Straw particle returning technology for rapidly increasing soil organic matter

Abstract

The invention discloses a straw particle returning technology capable of rapidly increasing soil organic matters, relates to the technical field of straw returning, solves the problems of slow straw decomposition, poor soil absorption capability, poor soil organic matter increasing effect and the like, and breaks through the technical bottleneck that a large amount of straws are difficult to return to the field due to large volume. The rapid and efficient black soil organic matter improving mechanism and effect based on the straw particle high-amount successive-year field returning technology are determined, and the method comprises the steps that micro-area tests are set, soil related parameters are measured, and the influence of straw particle single-time high-amount field returning and successive-year high-amount field returning on soil is analyzed to assist in determining the optimal field returning scheme. Technical guidance is provided for directional regulation and control of straw carbon mineralization and orientation and rapid and continuous increase of soil organic matter content, after operation of multiple sampling and testing methods is carried out on local soil, the optimal returning mode and returning age limit can be effectively determined in combination with the local actual situation, and the method is suitable for popularization and application. Therefore, the fertility of the soil can be more efficiently guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of returning straw to fields, and in particular to a straw particle returning technology for rapidly increasing soil organic matter. Background Art

[0002] The straw mulching and shallow rotation methods widely used in production mostly have problems such as slow straw decomposition, poor soil absorption capacity, and poor soil organic matter improvement effect. As a result, farmers are faced with the embarrassing situation of "not being able to return the large amount of remaining straw, having nowhere to put it, and not being allowed to burn it" due to the large amount of remaining straw.

[0003] Even if a high amount of straw pellets is returned to the field, although soil organic matter can be increased in the short term, it is difficult to maintain it in the long term, let alone continuously improve it. Therefore, it does not meet the existing needs. We have proposed a straw pellet return technology that can quickly increase soil organic matter. Summary of the Invention

[0004] The purpose of the present invention is to provide a straw pellet return technology that can quickly increase soil organic matter, so as to solve the problems raised in the above background technology that even if a high amount of straw pellet return technology is adopted, although the soil organic matter can be increased in the short term, it is difficult to maintain it in the long term, and it is even more difficult to continuously increase it.

[0005] To achieve the above-mentioned object, the present invention provides the following technical solution: a straw pellet returning technology for rapidly increasing soil organic matter, comprising the following steps:

[0006] First, collect and pre-treat the straw. Collect it immediately after the crop is harvested to avoid nutrient loss due to long-term stacking. Control the moisture content to 15%-20%. Remove impurities from the harvested straw and remove those with serious disease symptoms.

[0007] The straw is pelletized, and the pre-treated straw is crushed into ultra-short fibers of 0.5-1 cm to obtain straw shreds. The moisture content of the straw shreds is monitored again. If the moisture content is lower than 15%, water is sprayed to adjust the moisture content of the straw shreds. Water is sprayed to add moisture to 15%-20%. After the moisture content is confirmed, urea and decomposed manure are added to adjust the carbon-nitrogen ratio. Then, high pressure is applied to compress and granulate the straw to produce fine straw pellets.

[0008] Use the control variable method to carry out multi-mode soil return to the field in the soil area, analyze and compare the results, and obtain the optimal solution for returning the soil to the field;

[0009] Finally, the optimal plan for returning the soil to the field was adopted. Before application, water control operations were performed on the soil area to ensure that the soil moisture was 55%-60%. Straw particles were applied by broadcasting and inoculated with a mixed fungus of Bacillus subtilis and Trichoderma, and then a rotary tiller was used to turn the soil into a 20-25cm layer.

[0010] Preferably, the multi-mode soil return to the field in the controlled variable manner comprises the following steps:

[0011] Micro-plot experiments were conducted, using 13C to label straw. Based on the straw return form, single return, cumulative return, and multiple return rates, experiments were conducted on returning straw pellets to the field in high quantities over several years and returning straw pellets to the field in high quantities over a single time.

[0012] Determine soil moisture and temperature, soil nutrients and soil humus, soil aggregate fraction and organic carbon composition, and soil microbial community composition;

[0013] The effects of single high-amount straw pellet return and continuous high-amount straw pellet return on soil organic carbon content, composition and stability were analyzed, and the relationship between soil organic carbon functional groups, organic carbon mineralization and stimulation effect was obtained. The impact mechanism of continuous high-amount straw pellet return on soil carbon sequestration was clarified, and the optimal return scheme was obtained.

