A method for returning rice field straw to the field for carbon fixation and emission reduction

Abstract

The present invention discloses a method for returning rice straw to the field for carbon fixation and emission reduction, which mainly includes three aspects: first, all the straw of the field is concentrated in a small area in the field, and then the field is evenly plowed and returned, and no straw is returned to the field in the remaining area; second, rain-fed water management is performed in the rice growing season in the area where the straw is concentrated; third, the straw is concentrated in the next year to the area that was not returned to the field in the previous year, and the water management of the straw-returned area and the non-straw-returned area is carried out with reference to the previous year, and then the cycle is repeated every year. This technology not only retains the previous production habit of directly returning straw to the field, and is easy to implement in actual operation, but also the concentrated straw return area and the return amount can be flexibly planned according to the size of the field and the total amount of straw, which has strong flexibility. This technology can effectively reduce the total amount of greenhouse gas emissions from rice fields and increase the organic carbon content in the soil.

Description

Technical Field

[0001] The present invention relates to the field of agricultural planting technology, and more particularly to a method for returning rice straw to fields for carbon fixation and emission reduction. Background Art

[0002] Water management and organic material addition are the two most critical factors affecting methane emissions from rice fields, and rice fields are important sources of greenhouse gases CH4 and N2O. Since CH4 emissions from rice fields are much higher than N2O emissions, the focus of greenhouse gas emission reduction is to reduce CH4 emissions. In production practice, returning crop straw to the fields is beneficial to improving soil fertility, increasing production and generating income, but returning straw to the fields under flooded conditions will significantly promote methane emissions from rice fields, making rice fields a huge source of carbon emissions and hindering the smooth realization of the dual carbon goals of agriculture.

[0003] Compared with the conventional uniform mixing of straw and continuous flooding after returning the field, the early use of strip covering returning the field can significantly reduce methane emissions by reducing direct contact between straw and water, but the straw is difficult to shape under the long-term flooding before drainage and field baking (about 40 days after transplanting), which not only affects the strip effect, but also easily leads to the breeding of insect eggs and diseases. In recent years, the highly praised straw carbonization returning to the field has obvious methane emission reduction effect, but the straw needs to be returned to the field after leaving the field, and the comprehensive costs such as energy consumption of straw carbonization are high. When draining and baking the field, some biochar often floats away with the running water, making it difficult to promote and apply on a large scale in actual production.

[0004] In production, the direct return of straw to the field during the rice season can be changed to the return during the non-rice season, so as to promote the decomposition of straw in an aerobic environment and reduce CH4 emissions in subsequent rice seasons. However, this measure also requires the straw to be transported away from the field and left for a rice season before being returned to the field. On the one hand, it consumes a certain amount of manpower and material resources, and the carbon emissions during the storage of straw are often easily overlooked, resulting in an underestimated emission; on the other hand, it does not conform to the current habit of returning machine-harvested straw directly to the field, especially in double-season rice areas or rice-wheat rotation areas, where the rate of straw returning to the field in summer is high, resulting in the effective disposal of straw still not being well solved.

[0005] Therefore, how to provide a rice straw returning technology that can significantly reduce the total amount of greenhouse gas (CH4 and N2O) emissions during the rice growing season in the rice farming system and save time and effort is an urgent problem to be solved by technical personnel in this field. Summary of the invention

[0006] In view of this, the present invention provides a method for returning rice field straw to the fields for carbon fixation and emission reduction, which adopts a centralized rotation return to the fields coupled with a rain-fed planting model to significantly reduce CH4 emissions and total greenhouse gas emissions from rice fields.

