A method for safe application of biogas slurry

Abstract

This application relates to the field of biogas slurry agricultural application technology and discloses a safe application method for biogas slurry, including: determining the target crop type and target soil properties of the application area for which biogas slurry is to be applied; determining the concentrations of target harmful factors and the maximum harmful factor in the biogas slurry corresponding to the target crop type and target soil properties according to preset biogas slurry application standards; determining the initial harmful factor concentration of the target harmful factor in the biogas slurry to be applied; and diluting the biogas slurry to be applied to dilute the initial harmful factor concentration to below the maximum harmful factor concentration before application. Before applying biogas slurry, this application prepares biogas slurry of different concentrations based on factors such as soil properties, the initial harmful factor concentration of the biogas slurry to be applied, and crop type, thereby diluting the initial harmful factor concentration in the biogas slurry to be applied to below the maximum harmful factor concentration, effectively avoiding inhibitory effects on crops, improving the effectiveness of biogas slurry as an organic fertilizer to replace chemical fertilizers, and reducing resource waste.

Description

Technical Field

[0001] This application relates to the field of biogas slurry agricultural application technology, and in particular to a safe method for applying biogas slurry. Background Technology

[0002] In recent years, with the rapid development of large-scale livestock and poultry farming in my country, the output of livestock and poultry manure has increased year by year, requiring harmless treatment through anaerobic fermentation to avoid environmental pollution caused by direct discharge. After anaerobic fermentation, the gaseous product of livestock and poultry manure is biogas, which can be used as a clean energy source for power generation and heating; the liquid product is biogas slurry, which is rich in a large number of nutrients (N, P, K) required by crops and can be used as organic fertilizer to replace chemical fertilizers, thereby improving crop quality and yield while reducing the use of chemical fertilizers.

[0003] Because soil properties and biogas slurry composition vary from region to region, applying biogas slurry at the same concentration in different regions greatly limits its effectiveness as an organic fertilizer to replace chemical fertilizer, resulting in a waste of resources.

[0004] Therefore, how to improve the effectiveness of biogas slurry as an organic fertilizer to replace chemical fertilizer and reduce resource waste is a problem that needs to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this application is to provide a safe method for applying biogas slurry, which can improve the effectiveness of biogas slurry as an organic fertilizer to replace chemical fertilizer and reduce resource waste.

[0006] To address the aforementioned technical problems, this application provides a method for the safe application of biogas slurry, comprising:

[0007] Determine the target crop species and target soil properties of the application area for the biogas slurry;

[0008] The target harmful factors and the maximum harmful factor concentration in the biogas slurry corresponding to the target crop type and the target soil property are determined according to the preset biogas slurry application standard; wherein, the preset biogas slurry application standard includes the correspondence between crop type, soil property, harmful factor and maximum harmful factor concentration;

[0009] Determine the initial concentration of the target harmful factor in the biogas slurry to be applied. If the initial concentration of the harmful factor is greater than the maximum concentration of the target harmful factor, dilute the biogas slurry to be applied to reduce the initial concentration of the harmful factor to less than the maximum concentration of the target harmful factor before applying the biogas slurry.

[0010] Optionally, before determining the target harmful factor in the biogas slurry corresponding to the target crop type and the target soil property, and the concentration of the target maximum harmful factor corresponding to the target harmful factor, based on the preset biogas slurry application standard, the method further includes:

[0011] Biogas slurry samples were selected from different regions, and the composition of the biogas slurry samples was determined;

[0012] Pot experiments were used to determine the effects of each of the components on crops under different soil properties, and the components that produced inhibitory effects were identified as preliminary causative agents.

[0013] Field experiments were used to determine the effects of each of the preliminary harmful factors on crops under different soil properties, and the preliminary harmful factors that produced inhibitory effects were taken as the final harmful factors.

[0014] The maximum concentration of the ultimate harmful factor applied to crops in different soil properties is determined based on the crop impact indicators.

[0015] Based on the maximum harmful factor concentration corresponding to the ultimate harmful factor, the soil properties corresponding to the maximum harmful factor concentration, and the crop type corresponding to the maximum harmful factor concentration, a preset biogas slurry application standard is established, which includes the correspondence between the crop type, the soil properties, the harmful factor, and the maximum harmful factor concentration.

[0016] Optionally, before determining the effects of each of the components on crops under different soil properties using pot experiments, and before identifying the components that produce inhibitory effects as preliminary harmful factors, the method further includes:

[0017] Determine the proportion of each of the aforementioned components in the biogas slurry sample;

[0018] Components whose proportions are greater than a preset proportion are selected.

[0019] Optionally, the maximum concentration of the final harmful factor applied to the crop in different soil properties is determined based on crop impact indicators, including:

[0020] The impact indicators of crops treated with biogas slurry containing different concentrations of the final harmful factor were determined separately.

[0021] The degree of influence corresponding to each of the aforementioned influencing indicators is determined according to the evaluation criteria for crop growth inhibition; wherein, the evaluation criteria include the correspondence between the influencing indicators and the degree of influence;

[0022] The concentration corresponding to the degree of impact of the target is taken as the concentration of the most harmful factor.

[0023] Optionally, pot experiments are used to determine the effects of each of the components on crops under different soil properties, and the components that produce an inhibitory effect are taken as preliminary harmful factors, including:

[0024] Determine the average concentration of each component in the biogas slurry sample, and set a concentration range based on the average concentration;

[0025] Prepare solutions corresponding to each component; wherein each solution includes solutions of different concentrations, and each concentration of each solution is within the corresponding concentration range;

[0026] Different concentrations of the solution were applied to test pots, and the soil properties, crop types, components and concentrations of the applied solution, and crop impact indicators were recorded for each test pot.

[0027] Based on the aforementioned impact indicators, target solutions that inhibit crop growth in different soil properties are determined, and the target components corresponding to the target solutions are used as the preliminary causative factors.

[0028] Optionally, pot experiments are used to determine the effects of each of the components on crops under different soil properties, and the components that produce an inhibitory effect are taken as preliminary harmful factors, including:

[0029] Determine the average concentration of each component in the biogas slurry sample, and set a concentration range based on the average concentration;

[0030] The biogas slurry is modified to obtain multiple sets of modified biogas slurry; wherein the target components set in the modified biogas slurry in different sets are different, the target components set in each modified biogas slurry in the same set are the same, the concentrations of the target components in different modified biogas slurries in the same set are different, and the concentrations of each target component are all within the corresponding concentration range, and the concentrations of the other components except the target component are the same in different modified biogas slurries in the same set;

[0031] Each of the prepared biogas slurries was applied to a test pot, and the soil properties, crop types, target components and concentrations of the applied prepared biogas slurry, and crop impact indicators were recorded for each test pot.

[0032] Based on the aforementioned impact indicators, the target components that inhibit crop growth in different soil properties are identified as the preliminary harmful factors.

