CN113024894B

CN113024894B - Sowing type multifunctional gel mulching film for inhibiting weed growth and preparation and application thereof

Info

Publication number: CN113024894B
Application number: CN202110365647.4A
Authority: CN
Inventors: 蒋刚彪; 李珊珊; 胡甜; 杨子明; 吴官平
Original assignee: South China Agricultural University
Current assignee: South China Agricultural University
Priority date: 2021-04-06
Filing date: 2021-04-06
Publication date: 2022-06-28
Anticipated expiration: 2041-04-06
Also published as: CN113024894A

Abstract

The invention discloses a sowable multifunctional gel mulching film for inhibiting weed growth and preparation and application thereof. The invention takes a biomass material loaded with metal ions as a sustained and controlled release system, and forms a low-density cross-linked multifunctional gel mulching film by crosslinking the metal ions (copper, zinc and the like) and natural polymer base materials (chitosan, cellulose, sodium alginate and the like) and selectively adding functional substances (sodium chloride, glycerol and the like) with an anti-freezing effect according to environmental differences; the slow-release metal ions are used for forming a uniform gel mulching film on one hand, and the hydrogel has a high-fluidity network structure due to weak metal chelation with low crosslinking density on the other hand, and the hydrogel has the capacity of interface self-fusion due to the high-density hydrogen bonding effect, so that the gel mulching film can be restored into an original gel mulching film only by adding water when being damaged under the condition of complete dehydration, the preparation of the 'sowable' type gel mulching film is realized for the first time, and the convenience is brought to storage and transportation of the mulching film.

Description

Sowing type multifunctional gel mulching film for inhibiting weed growth and preparation and application thereof

Technical Field

The invention belongs to the field of agricultural high polymer materials, and particularly relates to a sowable multifunctional gel mulching film for inhibiting weed growth, and preparation and application thereof.

Background

Since the last century, people have realized that mulching films have the effects of preserving heat and water, improving soil properties, increasing crop yield and quality and the like, and are widely used in the world. At present, mulching films commonly used in agriculture are mainly divided into straw natural coverings, polyethylene plastic mulching films and degradable mulching films. When the straw natural covering is used for covering, weed seeds and pathogenic bacteria can be carried by the straw natural covering, so that the quantity of weeds in a farmland can be increased, the risk of crop diseases and insect pests is increased, the carbon-nitrogen ratio of the straw natural covering is too high, soil can be polluted, seedbed nitrogen can be exhausted, and the straw natural covering is not beneficial to the growth of crops; the polyethylene plastic mulching film has the problems of difficult recovery, high manual recovery cost and the like due to non-degradability and small thickness, most farmers choose to leave the polyethylene plastic mulching film in the soil continuously, and finally the polyethylene plastic mulching film becomes micro plastic which enters the deep layer of the soil and enters the environment according to water flow and enters a food chain through crops, so that certain harm is caused to human bodies and the environment, and the plastic mulching film can influence the development of plant root systems, hinder soil gas exchange, hinder moisture permeation and change the soil microbial community structure if being used for a long time; although most of materials are difficult to extract and have poor mechanical properties, the degradability of the degradable mulching film is still the development trend of the current agricultural mulching film. In addition, in the current mulching film market, farmers need to purchase mulching films according to the farming area, and the mulching films need to be cut to reserve the planting positions of crops in the covering process, so that the operation is complicated, and more time and labor cost are consumed, therefore, the development of the degradable mulching films which are simple and convenient to operate and can be purchased and used at any time is urgently needed.

Disclosure of Invention

In order to solve the defects and shortcomings of the prior art, the invention mainly aims to provide a preparation method of a sowable multifunctional gel mulching film for inhibiting weed growth.

The invention relates to a multifunctional gel mulching film capable of being sowed, which is prepared by chelating natural polymer base materials such as chitosan and the like with copper ions and adding antifreeze agents such as sodium chloride and the like. The natural polymer hydrogel has wide application in the fields of dressing, slow release systems and the like, but is applied for the first time in agriculture, and the gel mulching film not only needs to have degradability, but also needs to be planted from gelThe gel structure is controlled by factors such as the content of each component in the gel and the like, thereby realizing the operation of seeding. The natural polymer material based gel mulching film disclosed by the invention has good biocompatibility and biodegradability, can well solve the problem of white pollution caused by polyethylene mulching films, can be used in a seeding mode for the first time, can reduce the occupied area and cost of storage and transportation, can form mulching film coverage by only seeding and sprinkling water on the gel mulching film, and is simple and convenient to operate and short in time consumption. Cu in the gel mulching film ²⁺Chelating with natural polymer materials such as chitosan and the like, reducing the biotoxicity and residue of metal ions, and achieving the effects of inhibiting the growth of weeds, long-acting bacteriostasis and the like through the slow release of copper ions; and the gel mulching film can still be normally used in a low-temperature environment by adding anti-freezing agents such as glycerol, sodium chloride and the like.

The invention further aims to provide the sowable multifunctional gel mulching film for inhibiting the growth of weeds.

The invention also aims to provide application of the sowable multifunctional gel mulching film for inhibiting weed growth.