[0014] Preferably, the single high-volume straw pellet return to field experiment is conducted with no straw return to field and full straw pellet return to field at 15t / hm2. 2 , return twice the amount of straw pellets to the field, 30t / hm 2 3 times the amount of straw pellets returned to the field (45t / hm2) 2 , return 4 times the amount of straw pellets to the field (60t / hm2) 2 and straw pellets in 5 times the amount returned to the field (75t / hm2) 2 The experimental design was repeated four times in a randomized block experiment. The area of ​​a single random block was 16m 2 The straw pellet return treatment was to bury the returned material to a depth of 20-25 cm in the soil layer. After the straw pellets were applied once, no more straw was returned to the field during the experiment. The purpose was to explore the organic carbon residue 1 to 3 years after a single high-amount straw pellet return.

[0015] Preferably, the straw pellets were returned to the field in high quantities for consecutive years with a 5-fold amount of 75t / hm2. 2 For the experimental treatment, the straw was not returned to the field, and the straw was crushed and returned to the field at a rate of 15t / hm2. 2 Crush 5 times the amount of straw and return it to the field 75t / hm 2 For the control, the randomized block experiment was designed with four replicates and the area of ​​a single random block was 16m 2The straw pellet and straw crushing return to the field treatment is to bury the returned materials to a depth of 20-25cm in the soil layer, and explore the organic carbon accumulation effect of returning straw pellets to the field in high quantities for 1 to 6 years.

[0016] Preferably, the soil moisture and temperature are measured using a hydrothermal salt sensor to record soil moisture and temperature data every 2 hours, and the buried positions are 5 cm, 10 cm, 20 cm, 30 cm, 40 cm, 50 cm, 60 cm, 80 cm, and 100 cm from the ground surface, respectively.

[0017] Preferably, the soil nutrients and soil humus are determined by taking soil samples of 0-20 cm, 20-40 cm, 40-60 cm, 60-80 cm, and 80-100 cm three times in each plot using a stainless steel soil drill according to the diagonal method. The same soil layer is mixed evenly as a repeated sample. The soil sample is air-dried and passed through a 1 mm sieve to determine the total amount and effective amount of soil organic carbon, nitrogen, phosphorus, and potassium, as well as the content of each component of soil humus.

[0018] Preferably, soil organic carbon and total nitrogen are determined by elemental analyzer combustion method, total phosphorus is determined by NaOH fusion-molybdenum antimony scandium colorimetry, total potassium and available potassium are determined by flame photometry, available nitrogen is determined by alkaline diffusion method, and available phosphorus is determined by molybdenum antimony scandium colorimetry.

[0019] Preferably, soil humus includes humin organic carbon, humic acid carbon and fulvic acid carbon. Humin organic carbon is measured by potassium dichromate external heating method, humic acid carbon and fulvic acid carbon are measured by TOC-VCPH instrument, and the humin ratio and PQ value are calculated based on the measured values. The PQ value characterizes the change in the degree of soil humification after straw return to the field. The calculation formula of the PQ value is:

[0020] PQ = (HA-C) / (HA-C+FA-C);

[0021] Among them, HA-C is humic acid carbon, FA-C is fulvic acid carbon, Hu-C is humin organic carbon, PQ is the ratio of humic acid to extractable humic acid, and the Hu-to-Fullic Acid ratio is HA-C / FA-C.

[0022] Preferably, the soil aggregate classification and organic carbon component determination comprises the following steps:

[0023] S1: Place 60g of soil sample on a 2000μm sieve and soak in distilled water at room temperature for 5 minutes. Use an automated aggregate sieving machine to vibrate the sieve up and down with an amplitude of 3cm and a frequency of 50 times within 2 minutes. After vibration, collect the soil particles remaining on the sieve, which are considered aggregates >2000μm.

[0024] S2: The remaining soil sample solution is passed through a 250 μm sieve and shaken in the same manner to obtain 2000–250 μm particle size aggregates;

[0025] S3: Repeat step S2, and continue to pass the remaining soil sample solution through a 53 μm sieve to obtain 250–53 μm particle size aggregates. The remaining soil sample solution is centrifuged for 30 min to obtain fine clay particles <53 μm.

