains in each treatment group; Figure 3 Relative expression levels of TaNRT2.1 and TaAMT1.1 genes in wheat roots at the jointing stage in each treatment group; Figure 4 : Flag leaf GS enzyme activity during the grouting period in each treatment group; Figure 5 Nitrogen fertilizer utilization rate in each treatment group; Figure 6 Nutrient release rate of each treatment group. Detailed Implementation

[0023] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0024] As introduced in the background section, wheat grain protein accumulation depends not only on exogenous nitrogen absorbed by the roots, but also on the efficiency of nitrogen remobilization in vegetative organs. Traditional controlled-release fertilizer technology cannot respond to the crop's own physiological signals, nor can it actively regulate the two key physiological processes of root absorption and grain assimilation, thus making it difficult to achieve precise intervention in the process of wheat yield and quality formation.

[0025] Based on this, the purpose of this invention is to provide a controlled-release fertilizer containing signaling substances that promotes nitrogen transport in wheat roots and its preparation method. This invention has found that sophorolipids can specifically induce the upregulation of high-affinity nitrogen transporter genes (such as TaNRT2.1 and TaAMT1.1) in wheat roots, thereby enhancing the root system's ability to absorb nitrogen from the soil. T6P can increase the activity of key nitrogen assimilation enzymes (such as glutamine synthase GS) during the grain-filling stage, promoting the conversion of nitrogen to amino acids and driving its distribution to the grains. However, direct application of sophorolipids and T6P leads to their rapid degradation; and their functions have strict time limits, requiring continuous action in the rhizosphere from the wheat jointing to grain-filling stage (approximately 60-130 days after sowing). In response to these findings, this invention designs a novel controlled-release fertilizer that combines "intelligent nutrient controlled release," "signaling substance protection," and "intelligent synchronization of release behavior and physiological needs." The inner composite core material is prepared using sophorolipids and T6P as signaling substances, and the outer layer is coated with an enzyme-responsive ion-crosslinked dual-control membrane. The outer enzyme-responsive-ion crosslinked dual-control membrane introduces soil enzyme-responsive oligopeptides as "molecular switches," enabling the membrane layer to specifically respond to proteases in wheat root exudates, thus achieving the goal of membrane degradation being triggered by the crop's own physiological activities.

[0026] The mechanism of action of the controlled-release fertilizer of this invention is as follows: After fertilization, the outer enzyme-responsive-ion-crosslinked dual-control membrane swells under the influence of soil moisture, forming an initial physical barrier. During the wheat seedling to jointing stage, the membrane layer mainly relies on the dense structure of its gel network to control the slow release of nutrients. When wheat enters the vigorous growth period from jointing to grain filling, root physiological activity significantly increases, and the secretion of proteases increases. These proteases specifically recognize and cleave soil enzyme-responsive oligopeptides embedded in the membrane layer, leading to local dissociation of the membrane network structure and an increase in porosity and permeability. This process triggers the accelerated release of the internal composite core material. The simultaneously released sophorolipids are sensed by the roots, rapidly upregulating the expression of high-affinity nitrogen transporter genes such as TaNRT2.1 and TaAMT1.1, enhancing the root's nitrogen absorption capacity. The simultaneously released trehalose-6-phosphate (T6P) acts as a central signal for carbon and nitrogen metabolism, increasing the activity of key enzymes such as flag leaf glutamine synthase (GS) by 30%-40%, driving nitrogen assimilation and efficient transport to the grains. Throughout the release process, the controlled release of nitrogen, phosphorus, and potassium nutrients continuously provides material support, forming a synergy of "precise signal regulation and synchronous nutrient supply".

[0027] To enable those skilled in the art to better understand the technical solution of this application, the technical solution of this application will be described in detail below with reference to specific embodiments.

[0028] The test materials used in the embodiments of this invention are all conventional test materials in the art and can be purchased through commercial channels.