[0033] Optionally, the step of using field trials to determine the effects of each of the preliminary harmful factors on crops under different soil properties, and using the preliminary harmful factors that produce an inhibitory effect as the final harmful factors, includes:

[0034] The concentration range is set according to the average concentration of the preliminary harmful factors in the biogas slurry sample;

[0035] Prepare solutions corresponding to each of the aforementioned preliminary causative agents; wherein each solution comprises solutions of different concentrations, and each concentration of each solution falls within the corresponding concentration range;

[0036] Different concentrations of the solution were applied to the experimental fields, and the soil properties, crop types, preliminary harmful factors and concentrations of the applied solution, and crop impact indicators were recorded for each experimental field.

[0037] Based on the aforementioned impact indicators, target solutions that inhibit crop growth in different soil properties are determined, and the preliminary harmful factors corresponding to the target solutions are used as the final harmful factors.

[0038] Optionally, the step of using field trials to determine the effects of each of the preliminary harmful factors on crops under different soil properties, and using the preliminary harmful factors that produce an inhibitory effect as the final harmful factors, includes:

[0039] The concentration range is set according to the average concentration of the preliminary harmful factors in the biogas slurry sample;

[0040] The biogas slurry is modified to obtain multiple sets of modified biogas slurry; wherein, the target preliminary causative factor set in the modified biogas slurry in different sets is different, the target preliminary causative factor set in each modified biogas slurry in the same set is the same, the concentration of the target preliminary causative factor in different modified biogas slurries in the same set is different, and the concentration of each of the target preliminary causative factor is within the corresponding concentration range, and the concentration of the other components in different modified biogas slurries in the same set is the same except for the target preliminary causative factor.

[0041] Each of the prepared biogas slurries was applied to the experimental fields, and the soil properties, crop types, target preliminary harmful factors and concentrations of the applied prepared biogas slurry, and crop impact indicators were recorded for each experimental field.

[0042] Based on the aforementioned impact indicators, the target preliminary harmful factors that inhibit crop growth in different soil properties are determined as the final harmful factors.

[0043] Optionally, after diluting the biogas slurry to be applied to dilute the initial concentration of the harmful agent to less than the target maximum concentration of the harmful agent before applying the biogas slurry, the method further includes:

[0044] The actual inhibitory effect of the concentration of the target most harmful factor on crops was detected.

[0045] The concentration of the target maximum harmful factor is modified according to the actual degree of inhibition.

[0046] Optionally, diluting the biogas slurry to be applied to reduce the initial concentration of the harmful agent to less than the target maximum concentration of the harmful agent before application includes:

[0047] If there is only one target harmful factor, a first dilution factor is determined based on the initial harmful factor concentration and the maximum harmful factor concentration corresponding to the target harmful factor, and the biogas slurry to be applied is diluted according to the first dilution factor.

[0048] If there are multiple target harmful factors, the second dilution factor corresponding to each target harmful factor is determined according to the initial harmful factor concentration and the maximum harmful factor concentration, and the biogas slurry to be applied is diluted according to the largest dilution factor among the second dilution factors.

[0049] Optionally, when determining the effects of each of the aforementioned preliminary harmful factors on crops under different soil properties using field trials, the method further includes:

[0050] Field experiments were used to determine the effects of the aforementioned preliminary harmful factors on the crop at different growth stages under different soil properties.

[0051] This application provides a method for the safe application of biogas slurry, comprising: determining the target crop type and target soil properties of the application area; determining the target harmful factor and the maximum harmful factor concentration in the biogas slurry corresponding to the target crop type and target soil properties according to a preset biogas slurry application standard; wherein the preset biogas slurry application standard includes the correspondence between crop type, soil properties, harmful factor, and maximum harmful factor concentration; determining the initial harmful factor concentration of the target harmful factor in the biogas slurry to be applied; and diluting the biogas slurry to be applied to reduce the initial harmful factor concentration to below the maximum harmful factor concentration before application if the initial harmful factor concentration is higher than the maximum harmful factor concentration. Before applying biogas slurry, this application prepares biogas slurry of different concentrations based on factors such as soil properties, the initial harmful factor concentration of the biogas slurry to be applied, and crop type, thereby diluting the initial harmful factor concentration in the biogas slurry to be applied to below the maximum harmful factor concentration, effectively avoiding inhibitory effects on crops, improving the effectiveness of biogas slurry as an organic fertilizer to replace chemical fertilizers, and reducing resource waste. Attached Figure Description

[0052] To more clearly illustrate the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0053] Figure 1A flowchart illustrating a safe application method for biogas slurry, provided as an embodiment of this application;

[0054] Figure 2 A flowchart for establishing a preset biogas slurry application standard is provided for embodiments of this application;

[0055] Figure 3 A pot experiment showing the effect of a volatile fatty acid solution on wheat in non-alkaline soil, as provided in an embodiment of this application;

[0056] Figure 4 A pot experiment showing the effect of a volatile fatty acid solution on wheat in alkaline soil, as provided in an embodiment of this application;

[0057] Figure 5 Figure 1 shows the results of a pot experiment on the effects of biogas slurry containing different concentrations of volatile fatty acids on wheat in non-alkaline soil, which is provided as an embodiment of this application.

[0058] Figure 6 Figure 1 shows the results of a pot experiment on the effects of biogas slurry containing different concentrations of volatile fatty acids on wheat in alkaline soil, as provided in an embodiment of this application.

[0059] Figure 7 A pot experiment result diagram showing the effect of an inorganic ionic solution on wheat in non-alkaline soil, provided as an embodiment of this application;

[0060] Figure 8 A pot experiment result diagram showing the effect of an inorganic ionic solution on wheat in alkaline soil, provided as an embodiment of this application;

[0061] Figure 9 A field experiment diagram showing the effect of various monoacid solutions of volatile fatty acids on the tillering stage of wheat in alkaline soil, as provided in the embodiments of this application.

[0062] Figure 10 A field experiment diagram showing the effects of various monoacid solutions of volatile fatty acids on the overwintering period of wheat in alkaline soil, as provided in an embodiment of this application.

[0063] Figure 11 A field experiment diagram showing the effect of various monoacid solutions of volatile fatty acids on the jointing stage of wheat in alkaline soil, as provided in an embodiment of this application.

[0064] Figure 12 A field experiment diagram showing the effect of a mixed acid solution of volatile fatty acids on wheat at different growth stages in alkaline soil, as provided in an embodiment of this application.

[0065] Figure 13A field experiment diagram showing the effect of various monoacid solutions of volatile fatty acids on the tillering stage of wheat in non-alkaline soil, as provided in the embodiments of this application.

[0066] Figure 14 A field experiment diagram showing the effects of various monoacid solutions of volatile fatty acids on the overwintering period of wheat in non-alkaline soil, as provided in the embodiments of this application.

[0067] Figure 15 A field experiment diagram showing the effect of various monoacid solutions of volatile fatty acids on the jointing stage of wheat in non-alkaline soil, as provided in the embodiments of this application.

[0068] Figure 16 A field experiment diagram showing the effects of a mixed acid solution of volatile fatty acids on wheat at various growth stages in non-alkaline soil, as provided in this application embodiment.