[0026] S4: Through classification, the soil was separated into four types of water-stable aggregates, namely coarse aggregates > 2000 μm, fine aggregates 2000–250 μm, microaggregates 250–53 μm and clay particles < 53 μm;

[0027] S5: All particle-sized aggregates were dried at 60°C for analysis of aggregate-bound organic carbon and particulate organic carbon components;

[0028] S6: Coarse and fine aggregates are further separated into free particulate organic matter fPOM, occluded particulate organic matter iPOM and mineral-bound organic matter mSOM;

[0029] S7: The organic carbon content in the whole soil, aggregates and particulate organic matter components was determined by wet oxidation-reduction titration. The soil active organic carbon content was determined by 333mmolL-1KMnO4 oxidation method, and the particle composition in aggregates was determined by pipette method.

[0030] S8: Calculate the soil oxidation stability coefficient Kos and the soil aggregate stability evaluation index. The stability of the aggregates is evaluated by the average weight value MWD, geometric mean diameter GMD and the content of aggregates larger than 0.25 mm R 0.25 .

[0031] Preferably, the calculation formula of soil oxidation stability coefficient Kos is:

[0032] Kos = (total organic carbon - easily oxidizable organic carbon) / easily oxidizable organic carbon;

[0033] The stability of aggregates is calculated using the mean weight value MWD:

[0034]

[0035] The calculation formula of geometric mean diameter GMD is:

[0036]

[0037] The calculation formula for the content of aggregates larger than 0.25 mm, R0.25, is:

[0038]

[0039] where x i is the average diameter of aggregates of particle size i, w i is the proportion of the weight of the i-size aggregates, m i is the weight of soil aggregates of different particle sizes, M T is the total weight of the aggregates.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The present invention clarifies the response of soil organic matter changes to the continuous high-increase straw pellet return to the field, explores its mechanism, and provides technical guidance and theoretical support for the targeted regulation of straw carbon mineralization and fate, and the rapid and continuous improvement of soil organic matter content. After multiple sampling and testing methods are carried out on local soil, the optimal method and period of return to the field can be effectively determined based on the actual local conditions, which can more efficiently ensure the fertility of the soil.

[0042] The pretreated straw is crushed into ultra-short fibers of 0.5-1 cm to obtain straw fragments. With appropriate moisture content and high pressure, the obtained straw pellets are smaller and denser than those in the existing technology, which solves the problem that straw is difficult to return to the field due to its large quantity and size. When returning the straw pellets to the field, the soil moisture is maintained before application, and a mixed bacterial agent of Bacillus subtilis and Trichoderma is added. After subsequent tillage, the decomposition effect of the straw pellets can be effectively accelerated. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The graph is the characteristic curve of nutrient release of straw under different treatments;

[0044] Figure 2 Soil organic carbon in the sub-arable layer under different treatments 13 C NMR spectrum. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0046] See also Figures 1 to 2 The present invention provides an embodiment of a straw particle returning technology for rapidly increasing soil organic matter, comprising the following steps:

[0047] First, collect and pre-treat the straw. Collect it immediately after the crop is harvested to avoid nutrient loss due to long-term stacking. Control the moisture content to 15%-20%. Remove impurities from the harvested straw and remove those with serious disease symptoms.

[0048] The straw is pelletized, and the pre-treated straw is crushed into ultra-short fibers of 0.5-1 cm to obtain straw shreds. The moisture content of the straw shreds is monitored again. If the moisture content is lower than 15%, water is sprayed to adjust the moisture content of the straw shreds. Water is sprayed to add moisture to 15%-20%. After the moisture content is confirmed, urea and decomposed manure are added to adjust the carbon-nitrogen ratio. Then, high pressure is applied to compress and granulate the straw to produce fine straw pellets.

[0049] Use the control variable method to carry out multi-mode soil return to the field in the soil area, analyze and compare the results, and obtain the optimal solution for returning the soil to the field;

[0050] Finally, the optimal plan for returning the soil to the field was adopted. Before application, the soil area was water-controlled to ensure that the soil moisture was 55%-60%. The straw pellets were applied by broadcasting and inoculated with a mixed inoculum of Bacillus subtilis and Trichoderma. A rotary tiller was then used to turn the soil into a 20-25 cm layer to complete the return to the field.

[0051] The above-mentioned control variable method is used to return soil to the field in multiple modes, including:

[0052] Micro-plot experiments were conducted, using 13C to label straw. Based on the straw return form, single return, cumulative return, and multiple return rates, experiments were conducted on returning straw pellets to the field in high quantities over several years and returning straw pellets to the field in high quantities over a single time.

[0053] Determine soil moisture and temperature, soil nutrients and soil humus, soil aggregate fraction and organic carbon composition, and soil microbial community composition;

[0054] Soil moisture and temperature were measured using hydrothermal salt sensors, which recorded soil moisture and temperature data every 2 hours. The sensors were buried at 5 cm, 10 cm, 20 cm, 30 cm, 40 cm, 50 cm, 60 cm, 80 cm, and 100 cm from the ground surface.

