Straw returning method through thawing and wet puddling for saline-sodic paddy fields and application thereof

Abstract

Provided are a straw returning method through thawing and wet puddling for saline-sodic paddy fields and an application thereof, relating to the technical field of returning straws to fields in saline-sodic paddy fields. According to the disclosure, regional characteristics are fully considered, thawing is taken as the core and combined with wet puddling.

Claims

1. A straw returning method through thawing and wet puddling for saline-sodic paddy fields in western Songnen plain, comprising following steps: (1) harvesting rice with a high stubble left having a height of 30-40 cm under a condition of ensuring full harvest of rice ears, and crushing and scattering the straw on a ground, wherein an average length of the crushed straw after the crushing is 15 cm, a qualified rate of straw crushing lengths defined as 80% of straw pieces meeting the 15 cm length is 80%, and uniformity of straw scattering defined as even distribution across 80% of the field surface is 80%; (2) ploughing at a surface depth of 14-16 cm, breaking soil capillary pores and inhibiting salt accumulation, wherein a ploughing depth matches a cultivation layer depth of a saline-sodic paddy field, and a leakage ploughing rate defined as a percentage of unploughed field surface areas is 5%, and a re-ploughing rate defined as a percentage of overlapping plough passes is 5%; (3) excavating a water outlet at a ridge located at a topographic low point between two adjacent fields, wherein a depth is at a same level with a field surface, and excavated soil is piled adjacent to the water outlet for later closure of the water outlet; (4) fertilizing, wherein fertilizers applied in a fertilizing step comprise base fertilizer and urea; (5) closing the water outlet of the ridge: excavating loose soil thawed on a surface near the water outlet of the ridge, and closing the water outlet; (6) irrigating for thawing during March 26 to April 15, when a natural thawed depth of a soil layer reaches 6-8 cm, irrigating the field of step (3) until tops of soil slices produced during ploughing are submerged, and steeping the field for 1-2 hours; and promoting a shallow ploughed slice to thaw through a heat exchange between soil and water, wherein an overall thawed depth reaches 11-13 cm, and meanwhile frozen soil blocks are retained; (7) stringing water: digging the water outlet of the field buried in step (5), stringing open water in the field into a next field; when an open water area on the field surface accounts for no more than 20% of the total current field surface area, closing the water outlet again to stop stringing water, and meanwhile, diverting water from a water source to irrigate and thaw the next field; and when the field is a last field planned to be implemented on a same day, directly discharging the water of the field to a ditch through a drainage outlet, and completely draining water overnight; (8) wet puddling operation: after the field of step (6) is thawed, carrying out the wet puddling operation, wherein an operation depth of 11-13 cm is consistent with a depth of a thawed layer, and at this time, lower soil is in a frozen state to provide structural support for operating machinery, wheels roll frozen soil at a lower layer to form ruts with a depth of 2-3 cm, and a mud layer of 2-3 cm is formed by rolling repeatedly to match with 11-13 cm of puddling by a puddling machine thereby forming a cultivation layer with a depth of about 15 cm; and (9) drying, wherein a drying duration is not less than 20 days, a soil drying depth after the drying is not less than 10 cm, the frozen soil blocks gradually thaw and dry, retaining internal pore structures and forming staggered pores distributed in the cultivation layer soil, and the frozen soil blocks retain internal pore structures, and the frozen soil blocks are staggered, promoting formation of soil pores distributed in the cultivation layer; and improvement of water permeability of the cultivation layer soil relative to conventional spring puddling promotes dissolution of salts in soil into water, thus accelerating salt discharge of the saline-sodic soil, and improvement of air permeability of the cultivation layer soil relative to conventional spring puddling promotes a gas exchange between the soil and atmosphere, thus inhibiting biogas generation and accelerating discharge of harmful gases.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a flow chart of straw returning method through thawing and wet puddling for saline-sodic paddy fields in western Songnen plain.