The purpose of the invention is realized by the following technical scheme:

a preparation method of a sowable multifunctional gel mulching film for inhibiting weed growth comprises the following steps:

(1) adding p-aldehyde benzoic acid, 4-Dimethylaminopyridine (DMAP) and Dicyclohexylcarbodiimide (DCC) into the chitosan solution at room temperature under the protection of nitrogen or inert gas, reacting and purifying to obtain aldehyde chitosan powder;

(2) crushing the biomass raw material, sieving the crushed biomass raw material with a sieve of 80-100 meshes, soaking the crushed biomass raw material in a copper sulfate and/or zinc sulfate solution, washing and drying to obtain biomass copper/zinc particles;

(3) dissolving carboxymethyl cellulose, carboxymethyl chitosan or sodium alginate in water, adding aldehyde chitosan powder, mixing uniformly, adding biomass copper/zinc, stirring to obtain gel, and spreading and drying to obtain the gel mulching film.

When the gel mulching film is used, a certain amount of water is required to be added to form a wet gel mulching film.

Preferably, the mass ratio of the p-aldehyde benzoic acid, the 4-dimethylaminopyridine, the dicyclohexylcarbodiimide and the chitosan in the step (1) is (30-50): (0.5-2): (10-20): (15-30).

Preferably, the p-aldehyde benzoic acid, the 4-Dimethylaminopyridine (DMAP) and the dicyclohexylcarbodiimide in the step (1) are respectively added in the form of solution, wherein the concentration of the p-aldehyde benzoic acid solution is 10-30 wt%, the concentration of the 4-dimethylaminopyridine solution is 0.5-2 wt%, the concentration of the dicyclohexylcarbodiimide solution is 10-20 wt%, the concentration of the chitosan solution is 2-5 wt%, and the solvent of the solution is at least one of dimethyl sulfoxide and tetrahydrofuran.

Preferably, the molecular weight (weight average) of the chitosan in the step (1) is 800-1000, and the deacetylation degree is 75-85%.

Preferably, the reaction time in the step (1) is 24-72 h.

Preferably, the purification method in step (1) is: and adding the product mixed solution into deionized water for sedimentation, then alternately washing for 5-10 times by using ethanol and distilled water until the solution is colorless, performing suction filtration, and performing freeze drying to obtain aldehyde chitosan powder.

More preferably, the settling time is 5-24 hours, and the suction filtration refers to normal-temperature normal-pressure suction filtration.

Preferably, the biomass raw material in the step (2) is at least one of bagasse, crop straw and activated carbon.

Preferably, the biomass raw material in the step (2) is subjected to water washing and drying treatment before being crushed.

Preferably, the size of the biomass raw material sieved in the step (2) is 0.15-0.2 mm.

Preferably, the mass concentration of the copper sulfate and/or zinc sulfate solution in the step (2) is 40-80%, and the solvent is water.

Preferably, the mass ratio of the biomass raw material in the step (2) to the copper sulfate and/or the zinc sulfate is 1: 4-1: 2.

Preferably, the soaking time in the step (2) is 1-10 hours.

Preferably, the washing in step (2) refers to water washing, and the drying is conventional vacuum drying.

Preferably, the mass ratio of the carboxymethyl cellulose or carboxymethyl chitosan or sodium alginate, the aldehyde chitosan powder and the biomass copper/zinc in the step (3) is 150:15: 1-150: 15: 2.

Preferably, the concentration of the carboxymethyl cellulose, carboxymethyl chitosan or sodium alginate dissolved in the water in the step (3) is 40-80 mg/ml.

Preferably, after the carboxymethyl cellulose, the carboxymethyl chitosan or the sodium alginate in the step (3) is dissolved in water, an antifreezing agent can be added according to the difference of regions and temperatures, wherein the antifreezing agent is sodium chloride or glycerol and glycol, the mass concentration of the sodium chloride in the water is 5-80%, and the mass concentrations of the glycerol and the glycol in the water are 0.01-0.1% and 5-40% respectively.

Preferably, the aldehyde chitosan powder in the step (3) is added in the form of solution, and the concentration of the aldehyde chitosan powder is 10-50 mg/ml.

Preferably, the biomass copper/zinc in the step (3) is added in the form of solution, and the concentration of the solution is 4-8 mg/ml.

Preferably, the flat laying in the step (3) adopts a casting method, and the drying temperature is 50-70 ℃.

The multifunctional gel mulching film capable of being sown and inhibiting weed growth is prepared by the method.

The gel mulching film can be dried into a piece film or smashed into powder, when in use, the gel mulching film is scattered on the soil surface, a certain amount of water is poured, and after the mulching film absorbs water and returns to a gel state, the complete gel mulching film is formed.

The application of the sowable multifunctional gel mulching film for inhibiting weed growth in the field of plant planting is provided.

Compared with the prior art, the invention has the following advantages and beneficial effects:

1. the multifunctional gel mulching film can be prepared into a piece film or powder according to different use environments, can be restored and assembled into a whole at room temperature by adding water, realizes the use of the gel mulching film in a seeding mode, does not need to measure and cut the coverage area, greatly expands the applicable scene of the mulching film, simplifies the film laying step, and brings convenience for storing and transporting the mulching film.

2. The multifunctional gel mulching film has rich raw material sources and simple preparation, can be produced in a large scale, and can be prepared into the gel by mixing and stirring the raw materials in one pot at normal temperature. The natural polymer material selected by the invention has good biodegradability, the degradation time in soil is about 3 months, and the natural polymer material can be finally degraded into CO₂And H₂O, is an environment-friendly material. The biodegradability of the multifunctional gel mulching film provides a new entry point for finding a substitute of a plastic mulching film.