[0055] Soil nutrients and soil humus were determined in each plot using a stainless steel soil drill using the diagonal method. Soil samples were collected three times from 0-20 cm, 20-40 cm, 40-60 cm, 60-80 cm, and 80-100 cm. The same soil layer was mixed evenly and used as a replicate sample. The soil samples were air-dried and passed through a 1 mm sieve for determination of the total and effective amounts of soil organic carbon, nitrogen, phosphorus, and potassium, as well as the content of each component of soil humus.

[0056] Soil organic carbon and total nitrogen were determined by elemental analyzer combustion method, total phosphorus was determined by NaOH fusion-molybdenum antimony scandium colorimetry, total potassium and available potassium were determined by flame photometry, available nitrogen was determined by alkaline diffusion method, and available phosphorus was determined by molybdenum antimony scandium colorimetry.

[0057] Soil humus includes humin organic carbon, humic acid carbon and fulvic acid carbon. Humin organic carbon is determined by potassium dichromate external heating method, and humic acid carbon and fulvic acid carbon are determined by TOC-VCPH instrument. Humin organic carbon and fulvic acid carbon are calculated based on the measured values. The PQ value represents the change in the degree of soil humification after straw return. The calculation formula of PQ value is:

[0058] PQ = (HA-C) / (HA-C+FA-C);

[0059] Where HA-C is humic acid carbon, FA-C is fulvic acid carbon, Hu-C is humin organic carbon, PQ is the ratio of humic acid to extractable humic acid, and the Hu-to-Full ratio is HA-C / FA-C.

[0060] Soil aggregate classification and organic carbon component determination include the following steps:

[0061] S1: Place 60g of soil sample on a 2000μm sieve and soak in distilled water at room temperature for 5 minutes. Use an automated aggregate sieving machine to vibrate the sieve up and down with an amplitude of 3cm and a frequency of 50 times within 2 minutes. After vibration, collect the soil particles remaining on the sieve, which are considered aggregates >2000μm.

[0062] S2: The remaining soil sample solution is passed through a 250 μm sieve and shaken in the same manner to obtain 2000–250 μm particle size aggregates;

[0063] S3: Repeat step S2, and continue to pass the remaining soil sample solution through a 53 μm sieve to obtain 250–53 μm particle size aggregates. The remaining soil sample solution is centrifuged for 30 min to obtain fine clay particles <53 μm.

[0064] S4: Through classification, the soil was separated into four types of water-stable aggregates, namely coarse aggregates > 2000 μm, fine aggregates 2000–250 μm, microaggregates 250–53 μm and clay particles < 53 μm;

[0065] S5: All particle-sized aggregates were dried at 60°C for analysis of aggregate-bound organic carbon and particulate organic carbon components;

[0066] S6: Coarse and fine aggregates are further separated into free particulate organic matter fPOM, occluded particulate organic matter iPOM and mineral-bound organic matter mSOM;

[0067] S7: The organic carbon content in the whole soil, aggregates and particulate organic matter components was determined by wet oxidation-reduction titration. The soil active organic carbon content was determined by 333mmolL-1KMnO4 oxidation method, and the particle composition in aggregates was determined by pipette method.

[0068] S8: Calculate the soil oxidation stability coefficient Kos and the soil aggregate stability evaluation index. The stability of the aggregates is evaluated by the average weight value MWD, geometric mean diameter GMD and the content of aggregates larger than 0.25 mm R 0.25 ;

[0069] The calculation formula of soil oxidation stability coefficient Kos is:

[0070] Kos = (total organic carbon - easily oxidizable organic carbon) / easily oxidizable organic carbon;

[0071] The stability of aggregates is calculated using the mean weight value MWD:

[0072]

[0073] The calculation formula of geometric mean diameter GMD is:

[0074]

[0075] The calculation formula for the content of aggregates larger than 0.25 mm, R0.25, is:

[0076]

[0077] where x i is the average diameter of aggregates of particle size i, w i is the proportion of the weight of the i-size aggregates, m i is the weight of soil aggregates of different particle sizes, M T is the total weight of the aggregates;