(2) FIG. 2A shows a straw returning method of saline-sodic paddy fields through thawing and wet puddling, where 1frozen soil blocks (with different sizes and certain levels), and 2rice straw.

(3) FIG. 2B shows a straw returning method of conventional spring puddling, where 2rice straw, and 3ruts pressed by an operating vehicle.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(4) Various exemplary embodiments of the disclosure will now be described in detail, and this detailed description should not be considered as a limitation of the disclosure, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the disclosure.

(5) It should be understood that the terminology described in the disclosure is only for describing specific embodiments and is not used for limiting the disclosure. In addition, for the numerical range in the disclosure, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Intermediate values within any stated value or stated range, as well as each smaller range between any other stated value or intermediate values within the stated range are also included in the disclosure. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

(6) 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 disclosure relates. Although the disclosure only describes the preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the disclosure. All documents mentioned in this specification are incorporated by reference to disclose and describe methods and/or materials related to the documents. In case of conflict with any incorporated document, the contents of this specification shall prevail.

(7) It is obvious to those skilled in the art that many improvements and changes may be made to the specific embodiments of the present specification without departing from the scope or spirit of the disclosure. Other embodiments will be apparent to the skilled person from the description of the disclosure. The specification and embodiments of the disclosure are exemplary only.

(8) The terms including, comprising, having and containing used herein are all open terms, which means including but not limited to.

(9) The disclosure will be described in further detail with reference to specific embodiments.

Embodiment 1

(10) Embodiment 1 was carried out from the autumn of 2021 to the autumn of 2022. The saline-sodic paddy field was located in Niuxintaobao Reed Field, Da'an City, Jilin Province, with an area of 20 hectares. The soil of 0-15 cm cultivation layer was tested and analyzed with the soil-water ratio of 1:5, and the pH was 9.52-9.85, the salt content was 2.31-2.68 gram/kilogram (g/kg), and the exchangeable sodium percentage (ESP) was 14.2%-23.7%. As shown in FIG. 1, the specific steps are as follows.

(11) S1: rice harvesting with high stubble left and straw crushing and scattering: rice harvesting was carried out by using a full-feeding harvester combined with crushing and scattering devices. The rice did not lodge, the average stubble height was about 42 cm, the average length of crushed straw was 14 cm, and the qualified rate of straw crushing lengths was 80%. After crushing, the straw was evenly scattered on the ground, and the scattering uniformity was 80%.

(12) S2: shallow ploughing: a 90 horsepower tractor with a driving disk plough is used for shallow ploughing, with a depth of 15 cm, a leakage ploughing rate of 5% and a re-ploughing rate of 5%.

(13) S3: ridge excavation of water outlet: from Oct. 28 to 31, 2021, a water outlet with a width of about 50 cm was excavated at the ridge position corresponding to the low position where water easily flows between two adjacent fields, and the depth was at a same level with the field surface. The excavated soil was piled up on the ridge near the water outlet for later closure of the water outlet.

(14) S4: application of base fertilizer and quick-acting nitrogen fertilizer: on Mar. 19-21, 2022, according to local production experience, base fertilizer N:P.sub.2O.sub.5:K.sub.2O=90 kg/ha:100 kg/ha:110 kg/ha was applied, and at the same time, urea was added with 120 kg/ha.

(15) S5: closing the water outlet of the ridge: the loose soil thawed on the surface near the water outlet of the ridge was excavated, and the water outlet was closed to control the water to stay in the required field.

(16) S6: irrigating for thawing: from Apr. 8 to 12, 2022, the natural thawed depth of the soil layer reached about 8 cm, the field was irrigated, and the irrigation was stopped until the tops of the slices were submerged, and the field was steeped for 1 hour, the overall thawed depth reached about 12 cm.

