A nitrogen fertilizer application method for simulating high-concentration CO2 environment to enhance japonica rice yield and the effect of carbon dioxide fertilization

Abstract

This invention discloses a nitrogen fertilizer application method for improving japonica rice yield and the effect of carbon dioxide fertilization under simulated high-concentration CO2 environments. First, an open-top climate chamber (OTC) platform is constructed and CO2 concentration is controlled to simulate future scenarios of increased atmospheric CO2 concentration. Then, while maintaining the existing nitrogen fertilizer application rate throughout the rice season, the nitrogen fertilizer allocation is changed from the current basal-tillering fertilizer to panicle fertilizer ratio of 7:3 to 6:4. Finally, the rice yield and the effect of carbon dioxide fertilization under increased CO2 concentration are quantified. Compared to traditional nitrogen fertilizer allocation methods, this invention can increase rice yield by 11.05%, and the contribution rate of CO2 fertilization to yield is increased by 10.19%, providing a scientific basis for improving japonica rice yield and the effect of carbon dioxide fertilization by modifying nitrogen fertilizer allocation under continuously rising atmospheric CO2 concentrations.

Description

Technical Field

[0001] This invention relates to the field of agricultural production technology, and in particular to a nitrogen fertilizer application method that simulates a high-concentration CO2 environment to enhance the yield of japonica rice and the effect of carbon dioxide fertilization. Background Technology

[0002] Since the Industrial Revolution, global atmospheric carbon dioxide (CO2) concentrations have been rising continuously, currently exceeding 400 ppm, and are projected to reach or even exceed 700 ppm by the end of this century. As a primary substrate for plant photosynthesis, increased CO2 concentrations should theoretically promote crop photosynthesis, producing a "CO2 fertilization effect" and thus increasing crop yields. However, numerous studies have shown significant differences in the responses of different crops, and even different subspecies of the same crop, to increased CO2 concentrations.

[0003] Rice is one of the world's most important food crops. Japonica rice, in particular, is widely cultivated in northern my country and high-latitude regions due to its excellent eating quality and broad adaptability, resulting in huge consumer demand. Existing research indicates that compared to indica rice, japonica rice generally responds less strongly to increased CO2 concentrations, with significantly lower yield increases. Studies have revealed that under high CO2 concentrations, the decline in leaf nitrogen concentration during the reproductive growth stage of japonica rice leads to severe photosynthetic adaptation, which is the reason for its weaker CO2 response. Given the continued rise in CO2 concentrations, if the responsiveness of japonica rice to CO2 cannot be effectively improved, it will severely limit its future yield potential and pose a potential threat to food security in my country and globally.

[0004] Current research on rice cultivation management in high CO2 environments mainly focuses on variety selection and conventional fertilization optimization, lacking precise agronomic control measures designed based on the unique physiological response mechanisms of japonica rice. In particular, how to utilize nitrogen management methods to mobilize the physiological potential of japonica rice under high CO2 conditions and enhance its photosynthetic product allocation and grain filling capacity during the reproductive growth stage is a key scientific problem that urgently needs to be solved. Summary of the Invention

[0005] The purpose of this invention is to study the nitrogen absorption and transport patterns of japonica rice under high CO2 conditions, clarify that the reproductive growth period is the key window for japonica rice to respond to the CO2 fertilization effect, and that the demand for nitrogen in japonica rice is highly dependent during this period. Therefore, this invention provides a nitrogen fertilizer application method that simulates the effect of CO2 fertilization on japonica rice yield under high CO2 conditions. This method addresses the issue that the nitrogen concentration in japonica rice decreases during the reproductive growth period in high CO2 environments, while photosynthetic adaptation is stronger. By optimizing the ratio of basal and tillering fertilizer to panicle fertilizer, this method improves the yield of japonica rice and the effect of CO2 fertilization.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A nitrogen fertilizer application method for simulating the effects of carbon dioxide fertilization on japonica rice yield under high-concentration CO2 conditions includes the following steps:

[0008] Step 1: Construct an open-top climate chamber (OTC) platform to simulate a scenario of increased atmospheric CO2 concentration;

[0009] Step 2: Set the carbon dioxide concentration in the OTC container to simulate future atmospheric CO2 concentration levels;

[0010] Step 3: Select rice varieties that are in high demand but have a weaker response to high CO2 environments;

[0011] Step 4: Determine the total nitrogen fertilizer requirement for the entire rice season;

[0012] Step 5: Adjusting the ratio of nitrogen fertilizer used for basal tillering and panicle growth;

[0013] Step Six: Yield Measurement and Calculation of the Effect of Carbon Dioxide Fertilization.