3. The multifunctional gel mulching film prepared by the invention has certain weed growth inhibiting capacity and broad-spectrum antibacterial activity, and achieves the effects of inhibiting weed growth and reducing plant diseases and insect pests by slowly releasing metal ions such as copper and the like; meanwhile, the harm of free metal ions to the environment can be reduced by using natural polymer-based derivatives such as chitosan and the like as carriers. The prepared gel has certain self-repairing capacity and strong adhesiveness, has strong adhesion to soil, can resist scouring of storm and can fix sandy soil; in addition, the antifreeze such as sodium chloride and the like selectively added according to the difference of regions and temperatures can effectively increase the apparent viscosity of the gel, improve the thermal stability and the freezing resistance of the gel, and avoid the frostbite of the gel on the growth of crops in a low-temperature environment.

Drawings

Fig. 1 is a real object diagram of the simulated farmland environment of the gel mulching film of example 1, and the left diagram is a diagram in which a fragment film of the multifunctional gel mulching film prepared by the present invention is "sown" on the soil surface, and after a certain amount of water is applied, a complete gel mulching film is formed in a short time (5-20min), and the right diagram is obtained.

Fig. 2 is a real object diagram (24mg of bagasse copper, the situation after the mulch is added with water) of a farmland environment simulated by comparative example 1, and it is obvious from comparison with fig. 1 that the addition of high content of bagasse copper enhances the metal chelating ability, so that the network structure of the gel is irreversibly destroyed after drying, and the gel cannot be restored to the original gel state when a certain amount of water is applied, and thus it can be obtained that, in an agricultural mulch, if the application of the gel mulch is to be achieved, the concentration of the gel needs to be strictly controlled, and not all self-healing gels can be applied to the agricultural gel mulch.

FIG. 3 is a graph showing the weed-suppressing effect of the multifunctional gel mulching film, wherein the histograms of FIGS. 3a-b show the suppression of the purslane seeds of example 1 and the comprehensive weed seeds (purslane and crab grass) of example 4 in sequence, and the gel mulching film can effectively suppress the germination of weeds in the first twelve days when the seeds are critical to the germination, compared with the control group without the mulching film; FIG. 3c is a line graph showing the inhibition of purslane and crab grass (example 5) which have germinated and grown before mulching and natural comprehensive weeds (example 6), and from the general trend of the graph, the germination rate of the weeds can be remarkably reduced and delayed after mulching, the weeds which have germinated and grown can be obviously inhibited from continuing to grow, but the inhibition effect is not strong in seed germination inhibition; the potted plants of FIGS. 3d-e show the growth of the weeds "crab Tang" (example 7) and "Chenopodium quinoa" (example 3) before (left) and seven days after (right) mulching, indicating the growth inhibition of the weeds.

Fig. 4 is a diagram of a plant growth safety verification object of the non-target crop of example 2, from the left figure, it can be seen that the weed seeds after being filmed for several days have almost no germination sign, but the weeds around the weed seeds where the film is not being filmed can still grow tenaciously, and from the right figure, the crops which are not covered can still germinate and grow normally after being filmed for several days, which shows that the mulching film has no biological toxicity to the non-target plants and crops which are not covered, and actually the mulching film after being gelated for several days is adhered with soil to form a soil film structure.

Fig. 5 is a graph showing the antibacterial effect of the gel mulching film of example 1 (the left is Staphylococcus aureus (s. aureus, ATCC 6538, purchased from the collection and management center of microorganisms of guangdong china), and the right is Escherichia coli (ATCC 25922, purchased from the collection and management center of microorganisms of guangdong china)), from which it can be clearly seen that an obvious bacteriostatic circle is formed around the gel mulching film, which proves that the gel has a certain antibacterial effect on gram-negative bacteria such as Escherichia coli and Staphylococcus aureus, etc., can play a certain pest control effect in crop planting, and improve crop planting quality.

Fig. 6 is a graph of the degradation performance of the gel mulching film in the soil with the humidity controlled to be 30-50% in example 1, the degradation rate of the gel is maintained at 10% in the first 14 days of degradation of the gel mulching film, but in the subsequent degradation time, the average degradation rate per week is about 10%, and the degradation rate until the 63 rd day (the seventh week) reaches 80%, while the period of planting general crops is 2-3 months, the time and labor cost for farmers to recycle waste films can be effectively reduced, the residual mulching film is nearly completely degraded before the next re-planting, and a new round of film laying planting can be started.

Detailed Description

The present invention will be described in further detail with reference to examples and drawings, but the embodiments of the present invention are not limited thereto.

The examples of the present invention, in which specific conditions are not specified, were carried out according to conventional conditions or conditions recommended by the manufacturer. The raw materials, reagents and the like used without reference to manufacturers are all conventional products which can be obtained by commercial purchase.

The chitosan used in the embodiment of the invention has the molecular weight of 800-1000 and the deacetylation degree of 75-85%, and is model MB0036 of Dalian Meilun biotechnology Limited company.