[0007] To achieve the above object, the present invention adopts the following technical solution:

[0008] A method for returning rice straw to fields for carbon fixation and emission reduction comprises the following steps:

[0009] (1) dividing the field to be treated into a returning field area and a blank area, cutting all the straw in the field to be treated and returning it to the returning field area, and evenly plowing and returning the straw before transplanting;

[0010] (2) The rain-fed management mode is adopted in the returned farmland area, and the conventional water management mode is adopted in the blank area;

[0011] (3) In the next year, the crop straw is cut and concentrated in the blank area of ​​the previous year for returning to the field, that is, the blank area of ​​the previous year is converted into a returning field area and managed according to the management mode of step (2);

[0012] (4) According to the above steps, carry out circular returning of crops to the fields in the returning fields area and the blank areas.

[0013] Preferably, the area ratio of the returned field area and the blank area in step (1) is 1:(1-7).

[0014] Preferably, the straw cutting length in step (1) is about 15-20 cm.

[0015] Preferably, the rain-fed management mode in step (2) is specifically: flooding the rice fields for 10-15 days during rice transplanting, and then no artificial irrigation is performed in the rice fields until the rice is harvested.

[0016] Preferably, the conventional water management mode in step (2) is as follows: the field is kept flooded for 35-40 days after rice transplanting, and then drained and dried for 7-10 days in the middle term, followed by rewatering for 10-15 days, and the rice field is irrigated once every 10-15 days in the later period, and no irrigation is performed 7-10 days before rice harvest.

[0017] It can be seen from the above technical solutions that, compared with the prior art, the present invention discloses a method for returning rice straw to the field for carbon fixation and emission reduction, which has the following beneficial effects:

[0018] The rice season straw return technology of the present invention can not only significantly reduce the total amount of comprehensive greenhouse gas (CH4 and N2O) emissions during the rice growing season of the rice farming system, but also increase the soil organic carbon content, thereby achieving the purpose of carbon fixation and emission reduction. This technology not only retains the previous production habit of returning straw directly to the field, which is easy to implement in actual operation, but also the concentrated straw return area and the amount of return can be flexibly planned according to the size of the field and the total amount of straw, which has strong flexibility. Secondly, if the area of ​​the concentrated straw return area is too small but the amount of straw return is too large, it is even possible to choose to plant crops such as sweet potatoes, potatoes, cassava, etc. that consume less water and are more drought-resistant, so as to ensure the grain output of a whole piece of farmland, so it has strong selectivity. Finally, this technology can effectively reduce the total amount of greenhouse gas emissions from rice fields and increase the soil organic carbon content. The results of field tests confirmed that compared with the uniform mixing of straw, the concentrated rotation of straw returning to the field coupled with rain-fed planting mode significantly reduced the CH4 emissions and total greenhouse gas emissions of the entire rice field, ensuring rice yield while increasing the soil organic carbon content, thereby achieving carbon sequestration and emission reduction effects under stable yield conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0020] Figure 1 It is a technical solution pattern diagram of the present invention;

[0021] Figure 2 This is a comparison chart of greenhouse gas emission field experiments of Example 1 of the present invention and Comparative Example 1;

[0022] Figure 3 It is a comparison chart of the organic carbon sequestration rates of Example 1 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0023] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Example 1

[0025] The rice fields in Zhangdu Village, Dingshu Town, Yixing City (119.91°E, 31.28°N) were treated by the centralized straw rotation returning method of the present invention:

[0026] After the crops are harvested in the first year, all the straw is transported and concentrated to 1 / 2 of the field area as the return area, the straw is broken into 20 cm in length, and evenly plowed and returned to the field; the remaining 1 / 2 of the field area has no straw returned and serves as a blank area.

[0027] The returned rice fields are water-managed in a rain-fed manner, that is, the rice fields are flooded for 10-15 days when the rice is transplanted, and then no artificial irrigation is carried out until the rice is harvested while ensuring that the rice can grow normally;

[0028] The blank area is for conventional water management, that is, the fields are kept flooded for 35-40 days after rice transplanting, and then drained and baked for 7-10 days in the mid-term, followed by rewatering for 10-15 days. In the later period, the rice fields are irrigated once every 10-15 days, and no irrigation is done 7-10 days before rice harvest.