[0014] Furthermore, in step one: the open-top climate chamber platform is set in an open, flat open space, and its main body adopts a regular hexagonal prism structure, the frame is made of aluminum alloy profiles, the facade is inlaid with glass, and the top is kept open to utilize natural light and ventilation.

[0015] Furthermore, to avoid mutual interference between air chambers, the distance between adjacent open-top climate chamber platforms shall not be less than 20m.

[0016] Furthermore, in step two: the high carbon dioxide concentration is set to 550 ppm, and the current atmospheric CO2 concentration is set to 420 ± 20 ppm as a comparison environment.

[0017] Furthermore, in step three: the demand for japonica rice is constantly increasing, and japonica rice varieties are less responsive to carbon dioxide, so japonica rice varieties are selected.

[0018] Furthermore, in step four: based on the basic soil fertility, target yield, and fertilizer requirements of the japonica rice variety, and in accordance with local conventional fertilization rates, the total amount of nitrogen fertilizer applied throughout the entire growth period is determined to be 270 kg / ha.

[0019] Furthermore, in step five: the nitrogen fertilizer for the entire growth period of rice is divided into two parts: basal fertilizer and panicle fertilizer, and the mass ratio of the two is optimized. The mass ratio of basal fertilizer to panicle fertilizer is 7:3; and more preferably 6:4.

[0020] Furthermore, the specific fertilization procedures:

[0021] (1) Application of base fertilizer: One day before rice transplanting, apply the portion of the base fertilizer as base fertilizer evenly to the field surface, and then perform rotary tillage or harrowing to fully mix the fertilizer with the topsoil, so as to prolong the fertilizer release cycle and promote root growth.

[0022] (2) Application of tillering fertilizer: Seven days after rice transplanting, the remaining part of the basal tillering fertilizer is evenly spread as tillering fertilizer, and a shallow water layer of 3-5 cm is maintained in the field to promote early and rapid tillering and increase the number of effective panicles;

[0023] (3) Application of panicle fertilizer: At the beginning of panicle differentiation, apply the panicle fertilizer evenly at once. After application, keep the field in a shallow water layer for 5-7 days to facilitate the absorption and utilization of fertilizer, promote the formation of large panicles and grain filling.

[0024] Furthermore, in step six: representative consecutive plants in three holes are selected as one sample in the middle area of ​​each treatment chamber, and sampling is repeated three times in each chamber; then the following yield components are measured: effective panicle number, number of grains per panicle, seed setting rate, and thousand-grain weight; further, the carbon dioxide fertilization effect of high carbon dioxide on yield is calculated:

[0025]

[0026] In the formula, This refers to rice yield under high carbon dioxide levels. This refers to rice yield under atmospheric carbon dioxide levels.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] This invention addresses the problem of low leaf nitrogen concentration, strong photosynthetic adaptation, and limited yield increase in japonica rice during its reproductive growth stage under high CO2 conditions. It proposes a nitrogen fertilizer management method with a basal-tillering fertilizer:panicle fertilizer ratio of 6:4. Under high CO2 concentrations, this ratio significantly increases yield compared to the conventional 7:3 ratio, mitigates the decrease in leaf nitrogen concentration caused by rising carbon dioxide, enhances the photosynthetic effect of increased carbon dioxide, promotes the distribution of photosynthetic products to grains, prolongs the green period of functional leaves, and improves grain filling. This method is simple to operate, low in cost, does not rely on genetic engineering, and is applicable to major japonica rice producing areas, making it significant for addressing climate change and ensuring food security. Attached Figure Description

[0029] Figure 1 This is a flowchart of nitrogen fertilizer application in an embodiment of the present invention, simulating the effect of carbon dioxide fertilization on increasing the yield of japonica rice under a high concentration of CO2 environment. Detailed Implementation

[0030] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0031] like Figure 1As shown, this embodiment of the invention provides a nitrogen fertilizer application method for improving the yield of japonica rice and the effect of carbon dioxide fertilization under simulated high-concentration CO2 environment, including the following steps:

[0032] Step 1: Select an open, flat site and build an open-top climate chamber (OTC) platform to simulate the scenario of increased atmospheric CO2 concentration.

