CN113671130B - Method for researching prevention and control mechanism of interface barrier on weeds in paddy field - Google Patents
Method for researching prevention and control mechanism of interface barrier on weeds in paddy field Download PDFInfo
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Abstract
The invention relates to a method for researching a mechanism of preventing and controlling weeds in a rice field by interface barrier. The invention designs a device for researching an interface barrier weed control mechanism, which simulates the change of an interface barrier material in a paddy field environment to weed germination environment conditions directly or indirectly; sowing weed seeds in the device, transplanting rice and placing an interface barrier material for carrying out a test; investigating the change conditions of weed germination, interface barrier material properties, environmental elements and the like in the device; screening dominant environmental factors influencing weed occurrence by adopting a random forest algorithm for predicting a plurality of decision trees by combining random sampling and random input variable selection; the structural equation model which adopts the covariance matrix based on the variables and applies the linear equation to express the relation between the observed variables is adopted to verify the influence of the interface barrier on the environmental factors and the influence of the dominant environmental factors on the weed occurrence, so that a theoretical basis and a scientific basis are provided for the interface barrier weed control technology, and the method has very important significance for the popularization of the green ecological agricultural technology.
Description
Technical Field
The invention relates to the field of ecological weed prevention and control in farmlands, in particular to a research method of a weed prevention and control mechanism of an interface barrier in a paddy field.
Background
Rice is one of the main grain crops in China, and the wide application of chemical herbicides in rice fields after the green revolution brings about the problems of environmental pollution, phytotoxicity, increase of resistant weeds and the like. Under the ecological civilization background of developing ecological agriculture, protecting environment and protecting environment in China, an ecological weed prevention and control strategy is urgently needed in the sustainable production of rice. At present, main ecological grass control methods for rice fields comprise physical prevention and control (artificial weed removal, rice field film covering, water management, artificial weed seed bank cleaning and the like) and biological prevention and control (planting and breeding combination, ecological competition, allelopathy substances and the like), and the method achieves the aim of controlling grass by exhausting the rice field weed seed bank, forming a stress environment to inhibit the germination and growth of weed seeds, enhancing the competitive advantage of rice and the like.
The rice field interface barrier weed control comprises non-biological interface barrier and biological interface barrier, wherein the non-biological interface mainly refers to substances capable of covering and separating water, air and soil interfaces such as rice chaff, biological carbon or a polymer film; biological interfaces block plants such as duckweed, azolla, and algae that can rapidly grow, multiply, and form an interface covering. Chinese patent application CN104798669A discloses a method for controlling weeds in a rice field, which utilizes the characteristic that duckweed grows and breeds rapidly in the rice field to control weeds by optimizing the throwing time, throwing density and variety, and the control effect can reach more than 90%. The interface barrier controls weeds by changing the environmental conditions of weed germination and growth in the rice field, on one hand, the illumination intensity entering water and reaching soil is reduced through physical shielding effect, illumination is an indispensable energy source for plant photosynthesis, and the barrier of the interface barrier to the illumination can directly limit the growth of weeds. On the other hand, the comprehensive influence of the interface barrier material on various physical and chemical properties of the field water body can also comprise key factors of the interface barrier material which indirectly influence the growth of weeds by taking the field water as a carrier. However, the specific and quantitative mechanism for interface barrier weed control has not been clear so far.
Disclosure of Invention
In order to solve the above problems, the present invention aims to provide a method for studying the weed control mechanism of the interface barrier in the paddy field by a separation and permeation type device. The research of the interface barrier on the weed prevention and control mechanism of the paddy field is completed according to the flow of device design, culture process, factor screening, SEM sampling and recording weed, screening of the dominant environmental factors by a random forest algorithm, and verification of the dominant environmental factors by a structural equation model.