[0078] To determine soil microbial community composition, field soil samples (0-40 cm thick) were collected using sterile bags during corn harvest each year to measure bacterial and fungal community diversity. Total DNA was extracted from 0.5 g of fresh soil samples, and DNA concentration and quality were determined using a Nanodrop™ 2000 spectrophotometer and 1% agarose gel electrophoresis, respectively. For bacterial high-throughput sequencing, the 16S rRNA V3–V4 region was selected using PCR amplification primers 338F (5'-ACTCCTACGGGAGGCAGCAG-3') and 806R (5'-GGACTACHVGGGTWTCTAAT-3'). The amplification system volume is 20 μl: 4 μl of 5×FastPfu buffer, 2 μl of 2.5 mM dNTPs, 0.8 μl of each primer (5 μM), 10 ng of DNA template and 0.4 μl of FastPfu polymerase. Amplification procedure (PCR instrument: 9700) was as follows: pre-denaturation for 3 min (95°C), 27 cycles (denaturation for 30 s (95°C), annealing for 30 s (55°C), extension for 30 s (72°C)), followed by extension for 10 min (72°C);

[0079] Illumina Miseq high-throughput sequencing: PCR products were recovered on 2% agarose gels and purified using the AxyPrep DNA Gel Extraction Kit (Axygen Biosciences, Union City, CA, USA), followed by elution with Tris-HCl. Product quality was assessed by 2% agarose gel electrophoresis, and product quantification was performed using a Quantus™ Fluorometer (Promega, USA). A PE*300 library was constructed from the purified amplified fragments according to the standard operating procedures of the Illumina Miseq platform (Illumina, San Diego, USA). The construction steps were as follows: 1. ligation of Y-shaped adapters; 2. removal of adapter self-ligated fragments using magnetic bead screening; 3. enrichment of the library template by PCR amplification; and 4. denaturation with sodium hydroxide to generate single-stranded DNA fragments. High-throughput sequencing was performed using the Illumina MiSeq PE300 platform.

[0080] The effects of single high-amount straw pellet return and continuous high-amount straw pellet return on soil organic carbon content, composition and stability were analyzed, and the relationship between soil organic carbon functional groups, organic carbon mineralization and stimulation effect was obtained. The impact mechanism of continuous high-amount straw pellet return on soil carbon sequestration was clarified, and the optimal return scheme was obtained.

[0081] The present invention crushes pre-treated straw into ultra-short fibers of 0.5-1 cm in the field to obtain straw shreds, and with appropriate moisture content and high pressure, the resulting straw pellets are reduced in volume to 1 / 10-1 / 15 and increased in density by 7-10 times, thus solving the problem of straw being difficult to return to the field due to its large quantity and bulk.

[0082] According to the method of returning straw to the field proposed in this application, a field positioning test study on a high-amount single return of straw pellets to the field was carried out in the main grain-producing areas in northern my country. Preliminary studies found that even if the single return amount of straw pellets was as high as 5t / mu, the soil organic matter content showed a parabolic curve characteristic of first increasing and then decreasing with the increase in the return years, that is: compared with not returning straw to the field, the high-amount straw pellet return to the field increased the soil organic matter content in 1-3 years, but the soil organic matter content increased within 1-2 years after return, and began to decline after the third year.

[0083] The single high-volume straw pellet return experiment was conducted with no straw return and full straw pellet return at a rate of 15t / hm2. 2, return twice the amount of straw pellets to the field, 30t / hm 2 3 times the amount of straw pellets returned to the field (45t / hm2) 2 , return 4 times the amount of straw pellets to the field (60t / hm2) 2 and straw pellets in 5 times the amount returned to the field (75t / hm2) 2 The experimental design was repeated four times in a randomized block experiment. The area of ​​a single random block was 16m 2 The straw pellet return treatment was to bury the returned material to a depth of 20-25 cm in the soil layer. After the straw pellets were applied once, no more straw was returned to the field during the experiment. The purpose was to explore the organic carbon residue 1 to 3 years after a single high-amount straw pellet return.

[0084] The high-intake straw pellet return experiment for consecutive years was 5 times the amount returned to the field, 75t / hm 2 For the experimental treatment, the straw was not returned to the field, and the straw was crushed and returned to the field at a rate of 15t / hm2. 2 Crush 5 times the amount of straw and return it to the field 75t / hm 2 For the control, the randomized block experiment was designed with four replicates and the area of ​​a single random block was 16m 2 The straw pellet and straw crushing return to the field treatment is to bury the returned materials to a depth of 20-25cm in the soil layer, and explore the organic carbon accumulation effect of returning straw pellets to the field in high quantities for 1 to 6 years.