[0033] Choose an open, flat site. The main body adopts a regular hexagonal prism structure, with the frame made of aluminum alloy profiles. The facade is inlaid with glass, and the top is kept open to utilize natural light and ventilation. To avoid mutual interference between air chambers, the distance between adjacent air chambers is not less than 20 m.

[0034] Step 2: Set the carbon dioxide concentration in the OTC container to simulate the future atmospheric CO2 concentration level.

[0035] The high carbon dioxide concentration was set at 550 ppm to simulate the atmospheric CO2 concentration level in the middle of this century; the current atmospheric CO2 concentration can be preferably set at 420 ± 20 ppm as a comparison environment.

[0036] Step 3: Select rice varieties that will be in high demand in the future but are less responsive to high CO2 environments.

[0037] With the increasing demand for japonica rice, and the fact that japonica rice varieties are less responsive to carbon dioxide, the local japonica rice variety Wuyunjing 23 was selected for planting.

[0038] Step 4: Determine the total nitrogen fertilizer requirement for the entire rice season based on the rice variety, soil fertility, and target yield.

[0039] Based on the soil's basic fertility, target yield, and the nitrogen requirement of the Wuyunjing 23 rice variety, the total nitrogen fertilizer application during the entire growth period was determined to be 270 kg / ha.

[0040] Step 5: Adjusting the ratio of nitrogen fertilizer used for basal tillering and panicle growth.

[0041] Nitrogen fertilizer for the entire growth period of rice is divided into two parts: basal fertilizer and panicle fertilizer. The two are applied in a mass ratio of 6:4. Specific fertilization operations: (1) Basal fertilizer application: One day before rice transplanting, the basal fertilizer portion (urea 176.09 kg / ha) is evenly applied to the field surface. Then, rotary tillage or harrowing is carried out to fully mix the fertilizer with the topsoil to prolong the fertilizer release period and promote root development. (2) Tillering fertilizer application: Seven days after rice transplanting (i.e. after seedling survival), the remaining portion of the basal fertilizer is evenly spread as tillering fertilizer (urea 176.09 kg / ha). A shallow water layer of 3-5 cm is maintained in the field to promote early and rapid tillering and increase the number of effective panicles. (3) Application of panicle fertilizer: At the beginning of panicle differentiation (i.e. when the second leaf tip emerges), apply panicle fertilizer (urea 176.09 kg / ha) evenly in one go. After application, keep the field in a shallow water layer for 7 days to facilitate the absorption and utilization of fertilizer, promote the formation of large panicles and grain filling.

[0042] Step Six: Yield Measurement and Calculation of the Effect of Carbon Dioxide Fertilization.

[0043] In each treatment chamber, three representative consecutive plants were selected from the middle area as one sample, and sampling was repeated three times in each chamber. The following yield components were measured: number of effective panicles, number of grains per panicle, grain filling rate (number of full grains / total number of grains × 100%), and thousand-grain weight. The effect of high carbon dioxide on yield from carbon dioxide fertilization was calculated as follows:

[0044] (1)

[0045] In the formula, This refers to rice yield under high carbon dioxide levels. This refers to rice yield under atmospheric carbon dioxide levels.

[0046] Data were processed and tabulated using Excel 2016, and ANOVA was performed using SPSS (28.0). As shown in Table 1, different nitrogen fertilizer management strategies had different effects on rice yield under elevated carbon dioxide levels. Compared with treatment T1, the effect of elevated carbon dioxide on yield increased by 10.15% under treatment T2, and yield increased by 11.05% under elevated carbon dioxide conditions.

[0047] Table 1

[0048]

[0049] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the scope of protection of the present invention in any way, and all technical solutions obtained by equivalent substitution or other means fall within the scope of protection of the present invention. Parts not covered in this invention are the same as or can be implemented using existing technology.