The invention designs a device for researching an interface barrier weed control mechanism, which simulates the change of an interface barrier material (biological/non-biological) in a paddy field environment directly or indirectly on the weed germination environment condition; sowing weed seeds in the device, transplanting rice and placing an interface barrier material for carrying out a test; investigating the change conditions of weed germination, interface barrier material properties, environmental elements and the like in the device; screening dominant environmental factors influencing weed germination by adopting a random forest algorithm for predicting a plurality of decision trees by combining random sampling and random input variable selection; and verifying the influence of the interface barrier on the environmental factors and the influence of the dominant environmental factors on weed germination by adopting a structural equation model which expresses the relation between the observed variables by using a variable-based covariance matrix and a linear equation. The invention independently distinguishes the complex effect of the interface barrier on the environment by using the simple separation and permeation device, provides theoretical basis and scientific basis for the interface barrier grass control technology, and has very important significance for the popularization of the green ecological agricultural technology.
The purpose of the invention can be realized by the following technical scheme:
the invention aims to provide a method for researching a mechanism of preventing and controlling weeds in a rice field by interface barrier, which comprises the following steps:
(1) Manufacturing a separation and permeation type device;
(2) Dividing different research areas in the separated penetration type device, respectively scattering weed seeds in each research area, and planting rice, wherein interface barriers are arranged in part of the research areas, and interface barriers are not arranged in part of the research areas;
(3) Regularly acquiring environmental factor data in a research area and interface barrier data in the research area and in the neighborhood, and acquiring weed germination data in the research area;
(4) Based on the environmental factor data and the weed germination data, screening a dominant environmental factor influencing weed germination by adopting a random forest algorithm;
(5) And analyzing the influence of the interface obstruction on the dominant environmental factors and the influence of the dominant environmental factors on weed germination by adopting a structural equation model.
In one embodiment of the invention, in step (1), the different regions of interest of the compartmentalized osmotic device are separated by a mesh that blocks the interfacial barrier material from entering adjacent regions of interest,
meanwhile, the mesh can lead the light transmittance of the water surface of a research area with the interface barrier to be different from that of the research area without the interface barrier,
meanwhile, environmental factors such as soil temperature, water layer temperature, water pH, dissolved oxygen content, ammonia nitrogen concentration, nitrate nitrogen concentration, total nitrogen concentration and total phosphorus concentration between adjacent research areas are not influenced by the net piece;
the mesh selects black for shading side light.
In one embodiment of the present invention, in step (1), the permeation-barrier device is divided into four regions; in the step (2), a plurality of permeation-isolating devices are adopted for research, the proportion of the interfacial barrier region arranged in each permeation-isolating device is respectively 0, 1/2 and 1,
in two groups with the proportion of the interfacial barrier area being 1/2, the area without interfacial barrier and the area with interfacial barrier are both taken as research areas,
in two sets with a ratio of interfacial barrier zones of 1/2, the zones of interfacial barrier are separated by diagonal zones of the barrier device.
In one embodiment of the invention, the weeds include monocotyledonous, dicotyledonous and cyperaceous weeds, monocotyledonous weeds include moleplant, eclipta prostrata and amaranthus auriculata, and the weeds exclude weeds with particularly developed aeration tissues including the iris lactea.
In one embodiment of the invention, the interfacial barriers include biological and non-biological interfacial barriers,
the biological interface barrier selects plants which can rapidly grow, reproduce and form interface coverage, and preferably the plants are duckweed with few roots, duckweed with many roots, azolla or algae;
the non-biological interface barrier selects a substance capable of covering a water layer and separating a water-air interface, and is preferably rice chaff, biological carbon or a polymer film.
In one embodiment of the present invention, in the step (3), the environmental factors include water surface light transmittance, soil temperature, water layer temperature, water pH, dissolved oxygen content, ammonia nitrogen concentration, nitrate nitrogen concentration, total nitrogen concentration and total phosphorus concentration;
in the step (3), the interface barrier data comprises biological interface barrier data and non-biological interface barrier data;
the biological interface barrier data is an index capable of reflecting the biological interface shielding degree, and preferably covers area or biomass;
the non-biological interface blocking data is an index capable of reflecting the non-biological interface shielding degree, and preferably covers the area or the quality;
in the step (3), 1 time every 7 days after the weed seeds are scattered and the rice is planted, and respectively acquiring environmental factor data in a research area and interface barrier data in the research area and in the neighborhood on the 1 st day, the 8 th day, the 15 th day, the 22 th day and the 29 th day;
in the step (3), the weed germination data comprises weed species, weed density and weed biomass, wherein the weed biomass refers to the dry weight of weeds in a certain area, and the weed density refers to the number of plants of weeds in a certain area;
in the step (3), the time for acquiring the weed germination data is 30 days after the weed seeds are sown and the rice is planted.
