A GREEN AND ECONOMICAL WEEDS CONTROL AGENT SUITABLE FOR DRONE

: Weeds are one of the main factors affecting orchard yield, fruit quality and economic benefits. However, present methods have been lower effect and high labor intensity. To inhance the effect of weeds control on orchard, a new green and economic agent suitable for drone with choline chloride and eucalyptus oil as the main components was developed. Adopting optimized “3414” test design, the paper studied the prevention and control effect of this new weed control agent on 8 kinds of main weeds in the orchards of the Yellow-Huai Rivers. The results showed that T5 and T12 were significantly (P≤0.05) control the growth speed of 8 kinds of weeds, T4 was only inhibit the growth of Erigeron canadensis, Digitaria sanguinalis and Artemisia annua, T11 was only inhibit the growth of Tribulus terrestris, Humulus scandens and Cyperus rotundus, and T3 and T13 were promote the growth of weeds, which had the worst control effect among all treatments. Combined with the economic benefit analysis, the cost per 667m 2 of weed control of T12 was 124 RMB, which was the most economical compared with manual weeding and mechanical weeding. Therefore, applying 30g choline chloride, 120 mL eucalyptus oil and 75g sucrose ester to each 667m 2 is recommended to be popularized as a new green and economical weed control agent in the orchard production of the Yellow-Huai Rivers.


INTRODUCTION
Weed damage is one of the important factors causing the reduction of agricultural yield, and the yield reduction caused by weed damage is about 34% worldwide [1] .The discovery and application of herbicide have a huge impact on the traditional agricultural production mode, which accelerates the process of agricultural modernization.According to the statistics of Food and Agriculture Organization (FAO), at present, the wide use of herbicides has increased the global grain output by more than 10% [2] .
Herbicides refer to a class of pesticides used to block or inhibit the growth of weeds, including 13 categories such as organophosphorus, organic heterocyclic, amide, phenol and so on [3] .In the past few decades, herbicide has been broadly used worldwide, and its share in the pesticide market has surpassed that of insecticide and jumped to the top since 1980 [4] .Traditional chemical herbicides have the advantages of economy and high efficiency.However, with the appearance of a series of negative effects caused by chemical herbicides such as environmental pollution, land degradation, human and animal poisoning, production reduction of next plantation, and even the impacts on the stability of other populations in the environment, more than 100 kinds of chemical herbicides have been banned or canceled registration in more than 30 countries all over the world, indicating that it has become a new trend to study and develop more ecological green herbicides so as to replace traditional chemical herbicides [5][6].
Green herbicides can be roughly divided into two categories, chemical herbicides and biological herbicides.Among them, chemical herbicides, such as choline chloride, are regulators of retarding plant growth, which can inhibit the photorespiration of C3 plants, so as to inhibit the growth of above-ground parts and thus reduce plant height [7] .This characteristic can be used to inhibit the growth of weeds and achieve the purpose of weed control.Eucalyptus oil is a botanical herbicide, the main component of which is 1,8-cineole (C 10 H 18 O).Besides, eucalyptus oil mainly exists in Eucalyptus robusta and other plants, which plays an important role in plant heterogenesis and has high herbicidal activity [1,8] , but with a disadvantage of high volatility.The mechanism of action of eucalyptus have been not clear, but its main components have the same structural characteristics with natural products, pincer, and herbicide endoxychlor, which is able to inhibit plant respiration and mitosis.Recent research has shown that eucalyptus can effectively inhibit asparagine synthase, the target of most herbicides.
In the production of fruit trees, weed damage is a common problem.Weeds will compete with fruit trees for water and nutrients, provide a living environment for pests, breed pests and diseases in fruit trees, and have a bad impact on the ecological environment of orchards.These factors will eventually lead to the decline of the fruit trees growth, fruit quality and fruit yield, therefore, it is of significance to control weeds in orchards.At present, there have not been report on the study of weed control combining choline chloride with eucalyptus oil as functional components.In this test, the long-term inhibition of weed growth demonstrated by choline chloride and the chemotactile killing effect on weeds demonstrated by eucalyptus oil were combined, and an appropriate concentration of sucrose ester was added as a suspension agent, solving the problems of their compatibility and the volatility of eucalyptus oil.A weed control agent with inhibition and contact killing activity was researched and developed, which showed the characteristics of remarkable effect, environmental friendliness and economy in the practice of weed control in orchards.The report is as follows.

