Farm operation method using duckweed as season green manure of rice field

Abstract

The invention discloses a farming operation method using duckweed as rice field season green manure. The method comprises the following steps: (1) fertilizer application; (2) irrigating 1-2 days before rice transplanting; (3) shallow water irrigation is carried out in the period of rice reviving, the average depth of a rice field water layer is 3-5 cm, and a dry-wet alternate irrigation mode is adopted in the whole rice field water management process after reviving and before field drying; (4) water retention is needed in irrigation ditch facilities of the rice field during the field drying period; (5) after the field is dried and before the rice is harvested, continuously adopting a dry-wet alternate irrigation mode; and (6) when chemical weeding is carried out in the whole growth period of the rice, a herbicide with an obvious killing effect on the duckweed is not applied. The duckweed is used as the season green manure of the rice field, and the method is an ecological intensive rice field management mode. And continuous and repeated decomposition-regeneration cycle of the duckweed is realized by continuously regulating and controlling the dry and wet state of the rice field, so that the effect of accumulating and releasing nutrients in the duckweed body is achieved.

Description

Technical Field

[0001] The invention relates to a farming operation method for utilizing duckweed as seasonal green manure for rice fields, and belongs to the field of crop planting. Background Art

[0002] The information disclosed in this background technology section is only intended to increase some understanding of the overall background of the invention, and should not be necessarily regarded as an admission or any form of suggestion that the information constitutes the prior art already known to ordinary technicians in this field.

[0003] Rice is the most important food crop in my country, and its planting area accounts for more than 30% of the total area of ​​food crops all year round. In the rice field ecosystem, duckweed, as a typical aquatic floating plant, is widely distributed in various rice-growing areas in my country. Studies have shown that the existence of duckweed communities can effectively improve the diversity of rice field ecosystems, and through the synergistic effects of its photosynthetic carbon fixation and methanotrophic bacteria, it can significantly enhance the carbon sequestration capacity of rice fields and reduce greenhouse gas emissions. More importantly, the duckweed system has multiple ecological values. Its own nitrogen fixation function can improve the nitrogen cycle in rice fields, and its ability to quickly absorb phosphorus and potassium nutrients can not only reduce ammonia volatilization losses, but also reduce phosphorus runoff emissions, and improve the nitrogen utilization efficiency of rice fields. It is a type of biological resource with broad application prospects. However, the dynamic distribution of duckweed communities has significant temporal and spatial heterogeneity. Duckweed prefers a still water environment, so its abundance is easily affected by agricultural practices such as irrigation patterns and water management. Duckweed is hard to find in rice fields that are short of water for a long time, and its biomass may surge under continuous flooding conditions, thereby inhibiting the growth of rice. More importantly, farmers in some areas often regard duckweed as a harmful weed and manually salvage it or use pesticides to control it, which greatly increases labor costs. Therefore, how to build a dynamic regulation technology system for duckweed in rice fields, while giving full play to its ecological functions such as carbon fixation and emission reduction, and nutrient efficiency, while accurately preventing and controlling the negative impact of excessive biomass accumulation on rice production, has become a key issue that needs to be broken through in the current green rice technology innovation.

[0004] Compared with traditional dryland green manures such as astragalus, rapeseed and sweet potato, which all require separate allocation of arable land for sowing and involve multiple processes such as land preparation and turning, aquatic green manures such as azolla have inherent advantages such as saving time and labor, but the growth area of ​​azolla is limited by conditions such as water temperature and pH value, and the suitable planting range is limited. However, duckweed, with its wide distribution characteristics and strong adaptability, can achieve dynamic control of biomass through precise fertilizer and water regulation, and can form a spatially complementary three-dimensional fertilization model with rice in rice fields. In addition to the yield-increasing effect and soil fertility improvement function of conventional green manures, it can also use its unique nitrogen fixation system and rapid nutrient retention ability to synergistically reduce the loss of chemical fertilizers, saving multiple management links compared to traditional green manures, and playing a role in saving costs and increasing efficiency. Summary of the invention

[0005] In view of the problems existing in the above existing rice green manure application technology, the present invention provides a time-saving, land-saving, cost-saving and efficient rice fertilizer application method.