In one embodiment of the invention, in the step (4), the method for screening the dominant environmental factors influencing weed germination by using a random forest algorithm comprises the following steps:
randomly extracting ntree samples in an original sample set in a back-to-back mode by using a Bootstrap resampling method, performing decision tree modeling on each sample, randomly selecting mtry input variables at each node for separation, completely growing trees by using a CART method, and once the tree is constructed, combining the prediction of a plurality of decision trees and taking an average value to determine a final predicted value;
the values of ntree and mtry are selected based on the lowest error rate of the model, ntree defaults to 500, and mtry defaults to 1/3 of the total number of input variables; the data that is not extracted is called out-of-bag data and is used for estimating the performance of the model;
the importance of the environment element serving as the characteristic variable is evaluated according to the increase of mean square error (IncMSE) between the bag appearance observation value and the model prediction value, and the larger the value is, the larger the error of the model prediction is increased after the characteristic variable is randomly replaced, so the importance is higher. The importance of each environmental element is sorted, the significance is obtained through replacement test, and the environmental elements which have significant influence (P < 0.05) are screened out, namely the dominant environmental elements which influence the weed generation.
In one embodiment of the invention, in step (4), a random forest is constructed using the randomForest program package, and the significance of the feature variables in the random forest is checked using the rfPermute command.
In one embodiment of the invention, in the step (5), when the influence of the interface barrier on the dominant environmental factors and the influence of the dominant environmental factors on weed germination are analyzed by adopting a structural equation model,
the structural equation model adopts a maximum likelihood method to estimate parameters, data are preprocessed to enable samples to accord with normality, and a normalization method comprises dispersion standardization and square root conversion. The method comprises the steps of presetting influence on dominant environmental factors by research area interface barrier data and neighborhood interface barrier data, presetting influence on weed density and weed biomass by the dominant environmental factors, presetting a covariant relation between the weed density and the weed biomass, establishing a basic model, then measuring influence degrees between variables or effect sizes of the variables based on a covariance matrix of the variables, and integrally evaluating model fitting results according to a degree of freedom ratio (NC) of the model, a comparative adaptation index (CFI) and a standardized residual mean square root and square root (SRMR), wherein 1< NC <3 > represents that the model is well adapted, and CFI >0.90 and SRMR <0.05 represents that the fitting degree of the model can be accepted.
In one embodiment of the invention, in step (5), a structural equation model is constructed using the lavaan package and the results are evaluated.
Compared with the prior art, the invention has the following advantages and beneficial effects:
(1) The invention independently plays a role in shielding in the complex environment effect of the interface barrier effect by utilizing the design of a separation and permeation type device with low cost and simple equipment, and is simple and not rigorous.
(2) The invention utilizes the research method of main factor screening and structural equation model verification to define the main mechanism of controlling the weeds in the rice field by interface barrier, provides theoretical basis and scientific basis for the ecological weed control technology of the rice field, and has great significance for further popularization and application of ecological weed control.
Drawings
FIG. 1 is a schematic diagram of the experimental protocol.
FIG. 2 is a drawing of the test apparatus.
FIG. 3 is a schematic view of a compartmentalized osmotic engine.
FIG. 4 is a 29-day average of light transmittance over the pot test period for each treatment study area.
FIG. 5 is a 29 day average of soil temperature and water layer temperature over the pot test period for each treatment study area.
FIG. 6 is a plot of the mean of the surface water pH and dissolved oxygen content of the pots over the 29 day pot test period for each treatment study area.
FIG. 7 is the 29-day mean value of the pot test period for the concentrations of ammonia nitrogen, nitrate nitrogen, total nitrogen and total phosphorus in the pot surface water of each treatment study area.
FIG. 8 is a 29-day average of duckweed biomass for each treatment area in which duckweed was placed during the pot test period.
FIG. 9 shows the total weed biomass (g.m) in each treatment area -2 ) Schematic illustration.
FIG. 10 shows the total weed density (plant. M) in each treatment study area -2 ) Schematic representation.