[0029] Example 1: Preparation of a controlled-release fertilizer containing signaling substances to promote nitrogen translocation in wheat roots (1) Raw material preparation: urea (industrial grade, nitrogen content 46.4%), potassium dihydrogen phosphate (agricultural grade), potassium sulfate (agricultural grade), sophorolipid (purity 96%, purchased from Wuhan Kemike Biomedical Technology Co., Ltd.), trehalose-6-phosphate (T6P, agricultural grade, purchased from Hubei Luofu Biotechnology Co., Ltd.), sodium bentonite (200 mesh), xanthan gum (food grade), high acyl gellan gum (purchased from Jiangsu Huace Biotechnology Co., Ltd., gel strength ≥600 g / cm²), soil enzyme-responsive oligopeptide (sequence: Glu-Glu-Gly-Pro-Arg, customized by Shanghai Qiangyao Biotechnology Co., Ltd., purity >95%), calcium citrate (food grade, average particle size ≤50 μm), calcium chloride (analytical grade).

[0030] (2) Signal material pretreatment and carrier loading: Sophorolipid and trehalose-6-phosphate were dissolved in anhydrous ethanol at a mass ratio of 1:2 (0.1 kg sophorolipid, 0.2 kg trehalose-6-phosphate) to prepare a signal material solution with a total concentration of 5 wt%. 9 kg of bentonite was dried at 120 °C for 2 hours, cooled, and then placed in a high-speed mixer. The signal material solution was sprayed evenly while stirring. Subsequently, it was vacuum dried at 40 °C to constant weight to obtain the loaded signal carrier.

[0031] (3) Granulation of the inner composite core material: Weigh 42 kg of urea, 23 kg of potassium dihydrogen phosphate, and 19 kg of potassium sulfate respectively, crush them through a 100-mesh sieve, and mix them evenly with the loaded signal carrier obtained in step (2). Stir the mixture at 60°C for 15 minutes, utilizing the hygroscopic and slightly soluble surface of urea to generate an adhesive effect. Then, use a roller extrusion granulator, controlling the roller temperature at 60°C and the roller pressure at 12 MPa, to directly extrude and form short cylindrical particles with a particle size of 3-4 mm. Dry the obtained particles in hot air at 50°C for 1 hour to obtain the inner composite core material.

[0032] (4) Preparation of outer layer enzyme-responsive ion-crosslinked membrane solution: Add 2.5 kg xanthan gum and 3.5 kg high-acyl gellan gum to deionized water at 65 °C and stir until completely dissolved to form a homogeneous colloid. Add 80 g soil enzyme-responsive oligopeptide directly to the homogeneous colloid and stir to dissolve. Disperse 0.8 kg calcium citrate ultrasonically in 3.5 L of water, add it to the colloidal solution under high-speed shear at 18000 rpm, emulsify for 25 minutes, and cool to 40 °C for later use.

[0033] (5) One-step fluidized bed forming and pulsed crosslinking coating: Take 10 kg of the inner composite core material prepared in step (3), preheat it to 50°C, and place it in a fluidized bed coating machine. Spray the outer enzyme-responsive ion crosslinking membrane liquid prepared in step (4) onto the surface of the inner composite core material in a mist form through an ultrasonic atomizing nozzle (Shanghai Wuwang Environmental Protection Equipment Engineering Co., Ltd. ADG SK508). Control the inlet temperature of the fluidized bed coating machine to 65°C and the air volume to 220 m³ / h. 3 / h. Simultaneously, an independent pulse spray system (two-fluid atomizing nozzle + time relay controlling solenoid valve; two-fluid atomizing nozzle: Dongguan Shaou Spray System Co., Ltd. JBC air atomizing nozzle; time relay: Zhejiang Chuangcai Electric Co., Ltd. Delixi JSS48A-S; solenoid valve: Zhejiang Lingjun Pneumatic Technology Co., Ltd. 4V210-08 AC220V) is used. A 1.5 wt% calcium chloride aqueous solution was sprayed onto fertilizer granules in a fluidized bed using an intermittent pulse method (spray for 3 seconds, stop for 12 seconds) to trigger instantaneous ionic cross-linking of the membrane layer. Spraying was stopped when the membrane layer weight accounted for 6.0% of the total weight of the inner composite core material, and fluidized drying was continued for 12 minutes. After cooling, the controlled-release fertilizer product containing signaling substances that promote nitrogen transport in wheat roots was obtained.

[0034] Comparative Example 1: Controlled-release fertilizer without signaling substances The difference from Example 1 is that sophorolipids and trehalose-6-phosphate are not added; instead, bentonite is used directly as an inert filler in the same amount to obtain the fertilizer core. The final product is a controlled-release fertilizer that does not contain sophorolipids or trehalose-6-phosphate.