Test Site
The test site is located in the long-term test base of the Research Institute of Non-timber Forestry, Chinese Academy of Forestry, Xiguo Town, Mengzhou City, Henan Province (112°42'51" E， 34°51'35" N).The climate type of this site is warm temperate continental monsoon climate with four distinct seasons.The average annual temperature is 14.2℃, the average annual sunshine is 2160.4hours, the average annual precipitation is 586.9mm, the average annual evaporation is 1599.0mm,and the frost-free period is 209 days.The soil type is sandy land in the old course of the Yellow River.Within 20 cm, the content of total nitrogen is 0.033gꞏkg -1 , the content of total phosphorus is 0.05%, the content of total potassium is 0.10%, the hydrolyzed nitrogen is 48.79mgꞏkg -1 , the rapidly available phosphorus is 4.80mgꞏkg -1 , the rapidly available potassium is 156.62mgꞏkg - , the content of organic matter is 0.41%, the pH value of soil is 8.67, and the groundwater level is 2.5~3.0m.May to August of this site is the fast-growing period of jujube, apricot, peach, persimmon and other fruit trees and weeds, but the rainfall and evaporation are high, drought and flood occur alternately, and the soil water leakage and fertilizer leakage are very obvious, showing typical site characteristics of the sandy land of the old course of the Yellow-Huai River Plain.

Test Materials
Through the statistics of the weed species appearing in the jujube orchard, apricot orchard, persimmon orchard, peach orchard and other orchards in the early stage, it is determined that there are 8 kinds of weeds in the orchard of this area, namely Setaria viridis, Erigeron canadensis, Humulus scandens, Digitaria sanguinalis, Tribulus terrestris, Cyperus rotundus, Artemisia annua and Chenopodium album.

Instruments and Reagents
Choline chloride is chemically pure with a content of 98% and the effective content of eucalyptus oil is 80%, both of which were purchased from Shanghai McLean Biochemical Technology Limited Company (http://www.macklin.cn).Sucrose ester (food grade), meter ruler and vernier caliper were purchased from JingDong Mall (https://www.jd.com/).

Statistics of Weed Biomass
As for the statistics of weed species and dominant types, the five-point sampling method was adopted.Five quadrats were randomly selected, and the length and width of each quadrat were 1m, the subtotal of area of which was 1m 2 , with a total of 5m 2 , repeating for 3 times.
Mobile phone identification software developed on the basis of the plant classification data of the Chinese Academy of Science, Flower Companion 3.0" was adopted to initially record the weed species, photos were taken as preservation, and secondary identification with reference to literature [9] was conducted.For the weeds that cannot be identified or of controversy, the plant classification experts would conduct the eventual identification.Finally, the number of different weeds in each quadrant was counted.The measurement of weed biomass was set at each 7 days from March to May in 2020 and 2021 respectively.Meter ruler was used to measure the seedling height and crown width of weeds, and vernier caliper was used to measure the ground diameter 0.1m away from the ground.For creeping weeds, the measurement close to the ground and 0.1 m away from the root system shall prevail.

Data Collection, Statistics and Analysis
WPS 2019 was applied to log data and make charts, and DPS 7.05 was used to conduct analysis of variance and multiple comparisons.

The Impact of Different Treatments on Setaria Viridis
Setaria viridis is a common weed in China, whose stalk is upright or bents at the base, with a height of 10-100 cm, a base diameter of 3-7 mm, and a flowering and fruiting period of 5-10 months.It has strong growth potential, strong fecundity and serious harm, and it is one of the dominant species of weeds in orchards.The analysis of variance among different treatments showed that T14 had the best inhibition effect on the seedling height of S. viridis, followed by T5, but there was no significant difference between these two treatments (P≤0.05).The inhibition effect of T3 was the worst.In the aspect of ground diameter, T7 and T12 had better inhibition effect on the ground diameter of S. viridis, but there was no statistical difference between them.T1 (CK) had the worst effect.For the inhibition of crown width, T11 had the best inhibition effect on the crown width of S. viridis, followed by T5, meanwhile T13 had the worst inhibition effect.
In production, the two indexes of weed height and crown width directly affect the photosynthesis of fruit trees.Comprehensively considering various indexes, the inhibition effect of T5 on S. viridis is favorable, and the economic cost is low, so T5 is suitable for application in production.T2 and T3 had the worst inhibition effect on S. viridis, which may be related to the promoting effect of these two treatments on the growth of S. viridis.