FIG. 11 is a schematic diagram of an environment element importance ranking based on a random forest algorithm;
in the figure: the response variable is weed density in graph a and weed biomass in graph b.
FIG. 12 is a diagram illustrating a preset influence path of a structural equation model and a model operation result;
in the figure: the graph a is a preset influence path, and the graph b is an operation result.
The superscript letters (a, b, c, d, e, ab, bc, abc) corresponding to each processing in fig. 4, 5, 6, 7, 8, 9, 10 represent significant differences, the two groups of corresponding letters are different, indicating that there is a significant difference between the two groups, and the two groups of corresponding letters are the same or overlap, indicating that there is no significant difference between the two groups.
Detailed Description
Example 1
(1) In this embodiment, the interface barrier material used is duckweed, including duckweed with few roots and a plurality of duckweeds. The permeation-isolating device and the test scheme thereof are shown in figures 1, 2 and 3, the water surface is divided into four areas by using the partition plates, duckweeds are separated in diagonal areas, light is shielded only at the positions with the duckweeds, and other influences of the duckweeds can permeate to the positions without the duckweeds through the black film in the middle of the partition plates due to the permeation effect of water. The proportions of the duckweed putting areas are respectively set to be 0, 1/2 and 1, and the positions without duckweeds and the positions with duckweeds are respectively selected as research areas for two groups of the duckweed putting areas with the proportions of 1/2. The trial design was a randomized block design, for a total of six blocks. Based on the selection of different study subjects (duckweed minor and duckweed multiforme), a total of seven treatments were set up, as shown in table 1.
TABLE 1 potted plant test treatment set-up
(2) The separate permeation test was carried out on pot pots of 23.2cm x 23.2cm in caliber and 27.7cm in height using soil as topsoil (0-20 cm) of rice soil, taken from the Qingpu modern agricultural park (30 ° 58 "N, 121 ° 0" E), soil pH (soil to water ratio 1, 2.5) of 7.187, conductivity (soil to water ratio 1 -1 Total nitrogen content of 1.193 g/kg -1 The effective phosphorus content is 0.010 g.kg -1 . The water-soil ratio is a water-soil ratio set at the time of measuring the pH and conductivity of the soil, and is independent of the water-soil ratio in the actual pot culture. Due to different measuring methods, the required water-soil ratio configured during measurement is different.
The soil is screened by a 1cm mesh screen, and large pieces of soil are mixed after being smashed. The soil layer height is 18cm, the bottom layer is 13cm, 40g of green machine brand humic acid bio-organic fertilizer is uniformly mixed and potted, the upper layer soil is 4cm, the soil is baked for 0.5 hour at the temperature of 80 ℃ to inactivate weed seeds, 16g of organic fertilizer is uniformly mixed and potted, 80 special-shaped cyperus rotundus seeds, 40 eclipta prostrata seeds and 80 acalypha australis seeds are uniformly placed in the pot, and the activated soil is covered for 1cm. Selecting rice seedlings with the seedling ages of 25 days and uniform growth vigor, and transplanting one rice seedling in the center of each pot of four areas respectively. According to the processing setting, adding the duckweed with the coverage rate of 70% and the duckweed with the multiple roots in the corresponding areas respectively. The potting is arranged in random blocks, and the potting positions are changed every two days in the blocks. The height of the water layer is controlled to be 5cm (the height of the grid is 8 cm).
(3) The change of environmental elements in the potted study area was examined by sampling on days 1, 8, 15, 22 and 29 after sowing weed seeds and planting rice. The illumination above and below the field surface is horizontally measured by an illuminometer, the ratio is calculated to obtain the field surface Light Transmittance (LT), and the Soil Temperature (ST) and the field surface water temperature (FT) are measured by a thermometer. Sampling the surface water, measuring the pH value (pH) and the dissolved oxygen content (DO) of the surface water by using AN electrode method within 24 hours, measuring the ammonia nitrogen concentration (AN) of the surface water by using a Nash reagent spectrophotometry method, measuring the nitrate nitrogen concentration (NN) by using AN ultraviolet spectrophotometry method, measuring the total nitrogen concentration (TN) by using AN alkaline potassium persulfate digestion-ultraviolet spectrophotometry method, and measuring the total phosphorus concentration (TP) by using a potassium persulfate digestion-ammonium molybdate spectrophotometry method.