[0035] Comparative Example 2: Controlled-release fertilizer containing sophorolipids The difference from Example 1 is that trehalose-6-phosphate is not added. The final product is a controlled-release fertilizer containing sophorolipids.

[0036] Comparative Example 3: Controlled-release fertilizer containing trehalose-6-phosphate The difference from Example 1 is that no sophorolipids were added. The final product was a controlled-release fertilizer containing trehalose-6-phosphate.

[0037] Comparative Example 4: Controlled-release fertilizer with no soil enzyme response oligopeptides The difference from Example 1 is that no soil enzyme-responsive oligopeptides were added. The final product was a controlled-release fertilizer with no enzyme-responsive membrane layer.

[0038] Comparative Example 5: Castor Oil-Based Polyurethane Coated Controlled-Release Fertilizer The compound fertilizer core (urea, potassium dihydrogen phosphate, and potassium sulfate) was preheated to 60°C in a coating pan at a rotation speed of 25 r / min. The coating material was a mixture of castor oil and isocyanate (mass ratio of castor oil to isocyanate 1.2:1). A high-pressure spraying system was used, with the spraying pressure controlled at 9 MPa and the atomizing air pressure at 0.5 MPa. Each spraying volume was 0.5% of the total weight of the fertilizer core, with a 25-minute interval between coats. During spraying, the drum speed and material temperature were maintained to ensure uniform coating. After spraying, the drum continued to rotate for 15 minutes to allow the film to fully cure. The product was then discharged and cooled to obtain castor oil-based polyurethane-coated controlled-release fertilizer.

[0039] Experiment 1: Verification of the Field Application Effect of Controlled-Release Fertilizer 1. Experimental Design Experimental location: Shandong Agricultural University Experimental Station, Tai'an City, Shandong Province (soil organic matter content 5.79 g / kg, total nitrogen 0.65 g / kg, available phosphorus 4.67 mg / kg, available potassium 36.38 mg / kg) Experimental crop: Winter wheat variety "Jimai 22" Planting pattern: Conventional autumn-sown winter wheat, sown on October 15 and harvested on June 10 of the following year.

[0040] Experimental design: Eight treatments were set up, including a blank control, a conventional fertilization control, controlled-release fertilizers prepared in Example 1 and Comparative Examples 1-5, as detailed below: T1 (PK): Control group without nitrogen fertilizer. 400 kg / hm² of superphosphate (P2O5 12%) and 150 kg / hm² of potassium sulfate (K2O 50%) were applied as base fertilizer.

[0041] T2 (NPK): Conventional nitrogen, phosphorus, and potassium fertilizers are applied in multiple applications. The total nitrogen application rate is 210 kg N / hm² (calculated as urea), of which 60% is applied as basal fertilizer and 40% is applied as topdressing at the jointing stage. The application rates of phosphorus and potassium fertilizers are the same as those of T1.

[0042] T3: Apply the intelligent controlled-release fertilizer containing signaling substances prepared in Example 1 of this invention. Apply as a single basal application, with a pure nitrogen application rate of 210 kg N / hm², and phosphorus and potassium content equivalent to treatments T1 and T2.

[0043] T4: Apply the controlled-release fertilizer prepared in Comparative Example 1. The application method and dosage are the same as in T2.

[0044] T5: Apply the controlled-release fertilizer prepared in Comparative Example 2. The application method and dosage are the same as in T2.

[0045] T6: Apply the controlled-release fertilizer prepared in Comparative Example 3. The application method and dosage are the same as in T2.

[0046] T7: Apply the controlled-release fertilizer prepared in Comparative Example 4. The application method and dosage are the same as in T2.

[0047] T8: Apply the controlled-release fertilizer prepared in Comparative Example 5. The application method and dosage are the same as in T2.

[0048] Each treatment was repeated four times using a randomized block design. The plot size was 30 m². 2 (5 m × 6 m). All fertilizers (except for T2 top dressing) are applied at the time of sowing using a seed-fertilizer co-seeder, with a fertilization depth of 8-10 cm and a horizontal spacing of 5 cm between the fertilizer and the seed row.

