A natural herbicide and a method for preparing the same

Abstract

The present application relates to the field of agricultural plant protection and biological herbicide technology, and particularly relates to a natural herbicide and a preparation method thereof. The natural herbicide comprises water extract of the whole plant of Solanum incanum as an active ingredient. The preparation method of the natural herbicide comprises the following steps: (1) washing, drying and crushing the whole plant of Solanum incanum to obtain the whole plant powder of Solanum incanum; (2) mixing the whole plant powder of Solanum incanum with water, and extracting under low-temperature and dark conditions; (3) performing solid-liquid separation on the mixture after extraction, collecting the supernatant to obtain the natural herbicide. The present application not only solves the ecological damage caused by the overgrowth of Solanum incanum, but also replaces the chemical herbicide, reduces pesticide residues, and meets the development direction of green agriculture.

Description

Technical Field

[0001] This invention relates to the field of agricultural plant protection and bio-based herbicides, specifically to a natural herbicide and its preparation method. Background Technology

[0002] Weed infestation is one of the core limiting factors leading to reduced crop yields and lower quality. For a long time, chemical herbicides have been widely used due to their advantages such as high efficiency, rapid application, and low cost. However, their long-term excessive use has led to problems such as pesticide residues and herbicide resistance in weeds, which does not meet the requirements of green agriculture and sustainable development.

[0003] Existing plant-derived herbicides mostly use medicinal plants or cash crops as raw materials, which have drawbacks such as high raw material costs, limited sources, and unstable herbicidal activity. Products made from agricultural waste (such as straw, artemisia powder, etc.) suffer from problems such as low content of active ingredients and unstable efficacy.

[0004] Kaxi eggplant ( Solanum khasianum Solanum CB Clarke (Solanum caxifolium) is an invasive alien species belonging to the Solanaceae family. It is widely distributed in Yunnan, Guangxi, and Sichuan provinces of my country, posing a threat to the local ecological environment and biodiversity. The entire plant contains toxic alkaloids and has thorns, which also negatively impact agricultural production and animal husbandry. Currently, there is no technology to utilize the invasive plant Solanum caxifolium to prepare natural herbicides, thus achieving a resource utilization solution for "controlling farmland weeds with invasive weeds."

[0005] Therefore, developing a novel natural herbicide that is widely available, inexpensive, environmentally friendly, and has selective herbicidal activity is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to provide a natural herbicide and its preparation method, so as to solve the problems of environmental unfriendliness and weed resistance in existing chemical herbicides, as well as the defects of high raw material cost and unstable activity of existing plant-derived herbicides.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A natural herbicide containing calcifera ( Solanum khasianum The active ingredient is an aqueous extract of the whole plant of CB Clarke.

[0008] The present invention also includes a method for preparing the above-mentioned natural herbicide, comprising the following steps: (1) washing, drying and crushing the whole plant of *Solanum kaxiense* to obtain whole plant powder of *Solanum kaxiense*; (2) mixing the whole plant powder of *Solanum kaxiense* with water and extracting it under low temperature conditions in the dark; (3) separating the solid and liquid components of the extracted mixture and collecting the supernatant to obtain the natural herbicide.

[0009] Furthermore, the drying temperature in step (1) is 65°C.

[0010] Furthermore, the low temperature condition in step (2) is 4°C and the extraction time is 48h.

[0011] Furthermore, the mass-to-volume ratio of the whole plant powder of *Solanum lycopersicum* to water in step (2) is 1:5 (g / mL).

[0012] Furthermore, the solid-liquid separation in step (3) includes centrifugation, wherein the centrifugation speed is 8000 r / min and the time is 5 minutes.

[0013] The present invention also includes the application of the above-mentioned natural herbicides in the control of weeds in farmland.

[0014] Furthermore, the natural herbicide is applied in the form of a diluted solution or a dry powder mixture with soil, wherein the concentration of the diluted solution of the natural herbicide is 1-200 g / L, and the amount of the dry powder added to the soil is 2%-8% (w / w).