The average light transmission over the test period of 29 days for each treatment study area is shown in FIG. 4, with the light transmission of the CK group being at most 79.91%. The light transmittance of the 1/2LP (-) and 1/2SP (-) treatments was 64.71% and 64.35%, respectively, which were significantly reduced by 19.01% and 19.46%, respectively, compared to the CK group. The transmittance of the four treatments with shielding is not obviously different, and the values are all lower, only 5.33% -8.14%, and are obviously lower than that of the three groups without shielding, and the treatment of 1/2LP (+), LP, 1/2SP (+) and SP are respectively obviously reduced by 90.80%, 93.33%, 92.84% and 89.81% compared with the treatment of CK.
The mean of the soil and water layer temperatures at the study area of each treatment over the test period of 29 days is shown in fig. 5, where the soil temperature was significantly lower in the treatment with a lemna coverage area ratio of 1 than in the other treatments, with LP and SP at 29.49 and 29.48 c, respectively, which are significantly lower than the CK group by 0.23 and 0.24 c, respectively. The temperature of a water layer is the highest in the CK group and is 30.06 ℃, the temperature of other treatments is reduced by 0.09-0.16 ℃, and only the reduction of 1/2LP (-) treatment has significance.
The mean values of the basin surface water pH and dissolved oxygen content in the study areas of each treatment at 29 days of the test period are shown in fig. 6, the pH of the CK group was the highest and 8.29, and the treatments were not significantly different from the CK group except that the LP treatment was significantly reduced by 0.52 compared to the CK group. The dissolved oxygen content was significantly different between treatments, with all four treatments being significantly lower with masking than the three unmasked groups, with 1/2LP (+), LP, 1/2SP (+) and SP treatments being significantly lower than the CK group by 7.76%, 9.94%, 8.95% and 9.08%, respectively. In the unmasked three groups, the 1/2LP (-) and 1/2SP (-) treatments were significantly reduced by 3.90% and 5.51%, respectively, compared to the CK group. In addition, the dissolved oxygen content of the 1/2SP (-) treatment is significantly lower than that of the 1/2LP (-) treatment, which is significantly lower than that of the 1/2LP (+) treatment.
The mean values of the ammonia nitrogen, nitrate nitrogen, total nitrogen and total phosphorus concentrations of the basin surface water in each treatment research area in the test period of 29 days are shown in figure 7, the ammonia nitrogen concentration of LP treatment is the highest and is 1.10 mg.L < -1 >, the ammonia nitrogen concentration is obviously higher than that of CK, 1/2LP (-) and SP groups, the ammonia nitrogen concentration is obviously increased by 92.10% compared with that of the CK group, the ammonia nitrogen concentration of 1/2SP (-) treatment is obviously higher than that of the CK and 1/2LP (-) groups, and the ammonia nitrogen concentration of 1/2SP (-) treatment is obviously increased by 75.02% compared with that of the CK group. The concentration of nitrate nitrogen in the CK group is the highest, the concentration of nitrate nitrogen is 7.68 mg.L < -1 > 1/2LP (+) treatment is obviously lower than that of the CK group and the SP group, the LP treatment is obviously lower than that of the CK group, 1/2LP (+) and LP treatment are respectively and obviously reduced by 13.78 percent and 9.13 percent compared with that of the CK group, and the other groups have no obvious difference with the CK group. The nitrate nitrogen concentration of each treatment is integrally higher than that of ammonia nitrogen, and the difference of the total nitrogen concentration among the treatments is similar to that of nitrate nitrogen. The total nitrogen concentration of the CK group is the highest, the treatment of 16.99 mg.L-1,1/2 LP (+) is obviously lower than that of the CK and SP groups, and the 1/2LP (+) is obviously reduced by 24.81 percent compared with that of the CK group. The total phosphorus concentration did not differ significantly between treatments.
Investigating the duckweed biomass in the research area and in the neighborhood as an index for embodying the interface obstruction degree, wherein the sampling time is consistent with the environmental factors, and the sampling is 8cm 2 Duckweed in the range and dried at 70 ℃ for 72 hours and then measured for dry weight to obtain duckweed biomass. The 29-day mean values of duckweed biomass in the study area over the pot trial period are shown in fig. 8, and the results indicate that there was no significant difference in duckweed biomass between treatments in the study area.