[0069] Figure 17 A field experiment diagram showing the effects of biogas slurry containing different concentrations of volatile fatty acids on wheat at various growth stages in non-alkaline soil, as provided in this application embodiment;

[0070] Figure 18 A field experiment diagram showing the effects of biogas slurry containing different concentrations of volatile fatty acids on wheat at different growth stages in alkaline soil, provided as an embodiment of this application.

[0071] Figure 19 A comparative diagram showing the salt retention capacity of different concentrations of total salt solutions in non-alkaline and alkaline soils, provided for embodiments of this application. Detailed Implementation

[0072] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this application.

[0073] The core of this application is to provide a safe method for applying biogas slurry.

[0074] To enable those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0075] Figure 1 A flowchart of a safe application method for biogas slurry provided in this application embodiment is shown below. Figure 1 As shown, a safe method for applying biogas slurry includes:

[0076] S10: Determine the target crop species and target soil properties of the application area for the biogas slurry.

[0077] S11: Determine the target harmful factors and the maximum harmful factor concentration in the biogas slurry corresponding to the target crop type and target soil properties based on the preset biogas slurry application standards; wherein, the preset biogas slurry application standards include the correspondence between crop type, soil properties, harmful factors and maximum harmful factor concentration.

[0078] S12: Determine the initial concentration of the target harmful factor in the biogas slurry to be applied. If the initial concentration of the harmful factor is greater than the maximum concentration of the target harmful factor, dilute the biogas slurry to be applied to dilute the initial concentration of the harmful factor to less than the maximum concentration of the target harmful factor before applying the biogas slurry.

[0079] In this application embodiment, before applying biogas slurry, a preset biogas slurry application standard is used to determine the target harmful factors and the maximum concentration of the target harmful factors corresponding to the target crop type and target soil properties to which the biogas slurry is to be applied. For example, it determines the components of biogas slurry that have an inhibitory effect on wheat grown in alkaline soil when applied to wheat. As is well known, biogas slurry contains a variety of components, including ammonia nitrogen, total nitrogen, total phosphorus, total potassium, inorganic ions, and volatile fatty acids, etc. The components that inhibit crop growth are referred to as harmful factors in this application.

[0080] It is worth mentioning that the preset biogas slurry application standards can also include the crop's growth stage, that is, each growth stage of the crop has its corresponding maximum concentration of harmful factors. To make it easier to understand what the crop growth stage is, the following example is given: for example, the growth stages of wheat include the tillering stage, overwintering stage, jointing stage, and greening stage.

[0081] Regarding how to dilute the biogas slurry to be applied to reduce the initial concentration of the target harmful factor to below the maximum target harmful factor concentration before application, the following methods apply depending on the situation: If there is only one target harmful factor, determine the first dilution factor based on the initial and maximum target harmful factor concentrations, and then dilute the biogas slurry accordingly. If there are multiple target harmful factors, determine the second dilution factor for each target harmful factor based on its initial and maximum target harmful factor concentrations, and then dilute the biogas slurry using the largest of the second dilution factors. In short, the principle is to dilute the initial concentration of each target harmful factor in the biogas slurry to below its corresponding maximum target harmful factor concentration, thereby effectively avoiding any inhibitory effect on crops. The maximum target harmful factor concentration refers to the critical concentration that will not exhibit an inhibitory effect on a certain crop in a given soil environment; it can also be called the safe concentration.

[0082] Based on this, after diluting the biogas slurry to be applied to dilute the initial harmful factor concentration to less than the target maximum harmful factor concentration before applying the biogas slurry, the present application embodiment further includes: detecting the actual degree of inhibition of the target maximum harmful factor concentration on the crop; and modifying the target maximum harmful factor concentration according to the actual degree of inhibition.

[0083] This application provides a method for the safe application of biogas slurry, comprising: determining the target crop type and target soil properties of the application area; determining the target harmful factor and the maximum harmful factor concentration in the biogas slurry corresponding to the target crop type and target soil properties according to a preset biogas slurry application standard; wherein the preset biogas slurry application standard includes the correspondence between crop type, soil properties, harmful factor and maximum harmful factor concentration; determining the initial harmful factor concentration of the target harmful factor in the biogas slurry to be applied; if the initial harmful factor concentration is greater than the maximum harmful factor concentration, diluting the biogas slurry to be applied to reduce the initial harmful factor concentration to less than the maximum harmful factor concentration before application. Before applying biogas slurry, this application prepares biogas slurry of different concentrations according to factors such as soil properties, the initial harmful factor concentration of the biogas slurry to be applied, and crop type, thereby diluting the initial harmful factor concentration in the biogas slurry to be applied to less than the maximum harmful factor concentration, effectively avoiding inhibitory effects on crops, improving the effectiveness of biogas slurry as an organic fertilizer to replace chemical fertilizers, and reducing resource waste.

[0084] Based on the above embodiments, before determining the target harmful factors and the maximum harmful factor concentration in the biogas slurry corresponding to the target crop type and target soil properties according to the preset biogas slurry application standard, this application embodiment also includes establishing a preset biogas slurry application standard.

[0085] The embodiments of this application mainly establish preset biogas slurry application standards by using pot experiments and field experiments. It should be noted that the soil properties and crop types studied in the pot experiments and field experiments are consistent. Figure 2 A flowchart for establishing a preset biogas slurry application standard is provided for embodiments of this application, such as... Figure 2 As shown, the specific setup process includes:

[0086] S20: Select biogas slurry samples from different regions and determine the components in the biogas slurry samples.

[0087] In step S20, due to the significant differences in the properties of biogas slurry across different regions and processing methods, samples of biogas slurry from various regions and processing methods are taken as much as possible to determine the components in the samples. Before proceeding to the next step, the following steps are also included: determining the proportion of each component in the biogas slurry sample; screening out components with proportions greater than a preset proportion, and using the screened components for subsequent pot experiments. Considering that some components have a particularly small proportion in the biogas slurry and have little impact on crops, the impact of these components with small proportions on crops can be disregarded, thus reducing subsequent workload.

[0088] S21: Use pot experiments to determine the effects of each component on crops under different soil properties, and use the components that produce inhibitory effects as preliminary harmful factors.

[0089] The following describes the specific process of conducting pot experiment, including two research methods.

[0090] The first method involves determining the average concentration of each component in the biogas slurry sample and setting concentration ranges based on the average concentration; preparing solutions corresponding to each component; each solution includes solutions of different concentrations, and each concentration of each solution falls within its corresponding concentration range; applying solutions of different concentrations to experimental pots and recording the soil properties, crop type, components and concentrations of the applied solution, and crop impact indicators for each experimental pot; determining the target solutions that inhibit crop growth in different soil properties based on the impact indicators, and using the target components corresponding to the target solutions as preliminary causative agents.