(17) S7: stringing water: the water outlet of this field was dug, so that the open water in the field was stringed into the next field, and when the proportion of the open water area in the field surface was reduced to 20%, the water outlet was closed again to stop stringing water, and meanwhile, water was diverted from the water source to irrigate and thaw the next field. The water in the last field of the day's operation was directly discharged from the drainage outlet and did not string into the next field.

(18) S8: wet puddling, leveling and drainage: after the field was irrigated and thawed, a 90 horsepower tractor with a puddling machine was immediately used for wet puddling, and the depth of puddling operation was set to 12 cm, which was consistent with the depth of the thawed layer. At this time, the lower soil was in a frozen state, which may well support the operating machinery. Tractor wheels only made ruts with a depth of 2-3 cm when rolling the frozen soil in the lower layer, and the ruts were repeatedly rolled to form a mud layer with a depth of 2-3 cm, which was matched with 12 cm of puddling by the puddling machine to form a cultivation layer with a depth of about 15 cm. The tractor was also equipped with a leveler to even the field surface, and the field surface was observed until the straw was not obviously exposed and the height difference was not more than decimetre, then the mechanical operation was stopped, and the drainage outlet normally matched with the field was opened to discharge the muddy water on the field surface into the drainage ditch.

(19) S9: reconstruction of cultivation layer soil structure by drying: the field with muddy water drained was dried for 22 days, and criss-crossing cracks appeared on the field surface, and the drying depth of cultivation layer soil from the surface reached 10 cm.

(20) As shown in FIG. 2A, the technical effects achieved by the method of thawing and wet puddling in Embodiment 1 are as follows.

(21) In mid-May, a 50 cm profile was dug before transplanting rice seedlings for observation and sampling analysis. It was found that 15 cm below was a solid plough pan, and the 0-15 cm cultivation layer had a good structure of upper paste and lower loose, and the straw decomposition rate reached 30%. When transplanting rice seedlings, a rice transplanter operated smoothly, the seedlings were in lines and in rows, the missing transplanting rate was <1%, and the quality of transplanting rice seedlings was high. The field surface was observed during the peak biogas generation period, mid-June to mid-July, and no significant bubble generation was observed, indicating that no significant biogas occurred during the growing period. Table 1 shows the measured values of hydrogen sulfide content in the air from mid-June to mid-July, and the average value of four tests is about 0.10 part per million (ppm). The yield of rice harvested in autumn is 7367 kg/ha.

(22) TABLE-US-00001 TABLE 1 Hydrogen sulfide content in air from mid-June to mid-July in field of Embodiment 1 Hydrogen sulfide Detection date Detection period content (ppm) 2022 Jun. 15 12:00-14:00 0.09 2022 Jun. 25 12:00-14:00 0.11 2022 Jul. 5 12:00-14:00 0.11 2022 Jul. 15 12:00-14:00 0.10

Comparative Example 1

(23) In the Comparative example 1, the straw was returned to the field by conventional spring puddling, and the implementation time was from the autumn of 2021 to the autumn of 2022. The plot was adjacent to the plot of Embodiment 1, located in Niuxintaobao Reed Field, Da'an City, Jilin Province, with an area of 1 hectare, the soil salinity was the same, the pH was 9.52-9.85, the salt content was 2.31-2.68 g/kg, and the exchangeable sodium percentage (ESP) was 14.2%-23.7%. The specific steps are as follows.

(24) S1: rice harvesting and straw crushing and scattering: the rice was harvested by using a full-feeding harvester combined with crushing and scattering devices. The rice did not lodge, the average stubble height was about 15 cm, the average length of crushed straw was 14 cm, and the qualified rate of straw crushing lengths was 80%. After crushing, the straw was evenly scattered on the ground, and the scattering uniformity was 80%.

(25) S2: application of base fertilizer and quick-acting nitrogen fertilizer: on April 30th, 2022, base fertilizer N:P.sub.2O.sub.5:K.sub.2O=90 kg/ha:100 kg/ha:110 kg/ha was applied according to local production experience, and at the same time, urea was added with 120 kg/ha.