[0085] Experiment on high-dose return of isotope 13C-labeled straw particles to fields:

[0086] Setting up a micro-plot experiment: In order to reveal the soil carbon sequestration mechanism under the continuous straw pelletization and high-amount return to the field mode, a micro-plot experiment was set up on the basis of the field experiment. 1m2 was selected for each plot and separated by PVC pipes; corn was continuously fed with isotope 13CO2 gas, and the obtained straw was collected and the isotope 13C abundance was measured. Part of the obtained labeled straw was pelletized and the other part was crushed (completely consistent with the pelletized straw and crushed straw in the field state). The labeled straw was put into the micro-plot, and the contribution of straw carbon input to soil organic carbon accumulation was calculated based on the changes in soil isotope abundance, and the conversion rate of straw carbon to soil carbon under different straw return modes was compared.

[0087] An indoor incubation experiment was conducted: soil samples from different treatments were placed in incubation bottles at a constant temperature (25°C) for 90 days. A small beaker containing sodium hydroxide solution was placed inside the incubation bottle to collect the released CO2 gas, and the absorbed CO2 was calculated by hydrochloric acid back titration. Destructive sampling was also performed during the incubation process to determine changes in soil available nitrogen, phosphorus, and potassium. Under indoor incubation conditions, 13C-labeled straw (including pulverized straw and pelletized straw) was exogenously added. CO2 release was measured using the same method described above, and the isotopic abundance of BaCO3 precipitates was determined using an ANCA-IRMS mass spectrometer to calculate the stimulatory effect of straw addition on soil organic carbon mineralization. During the mineralization incubation, soil mineral nitrogen was determined using a flow analyzer, available phosphorus was determined using the sodium hydroxide method, and available potassium was determined using flame photometry.

[0088] Through indoor potted cultivation experiments, the decomposition and nutrient release characteristics of straw were preliminarily explored, such as Figure 1 As shown, returning pelletized straw to the field significantly increased straw decomposition rates. After 300 days of cultivation, the cumulative decomposition rate reached 80.81%, 8.7 percentage points higher than the control. Returning pelletized straw to the field also increased the rate of nutrient release from the straw, with the cumulative carbon and nitrogen release rates of straw pellets 11.0 and 13.2 percentage points higher than the control, respectively.

[0089] The preliminary evaluation of soil fertility quality of high-amount straw return is shown in Table 1. Through the study of straw deep burial in the field, it is found that in the first year T1 (6thm -2 )、T2(12thm -2 ) and T3(18th -2 ) The soil fertility quality scores were all positive, indicating that the soil fertility was on the rise; in the second year, the soil fertility quality score of T1 was negative, while that of T2 and T3 treatments was positive and higher than that of the first year, indicating that the improvement of soil fertility under T1 treatment began to decrease, and T2 and T3 treatments could still significantly improve the subsurface soil fertility due to the high amount of straw returned to the field; in the third year, the soil fertility quality scores of T1, T2 and T3 treatments were all lower than that of the second year, indicating that their improvement of soil fertility began to decrease.

[0090] The final conclusion shows that returning a high amount of straw to the fields can maintain high soil fertility for 2-3 consecutive years, but in order to maintain a continuous and effective improvement in soil fertility quality, straw should be returned to the fields again after 3 years.

[0091] Table 1 Factor scores and soil fertility comprehensive score

[0092]

[0093] like Figure 2As shown in the results, field experiments in the black soil region of Northeast China have preliminarily explored the effects of returning straw in different forms and at different times to the sub-arable layer. The study found that returning straw in different forms can significantly increase soil organic carbon (SOC), soluble organic carbon (SOC) and microbial biomass carbon (MBC) in the sub-arable layer. Returning straw pellets to the field has the effect of rapidly and significantly increasing soil organic carbon content and its accumulation rate, and coordinating nutrient ratios. High-amount straw return significantly increases SOC, C / N, C / P and C / K, and balances the ratio of C to N, P and K elements in the soil. High-amount straw return can also promote the increase in the content of soil humus components. Among them, high-amount straw pellet return can increase the aroma of humus, form more unstable organic carbon, and is more conducive to maintaining ecosystem stability in the long term.

[0094] As shown in Table 2, below, a preliminary study of the effects of high-intake straw incorporation on microbial community structure in the black soil region of Northeast China found that high-intake straw incorporation significantly improved soil physical and chemical properties, leading to differences in the distribution of microbial communities. High-intake pulverized straw significantly increased soil total phospholipid fatty acid content and fungal abundance, with increases of up to 71.0% and 120.5%, respectively, compared to the control. High-intake straw pellet incorporation had an even more significant effect on the increase in bacterial, Gram-positive, and Gram-negative bacteria, with increases of up to 41.6%, 29.7%, and 26.3%, respectively.