Example 1

(1) 2.5g of chitosan, 4.5g of p-aldehyde benzoic acid, 0.1g of 4-Dimethylaminopyridine (DMAP) and 1.68g of Dicyclohexylcarbodiimide (DCC) were weighed out and dissolved in a certain amount of dimethyl sulfoxide at concentrations of 3, 18, 0.9 and 14 wt%, respectively. Stirring by magnetic force until the solution is dissolved uniformly, and storing at low temperature for later use. Adding a p-aldehyde benzoic acid solution, a DMAP solution and a DCC solution into the prepared chitosan solution in sequence at a volume ratio of 5:2:1:1, magnetically stirring for reaction for 30h, taking out the mixed solution, adding a certain amount of deionized water for settling for 12h, alternately washing for 6 times by using ethanol and distilled water, performing suction filtration, and performing freeze drying to obtain aldehyde chitosan powder.

(2) Preparing bagasse copper: washing the recycled bagasse with distilled water, placing the bagasse in a constant-temperature drying oven at 105 ℃ to be dried to constant weight, crushing the dried bagasse with a high-speed crusher, sieving with a 80-mesh sieve to obtain bagasse particles with the particle size of 0.15-0.2mm, weighing 20g of the bagasse particles, soaking the bagasse particles in 100ml of a copper sulfate solution with the mass concentration of 60% for 3 hours, washing the bagasse particles with distilled water, performing suction filtration for several times, performing vacuum drying, and sealing the dried bagasse copper particles in a sample bag.

(3) 1.2g of carboxymethyl cellulose is weighed and dissolved in 20ml of deionized water, and the solution is stirred by magnetic force for 1 hour until the solution is clear.

(4) 0.12g of aldehyde chitosan is weighed in 4ml of deionized water, evenly dispersed by ultrasonic, added into the solution (3) and stirred for 2 hours by magnetic force.

(5) Weighing 12mg of bagasse copper in 2ml of deionized water, dispersing uniformly by ultrasonic, adding into the mixture obtained in the step (3), and stirring by magnetic force until the solution is in a gel state.

(6) And putting the prepared gel into a drying oven at 65 ℃ to be dried into a fragment film or smashed into powder.

(7) And (3) spreading the prepared gel mulching film on the surface of the flowerpot soil with the existing weed seeds of the purslane, pouring a certain amount of water, and recovering the gel mulching film into a gel state after the mulching film absorbs water to form the complete gel mulching film.

Example 2

(1) 2.5g of chitosan, 4.5g of p-aldehyde benzoic acid, 0.1g of 4-Dimethylaminopyridine (DMAP) and 1.68g of Dicyclohexylcarbodiimide (DCC) were weighed out and dissolved in a certain amount of dimethyl sulfoxide at concentrations of 3, 18, 0.9 and 14 wt%, respectively. Magnetically stirring until the solution is dissolved uniformly, and storing at low temperature for later use. Adding a p-aldehyde benzoic acid solution, a DMAP solution and a DCC solution into the prepared chitosan solution in sequence at a volume ratio of 5:2:1:1, magnetically stirring for reaction for 30h, taking out the mixed solution, adding a certain amount of deionized water for settling for 12h, alternately washing for 6 times by using ethanol and distilled water, performing suction filtration, and performing freeze drying to obtain aldehyde chitosan powder.

(2) Preparing bagasse copper: washing the recycled bagasse with distilled water, placing the bagasse in a constant-temperature drying oven at 105 ℃ to be dried to constant weight, crushing the dried bagasse with a high-speed crusher, sieving with a 80-mesh sieve to obtain bagasse particles with the particle size of 0.15-0.2mm, weighing 20g of the bagasse particles, soaking the bagasse particles in 100ml of copper acetate solution with the mass concentration of 60% for 3 hours, washing the bagasse particles with distilled water, performing suction filtration for several times, performing vacuum drying, and sealing the dried bagasse copper particles in a sample bag.

(3) 1.2g of carboxymethyl chitosan is weighed and dissolved in 20ml of deionized water, and the solution is stirred for 1 hour by magnetic force until the solution is clear.

(4) 0.12g of aldehyde chitosan is weighed in 4ml of deionized water, evenly dispersed by ultrasonic, added into the solution (3), and stirred for 2 hours by magnetic force.

(5) And (3) weighing 12mg of bagasse copper into 2ml of deionized water, ultrasonically dispersing the bagasse copper uniformly, adding the bagasse copper into the solution (3), and magnetically stirring the solution until the solution is in a gel state.

(6) And putting the prepared gel into a 65 ℃ oven to be dried into a chip film or smashed into powder.

(7) Spreading the prepared gel mulching film fragments in a flowerpot with weed seeds of crabgrass, pouring a certain amount of water, and recovering the gel mulching film to be in a gel state after the mulching film absorbs water to form the complete gel mulching film.

Example 3

(2) Preparing activated carbon copper: washing the recovered activated carbon with distilled water, placing the washed activated carbon in a constant-temperature drying box at 105 ℃ to be dried to constant weight, crushing the dried activated carbon with a high-speed crusher, sieving the crushed activated carbon with a 80-mesh sieve to obtain activated carbon particles with the particle size of 0.15-0.2mm, weighing 20g of the activated carbon particles, soaking the activated carbon particles in 100ml of copper sulfate solution with the mass concentration of 60% for 3 hours, washing the activated carbon particles with distilled water, performing suction filtration for several times, performing vacuum drying, and sealing the dried activated carbon copper particles in a sample bag.

(3) Weighing 1.2g of sodium alginate, dissolving in 20ml of deionized water, and magnetically stirring for 1 hour until the solution is clear.