Claims

1. A nitrogen fertilizer application method for simulating high-concentration CO2 environment to enhance japonica rice yield and the effect of carbon dioxide fertilization, characterized in that, Includes the following steps: Step 1: Construct an open-top climate chamber platform to simulate a scenario of increased atmospheric CO2 concentration; Step 2: Set the carbon dioxide concentration inside the open-top climate chamber platform to simulate future atmospheric CO2 concentration levels; Step 3: Select rice varieties that are in high demand but have a weaker response to high CO2 environments; Step 4: Determine the total nitrogen fertilizer requirement for the entire rice season; Step 5: Adjusting the ratio of nitrogen fertilizer used for basal tillering and panicle growth; Step Six: Yield Measurement and Calculation of the Effect of Carbon Dioxide Fertilization.

2. The nitrogen fertilizer application method for improving japonica rice yield and carbon dioxide fertilization effect under simulated high-concentration CO2 environment as described in claim 1, characterized in that, In step one: the open-top climate chamber platform is set in an open, flat open space, and its main body adopts a regular hexagonal prism structure, the frame is made of aluminum alloy profiles, the facade is inlaid with glass, and the top is kept open to utilize natural light and ventilation.

3. The nitrogen fertilizer application method for simulating high-concentration CO2 environment to enhance japonica rice yield and carbon dioxide fertilization effect as described in claim 2, characterized in that, The distance between adjacent open-top climate chamber platforms shall not be less than 20m.

4. The nitrogen fertilizer application method for improving japonica rice yield and carbon dioxide fertilization effect under simulated high-concentration CO2 environment as described in claim 1, characterized in that, In step two: the high carbon dioxide concentration is set to 550 ppm, and the current atmospheric CO2 concentration is set to 420 ± 20 ppm as a comparison environment.

5. The nitrogen fertilizer application method for improving japonica rice yield and carbon dioxide fertilization effect under simulated high-concentration CO2 environment as described in claim 1, characterized in that, In step three: the selected rice variety is japonica rice.

6. The nitrogen fertilizer application method for improving japonica rice yield and carbon dioxide fertilization effect under simulated high-concentration CO2 environment as described in claim 1, characterized in that, In step four: based on the local conventional fertilization rate, the total amount of nitrogen fertilizer applied throughout the entire growth period is determined to be 270 kg / ha.

7. The nitrogen fertilizer application method for improving japonica rice yield and carbon dioxide fertilization effect under simulated high-concentration CO2 environment as described in claim 1, characterized in that, In step five, nitrogen fertilizer for the entire growth period of rice is divided into two parts: basal fertilizer and panicle fertilizer, and the mass ratio of the two is optimized. The mass ratio of basal fertilizer to panicle fertilizer is 6:

4.

8. A nitrogen fertilizer application method for improving japonica rice yield and carbon dioxide fertilization effect under simulated high-concentration CO2 environment as described in claim 6, characterized in that, Specific fertilization procedures: (1) Application of base fertilizer: One day before rice transplanting, apply the portion of the base fertilizer as base fertilizer evenly to the field surface, and then perform rotary tillage or harrowing to fully mix the fertilizer with the topsoil, so as to prolong the fertilizer release cycle and promote root growth. (2) Application of tillering fertilizer: Seven days after rice transplanting, the remaining part of the basal tillering fertilizer is evenly spread as tillering fertilizer, and a shallow water layer of 3-5 cm is maintained in the field to promote early and rapid tillering and increase the number of effective panicles; (3) Application of panicle fertilizer: At the beginning of panicle differentiation, apply the panicle fertilizer evenly at once. After application, keep the field in a shallow water layer for 5-7 days to facilitate the absorption and utilization of fertilizer, promote the formation of large panicles and grain filling.

9. A nitrogen fertilizer application method for improving japonica rice yield and carbon dioxide fertilization effect under simulated high-concentration CO2 environment as described in claim 1, characterized in that, In step six: Three representative rice plants are selected from the middle area of ​​each treatment chamber as one sample, and sampling is repeated three times in each chamber; then the following yield components are measured: effective panicle number, number of grains per panicle, seed setting rate, and thousand-grain weight; further, the effect of high carbon dioxide on yield from carbon dioxide fertilization is calculated: In the formula, This refers to rice yield under high carbon dioxide levels. This refers to rice yield under atmospheric carbon dioxide levels.

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