[0095] Table 2 Changes in total PLFA in sub-cultivated soil and PLFA of each bacterial community under different treatments

[0096]

[0097] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

Claims

1. A straw pellet returning technology for rapidly increasing soil organic matter, characterized in that: The steps include: First, collect and pre-treat the straw. Collect it immediately after the crop is harvested to avoid nutrient loss due to long-term stacking. Control the moisture content to 15%-20%. Remove impurities from the harvested straw and remove those with serious disease symptoms. The straw is pelletized, and the pre-treated straw is crushed into ultra-short fibers of 0.5-1 cm to obtain straw shreds. The moisture content of the straw shreds is monitored again. If the moisture content is lower than 15%, water is sprayed to adjust the moisture content of the straw shreds. Water is sprayed to add moisture to 15%-20%. After the moisture content is confirmed, urea and decomposed manure are added to adjust the carbon-nitrogen ratio. Then, high pressure is applied to compress and granulate the straw to produce fine straw pellets. Use the control variable method to carry out multi-mode soil return to the field in the soil area, analyze and compare the results, and obtain the optimal solution for returning the soil to the field; Finally, the optimal plan for returning the soil to the field was adopted. Before application, water control operations were performed on the soil area to ensure that the soil moisture was 55%-60%. Straw particles were applied by broadcasting and inoculated with a mixed fungus of Bacillus subtilis and Trichoderma, and then a rotary tiller was used to turn the soil into a 20-25cm layer.

2. The straw pellet returning technology for rapidly increasing soil organic matter according to claim 1 is characterized by: The multi-mode soil return method for a soil area by controlling variables includes the following steps: Micro-plot experiments were conducted, using 13C to label straw. Based on the straw return form, single return, cumulative return, and multiple return rates, experiments were conducted on returning straw pellets to the field in high quantities over several years and returning straw pellets to the field in high quantities over a single time. Determine soil moisture and temperature, soil nutrients and soil humus, soil aggregate fraction and organic carbon composition, and soil microbial community composition; The effects of single high-amount straw pellet return and continuous high-amount straw pellet return on soil organic carbon content, composition and stability were analyzed, and the relationship between soil organic carbon functional groups, organic carbon mineralization and stimulation effect was obtained. The effect of continuous high-amount straw pellet return on soil carbon sequestration was clarified, and the optimal return scheme was obtained.

3. The straw pellet returning technology for rapidly increasing soil organic matter according to claim 2 is characterized by: The single high-volume straw pellet return experiment was conducted with no straw return and full straw pellet return at a rate of 15 t / hm2. 2 2. Return twice the amount of straw pellets to the field (30t / hm2) 2 3 times the amount of straw pellets returned to the field (45t / hm2) 2 , return 4 times the amount of straw pellets to the field (60t / hm2) 2 and straw pellets in 5 times the amount returned to the field 75t / hm 2 The experimental design was repeated four times in a randomized block experiment. The area of ​​a single random block was 16m 2 The straw pellet return treatment was to bury the returned material to a depth of 20-25 cm in the soil layer. After the straw pellets were applied once, no more straw was returned to the field during the experiment. The purpose was to explore the organic carbon residue 1 to 3 years after a single high-amount straw pellet return.

4. The straw pellet returning technology for rapidly increasing soil organic matter according to claim 3 is characterized by: The experiment of returning straw pellets to the fields in high quantities for consecutive years was conducted with 5 times the amount of straw pellets returned to the fields (75t / hm2). 2 For the experimental treatment, the straw was not returned to the field, and the straw was crushed and returned to the field at a rate of 15t / hm2. 2 Crush 5 times the amount of straw and return it to the field 75t / hm 2 For the control, the randomized block experiment was designed with four replicates and the area of ​​a single random block was 16m 2 The straw pellet and straw crushing return to the field treatment is to bury the returned materials to a depth of 20-25cm in the soil layer, and explore the organic carbon accumulation effect of returning straw pellets to the field in high quantities for 1 to 6 years.

5. The straw pellet returning technology for rapidly increasing soil organic matter according to claim 4 is characterized by: The soil moisture and temperature are measured using a hydrothermal salt sensor to record soil moisture and temperature data every 2 hours, and the buried positions are 5 cm, 10 cm, 20 cm, 30 cm, 40 cm, 50 cm, 60 cm, 80 cm, and 100 cm from the ground surface.