[0006] The technical solution adopted by the present invention is as follows: The present invention provides a farming operation method for utilizing duckweed as seasonal green manure for rice fields, the method comprising the following steps: (1) Fertilizer application: base fertilizer, tillering fertilizer and ear fertilizer, with a mass ratio of 2:1:1; (2) Introducing duckweed that grows naturally in rivers or irrigation ditches into rice fields 1 to 2 days before rice transplanting; (3) Shallow water irrigation is used during the period of rice regrowth, with an average water depth of 3 to 5 cm in the paddy field. Alternating dry and wet irrigation is used for water management of the paddy field from the time of rice regrowth to the time of drying the paddy field, with an irrigation cycle of 3 to 4 days. (4) During the drying period, duckweed in the paddy field will die in large numbers due to lack of water. At this time, water needs to be retained in the irrigation ditch facilities of the paddy field to conserve duckweed as a supplementary source of duckweed in the paddy field after the drying period. (5) Continue to use the alternating dry-wet irrigation method after the field is sun-dried until the rice is harvested. The irrigation frequency is maintained at 3 to 4 days during the rice jointing and heading period, and is extended to 4 to 5 days as the temperature and sunshine duration decrease, so as to give full play to the fertilizer effect of duckweed in the rice field; (6) When chemical weed control is carried out during the entire growth period of rice, herbicides that have a significant killing effect on duckweed shall not be used.

[0007] In step (1), the basal fertilizer is applied once during land preparation 3 to 4 days before rice planting. In terms of pure nitrogen content, organic fertilizer accounts for 1 / 3 of the total nitrogen fertilizer application. Commercial organic fertilizer or well-rotted farmyard manure can be used, and an appropriate amount of chemical fertilizer can be added to make the basal fertilizer account for 50% of the total nitrogen fertilizer application. The tillering fertilizer is applied 10 to 12 days after rice transplanting. Urea is recommended, and the nitrogen content accounts for 25% of the total nitrogen fertilizer application. The ear fertilizer is applied 40 to 45 days before heading. It is recommended to use a rice-specific compound fertilizer with a nitrogen, phosphorus and potassium ratio of 15:15:15, and the nitrogen content accounts for 25% of the total nitrogen fertilizer application.

[0008] In step (1), the farm organic fertilizer used can be decomposed by common pile fermentation treatment, and the manure of livestock and poultry such as chicken, duck, pig and cow can be used as the main raw material, and the materials can be obtained locally with no limit on the proportion. In addition to increasing the organic matter in the paddy field soil, the mixed organic fertilizer can also provide long-term nutrition for the growth of duckweed, avoiding the excessive nutrient caused by the one-time large-scale application of inorganic base fertilizer, which will cause duckweed outbreaks and have an adverse effect on the tillering of rice. Under the condition that organic fertilizer partially replaces inorganic fertilizer as base fertilizer, the long-term release of nutrients by organic fertilizer decomposition can supply duckweed growth, which has better ecological and environmental protection effects.

[0009] In step (2), when there is no duckweed in the irrigation water source, since duckweed seeds are not easy to collect, exogenous duckweed thalli can be scattered into the paddy field by artificial seeding, with a dosage of ≥ 3 kg (wet weight) per 667 m 2 2.

[0010] In step (2), the duckweed species introduced into the paddy field can include single varieties or mixtures of Wolffia arrhiza, Spirodela polyrhiza, and Lemna minor, depending on the local duckweed resources growing naturally in the current season. There are temporal and spatial variations in the composition of the duckweed population in the paddy field, and different types of duckweed may also have certain differences in the exertion of ecological benefits. However, considering factors such as the practicality, convenience, and cost control of the present invention, the types of duckweed are not strictly restricted. The timing of introducing duckweed is extremely important. Establishing a water layer too early to put duckweed has the risk of flooding and outbreak, while introducing it too late may limit the growth scale of the duckweed population and fail to fully exert the ecological benefits of duckweed.

[0011] In steps (2) to (5), the irrigation water source for the paddy field generally comes from surface water sources such as rivers, lakes, or ponds around the paddy field. There are significant differences between groundwater and surface water in terms of physical and chemical properties such as water temperature, nutrient content, and microbial activity.