(26) S3: rotary tillage: a 90 horsepower tractor with a rotary tiller was used for rotary tillage, and the operation depth was set to 15 cm.

(27) S4: steeping field: after 2 days of irrigation and steeping, drainage was performed, the soil on the field surface was saturated with water, and the remaining open water area accounted for about 20% of the field surface area.

(28) S5: puddling, leveling and drainage: on May 3, 2022, a 70 horsepower tractor with a puddling machine was used for puddling, and the operation depth was set to 15 cm, and the straw was completely pressed into the mud. The tractor was also equipped with a leveler to even the field surface, and the field surface was observed until the straw was not obviously exposed and the height difference was not more than decimetre, then the mechanical operation was stopped. After the muddy water on the field surface has settled, the drainage outlet of the field was opened and the surface open water of the field surface was drained into the drainage ditch.

(29) As shown in FIG. 2B, the technical effects of the conventional spring puddling method in Comparative example 1 are as follows.

(30) In mid-May, a 50 cm profile was dug before transplanting rice seedings for observation and sampling analysis. It was found that the plough pan did not appear until below 28 cm, and the 0-28 cm cultivation layer was basically uniform and muddy without structure, and the straw decomposition rate was only about 6%. When transplanting rice seedlings, the rice transplanter operated unsteadily, especially in the case of deep ruts under the pressure of the puddling machine, the seedlings were not in lines and not in rows, the missing transplanting rate was about 8%, and the quality of transplanting rice seedlings was poor. The field surface was observed during the peak biogas generation period, mid-June to mid-July, and obvious bubbles were observed, indicating that there was a strong biogas generation. Table 2 shows the measured values of hydrogen sulfide content in the air from mid-June to mid-July, and the average value of four tests is about 0.16 ppm. The yield of rice harvested in autumn is 5946 kg/ha.

(31) TABLE-US-00002 TABLE 2 Hydrogen sulfide content in air from mid-June to mid-July in field of Comparative example 1 Hydrogen sulfide Detection date Detection period content (ppm) 2022 Jun. 15 12:00-14:00 0.14 2022 Jun. 25 12:00-14:00 0.18 2022 Jul. 5 12:00-14:00 0.18 2022 Jul. 15 12:00-14:00 0.15

Embodiment 2

(32) Embodiment 2 was carried out from the autumn of 2022 to the autumn of 2023. The saline-sodic paddy field was located in Niuxintaobao Reed Field, Da'an City, Jilin Province, with an area of 50 hectares. The soil of 0-15 cm cultivation layer was tested and analyzed with the soil-water ratio of 1:5, with the pH of 9.15-9.62, the salt content of 1.73-2.03 g/kg and the exchangeable sodium percentage (ESP) of 12.3%-17.4%. The specific steps are as follows.

(33) S1: rice harvesting with high stubble left and straw crushing and scattering: the rice was harvested by a full-feeding harvester combined with crushing and scattering devices. The rice did not lodge, the average stubble height was about 40 cm, the average length of crushed straw was 15 cm, and the qualified rate of straw crushing lengths was 80%. After crushing, the straw was evenly scattered on the ground, and the scattering uniformity was 80%.

(34) S2: shallow ploughing: a 90 horsepower tractor with a driving disk plough was used for shallow ploughing, with a depth of 15 cm, a leakage ploughing rate of 5% and a re-ploughing rate of 5%.

(35) S3: ridge excavation of water outlet: from November 2 to 5, 2022, a water outlet with a width of about 50 cm was excavated at the ridge position corresponding to the low position where water easily flows between two adjacent fields, and the depth was at a same level with the field surface. The excavated soil was piled on the ridge near the water outlet for later closure of the water outlet.

(36) S4: application of base fertilizer and quick-acting nitrogen fertilizer: on Mar. 20-24, 2023, according to local production experience, base fertilizer N:P.sub.2O.sub.5:K.sub.2O=90 kg/ha:100 kg/ha:110 kg/ha was applied, and at the same time, urea was added with 150 kg/ha.