The Impact of Different Treatments on Erigeron Canadensis
Originated from North America, Erigeron canadensis is distributed in Northern and Southern provinces and regions of China.As a common weed, it often grows in wilderness, wasteland, field edge and roadside.E. canadensis has been listed in the list of alien invasive species in China.The analysis of variance among different treatments showed that T1, T4 and T5 had the best inhibition effect on the seedling height of E. canadensis; T5, T12 and T14 had the best inhibition effect on the ground diameter of E. canadensis; and T1, T4 and T5 had the best inhibition effect on the crown width of E. Canadensis.In production, seedling height is the main factor affecting the photosynthesis of fruit trees.All indexes considered, T1, T4 and T5 had the most significant inhibition effect on E. canadensis, so they are suitable for application in production.T2 and T13 had the worst inhibition effect on E. canadensis.

The Impact of Different Treatments on Humulus Scandens
Humulus scandens is distributed in all provinces and regions except Xinjiang and Qinghai in China.In addition, it is also distributed in southeast Asian countries such as Japan and Vietnam.The analysis of variance among different treatments showed that T1, T11 and T12 had the best inhibition effect on the seedling height of H. scandens; T11, T12 and T14 had the best inhibition effect on the ground diameter of H. scandens; and T12 and T13 had the best inhibition effect on the crown width of H. Scandens.In production, seedling height is the main factor affecting the photosynthesis of fruit trees.All indexes considered, the inhibition effect of T11 and T12 on H. scandens is the most significant, so these two treatments are suitable for application in production.T6 and T7 had the worst inhibition effect on H. scandens.

The Impact of Different Treatments on Digitaria Sanguinalis
Digitaria sanguinalis is mainly distributed in Tibet, Sichuan, Xinjiang, Shanxi, Gansu, Shanxi, Hebei, Henan and Anhui.Its seeds spread fast, it has strong fecundity, it grows rapidly, and it has many branches and strong competitiveness.D. sanguinalis grows widely in various herb communities such as field edge, roadside, ditch edge, beach and hillside, and even invades highly competitive communities such as Cynodon dactylon and Zoysia japonica Steud.The analysis of variance among different treatments showed that T1, T4 and T8 had the best inhibition effect on the seedling height of D. sanguinalis; T8, T10, T11 and T12 had the best inhibition effect on the ground diameter of D. sanguinalis; and T4, T6 and T8 had the best inhibition effect on the crown width of D. Sanguinalis.In production, seedling height is the main factor affecting the photosynthesis of fruit trees.All indexes considered, the inhibition effect of T4 and T8 on D. sanguinalis is the most significant, so these two treatments are suitable for application in production.T13 and T14 had the worst inhibition effect on D. sanguinalis.

The Impact of Different Treatments on Tribulus Terrestris
Tribulus terrestris is distributed all over the country.As a creeping weed, it grows in sandy land, wasteland, hillside and near residential areas.T. terrestris blooms from May to August and bears fruits from June to September.The fruit of T. terrestris has thorns and its root is difficult to eradicate.The analysis of variance among different treatments showed that T6, T11 and T14 had the best inhibition effect on the seedling height of T. terrestris; T9, T11 and T12 had the best inhibition effect on the ground diameter of T. terrestris; and T6, T12 and T14 had the best inhibition effect on the crown width of T. Terrestris.In production, seedling height is the main factor affecting the photosynthesis of fruit trees.All indexes considered, the inhibition effect of T11 and T14 on T. terrestris is the most significant, so these two treatments are suitable for application in production.T3 and T9 had the worst inhibition effect on T. terrestris.

The Impact of Different Treatments on Cyperus Rotundus
Cyperus rotundus is widely distributed all over the world.Growing in the grass of the hillside wasteland or in the wet place near the water, it has strong adaptability and overwinters with roots.It belongs to weeds difficult to eradicate.The analysis of variance among different treatments showed that T11, T12 and T14 had the best inhibition effect on the seedling height of C. rotundus; T7, T10 and T12 had the best inhibition effect on the ground diameter of C. rotundus; and T2, T7 and T14 had the best inhibition effect on the crown width of C. Rotundus .In production, seedling height is the main factor affecting the photosynthesis of fruit trees.All indexes considered, the inhibition effect of T12 on C. rotundus is the most significant, so this treatment is suitable for application in production.T3 had the worst inhibition effect on C. rotundus.

The Impact of Different Treatments on Artemisia Annua
Artemisia annua is widely distributed all over the world.It is a semi shrub with obvious main stem. A. annua grows fast and the whole plant contains volatile oil, which is easy to cause farmland fire after drying.The analysis of variance among different treatments showed that T1, T7 and T14 had the best inhibition effect on the seedling height of A. annua; T9, T10 and T12 had the best inhibition effect on the ground diameter of A. annua; and T9, T10 and T11 had the best inhibition effect on the crown width of A. Annua.In production, seedling height is the main factor affecting the photosynthesis of fruit trees.All indexes considered, the inhibition effect of T7 on A. annua is the most significant, so this treatment is suitable for application in production.T3 had the worst inhibition effect on A. annua.