[0049] 2. Measurement Indicators and Methods Grain yield and protein content: Wheat was harvested, threshed, and weighed separately in individual plots at maturity, and the yield was converted to hectares (grain moisture content was uniformly adjusted to 13%). Crude protein content (dry basis) of the grains was determined using a near-infrared grain analyzer.

[0050] Root nitrogen transport gene expression levels: In the mid-jointing stage of wheat (early April of the following year after sowing), representative plants from each plot were selected, and fresh root tip samples were taken and flash-frozen in liquid nitrogen. Total RNA was extracted using the TRIzol method, and after reverse transcription, the relative expression levels of TaNRT2.1 and TaAMT1.1 genes were determined using real-time quantitative PCR (qRT-PCR). TaActin gene was used as an internal control, and T2 treatment was used as a control to calculate the relative expression level.

[0051] Flag leaf glutamine synthase (GS) activity: Fifteen days after flowering (mid-grain-filling stage) of wheat, uniformly growing plants were selected from each plot, and a fragment from the middle of the flag leaf was collected and flash-frozen in liquid nitrogen. GS activity was determined using the hydroxylamine colorimetric method. 0.5 g of fresh sample was weighed, ground, and centrifuged in pre-cooled extraction medium, and the supernatant was used as the crude enzyme solution. In the reaction system, using glutamine and hydroxylamine as substrates, the reaction was carried out at 30℃ for 30 minutes. Enzyme activity was calculated by measuring the absorbance of the generated γ-glutamyl isohydroxamic acid at 540 nm, expressed as micromoles of product generated per gram of fresh weight per hour (μmol·g⁻¹). -1 FW·h -1 ).

[0052] Nitrogen fertilizer utilization efficiency: Aboveground plant samples from each treatment were collected at maturity, and grains and straw (including husks) were separated. After drying and pulverizing, the total nitrogen content was determined using the Kjeldahl method. Nitrogen fertilizer utilization efficiency (NUE) was calculated using the difference method, as shown in the following formula: NUE (%) = (Total nitrogen uptake by plants in the nitrogen-applied area - Total nitrogen uptake by plants in the non-nitrogen-applied area) / Nitrogen application rate × 100 The total nitrogen uptake by the plant is calculated as follows: nitrogen uptake by grains + nitrogen uptake by straw.

[0053] 3. Experimental Results (1) Wheat grain yield: Wheat grain yield of each treatment as follows Figure 1 As shown. The results indicate that the application of the controlled-release fertilizer (T3) prepared in Example 1 of this invention significantly increased wheat grain yield, with a 55.9% increase compared to the no-nitrogen treatment (T1) and an 18.3% increase compared to the conventional multi-application fertilization treatment (T2). Compared to Comparative Example 1, T3 increased yield by 10.7%; compared to Comparative Example 2, T3 increased yield by 8.4%; compared to Comparative Example 3, T3 increased yield by 7.1%; compared to Comparative Example 4, T3 increased yield by 6.7%; and compared to Comparative Example 5, T3 increased yield by 12.8%.

[0054] Application of the controlled-release fertilizer prepared in Comparative Example 1 (T4) increased wheat grain yield by 40.8% compared with T1 treatment and by 6.8% compared with T2 treatment.

[0055] Application of the controlled-release fertilizer prepared in Comparative Example 2 (T5) can increase wheat grain yield, with a yield increase of 43.8% compared with T1 treatment and a yield increase of 9.1% compared with T2 treatment.

[0056] Application of the controlled-release fertilizer prepared in Comparative Example 3 (T6) increased wheat grain yield by 45.6% compared with T1 treatment and by 10.5% compared with T2 treatment.

[0057] Application of the controlled-release fertilizer prepared in Comparative Example 4 (T7) can increase wheat grain yield, with a yield increase of 46.1% compared with T1 treatment and a yield increase of 10.9% compared with T2 treatment.

[0058] Application of the controlled-release fertilizer prepared in Comparative Example 5 (T8) increased wheat grain yield by 38.2% compared to the T1 treatment and by 4.9% compared to the T2 treatment.