(37) S5: closing the water outlet of the ridge: the loose soil thawed on the surface near the water outlet of the ridge was excavated, and the water outlet was closed to control the water to stay in the required field.

(38) S6: irrigating for thawing: from March 26th to Apr. 3, 2023, the natural thawed depth of the soil layer reached about 6 cm, the field was irrigated, and the irrigation was stopped until the tops of the slices were submerged, and the field was steeped for 2 hours, the overall thawed depth reached about 12 cm.

(39) S7: stringing water: the water outlet of this field was dug, so that the open water in the field was stringed into the next field, and when the proportion of the open water area in the field surface was reduced to 20%, the water outlet was closed again to stop stringing water, and meanwhile, water was diverted from the water source to irrigate and thaw the next field. The water in the last field of the day's operation was directly discharged from the drainage outlet and did not string into the next field.

(40) S8: wet puddling, leveling and drainage: after the field was irrigated and thawed, a 90 horsepower tractor with a puddling machine was immediately used for wet puddling, and the depth of puddling operation was set to 12 cm, which was consistent with the depth of the thawed layer. At this time, the lower soil was in a frozen state, which may well support the operating machinery. Tractor wheels only made ruts with a depth of 2-3 cm when rolling the frozen soil in the lower layer, and the ruts were repeatedly rolled to form a mud layer with a depth of 2-3 cm, which was matched with 12 cm of puddling by the puddling machine to form a cultivation layer with a depth of about 15 cm. The tractor was also equipped with a leveler to even the field surface, and the field surface was observed until the straw was not obviously exposed and the height difference was not more than decimetre, then the mechanical operation was stopped, and the drainage outlet normally matched with the field was opened to discharge the muddy water on the field surface into the drainage ditch.

(41) S9: reconstruction of cultivation layer soil structure by drying: the field with muddy water drained was dried for 30 days, and criss-crossing cracks appeared on the field surface, and the drying depth of cultivation layer soil from the surface reached 12 cm.

(42) The technical effects achieved by the method of thawing and wet puddling in Embodiment 2 are as follows.

(43) In mid-May, a 50 cm profile was dug before transplanting rice seedings for observation and sampling analysis. It was found that 15 cm below was a solid plough pan, and the 0-15 cm cultivation layer had a good structure of upper paste and lower loose, and the straw decomposition rate reached 32%. When transplanting rice seedlings, the rice transplanter operated smoothly, the seedlings were in lines and in rows, the missing transplanting rate was <1%, and the quality of transplanting rice seedlings was high. The field surface was observed during the peak biogas generation period, mid-June to mid-July, and no significant bubble generation was observed, indicating that no significant biogas occurred during the growing period. Table 3 shows the measured values of hydrogen sulfide content in the air from mid-June to mid-July, and the average value of four tests is about 0.08 ppm. The yield of rice harvested in autumn is 8364 kg/ha.

(44) TABLE-US-00003 TABLE 3 Hydrogen sulfide content in air from mid-June to mid-July in field of Embodiment 2 Hydrogen sulfide Detection date Detection period content (ppm) 2023 Jun. 15 12:00-14:00 0.07 2023 Jun. 25 12:00-14:00 0.08 2023 Jul. 5 12:00-14:00 0.09 2023 Jul. 15 12:00-14:00 0.08

Comparative Example 2

(45) In the Comparative example 2, the straw was returned to the field by conventional spring puddling, and the implementation time was from the autumn of 2022 to the autumn of 2023. The plot was adjacent to the plot of Embodiment 2, located in Niuxintaobao Reed Field, Da'an City, Jilin Province, with an area of 1 hectare, the soil salinity was the same, the pH was 9.15-9.62, the salt content was 1.73-2.03 g/kg, and the exchangeable sodium percentage (ESP) was 12.3%-17.4%. The specific steps are as follows.