[0091] To facilitate understanding, the following example illustrates the process: First, identify the components with the largest proportions in the biogas slurry, such as component A and component B. Calculate the average concentrations of components A and B in the biogas slurry sample. The upper limit of the concentration range = 1.5 × average concentration, and the lower limit of the concentration range = average concentration ÷ 1.5. Denote the concentration range corresponding to component A as the A concentration range, and the concentration range corresponding to component B as the B concentration range. Then, prepare solution A containing only component A and solution B containing only component B. Solution A includes solutions with different concentrations of component A: A1 solution, A2 solution, and so on. n Solution, and solution A1 to A n The concentrations of all solutions fall within the concentration range of A; solution B includes solutions B1, B2, ... B with different concentrations of component B. n Solution, and solution B1 to B n The concentrations of all solutions fall within the concentration range B. 2n test basins are set up, with one solution applied to each basin. For example, solution A1 is applied to the first test basin, and solution A2 is applied to the nth test basin. n Solution, application of solution B1 in the (n+1)th test pot, application of solution B in the 2nth test pot nThe soil properties and crop types in the 2n test pots are kept consistent. To ensure the accuracy of the experiment, multiple replicates can be set up for each solution; for example, three replicates can be set up for the test pots using solution A1. If other soil properties need to be studied, another 2n test pots can be set up, changing only the soil properties while keeping other factors constant, and then the A1 solution, A2 solution, etc., set up above can be applied respectively. n Solution and B1 solution, B2 solution...B n Solution. Influencing indicators can be plant abnormality rate and leaf damage rate. The test pots with plant abnormality rate or leaf damage rate greater than the preset value are identified, and the target components of the target solution applied in the test pots are taken as the preliminary causative factors.

[0092] The second method involves determining the average concentration of each component in the biogas slurry sample and setting concentration ranges based on the average concentration. The biogas slurry is then prepared into multiple groups. The target components set for the prepared biogas slurries differ between groups, while the target components are the same for all prepared biogas slurries within the same group. The concentrations of the target components differ among different prepared biogas slurries within the same group, and each concentration of the target component falls within its corresponding concentration range. The concentrations of all other components besides the target component are the same in different prepared biogas slurries within the same group. Each prepared biogas slurry is then applied to experimental pots, and the soil properties, crop type, target components and their concentrations, and crop impact indicators are recorded for each pot. Based on these impact indicators, the target components that inhibit crop growth in different soil properties are identified as preliminary harmful factors.

[0093] To facilitate understanding, the following example illustrates the process: First, identify the components with the largest proportions in the biogas slurry, such as component A and component B. Calculate the average concentrations of components A and B in the biogas slurry sample. The upper limit of the concentration range = 1.5 × average concentration, and the lower limit of the concentration range = average concentration ÷ 1.5. Denote the concentration range corresponding to component A as the A concentration range and the concentration range corresponding to component B as the B concentration range. Prepare two sets of modified biogas slurries. The target component of the first set is component A, and the target component of the second set is component B. The modified biogas slurry of the first set can include A1 biogas slurry, A2 biogas slurry, and so on. n biogas slurry, A1 biogas slurry, A2 biogas slurry...A n The concentrations of component A in the biogas slurry vary, but all concentrations fall within the range specified for component A. All other components remain the same. The second group of prepared biogas slurry may include solutions B1, B2, ..., B. n Solutions, B1 solution, B2 solution...B nThe concentrations of component B in the solution vary, but all concentrations fall within the B concentration range. All other components remain the same. 2n test basins are set up. Each test basin is treated with a different prepared biogas slurry; for example, the first test basin is treated with biogas slurry A1, the nth test basin with A... n Biogas slurry, B1 biogas slurry applied in the (n+1)th test pot, B applied in the 2nth test pot n Biogas slurry. The soil properties and crop types in 2n test pots are kept consistent. To ensure the accuracy of the experiment, multiple replicates can be set up for each prepared biogas slurry; for example, three replicates can be set up for the test pots applying biogas slurry A1. If other soil properties need to be studied, another 2n test pots can be set up, changing only the soil properties while keeping other factors constant, and then the aforementioned biogas slurry A1, A2, ... A2 can be applied respectively. n biogas slurry and B1 biogas slurry, B2 biogas slurry...B n Biogas slurry. Influencing indicators can be plant abnormality rate and leaf damage rate. For test pots where the plant abnormality rate or leaf damage rate is greater than the preset value, the target components of the modified biogas slurry applied in the test pot are used as preliminary harmful factors.

[0094] Regarding whether the preliminary causative factor is determined based on the first pot experiment or the second pot experiment, if the preliminary causative factor determined by the first pot experiment and the second pot experiment are the same, the preliminary causative factor is directly used in the subsequent field experiment; if the preliminary causative factor determined by the first pot experiment and the second pot experiment are different, the preliminary causative factor determined by both the first pot experiment and the second pot experiment is used in the subsequent field experiment.

[0095] S22: Field experiments were conducted to determine the effects of each preliminary harmful factor on crops under different soil properties, and the preliminary harmful factors that produced inhibitory effects were taken as the final harmful factors.

[0096] The following describes the specific process of conducting field trials, including two research methods.

[0097] The first method involves setting concentration ranges based on the average concentration of the initial harmful factors in the biogas slurry samples; preparing solutions corresponding to each initial harmful factor; each solution includes solutions of different concentrations, and each concentration of each solution falls within its corresponding concentration range; applying solutions of different concentrations to experimental fields, and recording the soil properties, crop types, the initial harmful factors and concentrations corresponding to the applied solutions, and the crop impact indicators for each experimental field; determining the target solutions that have an inhibitory effect on crops in different soil properties based on the impact indicators, and using the initial harmful factors corresponding to the target solutions as the final harmful factors.

[0098] For example, if the preliminary causative factor identified in the pot experiment is component A, the upper limit of the A concentration range = 1.5 × the average concentration of component A, and the lower limit of the A concentration range = the average concentration of component A ÷ 1.5. Then, solutions containing only component A are prepared. These solutions include A1, A2, ..., An solutions with different concentrations of component A, and all concentrations from A1 to An fall within the A concentration range. n experimental plots are set up, and each plot is treated with a different solution. For example, the first plot is treated with solution A1, and the nth plot is treated with solution A... n The soil properties and crop types in the n experimental plots are kept consistent. If other soil properties need to be studied, more n experimental plots can be set up, changing only the soil properties while keeping other factors constant, and then the solutions A1, A2, ... A2 are applied respectively. n The solution was used for investigation. If other crops need to be studied, n more experimental fields can be set up, changing only the crop type while keeping other factors constant. Then, solutions A1, A2, ..., An were applied to each field for investigation. The influencing indicators could be the plant abnormality rate and leaf damage rate. For experimental fields where the plant abnormality rate or leaf damage rate exceeded the preset value, the preliminary harmful factor corresponding to the target solution applied to that experimental field was taken as the final harmful factor.

[0099] The second method involves setting concentration ranges based on the average concentration of the preliminary harmful factors in the biogas slurry samples; preparing multiple sets of prepared biogas slurries; where the target preliminary harmful factors are different in different sets, the target preliminary harmful factors are the same in each prepared biogas slurry within the same set, the concentrations of the target preliminary harmful factors differ among different prepared biogas slurries within the same set, and all concentrations of the target preliminary harmful factors fall within their corresponding concentration ranges; and the concentrations of all other components besides the target preliminary harmful factors are the same in different prepared biogas slurries within the same set. Each prepared biogas slurry is then applied to an experimental field, and the soil properties, crop type, target preliminary harmful factors and their concentrations, and crop impact indicators are recorded for each field. Based on these impact indicators, the target preliminary harmful factors that inhibit crop growth in different soil properties are determined as the final harmful factors.