[0059] (2) Protein content of wheat grains: The protein content of the grains in each treatment is as follows: Figure 2 As shown. The results indicate that application of the controlled-release fertilizer (T3) prepared in Example 1 of this invention significantly increased the protein content of wheat grains, by 28.7% compared to the T1 treatment and by 13.0% compared to the T2 treatment. Compared to Comparative Example 1, T3 increased by 9.6%; compared to Comparative Example 2, T3 increased by 7.2%; compared to Comparative Example 3, T3 increased by 5%; compared to Comparative Example 4, T3 increased by 5.7%; and compared to Comparative Example 5, T3 increased by 11.3%.

[0060] The application of the controlled-release fertilizer prepared in Comparative Example 1 can increase the protein content of wheat grains by 17.4% compared with T1 treatment and by 3.1% compared with T2 treatment.

[0061] The application of the controlled-release fertilizer prepared in Comparative Example 2 can increase the protein content of wheat grains by 20.0% compared with T1 treatment and by 5.3% compared with T2 treatment.

[0062] The application of the controlled-release fertilizer prepared in Comparative Example 3 can increase the protein content of wheat grains by 22.6% compared with T1 treatment and by 7.6% compared with T2 treatment.

[0063] The application of the controlled-release fertilizer prepared in Comparative Example 4 can increase the protein content of wheat grains by 21.7% compared with T1 treatment and by 6.9% compared with T2 treatment.

[0064] The application of the controlled-release fertilizer prepared in Comparative Example 5 can increase the protein content of wheat grains by 15.7% compared with T1 treatment and by 1.5% compared with T2 treatment.

[0065] (3) Relative expression levels of nitrogen transport genes in roots during the jointing stage: The relative expression levels of root nitrogen transport genes at the jointing stage for each treatment are as follows: Figure 3 As shown. With T2 treatment as a control (expression level set to 1), the results showed that application of the controlled-release fertilizer prepared in Example 1 of this invention (T3) significantly upregulated the expression of nitrogen transporter genes in wheat roots. Compared with T2 treatment, the expression level of TaNRT2.1 gene increased by 150.0%, and the expression level of TaAMT1.1 gene increased by 110.0%. Compared with Comparative Example 1, the expression levels of TaNRT2.1 and TaAMT1.1 in T3 treatment increased by 127.3% and 110.0%, respectively. Compared with Comparative Example 2, they increased by 66.7% and 50.0%, respectively. Compared with Comparative Example 3, they increased by 56.3% and 31.3%, respectively. Compared with Comparative Example 4, they increased by 47.1% and 40.0%, respectively. Compared with Comparative Example 5, they increased by 150.0% and 133.3%, respectively.

[0066] The effect of applying control group 1 on increasing the expression levels of the two genes was not significantly different from that of T2 treatment.

[0067] Application of Comparative Example 2 increased the expression levels of both genes, with TaNRT2.1 and TaAMT1.1 expression levels increasing by 50.0% and 40.0% respectively compared to T2 treatment.

[0068] Application of Comparative Example 3 increased the expression levels of both genes, with TaNRT2.1 and TaAMT1.1 expression levels increasing by 60.0% compared to T2 treatment.

[0069] Application of Comparative Example 4 increased the expression levels of both genes, with TaNRT2.1 and TaAMT1.1 expression levels increasing by 70.0% and 50.0%, respectively, compared to the T2 treatment. The effect of application of Comparative Example 5 on gene expression levels was similar to that of the T2 treatment.

[0070] (4) Glutamine synthase (GS) activity in flag leaves during the grouting stage: Flag leaf GS activity during the grouting period of each treatment, such as Figure 4As shown. The results indicate that application of the controlled-release fertilizer (T3) prepared in Example 1 of this invention significantly improved the activity of flag leaf GS. Compared with T1 treatment, the activity increased by 58.6%; compared with T2 treatment, it increased by 37.8%. Compared with Comparative Example 1, T3 increased by 32.6%; compared with Comparative Example 2, it increased by 19.6%; compared with Comparative Example 3, it increased by 18.3%; compared with Comparative Example 4, it increased by 17.4%; and compared with Comparative Example 5, it increased by 34.9%.

[0071] The controlled-release fertilizer prepared in Comparative Example 1 had a limited effect on improving GS activity, increasing it by 19.6% compared to the T1 treatment and by 4.0% compared to the T2 treatment.