[0012] In step (3), the dry-wet alternate irrigation cycle depends on the growth of duckweed. When there is a water layer in the paddy field after the rice turns green, the visual coverage of duckweed ≥ 50%, and the dry matter mass per unit area ≥ 35 g·m -2 −2; before the field is drained for sunning, the visual coverage ≥ 70%, and the dry matter mass per unit area ≥ 50 g·m -2 −2; from after the field is drained for sunning to 7 days before rice harvest, during this period, rice becomes the dominant population, so the growth scale of duckweed can be appropriately expanded. The visual coverage of duckweed in the field ≥ 90%, and the dry matter mass per unit area ≥ 70 g·m -2 −2. The time control of the waterless period depends on the decomposition of duckweed. Generally, when the area of decomposed duckweed (the color changes from yellow to white or is completely submerged in water and no longer floats) accounts for 1 / 5 of the total area of the field plot, rewatering can be carried out.

[0013] In step (6), restricting the use of chemical agents refers to herbicides that have an obvious inhibitory effect on the normal growth of duckweed, such as sulfonylurea herbicides, fomesafen, bispyribac-sodium, florasulam, and isoproturon, etc., and appropriately using insecticides such as imidacloprid and abamectin.

[0014] The present invention continuously regulates the dry-wet state of the paddy field to achieve the continuous and repeated decomposition-regeneration cycle of duckweed, thereby achieving the effect of nutrient accumulation and release in duckweed, and further exerting its fertilizer effect to promote rice growth. This process runs through the entire growth period of rice and is more operable.

[0015] Compared with the related technologies known to the inventors, one of the technical solutions of the present invention has the following beneficial effects: The present invention uses duckweed as the green manure for the current season in paddy fields, which is an ecological and intensive paddy field management method. First, through the comprehensive regulation of fertilizer and water operations, the reproduction and growth of duckweed in paddy fields are controlled. In terms of fertilization methods, the traditional base fertilizer + top dressing mode is followed, which conforms to the farming operation habits in most regions; adding an appropriate amount of organic fertilizer can save costs and labor while providing a more gentle and long-term nutrient environment for the growth of duckweed and rice. Secondly, in terms of water management, compared with flood irrigation, alternate wet and dry irrigation can not only achieve the purpose of water saving, but also make duckweed undergo a cycle of death, decomposition and regeneration by changing the water environment in paddy fields, so as to exert the fertilizer effect of duckweed. Finally, compared with traditional rice green manure, the intercropping of duckweed does not occupy land and farming time alone, and can even be combined with comprehensive rice farming technologies such as raising ducks in paddy fields to improve the production efficiency of land per unit area. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The schematic diagrams of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0017] Figure 1 : Schematic diagram of the water layer management of alternate wet and dry irrigation in paddy fields and field real photos of the growth status of duckweed at corresponding periods. Among them, 1 is the growth status of rice and the initial distribution status of duckweed in the paddy field during the rice greening period, 2 is the growth status of rice and the distribution status of duckweed in the paddy field before the rice field is drained for sunning, 3 is the situation of the paddy field during the rice field drainage for sunning, 4 is the situation of introducing duckweed into the paddy field again from the irrigation ditch when the water is restored after the rice field drainage for sunning ends, the blue arrow indicates the water flow direction, 5 and 6 are the growth status of rice and duckweed when there is water layer and no water layer in the paddy field during the rice heading period respectively, and 7 is the effect diagram of the complete decomposition state of duckweed before rice harvest.

[0018] Figure 2 : Effects of different types of fertilizers on rice yield under the condition of duckweed associated growth in paddy fields.

[0019] Figure 3 : Seasonal changes in duckweed biomass in paddy fields under different fertilizer types. DETAILED DESCRIPTION OF THE INVENTION

[0020] It should be noted that the following detailed descriptions are all exemplary and are intended to provide further explanations of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0021] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations and / or combinations thereof.

[0022] The present invention discloses an agricultural operation method for using duckweed as green manure in a rice field, which specifically comprises: (1) introducing duckweed naturally grown in a river and / or ditch into a rice field through irrigation 1 to 2 days before transplanting rice; (2) using organic fertilizer to partially replace chemical fertilizer to avoid excessive reproduction of duckweed in the rice field due to rapid release of chemical fertilizer in the rice greening period, thereby affecting the tillering process of rice; (3) after the rice greening period and before the field sunning, using a light dry-wet alternating water management method, so that the duckweed in the rice field during this period is in a reciprocating cycle of reproduction (water layer)-partial death and decomposition (falling into water), thereby promoting the return of nitrogen from the duckweed source; (4) during the field sunning period, the irrigation ditch is moderately water-retained to conserve duckweed as a supplementary source of duckweed in the rice field after the field sunning. (5) after the field sunning period and before the rice harvest, the dry-wet alternating irrigation method is continued to exert the fertilizer effect of the duckweed in the rice field.