All weeds in each study area were sampled on day 30, weed species, number were recorded, and dry weight was measured after drying the weed plants at 70 ℃ for 72 hours. The density of total weeds is shown in FIG. 9, and there was no significant difference between the three unmasked groups and the four masked groups, respectively, comparing the total density of the three weeds between the treatments, and the 1/2LP (+), LP, 1/2SP (+) and SP treatments were significantly reduced by 69.27%, 74.90%, 52.19% and 53.44%, respectively, compared to the CK group, and the biomass of the total weeds is shown in FIG. 10, and the unmasked 1/2LP (-) and 1/2SP (-) treatments were significantly reduced by 64.74% and 42.33%, respectively, compared to the total biomass of the three weeds between the treatments, and there was no significant difference between the four masked treatments, and all were significantly reduced by more than 97.35% compared to the CK group.
(4) Selecting dominant environmental factors influencing weed germination from environmental factors by adopting a random forest algorithm, constructing a random forest by using a randomForest program package in R3.6.2 software, setting the number (ntree) of decision trees contained in the random forest to be 500, setting the number (mtry) of randomly selected characteristic variables of each node of the decision trees to be 3 based on the total number of environmental variables to be 9, setting the seed number to be 1 by using the R3.6.2 software to be repeated, testing the significance of the characteristic variables in the random forest by using an rfPermute command, evaluating the significance of the characteristic variables (environmental factors) according to the increment (IncMSE) of mean square error between a bag appearance observation value and a model prediction value, sequencing the significance and carrying out significance test on the characteristic variables by using a replacement test (the number of replacement is 100).
As a result, as shown in FIG. 11, both the transmittance and the water-dissolved oxygen content of the pot surface had extremely significant (P < 0.01) effects on the weed density and the weed biomass, and the increases in the mean square error of the transmittance and the dissolved oxygen content were 15.13% and 11.94%, respectively, when the response variable was the weed density, and 12.73% and 8.71%, respectively, when the response variable was the weed biomass. Thus, random forest results indicate that light transmittance and water-soluble oxygen content of the pot surface are the dominant environmental factors affecting weed density and biomass.
(5) And analyzing the influence of the duckweeds on the dominant environmental factors and the influence of the dominant environmental factors on weed generation (density and biomass) in the pot experiment by adopting a Structural Equation Model (SEM). Dividing the influence of the duckweed into a research region Duckweed Biomass (DBS) and a neighborhood Duckweed Biomass (DBN) according to sources, presetting an influence path among the duckweed biomass, the neighborhood duckweed biomass, light transmittance, water dissolved oxygen of a pot surface, weed density and weed biomass in the research region, representing causal relationship among variables by using a one-way arrow, and representing covariant relationship among the variables by using a two-way arrow, as shown in figure 12 a. And constructing a structural equation model by using a lavaan program package, estimating parameters by adopting a maximum likelihood method, and carrying out dispersion standardization and square root conversion on data in advance in order to enable the sample to accord with the assumption of normality.
As a result, as shown in fig. 12b, the numbers on the one-way arrows indicate normalized regression weights, i.e., normalized path coefficients, reflecting the magnitude of the inter-variable influence, the numbers on the two-way arrows indicate correlation coefficients, and P reflects the significance of the inter-variable influence. And integrally evaluating the model fitting result, wherein the degree of freedom ratio NC =3.743, the value is less than 5, which indicates that the preset influence path can be accepted, the comparative adaptation index CFI =0.943, the value is greater than 0.90, which indicates that the model path diagram is adapted to the actual data, the normalized residual mean square and square root SRMR =0.039, the value is less than 0.05, which also indicates that the model fitting degree can be accepted.