[0015] Furthermore, the weeds include one or more of the following: amaranth, lambsquarters, crabgrass, and goosegrass.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention addresses the lack of a comprehensive existing research system for the weed control of *Solanum kaxiense*. Through selective safety verification and pot-based simulated field application, it achieves a technological breakthrough, moving from laboratory evaluation to pot-based simulation experiments regarding the weed control effect of *Solanum kaxiense*. Specific advantages are as follows: 1. A complete experimental system integrating "laboratory + potted plant simulation" was constructed. This invention not only precisely quantifies the weed-suppressing activity of *Solanum kaxiense* through laboratory petri dish experiments, but also verifies the sustained weed-suppressing effect of *Solanum kaxiense* powder in soil through pot experiments simulating real field soil environments, thus avoiding the limitations of a single experimental method.

[0017] 2. The selective herbicidal effect of *Solanum kaxiense* was clearly demonstrated for the first time. Commonly used forage grasses such as alfalfa, red clover, oats, and perennial ryegrass were selected, and gradient concentration treatments consistent with those for weeds were carried out simultaneously. This study clarified the strong inhibitory effect of *Azolla casis* extract on weeds and its low impact on forage grasses, verifying its selective weed control advantage of "suppressing only weeds without harming forage grasses." This approach overcomes the shortcomings of existing technologies that cannot distinguish the allelopathic differences between weeds and forage grasses and cannot guarantee grassland ecological safety, laying a safe foundation for the application of *Azolla casis* as a natural herbicide in natural grasslands and artificial grasslands.

[0018] 3. To realize the resource utilization of Kaxi eggplant, achieving both environmental and economic benefits. Kaxi solanum is an invasive plant, and current technologies have not enabled its resource utilization. This invention develops it into a plant-derived herbicide, solving the ecological damage caused by its proliferation and replacing chemical herbicides, reducing pesticide residues and aligning with the development direction of green agriculture. It has a wide distribution, large biomass, and strong reproductive capacity. The extraction process uses only water extraction, requiring no complex organic solvents, making it simple to operate, low-cost, and suitable for large-scale production. This solves the problems of scarce raw materials and high extraction costs associated with existing plant-derived herbicides. The entire process uses water extraction and low-temperature extraction, leaving no toxic organic solvent residues, making it environmentally friendly.

[0019] 4. It is easy to operate and has wide applicability, making it suitable for promotion and application in multiple scenarios. Attached Figure Description

[0020] Figure 1 Germination rate of seeds of Amaranthus retroflexus, Chenopodium album, Digitaria sanguinalis and Eleusine indica 7 days after treatment with Kashi eggplant extract; Figure 2 Germination rate of alfalfa, red clover, oats and ryegrass seeds 7 days after treatment with Kashi eggplant extract; Figure 3 Root length of seedlings of Amaranthus retroflexus, Chenopodium album, Digitaria sanguinalis and Eleusine indica 7 days after treatment with Kashi eggplant extract; Figure 4 Seedling growth of *Amaranthus retroflexus*, *Chenopodium album*, *Digitaria sanguinalis* and *Eleusine indica* 7 days after treatment with *Solanum lyratum* extract; Figure 5 Fresh weight of seedlings of Amaranthus retroflexus, Chenopodium album, Digitaria sanguinalis and Eleusine indica 7 days after treatment with Kashi eggplant extract; Figure 6 Growth status of Dioscorea opposita in soil treated with Kashi eggplant powder for 14 days. Detailed Implementation

[0021] Example 1 Preparation of Kashi eggplant extract and germination experiment of weed / pasture seeds (1) Collection and pretreatment of Kaxi eggplant samples Wild *Solanum kaxiense* plants were collected, ensuring they were robust, free from pests, diseases, and mechanical damage. The plant surfaces were thoroughly rinsed with water to remove dirt and sand, and then dried using sterile filter paper. The roots, stems, leaves, and fruits were dried to constant weight in a 65°C oven. The dried tissue was cut into small pieces, pulverized using a high-speed grinder, and sieved to obtain a mixed powder of the entire *Solanum kaxiense* plant. This powder was then sealed and stored in a 4°C refrigerator away from light for later use.