6. The straw pellet returning technology for rapidly increasing soil organic matter according to claim 5 is characterized by: The soil nutrients and soil humus were determined by taking soil samples at 0-20 cm, 20-40 cm, 40-60 cm, 60-80 cm, and 80-100 cm three times in each plot using a stainless steel soil drill according to the diagonal method. The same soil layer was mixed evenly and used as a repeated sample. The soil samples were air-dried and passed through a 1 mm sieve to determine the total amount and effective amount of soil organic carbon, nitrogen, phosphorus, and potassium, as well as the content of each component of soil humus.

7. The straw pellet returning technology for rapidly increasing soil organic matter according to claim 6 is characterized by: Soil organic carbon and total nitrogen were determined by elemental analyzer combustion method, total phosphorus was determined by NaOH fusion-molybdenum antimony scandium colorimetric method, total potassium and available potassium were determined by flame photometer method, available nitrogen was determined by alkaline diffusion method, and available phosphorus was determined by molybdenum antimony scandium colorimetric method.

8. The straw pellet returning technology for rapidly increasing soil organic matter according to claim 2 is characterized by: Soil humus includes humin organic carbon, humic acid carbon and fulvic acid carbon. Humin organic carbon is determined by potassium dichromate external heating method, and humic acid carbon and fulvic acid carbon are determined by TOC-VCPH instrument. Humin organic carbon and fulvic acid carbon are calculated based on the measured values. The PQ value represents the change in the degree of soil humification after straw return. The calculation formula of PQ value is: PQ = (HA-C) / (HA-C+FA-C); Among them, HA-C is humic acid carbon, FA-C is fulvic acid carbon, Hu-C is humin organic carbon, PQ is the ratio of humic acid to extractable humic acid, and the Hu-to-Fullic Acid ratio is HA-C / FA-C.

9. The straw pellet returning technology for rapidly increasing soil organic matter according to claim 2 is characterized by: The soil aggregate classification and organic carbon component determination include the following steps: S1: Place 60g of soil sample on a 2000μm sieve and soak in distilled water at room temperature for 5 minutes. Use an automated aggregate sieving machine to vibrate the sieve up and down with an amplitude of 3cm and a frequency of 50 times within 2 minutes. After vibration, collect the soil particles remaining on the sieve, which are considered aggregates >2000μm. S2: The remaining soil sample solution is passed through a 250 μm sieve and shaken in the same manner to obtain 2000–250 μm particle size aggregates; S3: Repeat step S2, and continue to pass the remaining soil sample solution through a 53 μm sieve to obtain 250–53 μm particle size aggregates. The remaining soil sample solution is centrifuged for 30 min to obtain fine clay particles <53 μm. S4: Through classification, the soil was separated into four types of water-stable aggregates, namely coarse aggregates > 2000 μm, fine aggregates 2000–250 μm, microaggregates 250–53 μm and clay particles < 53 μm; S5: All particle-sized aggregates were dried at 60°C for analysis of aggregate-bound organic carbon and particulate organic carbon components; S6: Coarse and fine aggregates are further separated into free particulate organic matter fPOM, occluded particulate organic matter iPOM and mineral-bound organic matter mSOM; S7: The organic carbon content in the whole soil, aggregates and particulate organic matter components was determined by wet oxidation-reduction titration. The soil active organic carbon content was determined by 333mmolL-1KMnO4 oxidation method, and the particle composition in aggregates was determined by pipette method. S8: Calculate the soil oxidation stability coefficient Kos and the soil aggregate stability evaluation index. The stability of the aggregates is evaluated by the average weight value MWD, geometric mean diameter GMD and the content of aggregates larger than 0.25 mm R 0.25 .

10. The straw pellet returning technology for rapidly increasing soil organic matter according to claim 1 is characterized by: The calculation formula of soil oxidation stability coefficient Kos is: Kos = (total organic carbon - easily oxidizable organic carbon) / easily oxidizable organic carbon; The stability of aggregates is calculated using the mean weight value MWD: The calculation formula of geometric mean diameter GMD is: The calculation formula for the content of aggregates larger than 0.25 mm, R0.25, is: where x i is the average diameter of aggregates of particle size i, w i is the proportion of the weight of the i-size aggregates, m i is the weight of soil aggregates of different particle sizes, M T is the total weight of the aggregates.

Images