[0100] For example, if the preliminary causative factor identified in the pot experiment is component A, the upper limit of the A concentration range = 1.5 × the average concentration of component A, and the lower limit of the A concentration range = the average concentration of component A ÷ 1.5. A set of prepared biogas slurries is prepared, with component A as the target component. This set of prepared biogas slurries can include A1 biogas slurry, A2 biogas slurry, ..., A n biogas slurry, A1 biogas slurry, A2 biogas slurry...A nThe concentrations of component A in the biogas slurry vary, but all concentrations fall within the A concentration range. All other components remain the same. n experimental plots are set up, each treated with a different biogas slurry. For example, the first experimental plot is treated with biogas slurry A1, and the nth experimental plot is treated with A... n For the biogas slurry, the soil properties and crop types in the n experimental plots are kept consistent. If other soil properties need to be studied, more n experimental plots can be set up, changing only the soil properties while keeping other factors constant, and then the biogas slurry A1, A2, ... A2 samples are applied respectively. n Biogas slurry. If research on other crops is needed, n more experimental plots can be set up, changing only the crop type while keeping other factors constant, and then the biogas slurry A1, A2, ... A2 prepared as described above can be applied respectively. n The biogas slurry was investigated. The influencing indicators could be the plant abnormality rate and the leaf damage rate. For experimental fields where the plant abnormality rate or leaf damage rate was greater than the preset value, the target preliminary harmful factor of the modified biogas slurry applied to the experimental field was taken as the final harmful factor.

[0101] When using field experiments to determine the effects of each preliminary harmful factor on crops in different soil properties, it also includes: using field experiments to determine the effects of each preliminary harmful factor on crops at different growth stages in different soil properties.

[0102] S23: Determine the maximum concentration of the final harmful factor applied to crops in different soil properties based on the crop impact index.

[0103] The impact indicators of crops treated with biogas slurry containing different concentrations of the ultimate harmful factor were determined. The degree of impact of each impact indicator was determined according to the evaluation criteria for crop growth inhibition. The evaluation criteria included the correspondence between the impact indicator and the degree of impact. The concentration corresponding to the target degree of impact was taken as the maximum harmful factor concentration.

[0104] The specific details are as follows: The influencing indicators are the plant abnormality rate or leaf damage rate, and the evaluation criteria are detailed in Table 1.

[0105] Table 1. Crop Impact Indicators at Level VI

[0106]

[0107] If the plant abnormality rate equals the leaf damage rate, the degree of impact is determined based on either the plant abnormality rate or the leaf damage rate. If the plant abnormality rate is greater than the leaf damage rate, the degree of impact is determined based on the plant abnormality rate. If the plant abnormality rate is less than the leaf damage rate, the degree of impact is determined by the target leaf damage rate. For example, if the plant abnormality rate is 15% but the leaf damage rate is 25%, the crop's impact level should correspond to the leaf damage rate of 25%, i.e., it is level 3 impact.

[0108] In this embodiment, the concentration corresponding to a target impact level of 1 is taken as the maximum harmful factor concentration. That is, the impact of the maximum harmful factor concentration on the crop must be less than 1.

[0109] S24: Establish a pre-set biogas slurry application standard based on the maximum harmful factor concentration corresponding to the final harmful factor, the soil properties corresponding to the maximum harmful factor concentration, and the crop type corresponding to the maximum harmful factor concentration. This standard includes the correspondence between crop type, soil properties, harmful factors, and maximum harmful factor concentration.

[0110] Based on the above field experiments, the effects of harmful factors on different growth stages of crops in different soil properties were also studied. Therefore, the pre-set biogas slurry application standards can also include the corresponding relationship between crop type, crop growth stage, soil properties, harmful factors and the concentration of the most harmful factor.

[0111] To facilitate understanding of the process of establishing preset biogas slurry application standards, the following example illustrates the process. Specifically, wheat is used as an example of crop type, and alkaline soil (pH=8.5) and non-alkaline soil (pH=5.0) are used as examples of soil properties.

[0112] 1. Select biogas slurry samples

[0113] A total of 6,651 biogas slurry samples were collected from pig farms in different regions.

[0114] 2. Analysis of biogas slurry composition (Table 2)

[0115] Table 2. Composition and average concentration of pig manure biogas slurry

[0116]

[0117] Table 2 shows that the pH of the biogas slurry was neutral (7.4), and total nitrogen (1113.64 mg / L) accounted for the largest proportion of inorganic matter. The main metal ions were potassium (500.5 mg / L) and sodium (343 mg / L). The content of each component of volatile fatty acids decreased with increasing carbon chain length. Based on the proportion of each component in the biogas slurry, inorganic ions and volatile fatty acids were selected for further research.

[0118] 3. Selecting an experimental site

[0119] Regions with different soil properties were selected as experimental sites. These mainly included alkaline soils (pH=8.5) and non-alkaline soils (pH=5.0).

[0120] 4. Soil property analysis

[0121] The physicochemical properties of the soil used in the pot experiments are shown in Table 3:

[0122] Table 3 Soil properties from pot experiments

[0123]

[0124] The physicochemical properties of the soils used in the field experiment are shown in Table 4:

[0125] Table 4 Soil properties from field experiments

[0126]

[0127] Both the pot experiment soil and the field experiment soil were used to study alkaline soil (pH=8.5) and non-alkaline soil (pH=5.0).

[0128] 5. Criteria for determining the degree of crop suppression

[0129] As shown in Table 1, the influencing indicators are the plant abnormality rate or leaf damage rate, and the degree of influence includes 6 levels, namely level 0, level 1, level 2, level 3, level 4 and level 5.

[0130] 6. Pot experiment

[0131] 6.1 Effects of Volatile Fatty Acids

[0132] The results of a pot experiment on the effects of volatile fatty acids (VFAs) on wheat are as follows: Figure 3 , 4 As shown in Figures 5 and 6. Figure 3 A pot experiment showing the effect of a volatile fatty acid solution on wheat in non-alkaline soil, as provided in an embodiment of this application; Figure 4 A pot experiment showing the effect of a volatile fatty acid solution on wheat in alkaline soil, as provided in an embodiment of this application; Figure 5 Figure 1 shows the results of a pot experiment on the effects of biogas slurry containing different concentrations of volatile fatty acids on wheat in non-alkaline soil, which is provided as an embodiment of this application. Figure 6 Figure 1 shows the results of a pot experiment on the effects of biogas slurry containing different concentrations of volatile fatty acids on wheat in alkaline soil, as provided in an embodiment of this application. Figure 3 Prepare the solution and apply it to the potting soil at pH 5.0; Figure 4 Prepare the solution and apply it to the potting soil at a pH of 8.5; Figure 5 Pot experiment on actual biogas slurry applied to soil with pH 5.0; Figure 6 Pot experiment on actual biogas slurry applied to soil with pH 8.5.