[0072] Application of Comparative Example 2 can improve GS activity by 32.6% compared with T1 treatment and by 15.2% compared with T2 treatment.

[0073] Application of Comparative Example 3 can improve GS activity by 34.0% compared with T1 treatment and by 16.5% compared with T2 treatment.

[0074] Application of Comparative Example 4 improved GS activity by 35.1% compared to T1 treatment and by 17.4% compared to T2 treatment. The effect of application of Comparative Example 5 on GS activity was similar to that of T2 treatment.

[0075] (5) Nitrogen fertilizer utilization rate: Nitrogen fertilizer utilization rates for each nitrogen application treatment are as follows: Figure 5 As shown. The results indicate that the application of the controlled-release fertilizer (T3) prepared in Example 1 of this invention can significantly improve nitrogen fertilizer utilization rate, reaching 53.5%, which is 18.5 percentage points higher than the conventional multiple fertilization treatment (T2, 35.0%), with a relative improvement of 52.9%. Compared with Comparative Example 1 (T4, 42.2%), T3 improved by 11.3 percentage points (relative improvement of 26.8%); compared with Comparative Example 2 (T5, 46%), it improved by 7.5 percentage points (relative improvement of 16.3%); and compared with Comparative Example 3 (T6, 47.5%), it improved by 6 percentage points (relative improvement of 12.6%).

[0076] Compared with Comparative Example 4 (T7, 45.8%), it increased by 7.7 percentage points (relative increase of 16.8%); compared with Comparative Example 5 (T8, 39.7%), it increased by 13.8 percentage points (relative increase of 34.8%).

[0077] Application of the controlled-release fertilizer prepared in Comparative Example 1 improved nitrogen fertilizer use efficiency by 7.2 percentage points compared to treatment T2 (a relative increase of 20.6%). Application of the controlled-release fertilizer prepared in Comparative Example 2 improved nitrogen fertilizer use efficiency by 11 percentage points compared to treatment T2 (a relative increase of 31.4%). Application of the controlled-release fertilizer prepared in Comparative Example 3 improved nitrogen fertilizer use efficiency by 12.5 percentage points compared to treatment T2 (a relative increase of 35.7%). Application of the controlled-release fertilizer prepared in Comparative Example 4 improved nitrogen fertilizer use efficiency by 10.8 percentage points compared to treatment T2 (a relative increase of 30.9%). Application of the controlled-release fertilizer prepared in Comparative Example 5 improved nitrogen fertilizer use efficiency by 4.7 percentage points compared to treatment T2 (a relative increase of 13.4%).

[0078] Experimental Example 2: Determination of Controlled-Release Performance Methods: Following the GB / T 23348-2009 standard for slow-release fertilizers, the nitrogen release characteristics were determined using the 25℃ static water immersion method. 10.0 g of each of the controlled-release fertilizer samples prepared in Example 1 and Comparative Examples 4 and 5 were accurately weighed and placed in a 150-mesh nylon mesh bag. The mesh bag was immersed in an Erlenmeyer flask containing 200 mL of deionized water and incubated statically at 25℃. Samples were taken at regular intervals on days 10, 30, 40, 60, 80, 100, 130, 160, and 200 after immersion. The ammonium nitrogen and nitrate nitrogen contents in the immersion solution were measured, the cumulative nitrogen release rate was calculated, and a release curve was plotted.

[0079] Results: The cumulative nitrogen release curves of different controlled-release fertilizers are shown below. Figure 6 As shown in the figure. The results show that the release curve of product 1 (T3) exhibits an ideal three-stage intelligent release characteristic of "slow-fast-slow". In the early stage of cultivation (0-40 days, simulating the overwintering-greening period of wheat), nitrogen release is slow, with a cumulative release rate of about 25%-30%, which can meet the basic needs of wheat in the early stage while avoiding excessive losses. Entering the middle stage of cultivation (40-130 days, simulating the key growth period of wheat from jointing to heading to grain filling), the release rate accelerates significantly, with the cumulative release rate increasing to about 90%-93%, which is highly matched with the vigorous demand for nitrogen by wheat at this stage. In the late stage of cultivation (130-200 days, simulating the grain filling-maturity period), the release rate tends to stabilize again, continuously supplying the remaining nutrients, and the cumulative release rate finally reaches 98%-100%. In contrast, the release curve of the comparative product lacks obvious stage acceleration characteristics.