[0023] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0024] Example 1 A method for converting duckweed into green manure for rice in season comprises the following steps: (1) In the japonica rice planting area using machine transplanting, under medium soil fertility conditions, the total amount of pure nitrogen used is 20 kg·667m -2 The fertilizer was applied three times, namely, basal fertilizer, tillering fertilizer and panicle fertilizer, with a mass ratio of 2:1:1. The basal fertilizer was applied once when the land was acquired 3 days before rice planting. Among them, organic fertilizer accounted for 1 / 3 of the total nitrogen fertilizer application. Based on the pure nitrogen content of 1%, the application amount was 670 kg·667 m -2 ; Chemical fertilizer application: 20 kg·667 m3 of rice-specific compound fertilizer with a nitrogen, phosphorus and potassium mass ratio of 15:15:15 -2 Add urea 5 kg·667 m -2 Tillering fertilizer was applied 10 days after rice transplanting, using 10.9 kg·667 m -2 The ear fertilizer should be applied 40 days before heading. It is recommended to use a rice-specific compound fertilizer with a nitrogen, phosphorus and potassium ratio of 15:15:15 (17.3 kg·667 m -2 and urea 5.2 kg·667 m -2 .

[0025] (2) One day before transplanting rice, the river water was introduced into the paddy field through irrigation; the irrigation water source in this example did not contain duckweed. Since duckweed seeds were not easy to collect, exogenous duckweed thalli were scattered into the paddy field by artificial release, with a dosage of 3.5 kg (wet weight) per 667 m 2

[0026] (3) During the rice green-recovery period, shallow irrigation was carried out, and the average depth of the paddy field water layer was 3 - 5 cm. After the rice turned green until before the field was dried, the water management of the paddy field adopted the alternate wetting and drying irrigation method throughout the process, with an irrigation cycle of 3 - 4 days, depending on the weather and the growth of duckweed ( Figure 1 as shown in 1). Figure 1 In 2, it shows the growth state of rice and the distribution state of duckweed in the paddy field before the field was dried.

[0027] (4) During the field-drying period, a large number of duckweeds in the paddy field would die due to water shortage. At this time, the irrigation ditch facilities in the paddy field needed to retain an appropriate amount of water to conserve duckweed as a supplementary source of duckweed in the paddy field after the field was dried ( Figure 1 as shown in 3).

[0028] (5) After the field was dried until before the rice was harvested, the alternate wetting and drying irrigation method was continued. During the rice jointing and heading period, the irrigation frequency could still be maintained at 3 - 4 days, and as the temperature and sunshine duration decreased, it could be appropriately extended to 4 - 5 days to exert the fertilizer effect of duckweed in the paddy field ( Figure 1 as shown in 5 and Figure 1 as shown in 6). Figure 1 In 4, it shows the situation of introducing duckweed from the irrigation ditch into the paddy field again when the water was restored after the field-drying of rice. Figure 1 In 7, it shows the effect diagram of the completely decomposed state of duckweed before the rice was harvested.

[0029] (6) When carrying out chemical weeding during the whole growth period of rice, herbicides with obvious killing effects on duckweed should not be applied.

[0030] Example 2 A method for converting duckweed into green manure for rice in the current season, comprising the following steps: (1) In the indica rice planting area with machine transplanting, under the condition of medium soil fertility, the total amount of pure nitrogen used was 16 kg·667 m -2 , which was applied in three times as basal fertilizer, tillering fertilizer and panicle fertilizer, with a mass ratio of 2:1:1. The basal fertilizer was applied once when the land was ploughed 4 days before rice transplanting. Among them, the organic fertilizer accounted for 1 / 3 of the total nitrogen fertilizer usage. Calculated by 1% of pure nitrogen content, the usage amount was 536 kg·667 m -2 ; for chemical fertilizers, 16 kg·667 m of rice special compound fertilizer with a nitrogen, phosphorus and potassium mass ratio of 15:15:15 -2 plus 4 kg·667 m of urea -2。The tillering fertilizer is applied 12 days after rice transplanting, with 8.7 kg of urea per 667 m -2 。The panicle fertilizer is applied 35 days before heading, and it is recommended to use 13.8 kg of a special compound fertilizer for rice with a nitrogen - phosphorus - potassium ratio of 15:15:15 per 667 m -2 and 4.2 kg of urea per 667 m -2 。