(5) And (3) weighing 12mg of activated carbon copper in 2ml of deionized water, uniformly dispersing by ultrasonic, adding into the solution (3), and magnetically stirring until the solution is in a gel state.

(7) Spreading the prepared gel mulching film fragments in a flowerpot with Chenopodium quinoa, pouring a certain amount of water, and recovering to gel state after the mulching film absorbs water to form a complete gel mulching film.

Example 4

(2) Preparing activated carbon copper: washing the recovered activated carbon with distilled water, placing the washed activated carbon in a constant-temperature drying oven at 105 ℃ for drying to constant weight, crushing the dried activated carbon with a high-speed crusher, sieving with a 80-mesh sieve to obtain activated carbon particles with the particle size of 0.15-0.2mm, weighing 20g of the activated carbon particles, soaking the activated carbon particles in 100ml of 60% copper acetate solution for 3 hours, washing with distilled water for several times of suction filtration, performing vacuum drying, and sealing the dried activated carbon copper particles in a sample bag.

(5) Weighing 12mg of activated carbon copper in 2ml of deionized water, uniformly dispersing by ultrasonic, adding into the solution (3), and magnetically stirring until the solution is in a gel state.

(7) The prepared gel mulching film fragments are flatly laid in flowerpots with weed seeds of purslane and crab grass, a certain amount of water is poured, and after the mulching film absorbs water and recovers to a gel state, a complete gel mulching film is formed.

Example 5

(1) 2.5g of chitosan, 4.5g of p-aldehyde benzoic acid, 0.1g of 4-Dimethylaminopyridine (DMAP) and 1.68g of Dicyclohexylcarbodiimide (DCC) are respectively weighed and dissolved in a certain amount of dimethyl sulfoxide, and the concentrations are respectively 3, 18, 0.9 and 14 wt%. Stirring by magnetic force until the solution is dissolved uniformly, and storing at low temperature for later use. Adding a p-formyl benzoic acid solution, a DMAP solution and a DCC solution into the prepared chitosan solution in sequence according to the volume ratio of 5:2:1:1, magnetically stirring for reaction for 30 hours, taking out the mixed solution, adding a certain amount of deionized water for settling for 12 hours, alternately washing for 6 times by using ethanol and distilled water, carrying out suction filtration, and carrying out freeze drying to obtain formyl chitosan powder.

(2) Preparing bagasse copper: washing the recycled bagasse with distilled water, placing the bagasse in a constant-temperature drying oven at 105 ℃ to be dried to constant weight, crushing the dried bagasse with a high-speed crusher, sieving with a 80-mesh sieve to obtain bagasse particles with the particle size of 0.15-0.2mm, weighing 20g of the bagasse particles, soaking the bagasse particles in a copper sulfate solution with the mass concentration of 60% for 3 hours, washing with distilled water, performing suction filtration for several times, performing vacuum drying, and sealing the dried bagasse copper particles in a sample bag.

(3) 1.2g of sodium chloride are metered in and dissolved in 20ml of deionized water.

(4) Weighing 1.2g of carboxymethyl chitosan, dissolving the carboxymethyl chitosan in the solution (3), and magnetically stirring the solution for 1 hour until the solution is clear.

(5) 0.12g of aldehyde chitosan is weighed in 4ml of deionized water, evenly dispersed by ultrasonic, added into the solution (3) and stirred for 2 hours by magnetic force.

(6) Weighing 12mg of bagasse copper in 2ml of deionized water, dispersing uniformly by ultrasonic, adding into the mixture obtained in the step (3), and stirring by magnetic force until the solution is in a gel state.

(7) And putting the prepared gel into a drying oven at 65 ℃ to be dried into a fragment film or smashed into powder.

(8) And flatly paving the prepared gel mulching film fragments in flowerpots full of weed purslane and crab grass, watering a certain amount of water, and recovering the gel mulching film to be in a gel state after the mulching film absorbs water to form a complete gel mulching film.

Example 6

(1) 2.5g of chitosan, 4.5g of p-aldehyde benzoic acid, 0.1g of 4-Dimethylaminopyridine (DMAP) and 1.68g of Dicyclohexylcarbodiimide (DCC) are respectively weighed and dissolved in a certain amount of dimethyl sulfoxide organic solvent, and the concentrations are respectively 3, 18, 0.9 and 14 wt%. Stirring by magnetic force until the solution is dissolved uniformly, and storing at low temperature for later use. Adding a p-aldehyde benzoic acid solution, a DMAP solution and a DCC solution into the prepared chitosan solution in sequence at a volume ratio of 5:2:1:1, magnetically stirring for reaction for 30h, taking out the mixed solution, adding a certain amount of deionized water for settling for 12h, alternately washing for 6 times by using ethanol and distilled water, performing suction filtration, and performing freeze drying to obtain aldehyde chitosan powder.

(2) Preparing bagasse zinc: washing the recycled bagasse by using distilled water, placing the washed bagasse in a constant-temperature drying box at 105 ℃ to be dried to constant weight, crushing the dried bagasse by using a high-speed crusher, sieving the crushed bagasse by using a 80-mesh sieve to obtain bagasse particles with the particle size of 0.15-0.2mm, weighing 20g of the bagasse particles, soaking the bagasse particles in 100ml of zinc sulfate solution with the mass concentration of 60% for 3 hours, washing the bagasse particles with distilled water, performing suction filtration for several times, performing vacuum drying, and sealing the dried bagasse zinc particles in a sample bag.