(46) S1: rice harvesting and straw crushing and scattering: the rice was harvested by using a full-feeding harvester combined with crushing and scattering devices. The rice did not lodge, the average stubble height was about 15 cm, the average length of crushed straw was 15 cm, and the qualified rate of the straw crushing length was 80%. After crushing, the straw was evenly scattered on the ground, and the scattering uniformity was 80%.

(47) S2: application of base fertilizer and quick-acting nitrogen fertilizer: on Apr. 29, 2023, base fertilizer N:P.sub.2O.sub.5:K.sub.2O=90 kg/ha:100 kg/ha:110 kg/ha was applied according to local production experience, and at the same time, urea was added with 150 kg/ha.

(48) S3: rotary tillage: a 90 horsepower tractor with a rotary tiller was used for rotary tillage, and the operation depth was set to 15 cm.

(49) S4: steeping field: after 2 days of irrigation and steeping, drainage was performed, the soil on the field surface was saturated with water, and the remaining open water area accounted for about 20% of the field surface area.

(50) S5: puddling, leveling and drainage: on May 3, 2023, a 70 horsepower tractor with a puddling machine was used for puddling, and the operation depth was set to 15 cm, and the straw was completely pressed into the mud. The tractor was also equipped with a leveler to even the field surface, and the field surface was observed until the straw was not obviously exposed and the height difference was not more than decimetre, then the mechanical operation was stopped. After the muddy water on the field surface has settled, the drainage outlet of the field was opened and the surface open water of the field surface was drained into the drainage ditch.

(51) The technical effects of the conventional spring puddling method in Comparative example 2 are as follows.

(52) In mid-May, a 50 cm profile was dug before transplanting rice seedings for observation and sampling analysis. It was found that the plough pan appeared at 25 cm, and the 0-25 cm cultivation layer was basically uniform and muddy without structure, and the straw decomposition rate was only about 8%. When transplanting rice seedlings, the rice transplanter operated unsteadily, especially in the case of deep ruts under the pressure of the puddling machine, the seedlings were not in lines and not in rows, the missing transplanting rate was about 5%, and the quality of transplanting rice seedlings was poor. The field surface was observed during the peak biogas generation period, mid-June to mid-July, and obvious bubbles were found, indicating that there was a strong biogas generation. Table 4 shows the measured values of hydrogen sulfide content in the air from mid-June to mid-July, and the average value of four tests is about 0.13 ppm. The yield of rice harvested in autumn is 7361 kg/ha.

(53) TABLE-US-00004 TABLE 4 Hydrogen sulfide content in air from mid-June to mid-July in field of Comparative example 2 Hydrogen sulfide Detection date Detection period content (ppm) 2023 Jun. 15 12:00-14:00 0.12 2023 Jun. 25 12:00-14:00 0.15 2023 Jul. 5 12:00-14:00 0.14 2023 Jul. 15 12:00-14:00 0.12

(54) The implementation results show that the saline-sodic paddy field with pH of 9.15-9.85, salt content of 1.73-2.68 g/kg and an exchangeable sodium percentage (ESP) of 12.3%-23.7% has a good structure of upper paste and lower loose at the 0-15 cm cultivation layer, and the straw decomposition rate may reach 30%-32% before transplanting rice seedlings, the rice transplanter operates smoothly, the seedlings are in lines and in rows, the missing transplanting rate is <1%, the quality of transplanting rice seedlings is high, there is no obvious biogas generation during the growing period, and the rice yield reaches 7367-8364 kg/ha.

(55) The above-mentioned embodiments only describe the preferred mode of the disclosure, and do not limit the scope of the disclosure. Under the premise of not departing from the design spirit of the disclosure, various modifications and improvements made by ordinary technicians in the field to the technical scheme of the disclosure shall fall within the protection scope determined by the claims of the disclosure.