[0133] Depend on Figure 3 and 4 It can be seen that VFAs have a certain impact on wheat in non-alkaline soils. Figure 3 The degree of influence in alkaline soils is greater than Figure 4More clearly, the specific phenomena are as follows: i) In non-alkaline soil (pH=5.0), the applied acid concentration of 8.8 mmol / L has a Grade 1 effect on wheat, therefore the limiting concentration in the pot germination environment is 8 mmol / L, while the corresponding limiting concentration of acid in alkaline soil is 17 mmol / L, which is 2.215 times the safe concentration in non-alkaline soil; ii) Within the same concentration range (0-35 mmol / L), volatile fatty acids have a Grade 4 effect on wheat in non-alkaline soil, while the maximum effect in alkaline soil is Grade 3; iii) When the concentration range is the same, acetic acid to isovaleric acid in non-alkaline soil all have at least a Grade 2 effect on wheat, while in alkaline soil, only the long-chain volatile fatty acids isobutyric acid and isovaleric acid have an effect on wheat.

[0134] In addition, prepare the solution ( Figure 3 , 4 ) and actual biogas slurry ( Figure 5 , 6 When the concentration of volatile fatty acids in the prepared solution is consistent (0–40 mmol / L), the inhibitory effect of volatile fatty acids on crops is greater. This is because the prepared solution has undergone acidification treatment, so most of the volatile fatty acids exist in molecular form. Alkaline soil has limited ability to neutralize acid molecules, causing some volatile fatty acid molecules to act on root cells, producing a significant inhibitory effect on wheat growth. In actual biogas slurry, the pH is neutral, at which point most VFAs exist in the form of acid anions, and therefore have virtually no inhibitory effect on wheat.

[0135] 6.2 Influence of Inorganic Ions

[0136] The inhibitory effect of inorganic ions on wheat, such as Figure 7 and Figure 8 As shown. Figure 7 A pot experiment result diagram showing the effect of an inorganic ionic solution on wheat in non-alkaline soil, provided as an embodiment of this application; Figure 8 Figure 1 shows the results of a pot experiment on the effect of an inorganic ion solution on wheat in alkaline soil, as provided in an embodiment of this application. Figure 7 The potting soil has a pH of 5.0; Figure 8 The potting soil has a pH of 8.5.

[0137] Inorganic ions affect wheat growth in both alkaline and non-alkaline soils, with the highest impact level being Grade 1. The results indicate that the effect of inorganic ions on wheat is stronger in alkaline soils. For example, a magnesium ion concentration of 150 mg / L in alkaline soils exhibits a Grade 1 effect on wheat, while in non-alkaline soils, the concentration reaching Grade 1 is 1200 mg / L. The adsorption capacity of inorganic ions by colloids in alkaline and non-alkaline soils differs, resulting in a higher concentration of inorganic ions retained in the topsoil (root zone) of alkaline soils at the same application rate and concentration. Therefore, subsequent field trials should investigate the retention capacity of different soils for inorganic ions and their impact on crops to avoid crop growth inhibition caused by excessively high levels of inorganic ions.

[0138] 7. Impact of initial screening

[0139] The results of the pot experiment showed that volatile fatty acids and inorganic ions were both preliminary harmful factors. Therefore, further field experiments should be conducted to investigate their inhibitory effects on crop growth.

[0140] 8. Field trials

[0141] 8.1 Effects of Volatile Fatty Acids

[0142] First, an alkaline soil (pH 8.5) was studied. Different concentrations of volatile fatty acids were applied during the wheat tillering, overwintering, jointing, and greening stages to investigate the effects of mono- and mixed acids on wheat. Figure 9 A field experiment diagram showing the effect of various monoacid solutions of volatile fatty acids on the tillering stage of wheat in alkaline soil, as provided in the embodiments of this application. Figure 10 A field experiment diagram showing the effects of various monoacid solutions of volatile fatty acids on the overwintering period of wheat in alkaline soil, as provided in an embodiment of this application. Figure 11 A field experiment diagram showing the effect of various monoacid solutions of volatile fatty acids on the jointing stage of wheat in alkaline soil, as provided in an embodiment of this application. Figure 12 The figure shows the results of a field experiment on the effects of a mixed acid solution of volatile fatty acids on wheat at different growth stages in alkaline soil, as provided in the embodiments of this application.

[0143] like Figure 9 As shown, during the tillering and greening stages of wheat, various volatile fatty acids had no significant effect on wheat (the greening stage coincides with the tillering stage, and the data is not shown in the figure); Figure 10 As shown, during the overwintering period, acetic acid, propionic acid, and butyric acid had no effect on wheat, while valeric acid, isobutyric acid, and isovaleric acid showed a first-order effect on wheat at concentrations of 39.2 mmol / L, 28.3 mmol / L, and 29.4 mmol / L, respectively. The concentration of volatile fatty acids should be controlled to not exceed 28 mmol / L. Figure 11As shown, during the jointing stage of wheat, the concentration of volatile fatty acids should be controlled below 22 mmol / L. Figure 12 As shown, the results of the effects of mixed acids on crops at different stages indicate that when the concentration of mixed acids exceeds 174 mmol / L, it has a significant inhibitory effect on crops (level 3-5).

[0144] Secondly, a study was conducted on non-alkaline soils (pH 5.0). Figure 13 A field experiment diagram showing the effect of various monoacid solutions of volatile fatty acids on the tillering stage of wheat in non-alkaline soil, as provided in the embodiments of this application. Figure 14 A field experiment diagram showing the effects of various monoacid solutions of volatile fatty acids on the overwintering period of wheat in non-alkaline soil, as provided in the embodiments of this application. Figure 15 A field experiment diagram showing the effect of various monoacid solutions of volatile fatty acids on the jointing stage of wheat in non-alkaline soil, as provided in the embodiments of this application. Figure 16 The figure shows the results of a field experiment on the effects of a mixed acid solution of volatile fatty acids on wheat at different growth stages in non-alkaline soil, as provided in the embodiments of this application.

[0145] like Figure 13 As shown, during the wheat tillering stage, all types of volatile fatty acids affected wheat growth, with the maximum impact level being 5. Furthermore, the concentrations of acetic acid, propionic acid, and isovaleric acid that produced a level 2 effect were 26.6 mmol / L, 12.2 mmol / L, and 7.83 mmol / L, respectively, indicating that volatile fatty acids with longer carbon chains had a greater inhibitory effect on crops. Figure 14 As shown, during the wintering period of wheat, the concentrations of various acids that had a first-order effect on wheat were propionic acid 32.4 mmol / L, butyric acid 13.6 mmol / L, valeric acid 11.7 mmol / L, isobutyric acid 9.08 mmol / L, and isovaleric acid 7.83 mmol / L, respectively. This also indicates that volatile fatty acids with longer carbon chains have a stronger inhibitory effect on crops; for example... Figure 15 As shown, during the wheat jointing stage, at a concentration of 13.5 mmol / L, the effects of acetic acid, butyric acid, and valeric acid on wheat were graded as 0.5, 1, and 3, respectively. The effects of long-chain volatile fatty acids on wheat followed the same pattern as during the tillering and overwintering stages. Furthermore, as... Figure 16 As shown, the effects of mixed acids on crops at different stages indicate that: i) the effect of mixed acids on the tillering stage is significantly higher in non-alkaline soils than on the overwintering stage. This is because the temperature is higher during the wheat tillering stage than during the overwintering stage, at which time the acid radicals in the biogas slurry hydrolyze into molecules, corroding root cells and thus exhibiting a more obvious inhibitory effect on wheat growth; ii) in soil with a pH of 5.0, the concentration of volatile fatty acids is 9.5 mmol / L, which has a first-order effect on wheat during the tillering, overwintering, and greening stages. Therefore, the concentration of volatile fatty acids should be controlled to not exceed 9 mmol / L.