(5) 0.12g of aldehyde chitosan is weighed in 4ml of deionized water, evenly dispersed by ultrasonic, added into the solution (3), and stirred for 2 hours by magnetic force.

(6) And (3) weighing 12mg of bagasse zinc in 2ml of deionized water, uniformly dispersing by ultrasonic waves, adding into the mixture in the step (3), and magnetically stirring until the solution is in a gel state.

(7) And putting the prepared gel into a 65 ℃ oven to be dried into a chip film or smashed into powder.

(8) And spreading the prepared gel mulching film fragments in a flowerpot full of natural comprehensive weeds, pouring a certain amount of water, and recovering the gel mulching film to be in a gel state after the mulching film absorbs water to form the complete gel mulching film.

Example 7

(1) 2.5g of chitosan, 4.5g of p-aldehyde benzoic acid, 0.1g of 4-Dimethylaminopyridine (DMAP) and 1.68g of Dicyclohexylcarbodiimide (DCC) were respectively weighed and dissolved in a certain amount of dimethyl sulfoxide organic solvent, and the concentrations were 3, 18, 0.9 and 14 wt%. Magnetically stirring until the solution is dissolved uniformly, and storing at low temperature for later use. Adding a p-aldehyde benzoic acid solution, a DMAP solution and a DCC solution into the prepared chitosan solution in sequence at a volume ratio of 5:2:1:1, magnetically stirring for reaction for 30h, taking out the mixed solution, adding a certain amount of deionized water for settling for 12h, alternately washing for 6 times by using ethanol and distilled water, performing suction filtration, and performing freeze drying to obtain aldehyde chitosan powder.

(2) Preparing activated carbon zinc: washing the recovered activated carbon with distilled water, placing the washed activated carbon in a constant-temperature drying box at 105 ℃ for drying to constant weight, crushing the dried activated carbon with a high-speed crusher, sieving with a 80-mesh sieve to obtain activated carbon particles with the particle size of 0.15-0.2mm, weighing 20g of the activated carbon particles, soaking the activated carbon particles in 100ml of zinc sulfate solution with the mass concentration of 60% for 3 hours, washing with distilled water for suction filtration for several times, drying in vacuum, and sealing the dried activated carbon zinc particles in a sample bag.

(5) Weighing 12mg of activated carbon zinc in 2ml of deionized water, uniformly dispersing by ultrasonic, adding into the solution (3), and magnetically stirring until the solution is in a gel state.

(8) Spreading the prepared gel mulching film fragments in a flowerpot with the existing weed crabgrass, pouring a certain amount of water, and recovering the gel mulching film to be in a gel state after the mulching film absorbs water to form a complete gel mulching film.

Example 8

(3) 1.2g of sodium chloride was weighed out and dissolved in 20ml of deionized water.

(4) Weighing 1.2g of carboxymethyl chitosan to be dissolved in the solution (3), and magnetically stirring for 1h until the solution is clear.

(8) Spreading the prepared gel mulching film fragments in a flowerpot with weed seeds such as purslane and crab grass, pouring a certain amount of water, and recovering the gel mulching film to be in a gel state after the mulching film absorbs water to form the complete gel mulching film.

Example 9

(2) Preparing bagasse copper: washing the recycled bagasse with distilled water, placing the washed bagasse in a constant-temperature drying box at 105 ℃ to be dried to constant weight, crushing the dried bagasse with a high-speed crusher, sieving the crushed bagasse with a 80-mesh sieve to obtain bagasse particles with the particle size of 0.15-0.2mm, weighing 20g of the bagasse particles, soaking the bagasse particles in 100ml of copper sulfate solution with the mass concentration of 60% for 3 hours, washing the bagasse particles with distilled water, performing suction filtration for several times, performing vacuum drying, and sealing the dried bagasse copper particles in a sample bag.

(3) 1.2g of carboxymethyl cellulose was weighed out and dissolved in 20ml of deionized water, and the solution was stirred magnetically for 1 hour until the solution was clear.

(5) Weighing 8mg of bagasse copper in 2ml of deionized water, uniformly dispersing by ultrasonic waves, adding into the solution (3), and magnetically stirring until the solution is in a gel state.

Example 10

(5) Weighing 16mg of bagasse copper in 2ml of deionized water, uniformly dispersing by ultrasonic waves, adding into the solution (3), and magnetically stirring until the solution is in a gel state.

Comparative example 1

(2) Preparing bagasse copper: washing the recycled bagasse with distilled water, placing the bagasse in a constant-temperature drying oven at 105 ℃ to be dried to constant weight, crushing the dried bagasse with a high-speed crusher, sieving with a 80-mesh sieve to obtain bagasse particles with the particle size of 0.15-0.2mm, weighing 20g of the bagasse particles, soaking the bagasse particles in 100ml of copper sulfate solution with the mass concentration of 60% for 3 hours, washing the bagasse particles with distilled water, performing suction filtration for several times, performing vacuum drying, and sealing the dried bagasse copper particles in a sample bag.

(3) 2 parts of 1.2g sodium chloride are weighed out and dissolved in 20ml of deionized water.

(4) Weighing 2 parts of 1.2g carboxymethyl chitosan, respectively dissolving in the sodium chloride solution (3), and magnetically stirring for 1h until the solution is clear.