[0022] (2) Preparation of Kaxi Solanum extract Weigh 50 g of whole-plant powder of *Solanum kaxiense* and place it in a 500 mL Erlenmeyer flask. Add 250 mL of distilled water, seal the flask, and place it in a constant temperature shaker at 4℃ for 48 h in the dark. After extraction, transfer the extract to a 50 mL centrifuge tube and centrifuge at 8000 r / min for 5 min. Collect the supernatant, filter it, and remove the residue to obtain the mother liquor of *Solanum kaxiense* extract (concentration 200 g / L). Dilute the mother liquor stepwise with distilled water to prepare extracts with concentrations of 1, 5, 25, 50, 100, 125, and 200 g / L, and store them at 4℃ for later use.

[0023] (3) Seed pretreatment Seeds of noxious weeds such as Amaranthus retroflexus, lambsquarters, crabgrass, and goosegrass, and seeds of four forage grasses such as alfalfa, red clover, oats, and ryegrass were selected. Plump and undamaged seeds were screened, disinfected with 75% ethanol for 15 seconds, rinsed 5 times with sterile water, and air-dried for later use.

[0024] (4) Seed germination experiment Researchers placed two layers of sterile qualitative filter paper at the bottom of 9 cm sterile petri dishes and added 3 mL of different concentrations (1, 5, 25, 50, 100, 125, 200 g / L) of whole-plant extract of *Solanum lycopersiconae* to each dish. The control group received 3 mL of distilled water. Each group was replicated four times. Thirty pre-treated seeds were evenly sown in each dish (weeds / grass were tested independently). The petri dishes were sealed with sealing film to prevent moisture evaporation. The petri dishes were then placed in an artificial climate chamber with the following conditions: temperature 25 ℃, light intensity 15000 lx, and a photoperiod of 12h / 12h (day / night). 3 mL of the corresponding concentration solution was added every 3 days to keep the filter paper moist.

[0025] (5) Indicator measurement and effect data The number of seeds that germinated on day 7 was counted (germination was defined as radicle length ≥ 2 mm), and the relative germination rate was calculated.

[0026] The calculation formula is as follows: Relative germination rate (%) = Number of germinated plants in the treatment group / Number of germinated plants in the control group × 100%.

[0027] Experimental data: from Figure 1 , Figure 2It was found that the extract of *Solanum kaxiense* significantly inhibited the germination of seeds from all four weed species. However, at low concentrations, the extract showed no significant inhibitory effect on the germination of alfalfa, red clover, oats, and perennial ryegrass, and even promoted germination at some concentrations. Only at high concentrations did the extract inhibit germination, indicating that the extract is relatively safe for forage grasses within a certain concentration range. After treatment with 50 g / L *Solanum kaxiense* whole-plant extract for 7 days, the relative germination rates of *Amaranthus retroflexus*, *Chenopodium album*, *Digitaria sanguinalis*, and *Eleusine indica* were 34.33%, 37.55%, 55.38%, and 42.78%, respectively. The relative germination rates for alfalfa, red clover, oats, and perennial ryegrass were as high as 70.77%, 97.79%, 79.89%, and 73.46%, respectively. These results directly verify the selective weeding effect of *Solanum kaxiense*, which strongly inhibits weeds and has a low impact on forage grasses.

[0028] The germination rate (GR) of *Solanum lyratum* extract on the seeds of four weeds was investigated using the dose-response curve method. 50 The values ​​ranged from 31.19 to 65.04 g / L. Among them, quinoa showed the strongest sensitivity to the extract, with GR... 50 The value was 31.19 ± 4.17 g / L; crabgrass showed the strongest tolerance, GR 50 The value was 65.04±4.32 g / L; the GR values ​​for *Amaranthus retroflexus* and *Eleusine indica* were... 50 The values ​​were 34.60±4.78 g / L and 38.88±2.59 g / L, respectively. The sensitivity of the four weeds, from highest to lowest, was: lambsquarters, amaranth, goosegrass, and crabgrass. Among them, there was no significant difference in sensitivity among lambsquarters, amaranth, and goosegrass. P >0.05), while the tolerance of crabgrass was significantly higher than that of the other three weeds ( P <0.05); This extract showed the strongest inhibitory effect on the germination activity of broadleaf weeds, and exhibited obvious selective inhibition characteristics in different weeds.