[0031] (2)Two days before rice transplanting, the river water is introduced into the paddy field through irrigation; the irrigation water source in this embodiment does not contain duckweed. Since duckweed seeds are not easy to collect, exogenous duckweed thalli can be scattered into the paddy field by artificial input, with a dosage of 4 kg (wet weight) per 667 m 2 。

[0032] (3)During the rice green - returning period, shallow irrigation is carried out, and the average depth of the paddy - field water layer is 3 - 5 cm. After the rice returns to green until before the field - drying, the water management of the paddy field adopts the alternate wet - and - dry irrigation method throughout the process, with an irrigation cycle of 3 - 4 days, depending on the weather and the growth of duckweed ( Figure 1 in 1). Figure 1 Figure 2 shows the growth state of rice and the distribution state of duckweed in the paddy field before field - drying.

[0033] (4)During the field - drying period, a large number of duckweeds in the paddy field will die due to water shortage. At this time, the irrigation ditch facilities in the paddy field need to retain water moderately to conserve duckweed as a supplementary source of duckweed in the paddy field after field - drying ( Figure 1 in 3).

[0034] (5)After field - drying until before rice harvest, the alternate wet - and - dry irrigation method is continued. During the rice jointing and heading period, the irrigation frequency can still be maintained at 3 - 4 days, and it can be appropriately extended to 4 - 5 days as the temperature and sunshine duration decrease, so as to exert the fertilizer effect of duckweed in the paddy field ( Figure 1 in 5 and Figure 1 in 6). Figure 1 Figure 4 shows the situation of introducing duckweed into the paddy field again from the irrigation ditch when the water is restored after the field - drying of rice. Figure 1 Figure 7 shows the effect picture of the completely decomposed state of duckweed before rice harvest.

[0035] (6)During the whole growth period of rice, when using chemical weeding, herbicides with obvious killing effects on duckweed shall not be applied.

[0036] Comparative Example 1 The growth of duckweed and the rice yield under two irrigation methods of flooding irrigation for rice and alternate wet - and - dry irrigation in Example 1 were compared and analyzed, and the test results are shown in the following table.

[0037] Among them, the difference between the flooding irrigation of rice and Example 1 is that the alternate wet - and - dry irrigation in Example 1 is replaced by flooding irrigation, and other steps and methods are the same as those in Example 1.

[0038] Table 1 Effects of Different Irrigation Methods on Rice Yield and Duckweed Biomass Maintaining a water layer for a long time will lead to excessive reproduction of duckweed (duckweed biomass increases by 45.6%), significantly reducing the number of panicles per unit area of rice, and thus having a negative impact on rice yield (a 14.0% decrease). It can be seen that compared with flooding irrigation, alternate wetting and drying irrigation can effectively control the growth of duckweed, give full play to the fertilizer effect of duckweed, and is beneficial to the growth of rice.

[0039] Comparative Example 2 To verify the effects of different types of fertilizers on rice yield under the condition of duckweed association, the effects of three different types of fertilizers, namely organic fertilizer (OF), chemical fertilizer (CF), and the compound fertilizer in Example 2 (one-third organic fertilizer and two-thirds chemical fertilizer, COF) with the same total nitrogen application rate (both 20 kg·667 m -2 ), on rice grain yield were compared ( Figure 2 ). The differences between the OF group, CF group and Example 2 are: in Example 2, the compound fertilizer is replaced by organic fertilizer and chemical fertilizer, and other steps and methods are the same as those in Example 2.

[0040] Compared with chemical fertilizer and organic fertilizer, the rice grain yield of applying the compound fertilizer increased by 6.0% and 20.3% on average in 2 years respectively. In addition, the compound fertilizer can also make the duckweed in the paddy field germinate early and grow fast, which is beneficial to better play the fertilizer effect of duckweed ( Figure 3 ).

[0041] Based on Comparative Examples 1 and 2, it can be seen that the overall management method of combining alternate wetting and drying irrigation with compound fertilizer can dynamically regulate the growth of duckweed in the paddy field ( Figure 3 ), making it fit the fertilizer requirement rule of rice, so as to give full play to the fertilizer effect of duckweed in the paddy field and then increase rice yield, which is a key measure to achieve the purpose of the present invention.