(5) Weighing 2 parts of 0.12g aldehyde chitosan, respectively adding into 4ml deionized water, dispersing uniformly by ultrasonic, adding into the solution (3), and stirring for 2h by magnetic force.

(6) 4mg and 24mg of bagasse copper are weighed and respectively placed in 2ml of deionized water, the ultrasonic dispersion is uniform, the bagasse copper is respectively added into 2 parts of the solution (3), and the solution is stirred by magnetic force until the solution is in a gel state.

(8) The prepared gel mulching film fragments are flatly laid in a flowerpot of the crabgrass which is the existing weed seed, a certain amount of water is poured, and the gel mulching film is restored to a gel state after the water is absorbed by the mulching film, so that the complete gel mulching film is formed.

The result shows that the solution can not be gelatinized due to the excessively low concentration of the 4mg bagasse copper, the structure is damaged due to the higher metal chelating capacity of the gel added with the 24mg bagasse copper after drying, and the gel can not be recovered into gel after applying water, which proves that the concentration of metal ions needs to be strictly selected when the gel mulching film is manufactured.

Comparative example 2

(2) Preparing activated carbon copper: washing the recovered activated carbon with distilled water, placing the washed activated carbon in a constant-temperature drying box at 105 ℃ for drying to constant weight, crushing the dried activated carbon with a high-speed crusher, sieving with a 80-mesh sieve to obtain activated carbon particles with the particle size of 0.15-0.2mm, weighing 20g of the activated carbon particles, soaking the activated carbon particles in 100ml of copper sulfate solution with the mass concentration of 60% for 3 hours, washing with distilled water for suction filtration for several times, drying in vacuum, and sealing the dried activated carbon copper particles in a sample bag.

(5) Weighing 2 parts of 0.12g aldehyde chitosan, respectively putting into 4ml deionized water, uniformly dispersing by ultrasonic, respectively adding into 2 parts of (3) solution, and magnetically stirring for 2 h.

(6) Weighing 4mg and 24mg of activated carbon copper respectively in 2ml of deionized water, uniformly dispersing by ultrasonic, respectively adding into 2 parts of (3), and magnetically stirring until the solution is in a gel state.

(8) Spreading the prepared gel mulching film fragments in a flowerpot with weed seeds of crabgrass, pouring a certain amount of water, and recovering the gel mulching film to be in a gel state after the mulching film absorbs water to form the complete gel mulching film.

The result shows that the solution can not be gelatinized due to the excessively low concentration of the 4mg of activated carbon copper, the structure is damaged due to the higher chelating capacity and the stronger chelating capacity of the gel added with 24mg of activated carbon copper after drying, and the gel can not be recovered by applying water, which proves that the concentration of metal ions needs to be strictly selected when the gel mulching film is manufactured.

Comparative example 3

(2) Preparing bagasse copper: washing the recycled bagasse with distilled water, placing the washed bagasse in a constant-temperature drying box at 105 ℃ to be dried to constant weight, crushing the dried bagasse with a high-speed crusher, sieving the crushed bagasse with a 80-mesh sieve to obtain bagasse particles with the particle size of 0.15-0.2mm, weighing 20g of the bagasse particles, soaking the bagasse particles in 100ml of copper acetate solution with the mass concentration of 60% for 3 hours, carrying out vacuum drying, and sealing the dried bagasse copper particles in a sample bag.

(3) 1 part of 1.2g of sodium chloride was weighed out and dissolved in 20ml of deionized water.

(4) 1 part of 1.2g carboxymethyl chitosan is weighed and respectively dissolved in the sodium chloride solution (3), and the solution is stirred for 1 hour by magnetic force until the solution is clear.

(5) Weighing 1 part of 0.12g aldehyde chitosan, respectively dissolving in 4ml deionized water, uniformly dispersing by ultrasonic, adding into 2 parts of the solution (3), and magnetically stirring for 2 hours.

(6) 12mg of bagasse (acetic acid) copper particles are weighed into 2ml of deionized water, uniformly dispersed by ultrasonic, added into 2 parts of the mixture (3), and stirred by magnetic force until the solution is in a gel state.

The result shows that the effect of inhibiting the growth of weeds by the bagasse copper gel mulching film soaked by the copper acetate solution is poor, and the release rate of bagasse (copper acetate) is slow, so that the effect of inhibiting weeds is not obvious after the gel mulching film is applied, the inhibition efficiency is low, and part of weeds germinate.

Comparative example 4

(1) Respectively weighing a certain amount of chitosan, p-aldehyde benzoic acid, 4-Dimethylaminopyridine (DMAP) and Dicyclohexylcarbodiimide (DCC) and dissolving the chitosan, the p-aldehyde benzoic acid, the 4-Dimethylaminopyridine (DMAP) and the Dicyclohexylcarbodiimide (DCC) in a certain amount of dimethyl sulfoxide, wherein the concentrations are respectively 3, 18, 0.9 and 14 wt%. Magnetically stirring until the solution is dissolved uniformly, and storing at low temperature for later use. Adding a p-aldehyde benzoic acid solution, a DMAP solution and a DCC solution into the prepared chitosan solution in sequence at a volume ratio of 5:2:1:1, magnetically stirring for reaction for 30h, taking out the mixed solution, adding a certain amount of deionized water for settling for 12h, alternately washing for 6 times by using ethanol and distilled water, performing suction filtration, and performing freeze drying to obtain aldehyde chitosan powder.