The Impact of Different Treatments on Chenopodium Album
Chenopodium album is distributed in temperate and tropical regions around the world and all over China.It is often found near farmland, vegetables gardens, cottages or slightly saline land, and it has strong adaptability.The analysis of variance among different treatments showed that T4, T5 and T7 had the best inhibition effect on the seedling height of C. album; T5, T6, T8 and T9 had the best inhibition effect on the ground diameter of C. album; and T2, T4 and T9 had the best inhibition effect on the crown width of C. Album.In production, seedling height is the main factor affecting the photosynthesis of fruit trees.All indexes considered, the inhibition effect of T5 on C. album is the most significant, so this treatment is suitable for application in production.T12 and T14 had the worst inhibition effect on C. album.

Cost Calculation
According to the weed control effect of each treatment, there is no significant difference between T5 and T12 on the prevention and control of 8 kinds of weeds.Combined with the cost analysis, the cost of T12 is the lowest, about 124.0 RMB, 2 RMB lower than T5 per 667 m 2 , only 31.8% of the cost of manual weeding, and 36 RMB lower than that of mechanical weeding per 667 m 2 (Table 2).Therefore, T12 is deemed to be popularized and applied as a green and simple method for orchard weed control in the Yellow-Huai Rivers.Note: the price of CC is 420 RMB per 2.5 kg, the price of EO is 1445 RMB per 2.5 L, the price of SE is 50 RMB per 2.5 kg, the price of labor in the test site is 65 RMB per day, and it takes three people to work a day for every 667m 2 of manual weeding in the weed growing season; mechanical weeding costs 25 RMB per 667 m 2 .In addition, manual cooperation is also required to conduct secondary cleaning for weeds around the fruit trees.The cost of manual cooperation is 15 RMB per 667 m 2 .The growing season of fruit trees in the test site coincides with the rainy season from May to August, and mechanical weeding requires 4 times a year.The dosage of pesticide is 30 L standard solution per 667 m 2 .

4.DISCUSSION
The time of spraying and the sequence of solution preparation determine the weed control effect.The best time for the first spraying in the Huang-Huai River Basin is in the middle of March in the spring, and the control effect is the best when the height of weed is within 20 cm.In the preparation of weed control agent in this study, choline chloride needed to be dissolved as the base solution, then the diluted sucrose ester needed to be slowly poured into the base solution, and finally eucalyptus oil needed to be added before spraying on the leaves of weeds to prevent excessive volatilization.

CONCLUSION
This study took eight main weeds of high incidence in orchard, S. viridis, E. canadensis, H. scandens, D. sanguinalis, T. terrestris, C. rotundus, A. annua and C. album in the the Yellow-Huai Rivers as the objects of prevention and control, and took choline chloride, eucalyptus oil and sucrose ester as the weed control factors to carry out an orthogonal test.Comprehensively considering the inhibition effect and economic cost, T12, which refers to spraying 30 L solution formulated by 30 g choline chloride, 120 mL eucalyptus oil and 75 g sucrose ester on every 667m 2 , can achieve the ideal weed control effect, suitable to be popularized and applied as a new green and economical weed control agent in orchards.
This study only evaluated the weed control effect of choline chloride and eucalyptus oil, and did not carry out in-depth research on the impacts on associated fruit trees.Meanwhile, the solubility of sucrose ester in the test was poor, and there was much foam, leading to that it may not have the optimal fixation effect on the volatilization of eucalyptus oil.In the future, it is necessary to introduce new reagents or optimize with other dissolution method to improve the prevention and control effect of weed control agents.
At present, the commercial broad-spectrum sterilant herbicide has the characteristics of wide range of the spectrum of weed killing, high weeding efficiency and economy, but it is also easy to cause pesticide damage to the environment and organisms, leading to the metamorphosis or even death, no yield and no harvest of plant, thus causing relatively huge economic losses and even far-reaching impact on human body, biodiversity and other industries [10] .The development of green, harmless and naturally degradable biological herbicidal active substances will become the direction in the future.More than 2000 kinds of natural compounds with herbicidal activity have been found from over 30 families of plants all over the world [11] , providing the research of natural herbicidal active substances with rich materials.

Table 1 "
3414" complete test scheme and factor levels

Table 2
Cost comparison between optimal treatment and traditional weed control