[0146] Figure 17 A field experiment diagram showing the effects of biogas slurry containing different concentrations of volatile fatty acids on wheat at various growth stages in non-alkaline soil, as provided in this application embodiment; Figure 18 The figure shows the results of a field experiment on the effects of biogas slurry containing different concentrations of volatile fatty acids on wheat at different growth stages in alkaline soil, as provided in the embodiments of this application.

[0147] Simultaneously, field trials were conducted by applying biogas slurry with a known total amount of volatile fatty acids to alkaline and non-alkaline soils, such as... Figure 17 As shown, the results indicate that in non-alkaline soil (pH 5.0), the concentration of volatile fatty acids that has a first-order effect on wheat during the greening stage is 10 mmol / L, and during the tillering stage it is 18 mmol / L, verifying the effectiveness of the 9 mmol / L safe concentration under these conditions; Figure 18 As shown, in alkaline soils, a volatile fatty acid concentration of 90 mmol / L has no effect on crops; therefore, no additional control of volatile fatty acid concentration is required in alkaline soils. Furthermore, to adapt to different crop stages and soil properties, safe concentration control of volatile fatty acids should be implemented for different soil pH levels (<7.5) and different wheat growth stages.

[0148] 8.2 Inorganic Ions

[0149] Figure 19 This is a comparison chart showing the salt retention capacity of different concentrations of total salt solutions in non-alkaline and alkaline soils, provided as an embodiment of this application. Figure 19 As shown, applying the same total salt concentration solution to both alkaline (pH 8.5) and non-alkaline (pH 5.0) soils in the topsoil increases the total salt concentration. Alkaline soils, with a base total salt concentration of 0.8 g / kg, saw their total salt concentration increase to 6.8 g / kg (an increase of 750.0%) and 7.4 g / kg (an increase of 825.0%) after applying salt solutions with concentrations of 16.0 g / L and 20.6 g / L, respectively. Non-alkaline soils, with a base total salt concentration of 0.7 g / kg, saw their total salt concentration increase to 1.6 g / kg (an increase of 128.5%) and 1.9 g / kg (an increase of 171.4%) after applying salt solutions with concentrations of 15.1 g / L and 19.4 g / L, respectively. This comparison demonstrates that alkaline soils have a significantly higher capacity for carrying inorganic ions than non-alkaline soils, exhibiting a stronger salt retention capacity. This is because non-alkaline soils contain a large amount of acidifying ions (Al). 3+ and H +In alkaline soils, the base saturation is low, making it difficult for inorganic ions to be adsorbed by soil colloids; in alkaline soils, the base saturation is high, resulting in a high proportion of exchangeable inorganic ions, which are easily adsorbed by soil colloids and are not easily leached away. Therefore, under the same application rate and concentration, the critical concentration at which inorganic ions inhibit wheat growth in alkaline soils is lower, and the inhibitory effect occurs faster and lasts longer.

[0150] 9. Determine the ultimate causative agent.

[0151] The main components of inorganic ions in biogas slurry indicate that they are primarily basic ions of nutrients such as N, P, and K required by plants. In actual application, biogas slurry is applied based on soil testing and fertilizer recommendation principles. These principles regulate and resolve the conflict between crop nutrient requirements and soil nutrient supply, while also specifically supplementing the nutrients needed by crops to achieve a balanced supply of various nutrients. When biogas slurry is applied based on soil testing and fertilizer recommendation principles, nutrients are applied as needed, and inorganic ions do not inhibit wheat growth. However, long-term application of biogas slurry exceeding wheat's nutrient requirements can lead to an increase in soil profile conductivity, accumulation of inorganic ions in the soil, and their migration into deeper soil layers, posing a significant risk of soil pollution. Therefore, in the agricultural use of biogas slurry, the application rate should be determined based on crop nutrient requirements, and long-term, fixed-point soil monitoring and real-time evaluation should be conducted to avoid crop growth inhibition and soil pollution.

[0152] 10. Establish standards

[0153] Volatile fatty acids are corrosive only when they exist in molecular form. In alkaline environments such as biogas slurry or alkaline soil, they mostly exist as anions and are not corrosive. Therefore, the concentration of volatile fatty acids in biogas slurry returned to the field needs to be controlled in non-alkaline soils. Long-chain volatile fatty acids have the strongest inhibitory effect on wheat and should ideally be controlled at their safe concentration. However, in the anaerobic fermentation process of pig manure, long-chain volatile fatty acids only exist in the acidification process, and the amount of long-chain volatile fatty acids in agricultural biogas slurry is relatively small. Therefore, the total amount of volatile fatty acids should be controlled to facilitate concentration detection in practice and avoid the risks caused by excessive application of biogas slurry. Specific standards are shown in Table 5 below:

[0154] Table 5 Control Standards for Volatile Fatty Acids (VFAs - mmol / L) in Wheat Biogas Slurry Resource Utilization

[0155]

[0156] In Table 5, a decrease of 1 in soil pH corresponds to a 1.5-fold decrease in the application concentration of volatile fatty acids. The correlation between the application concentration of volatile fatty acids and soil pH in Table 5 can be further verified through the aforementioned field experiment.

[0157] The above provides a detailed description of a safe application method for biogas slurry provided in this application. The various embodiments in the specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. It should be noted that those skilled in the art can make various improvements and modifications to this application without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this application.