(2) Preparing bagasse copper: washing the recycled bagasse with distilled water, placing the washed bagasse in a constant-temperature drying box at 105 ℃ to be dried to constant weight, crushing the dried bagasse with a high-speed crusher, respectively sieving with a 150-mesh sieve and a 60-mesh sieve to obtain bagasse particles of 0.1-0.14mm and 0.21-0.25mm, weighing 20g of the bagasse particles, soaking the bagasse particles in 100ml of copper sulfate solution with the mass concentration of 60% for 3 hours, washing with distilled water, performing suction filtration for several times, performing vacuum drying, and sealing the dried bagasse copper particles in a sample bag.

(6) 12mg of bagasse copper with the particle size of 0.1-0.15mm and 0.2-0.25mm are weighed and respectively placed in 2ml of deionized water, the uniform ultrasonic dispersion is carried out, the bagasse copper is respectively added into 2 parts of the solution (3), and the solution is stirred by magnetic force until the solution is in a gel state.

The result shows that the smaller the bagasse particles are, the larger the surface area is, the faster the prepared bagasse copper gel releases copper ions, wherein the particle size is too small, the release speed is too high, the time film cannot release the efficacy again when weeds continue to invade in the later period, while the particle size is too large, the release speed is too slow, the weed inhibition effect is not remarkable, the inhibition efficiency is low, and part of weeds germinate.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such modifications are intended to be included in the scope of the present invention.

Claims

1. A preparation method of a sowable multifunctional gel mulching film for inhibiting weed growth is characterized by comprising the following steps:

(1) adding p-aldehyde benzoic acid, 4-dimethylaminopyridine and dicyclohexylcarbodiimide into a chitosan solution at room temperature under the protection of nitrogen or inert gas, reacting and purifying to obtain aldehyde chitosan powder;

(3) dissolving carboxymethyl cellulose, carboxymethyl chitosan or sodium alginate in water, adding aldehyde-based chitosan powder, uniformly mixing, adding biomass copper/zinc, stirring to obtain gel, and flatly paving and drying to obtain the gel mulching film;

the mass ratio of the biomass raw material to the copper sulfate and/or zinc sulfate in the step (2) is 1: 4-1: 2;

The mass ratio of the carboxymethyl cellulose or carboxymethyl chitosan or sodium alginate to the aldehyde chitosan powder to the biomass copper/zinc in the step (3) is 150:15: 1-150: 15: 2;

the biomass raw material in the step (2) is at least one of bagasse, crop straw and activated carbon;

the size of the biomass raw material sieved in the step (2) is 0.15-0.2 mm.

2. The preparation method of the sowable multifunctional gel mulching film for inhibiting the growth of weeds according to claim 1, wherein the copper sulfate and/or zinc sulfate solution in the step (2) is 40-80% in mass concentration, and the solvent is water; and (3) soaking for 1-10 hours.

3. The preparation method of the sowable multifunctional gel mulching film for inhibiting the growth of weeds according to claim 1, wherein the concentration of the carboxymethyl cellulose, carboxymethyl chitosan or sodium alginate dissolved in water in the step (3) is 40-80 mg/ml; the aldehyde chitosan powder is added in the form of aldehyde chitosan solution, and the concentration of the aldehyde chitosan solution is 10-50 mg/ml; the biomass copper/zinc is added in a liquid form, and the concentration of the liquid is 4-8 mg/ml.

4. The preparation method of the sowing-type multifunctional gel mulching film for inhibiting weed growth according to claim 1, wherein the mass ratio of the p-aldehyde benzoic acid, the 4-dimethylamino pyridine, the dicyclohexyl carbodiimide and the chitosan in the step (1) is (30-50): (0.5-2): (10-20): (15-30);

the p-aldehyde benzoic acid, the 4-dimethylaminopyridine and the dicyclohexylcarbodiimide in the step (1) are added in a solution form respectively, wherein the concentration of a p-aldehyde benzoic acid solution is 10-30 wt%, the concentration of a 4-dimethylaminopyridine solution is 0.5-2 wt%, the concentration of a dicyclohexylcarbodiimide solution is 10-20 wt%, and the concentration of a chitosan solution is 2-5 wt%;

in the step (1), the molecular weight of the chitosan is 800-1000, and the deacetylation degree is 75-85%; the reaction time is 24-72 h.

5. The method for preparing the sowable multifunctional gel mulching film for inhibiting the growth of weeds according to claim 1, wherein an antifreezing agent is further added after the carboxymethyl cellulose, the carboxymethyl chitosan or the sodium alginate in the step (3) are dissolved in water, wherein the antifreezing agent is sodium chloride or glycerol or ethylene glycol, the mass concentration of the sodium chloride in the water is 5-80%, and the mass concentrations of the glycerol and the ethylene glycol in the water are 0.01-0.1% and 5-40%, respectively.

6. The method for preparing the multifunctional sowable gel mulching film for inhibiting the growth of weeds according to claim 1, wherein the step (3) of spreading the film by a tape casting method, and the drying temperature is 50-70 ℃.

7. A sowable multifunctional gel mulching film for suppressing the growth of weeds, which is prepared by the method as claimed in any one of claims 1 to 6.

8. The use of the multifunctional sowable gel mulching film for inhibiting weed growth in the field of plant cultivation as claimed in claim 7.