[0029] The four forage seeds generally showed higher tolerance to *Solanum kaxiense* extract than weeds, and their GR (graft tolerance) was higher. 50 The values ​​ranged from 75.18 to 114.07 g / L. Among them, perennial ryegrass showed relatively low tolerance, GR 50 The value was 75.18±4.72 g / L; alfalfa showed the highest tolerance, GR 50 The value was 114.07±10.31 g / L; the GR of red clover and oats 50 The values ​​were 112.58±1.64 g / L and 104.32±4.87 g / L, respectively. The tolerance of the four forage grasses to the extract of *Solanum kaxifolia*, from highest to lowest, was alfalfa, red clover, oats, and perennial ryegrass.

[0030] A comprehensive comparison of the growth rates of four types of weeds and four types of forage grasses. 50 Data shows that the GR of weeds 50 The values ​​are generally lower than those of forage grass, indicating that the extract of *Solanum lyratum* has stronger inhibitory activity against weed seed germination, possesses certain weed control potential and good forage grass safety, and has potential value in the field of weed ecological control in farmland and grassland ecosystems.

[0031] Example 2 Experiment to determine the growth inhibition effect of weed seedlings Recipient weed seeds were germinated in distilled water until the radicle emerged. Twenty seeds with uniform growth and emerging radicles were selected and added to different concentrations of *Solanum lyratum* extract, while the control group was added to distilled water. Under the same germination conditions, the seeds were cultured continuously for 7 days. Ten seedlings were randomly selected, their surface moisture was wiped dry, and root length, seedling length, and fresh weight were measured.

[0032] Relative root length (%) = (Treatment group root length / Control group root length) × 100% Relative seedling length (%) = (Treatment group seedling length / Control group seedling length) × 100% Relative fresh weight (%) = Fresh weight of treatment group / Fresh weight of control group × 100% Experimental data: from Figure 3 , Figure 4 , Figure 5 The results showed that, considering the responses to root length, seedling length, and fresh weight, the four weeds exhibited significant differences in sensitivity to the extract of *Eclipta prostrata*. *Chenopodium album* showed a slight promoting effect on root and seedling length and a slight inhibiting effect on fresh weight at a low concentration of 1 g / L. With increasing extract concentration, the inhibitory effects on root length, seedling length, and fresh weight all increased, and root growth was inhibited at a high concentration of 200 g / L. *Digitaria sanguinalis* showed the most significant promoting effect on root and seedling length at a low concentration of 1 g / L, while fresh weight was inhibited at all experimental concentrations, with the inhibitory effect significantly increasing with increasing concentration. Growth was almost completely inhibited at a high concentration of 200 g / L. *Amaranthus retroflexus* showed only a slight promoting effect at a low concentration of 1 g / L. At low concentrations, seedling growth showed a slight promoting effect, while root length and fresh weight showed an inhibitory effect at all extract concentrations. The inhibitory effect gradually increased with increasing concentration, and the overall degree of inhibition was at a moderate level. At all extract concentrations, the root length, seedling length, and fresh weight of the *Eleusine indica* seedlings showed only an inhibitory effect, with no promoting effect. At a high concentration of 200 g / L, growth was almost completely inhibited.

[0033] Overall, the extract of *Solanum kaxiense* showed a systematic concentration-dependent inhibitory effect on the growth of seedlings of the tested weeds. Only at extremely low concentrations did it have a slight promoting effect on the root or seedling length of some weeds. The fresh weight of all tested weeds showed an inhibitory effect at all extract concentrations.

[0034] Example 3 Potted weed suppression experiment with the addition of Kashi eggplant powder to soil (1) Preparation of experimental materials Kaxi eggplant powder: Take the whole plant powder of Kaxi eggplant prepared in Example 1, sieve it, and seal it for later use.

[0035] Potting soil: Collect topsoil from farmland (0-20 cm), air dry naturally, and then pass it through a 2 mm sieve to remove stones and plant debris.

[0036] Weed seeds: Crataegus pinnatifida seeds were selected, and the pretreatment method was the same as in Example 1.

[0037] Forage seeds: Alfalfa seeds were selected, and the pretreatment method was the same as in Example 1.