[0042] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. An agricultural operation method using duckweed as the green manure for the current season in paddy fields, characterized in that The method comprises the following steps: (1) Fertilizer application: base fertilizer, tillering fertilizer and ear fertilizer, with a mass ratio of 2:1:1; (2) Introducing duckweed that grows naturally in rivers or irrigation ditches into rice fields 1 to 2 days before rice transplanting; (3) Shallow water irrigation is used during the period of rice regrowth, with an average water depth of 3 to 5 cm in the paddy field. Alternating dry and wet irrigation is used for water management of the paddy field from the time of rice regrowth to the time of drying the paddy field, with an irrigation cycle of 3 to 4 days. (4) During the drying period, duckweed in the paddy field will die in large numbers due to lack of water. At this time, water needs to be retained in the irrigation ditch facilities of the paddy field to conserve duckweed as a supplementary source of duckweed in the paddy field after the drying period. (5) Continue to use the alternating dry-wet irrigation method after the field is sun-dried until the rice is harvested. The irrigation frequency is maintained at 3 to 4 days in the early stage, and is extended to 4 to 5 days as the temperature and sunshine duration decrease, so as to give full play to the fertilizer effect of duckweed in the rice field; (6) When chemical weed control is carried out during the entire growth period of rice, herbicides that have a significant killing effect on duckweed shall not be used.

2. The agricultural operation method of using duckweed as the green manure in the current season of paddy fields as claimed in claim 1, characterized in that, In step (1), the basal fertilizer is applied once when the land is acquired 3 to 4 days before rice planting. In terms of pure nitrogen content, organic fertilizer accounts for 1 / 3 of the total nitrogen fertilizer application. Commercial organic fertilizer or well-rotted farmyard manure can be used, and an appropriate amount of chemical fertilizer can be added to make the basal fertilizer account for 50% of the total nitrogen fertilizer application. The tillering fertilizer is applied 10 to 12 days after rice transplanting. Urea is recommended, and the nitrogen content accounts for 25% of the total nitrogen fertilizer application. The ear fertilizer is applied 40 to 45 days before heading. It is recommended to use a rice-specific compound fertilizer with a nitrogen, phosphorus and potassium ratio of 15:15:15, and the nitrogen content accounts for 25% of the total nitrogen fertilizer application.

3. The agricultural operation method of using duckweed as the current-season green manure in paddy fields as described in claim 1 is characterized in that, In step (1), the farmyard manure used is decomposed by common pile fermentation treatment, and chicken, duck, pig and cattle manure can be used as the main raw material.

4. The agricultural operation method of using duckweed as the current-season green manure in paddy fields according to claim 1, characterized in that, In step (2), when the irrigation water source does not contain duckweed, since duckweed seeds are not easy to collect, exogenous duckweed thalli can be scattered into the paddy field by manual placement, with a dosage of ≥ 3 kg per 667 m 2 ².

5. The agricultural operation method of using duckweed as the green manure in the current season of paddy fields as described in claim 1, characterized in that, In step (2), the duckweed species introduced into the rice field may include single species or a mixture of D. natans, D. rubrum and D. truncatula.

6. The farming operation method of using duckweed as the current-season green manure in paddy fields as described in claim 1 is characterized in that, In steps (2) to (5), the irrigation water for the rice fields comes from surface water sources such as rivers, lakes or ponds surrounding the rice fields.

7. The agricultural operation method of using duckweed as the current-season green manure in paddy fields as claimed in claim 1, wherein In step (3), when there is a water layer in the paddy field after the rice turns green, the visual coverage of duckweed ≥ 50%, and the dry matter mass per unit area ≥ 35 g·m -2 ; before field drying, the visual coverage ≥ 70%, and the dry matter mass per unit area ≥ 50 g·m -2 ; from after field drying to 7 days before rice harvest, during this period, rice becomes the dominant population, so the growth scale of duckweed is amplified, and the visual coverage of duckweed in the field ≥ 90%, and the dry matter mass per unit area ≥ 70 g·m -2 . When the area of ​​duckweed decomposition during the waterless period accounts for 1 / 5 of the total area of ​​the field, water can be restored.

8. The farming operation method of using duckweed as the current-season green manure in paddy fields as described in claim 1, wherein In step (3) and step (6), the restricted use of chemical agents refers to herbicides that have a significant inhibitory effect on the normal growth of duckweed, such as sulfonylurea herbicides, fomesafen, bispyribac-butyl, bispyribac-sodium and isoproturon. Imidacloprid and avermectin insecticides can be used.

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