[0080] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A controlled-release fertilizer containing signaling substances to promote nitrogen translocation in wheat roots, characterized in that, The ingredients include the following parts by weight: The inner composite core material consists of 93-95 parts, and the outer enzyme-responsive-ion cross-linked dual-control membrane consists of 5-8 parts. The inner composite core material comprises the following raw materials in parts by weight: Urea 40-45 parts, potassium dihydrogen phosphate 20-25 parts, potassium sulfate 16-20 parts, sophorolipid 0.05-0.1 parts, trehalose-6-phosphate 0.1-0.2 parts, bentonite 8-10 parts; The outer enzyme-responsive-ion crosslinked dual-control membrane comprises the following raw materials in parts by weight: 2-3 parts xanthan gum, 3-4 parts gellan gum, 0.05-0.1 parts soil enzyme-responsive oligopeptide, and 0.5-1 parts calcium citrate.

2. The controlled-release fertilizer according to claim 1, characterized in that, The gellan gum is a high-acyl gellan gum with a gel strength ≥600 g / cm³. 2 The amino acid sequence of the soil enzyme-responsive oligopeptide is Glu-Glu-Gly-Pro-Arg.

3. The controlled-release fertilizer according to claim 1, characterized in that, The time required for 90% of the nitrogen to be cumulatively released is 130 ± 3 days.

4. The method for preparing the controlled-release fertilizer according to any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Sophorolipid and trehalose-6-phosphate were dissolved in anhydrous ethanol to obtain a signal substance solution; the bentonite was sprayed into the signal substance solution while stirring, and then vacuum dried to constant weight to obtain a loaded signal carrier; (2) Urea, potassium dihydrogen phosphate and potassium sulfate are crushed and sieved respectively, added to the loaded signal carrier prepared in step (1), heated and mixed, then granulated and dried to obtain granular inner layer composite core material. (3) Add xanthan gum and gellan gum to hot water and stir until completely dissolved to form a homogeneous colloid; add soil enzyme-responsive oligopeptide to the homogeneous colloid and stir evenly to obtain a colloidal solution; ultrasonically disperse calcium citrate in deionized water, add the colloidal solution, emulsify under high-speed shear, and cool to obtain an enzyme-responsive-ion crosslinked membrane solution. (4) Preheat the inner composite core material; spray the enzyme-responsive-ion crosslinking membrane solution onto the surface of the inner composite core material in a mist, and intermittently pulse atomize and spray calcium chloride aqueous solution. After spraying, continue fluidized drying and cool to obtain controlled-release fertilizer containing signaling substances that promote nitrogen transport in wheat roots.

5. The preparation method according to claim 4, characterized in that, In step (1), the concentration of the signal substance solution is 5 wt%; the bentonite is bentonite dried at 120°C; and the vacuum drying temperature is 40°C.

6. The preparation method according to claim 4, characterized in that, In step (2), the heating and mixing temperature is 60-65℃; the granulation is roller extrusion granulation with a roller temperature of 60-65℃ and a roller pressure of 10-15 MPa; the drying is drying for 1 hour under hot air at 50-55℃.

7. The preparation method according to claim 4, characterized in that, In step (3), the hot water is deionized water at 60-70℃; the high-speed shearing speed is 15000-20000 rpm; the emulsification time is 20-30 min; and the cooling temperature is 40-45℃.

8. The preparation method according to claim 4, characterized in that, In step (4), the preheating temperature is 45-50℃; the mist spraying control inlet temperature is 60-65℃ and the air volume is 200-250m³ / h. 3 / h; the concentration of the calcium chloride aqueous solution is 1.5wt%; the intermittent pulse atomization spray is 3 seconds of spray followed by 12 seconds of pause.

9. The use of the controlled-release fertilizer according to any one of claims 1 to 3 in at least one of the following: 1) to 3) 1) Increase wheat grain yield; 2) Activate the expression of nitrogen transporter genes in wheat roots; 3) Promote the efficient transport and accumulation of nitrogen in wheat grains.

10. The application according to claim 9, characterized in that, The wheat root nitrogen transporter genes include TaNRT2.1 and TaAMT1.1.

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