[0158] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

Claims

1. A method for the safe application of biogas slurry, characterized in that, include: Determine the target crop species and target soil properties of the application area for the biogas slurry; The target harmful factors and the maximum harmful factor concentration in the biogas slurry corresponding to the target crop type and the target soil property are determined according to the preset biogas slurry application standard; wherein, the preset biogas slurry application standard includes the correspondence between crop type, soil property, harmful factor and maximum harmful factor concentration; Determine the initial concentration of the target harmful factor in the biogas slurry to be applied. If the initial concentration of the harmful factor is greater than the maximum concentration of the target harmful factor, dilute the biogas slurry to be applied to dilute the initial concentration of the harmful factor to less than the maximum concentration of the target harmful factor before applying the biogas slurry. Before determining the target harmful factor in the biogas slurry corresponding to the target crop type and the target soil property, and the concentration of the target maximum harmful factor corresponding to the target harmful factor, based on the preset biogas slurry application standard, the process also includes: Biogas slurry samples were selected from different regions, and the composition of the biogas slurry samples was determined; Pot experiments were used to determine the effects of each of the components on crops under different soil properties, and the components that produced inhibitory effects were identified as preliminary causative agents. Field experiments were used to determine the effects of each of the preliminary harmful factors on crops under different soil properties, and the preliminary harmful factors that produced inhibitory effects were taken as the final harmful factors. The maximum concentration of the ultimate harmful factor applied to crops in different soil properties is determined based on the crop impact indicators. Based on the maximum harmful factor concentration corresponding to the ultimate harmful factor, the soil properties corresponding to the maximum harmful factor concentration, and the crop type corresponding to the maximum harmful factor concentration, a preset biogas slurry application standard is established, which includes the correspondence between the crop type, the soil properties, the harmful factor, and the maximum harmful factor concentration.

2. The method for safe application of biogas slurry according to claim 1, characterized in that, Before determining the effects of each of the aforementioned components on crops under different soil properties using pot experiments, and before considering the components that produce inhibitory effects as preliminary harmful factors, the process also includes: Determine the proportion of each of the aforementioned components in the biogas slurry sample; Components whose proportions are greater than a preset proportion are selected.

3. The method for safe application of biogas slurry according to claim 1, characterized in that, The maximum concentration of the ultimate harmful factor applied to crops in different soil properties was determined based on crop impact indicators, including: The impact indicators of crops treated with biogas slurry containing different concentrations of the final harmful factor were determined separately. The degree of influence corresponding to each of the aforementioned influencing indicators is determined according to the evaluation criteria for crop growth inhibition; wherein, the evaluation criteria include the correspondence between the influencing indicators and the degree of influence; The concentration corresponding to the degree of impact of the target is taken as the concentration of the most harmful factor.

4. The method for safe application of biogas slurry according to claim 1, characterized in that, Pot experiments were used to determine the effects of each of the aforementioned components on crops under different soil properties. Components that produced inhibitory effects were identified as preliminary causative agents, including: Determine the average concentration of each component in the biogas slurry sample, and set a concentration range based on the average concentration; Prepare solutions corresponding to each component; wherein each solution includes solutions of different concentrations, and each concentration of each solution is within the corresponding concentration range; Different concentrations of the solution were applied to test pots, and the soil properties, crop types, components and concentrations of the applied solution, and crop impact indicators were recorded for each test pot. Based on the aforementioned impact indicators, target solutions that inhibit crop growth in different soil properties are determined, and the target components corresponding to the target solutions are used as the preliminary causative factors.

5. The method for safe application of biogas slurry according to claim 1, characterized in that, Pot experiments were used to determine the effects of each of the aforementioned components on crops under different soil properties. Components that produced inhibitory effects were identified as preliminary causative agents, including: Determine the average concentration of each component in the biogas slurry sample, and set a concentration range based on the average concentration; The biogas slurry is modified to obtain multiple sets of modified biogas slurry; wherein the target components set in the modified biogas slurry in different sets are different, the target components set in each modified biogas slurry in the same set are the same, the concentrations of the target components in different modified biogas slurries in the same set are different, and the concentrations of each target component are all within the corresponding concentration range, and the concentrations of the other components except the target component are the same in different modified biogas slurries in the same set; Each of the prepared biogas slurries was applied to a test pot, and the soil properties, crop types, target components and concentrations of the applied prepared biogas slurry, and crop impact indicators were recorded for each test pot. Based on the aforementioned impact indicators, the target components that inhibit crop growth in different soil properties are identified as the preliminary harmful factors.

6. The method for safe application of biogas slurry according to claim 1, characterized in that, The method involves using field trials to determine the effects of each of the preliminary harmful factors on crops under different soil properties, and identifying the preliminary harmful factors that produce an inhibitory effect as the final harmful factors, including: The concentration range is set according to the average concentration of the preliminary harmful factors in the biogas slurry sample; Prepare solutions corresponding to each of the aforementioned preliminary causative agents; wherein each solution comprises solutions of different concentrations, and each concentration of each solution falls within the corresponding concentration range; Different concentrations of the solution were applied to the experimental fields, and the soil properties, crop types, preliminary harmful factors and concentrations of the applied solution, and crop impact indicators were recorded for each experimental field. Based on the aforementioned impact indicators, target solutions that inhibit crop growth in different soil properties are determined, and the preliminary harmful factors corresponding to the target solutions are used as the final harmful factors.

7. The method for safe application of biogas slurry according to claim 1, characterized in that, The method involves using field trials to determine the effects of each of the preliminary harmful factors on crops under different soil properties, and identifying the preliminary harmful factors that produce an inhibitory effect as the final harmful factors, including: The concentration range is set according to the average concentration of the preliminary harmful factors in the biogas slurry sample; The biogas slurry is modified to obtain multiple sets of modified biogas slurry; wherein, the target preliminary causative factor set in the modified biogas slurry in different sets is different, the target preliminary causative factor set in each modified biogas slurry in the same set is the same, the concentration of the target preliminary causative factor in different modified biogas slurries in the same set is different, and the concentration of each of the target preliminary causative factor is within the corresponding concentration range, and the concentration of the other components in different modified biogas slurries in the same set is the same except for the target preliminary causative factor. Each of the prepared biogas slurries was applied to the experimental fields, and the soil properties, crop types, target preliminary harmful factors and concentrations of the applied prepared biogas slurry, and crop impact indicators were recorded for each experimental field. Based on the aforementioned impact indicators, the target preliminary harmful factors that inhibit crop growth in different soil properties are determined as the final harmful factors.

8. The method for safe application of biogas slurry according to claim 1, characterized in that, After diluting the biogas slurry to be applied to reduce the initial concentration of the harmful agent to less than the target maximum concentration of the harmful agent before applying the biogas slurry, the process further includes: The actual inhibitory effect of the concentration of the target most harmful factor on crops was detected. The concentration of the target maximum harmful factor is modified according to the actual degree of inhibition.

9. The method for safe application of biogas slurry according to claim 1, characterized in that, Diluting the biogas slurry to be applied to reduce the initial concentration of the harmful agent to less than the target maximum concentration of the harmful agent before application includes: If there is only one target harmful factor, a first dilution factor is determined based on the initial harmful factor concentration and the maximum harmful factor concentration corresponding to the target harmful factor, and the biogas slurry to be applied is diluted according to the first dilution factor. If there are multiple target harmful factors, the second dilution factor corresponding to each target harmful factor is determined according to the initial harmful factor concentration and the maximum harmful factor concentration, and the biogas slurry to be applied is diluted according to the largest dilution factor among the second dilution factors.

10. The method for safe application of biogas slurry according to claim 1, characterized in that, When determining the effects of each of the aforementioned preliminary harmful factors on crops under different soil properties using field trials, the following steps are also included: Field experiments were used to determine the effects of the aforementioned preliminary harmful factors on the crop at different growth stages under different soil properties.

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