The result shows that the normalized path coefficient between the duckweed biomass and the light transmittance of the research area is-0.966 (P is less than 0.001), and the research area shows that the duckweed biomass has extremely remarkable negative influence on the light transmittance of the area. The normalized path coefficients between the research region duckweed biomass and the dissolved oxygen content and between the field duckweed biomass and the dissolved oxygen content are-0.816 (P < 0.001) and-0.349 (P < 0.001), respectively, so that the research region duckweed biomass and the field duckweed biomass have extremely obvious negative effects on the dissolved oxygen content. The normalized path coefficients between transmittance and weed density and transmittance and weed biomass were 0.536 (P = 0.001) and 0.778 (P < 0.001), respectively, indicating that transmittance has a significant and very significant positive effect on both weed density and biomass, respectively. The correlation coefficient between weed density and biomass was 0.584 (P = 0.001), indicating that both are significantly correlated.
Further results are shown in Table 2, where the total effect of duckweed biomass on weed density in the study area was-0.669, with an indirect effect mediated by light transmittance of-0.518 in the major portion and an indirect effect mediated by dissolved oxygen content of-0.151 in the minor portion. The total effect of the duckweed biomass on the weed biomass in the study area is-0.734, and the indirect effect mediated by the light transmittance is still the main part, and the indirect effect mediated by the dissolved oxygen content is an extremely low positive effect. The total effect of the duckweed biomass on weed density and weed biomass was low, at-0.091 and-0.032, respectively. Thus, the reduction of light by duckweed in the study area is the primary reason for the reduction of weed density and biomass, and the reduction of dissolved oxygen by duckweed in the study area may be a secondary reason for the reduction of weed density.
TABLE 2 Indirect and Total Effect of Duckweed Biomass on weed Density and weed Biomass
The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.
Claims (10)
1. A method for researching a weed prevention and control mechanism of an interface barrier to a paddy field is characterized by comprising the following steps:
(1) Manufacturing a separation permeation type device;
(2) Dividing different research areas in the separation and penetration type device, respectively scattering weed seeds in each research area, and planting rice, wherein part of the research areas are provided with interface barriers, and part of the research areas are not provided with interface barriers;
(3) Periodically acquiring environmental factor data in a research area and interface barrier data in the research area and the neighborhood, and acquiring weed germination data in the research area;
(4) Screening the dominant environmental factors influencing weed occurrence by adopting a random forest algorithm based on the environmental factor data and the weed germination data;
(5) Analyzing the influence of interface obstruction on the dominant environmental factors and the influence of the dominant environmental factors on weed occurrence by adopting a structural equation model;
in step (1), different research areas of the partitioned osmotic device are separated by a mesh which can block the interface barrier material from entering the adjacent research areas,
meanwhile, the mesh can lead the light transmittance of the water surface of a research area with the interface barrier to be different from that of the research area without the interface barrier,
meanwhile, environmental factors such as soil temperature, water layer temperature, water pH, dissolved oxygen content, ammonia nitrogen concentration, nitrate nitrogen concentration, total nitrogen concentration and total phosphorus concentration between adjacent research areas are not influenced by the net piece;
the mesh selects black to shield sidelight;
in the step (3), the environmental factors comprise water surface light transmittance, soil temperature, water layer temperature, water pH, dissolved oxygen content, ammonia nitrogen concentration, nitrate nitrogen concentration, total nitrogen concentration and total phosphorus concentration;
in the step (3), the interface barrier data comprises biological interface barrier data and non-biological interface barrier data;
the biological interface barrier data is an index capable of reflecting the biological interface shielding degree;
the abiotic interface barrier data is an index capable of reflecting the abiotic interface shielding degree;
in the step (3), 1 time every 7 days after the weed seeds are scattered and the rice is planted, and respectively acquiring environmental factor data in a research area and interface barrier data in the research area and in the neighborhood on the 1 st day, the 8 th day, the 15 th day, the 22 th day and the 29 th day;
in the step (3), the weed germination data comprise weed species, weed density and weed biomass, wherein the weed biomass refers to the dry weight mass of weeds in a certain area, and the weed density refers to the plant number of weeds in a certain area;
in the step (3), the time for acquiring the weed germination data is 30 days after the weed seeds are sown and the rice is planted.