[0038] (2) Preparation of potting soil Four treatment groups were set up, with four replicates per group. Each pot contained 500 g of soil: the control group (CK) contained pure field soil without the addition of Kaxi eggplant powder; the treatment groups T1, T2, T3, and T4 contained 2%, 4%, 6%, and 8% Kaxi eggplant powder by weight, respectively, corresponding to the following ratios: 10 g powder + 490 g soil, 20 g powder + 480 g soil, 30 g powder + 470 g soil, and 40 g powder + 460 g soil. The Kaxi eggplant powder was thoroughly mixed with the soil, and the mixture was placed in plastic flower pots with a diameter of 7 cm and a height of 10 cm. The pots were then thoroughly watered and sown.

[0039] (3) Sowing and Cultivation Sow 16 crabgrass seeds evenly in each pot, cover with 0.5 cm of soil, and water thoroughly. Place the pots in an incubator with the following environmental conditions: temperature 25 ℃, natural light, and relative humidity 60%~70%. Water every 5-6 days and remove non-tested weeds regularly.

[0040] Each pot was evenly sown with 16 alfalfa seeds. The treatment group was T4, and all other conditions were the same as above.

[0041] (4) Indicator measurement and effect data After 14 days of cultivation, the weed emergence rate was measured.

[0042] Germination rate (%) = (Number of germinated seedlings / Number of seeds tested) × 100% Experimental results data: by Figure 6It was found that the inhibitory effect of Kaxi eggplant powder on the emergence of barnyardgrass exhibited a concentration-dependent gradient: as the treatment concentration increased from 2% to 8%, the inhibition rate of weed emergence gradually increased, with the 8% treatment group showing the lowest emergence rate at 29.81%, significantly lower than the low-concentration treatment group. This verified the dose-response relationship that the herbicidal activity of Kaxi eggplant powder increased with increasing application rate. Under the same treatment conditions, the emergence rate of alfalfa in the 8% treatment group was 88.24%, while the inhibition rate was only 11.76%. This indicates that Kaxi eggplant powder, at an 8% concentration, showed a very strong inhibitory effect on barnyardgrass, while having almost no significant inhibitory effect on alfalfa emergence, exhibiting a selective herbicidal effect, as shown in Table 1 below.

[0043] Table 1. Relative emergence rates of crabgrass and alfalfa 14 days after treatment with Kashi eggplant powder in soil.

[0044] Note: Alfalfa was only tested in potted weed suppression experiments at 0% and 8% treatments.

[0045] Therefore, considering both weed control effectiveness and crop safety, 8% is the recommended application concentration for Kaxi eggplant powder, with an alfalfa emergence rate of 88.24%.

Claims

1. A natural herbicide, characterized in that: The natural herbicide contains an aqueous extract of the entire *Solanum kaxiense* plant as its active ingredient, and its preparation method includes the following steps: (1) Wash, dry and crush the whole plant of Kaxi eggplant to obtain Kaxi eggplant powder; (2) Mix the whole plant powder of the Kaxi eggplant with water and extract it under low temperature conditions in the dark; (3) The mixture after extraction is subjected to solid-liquid separation, and the supernatant is collected to obtain the natural herbicide, wherein the low temperature condition in step (2) is 4°C and the extraction time is 48h.

2. The natural herbicide according to claim 1, characterized in that: The drying temperature in step (1) is 65°C.

3. The natural herbicide according to claim 1, characterized in that: The mass-to-volume ratio of the whole plant powder of *Solanum lycopersicum* to water in step (2) is 1:5 (g / mL).

4. The natural herbicide according to claim 1, characterized in that: The solid-liquid separation in step (3) includes centrifugation, wherein the centrifugation speed is 8000 r / min and the time is 5 minutes.

5. The application of the natural herbicide according to claim 1 in controlling weeds in farmland, wherein the weeds are one or more of the following: Amaranthus retroflexus, lambsquarters, crabgrass, and goosegrass.

6. The application as described in claim 5, characterized in that: The natural herbicide is applied as a mixture of its diluted solution or dry powder and soil. The concentration of the diluted solution of the natural herbicide is 1-200 g / L, and the amount of the dry powder added to the soil is 2%-8% (w / w).

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