[0029] In the second year, the crop straw will be concentrated in the blank area of ​​the first year, that is, the returning area and the blank area will be exchanged in the second year, and the cycle will be carried out in this way.

[0030] Example 2

[0031] The difference from Example 1 is that 1 / 4 of the field area is selected as the returning field area and 3 / 4 of the area is selected as the blank area every year.

[0032] Example 3

[0033] The difference from Example 1 is that 1 / 8 of the field area is selected as the returning field area and 7 / 8 of the area is selected as the blank area every year.

[0034] Comparative Example 1

[0035] Evenly mix straw and return it to the field: After the crops are harvested, the straw is broken into 20cm lengths and directly and evenly plowed and returned to the field. Before rice transplanting, the paddy field is plowed, harrowed, leveled, and other operations are carried out for the second time according to local production habits before rice planting. After rice transplanting, field water management is carried out according to local routine water management. The local routine water management is that the field is kept in a flooded state for 35-40 days after rice transplanting, and then the field is drained and baked for 7-10 days in the middle term, followed by rehydration for 10-15 days, and irrigation is carried out every 10-15 days in the later period, and no irrigation is carried out 7-10 days before rice harvest.

[0036] Experimental example

[0037] During the rice growth period, the static chamber method was used to collect gas samples from the fields of Example 1 and Comparative Example 1, and the gas samples were collected every 4 days. On each sampling day, 4 gas samples were collected from each chamber every 10 minutes from 9:00 to 11:30 in the morning using a 24 mL vacuum bottle.

[0038] The results of two consecutive years of field trials show that (see Figure 2 ), in the rice season, CH4 emissions and total greenhouse gas emissions from concentrated straw return to the field were 96.0-102 kg ha –1 and 3.12-3.34t CO2-eq t -1 The rice yield of concentrated straw return was 5.61-5.77t ha. –1 Compared with the uniform application of straw, there was no significant difference (5.59-6.08t ha –1 In addition, the soil organic carbon sequestration rate of concentrated straw return to the field is 0.37 t C ha –1 yr –1 , 0.12t C ha higher than straw uniform mixing –1 yr –1 (See Figure 3 ). Therefore, during the rice season, returning straw to the fields in a centralized manner and combining it with rain-fed water management in some areas can significantly reduce total greenhouse gas emissions while ensuring yields, and increase the rate of soil organic carbon sequestration, which is an effective field management technology for carbon sequestration and emission reduction.

[0039] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0040] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for returning rice field straw to fields for carbon fixation and emission reduction, characterized in that: The following steps are involved: (1) dividing the field to be treated into a returning field area and a blank area, cutting all the straw in the field to be treated and returning it to the returning field area, and evenly plowing and returning the straw before transplanting; (2) The rain-fed management mode is adopted in the returned farmland area, and the conventional water management mode is adopted in the blank area; The rain-fed management mode is specifically as follows: the rice fields are flooded for 10-15 days when the rice is transplanted, and then no artificial irrigation is performed on the rice fields until the rice is harvested; the conventional water management mode is specifically as follows: the fields are flooded for 35-40 days after the rice is transplanted, and then the fields are drained and baked for 7-10 days in the middle term, and then re-watered for 10-15 days, and the rice fields are irrigated once every 10-15 days in the later period, and no irrigation is performed 7-10 days before the rice is harvested; (3) In the next year, the crop straw is cut and concentrated in the blank area of ​​the previous year for returning to the field, that is, the blank area of ​​the previous year is converted into a returning field area and managed according to the management mode of step (2); (4) According to the above steps, carry out circular returning of crops to the fields in the returning fields area and the blank areas.

2. The method for returning rice straw to fields for carbon sequestration and emission reduction according to claim 1, characterized in that: The area ratio of the returned field area and the blank area in step (1) is 1:(1-7).

3. The method for returning rice straw to fields for carbon fixation and emission reduction according to claim 1, characterized in that: The straw cutting length in step (1) is 15-20 cm.

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