2. The method for researching weed control mechanism of rice field by interfacial barriers according to claim 1, wherein in the step (1), the partitioned permeable unit is divided into four regions,
in the step (2), a plurality of separation and permeation devices are adopted for research, the proportion of the interface barrier area arranged in each separation and permeation device is respectively 0, 1/2 and 1,
in two groups with the proportion of the interfacial barrier area being 1/2, the area without interfacial barrier and the area with interfacial barrier are both taken as research areas,
in two sets where the ratio of interfacial barrier zones is set to 1/2, the interfacial barrier zones are separated in diagonal zones of the partitioned osmotic engine.
3. The method for researching the weed control mechanism of the rice field by the interfacial barrier according to claim 1, wherein the weeds comprise monocotyledonous, dicotyledonous and cyperaceae weeds, the monocotyledonous weeds comprise caper euphorbia seed, eclipta prostrata and amaranthus auriculata, and the weeds exclude weeds with particularly developed aeration tissues including the iris lactea.
4. The method for researching weed control mechanism of paddy field by using interface barrier as claimed in claim 1, wherein the interface barrier comprises biological interface barrier and non-biological interface barrier,
the biological interface barrier selects plants which can rapidly grow, reproduce and form interface coverage;
the non-biological interface barrier is selected to cover the water layer and separate the water-air interface.
5. The method for researching the weed control mechanism of the rice field by the interface barrier as claimed in claim 4, wherein the biological interface barrier is selected from the group consisting of duckweed, azolla and algae;
the non-biological interface barrier is selected from rice chaff, biological carbon or a polymer film.
6. The method for researching the weed control mechanism of the rice field by the interface barrier as claimed in claim 1, wherein the biological interface barrier data is coverage area or biomass;
the non-biological interface barrier data is hiding area or mass.
7. The method for researching the weed prevention and control mechanism of the rice field by the interface barrier as claimed in claim 1, wherein in the step (4), the method for screening the dominant environmental factors influencing the weed generation by adopting the random forest algorithm comprises the following steps:
randomly extracting ntree samples in an original sample set in a back-to-back mode by using a Bootstrap resampling method, performing decision tree modeling on each sample, randomly selecting mtry input variables at each node for separation, completely growing trees by using a CART method, and once the tree is constructed, combining the prediction of a plurality of decision trees and taking an average value to determine a final predicted value;
the values of ntree and mtry are selected based on the lowest error rate of the model, the ntree defaults to 500, and the mtry defaults to 1/3 of the total number of input variables; the data that is not extracted is called out-of-bag data and is used for estimating the performance of the model;
evaluating the importance of the environment elements serving as the characteristic variables according to the increment of the mean square error between the bag appearance observed value and the model predicted value, wherein the larger the value is, the larger the error of the model prediction is after the characteristic variables are randomly replaced is, and the larger the importance is; the importance of each environmental element is sorted, the significance is obtained through replacement inspection, and the environmental elements which have significant influence, namely P <0.05, are screened out and are the dominant environmental factors which influence the weed generation.
8. The method for researching the weed control mechanism of the rice field by the interfacial barriers according to claim 7, wherein in the step (4), random Forest program package is used for constructing random Forest, and rfPermute command is used for testing the significance of characteristic variables in the random Forest.
9. The method for researching the weed control mechanism of the interface barrier in the paddy field according to claim 1, wherein in the step (5), when the influence of the interface barrier on the dominant environmental factors and the influence of the dominant environmental factors on the weed germination are analyzed by using a structural equation model,
the structural equation model adopts a maximum likelihood method to estimate parameters, data are preprocessed to enable a sample to accord with normality, and the normalization method comprises dispersion standardization and square root conversion; presetting study area interface barrier data and neighborhood interface barrier data to influence dominant environmental factors, presetting the dominant environmental factors to influence weed density and weed biomass, presetting a covariant relation between the weed density and the weed biomass, establishing a basic model, then measuring influence degrees between variables or effect sizes of the variables based on a covariance matrix of the variables, integrally evaluating model fitting results according to a degree of freedom ratio NC, a comparative adaptation index CFI, a standard residual mean square and a square root SRMR of the model, 1< > NC < > 3 indicates that the model is well adapted, CFI >0.90 and SRMR <0.05 indicates that the degree of adaptation of the model can be accepted.
10. The method for researching the weed control mechanism of the rice field by the interface barrier as claimed in claim 9, wherein in the step (5), a structural equation model is constructed by using a lavaan program package and the result is evaluated.
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