Control Efficacy of Natural Products on Broadleaf and Grass Weeds Using Various Application Methods
Department of Bio-Oriental Medicine Resources, Sunchon National University, Suncheon 57922, Republic of Korea
*
Author to whom correspondence should be addressed.
Agronomy 2023, 13(9), 2262; https://doi.org/10.3390/agronomy13092262
Submission received: 2 August 2023
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Revised: 22 August 2023
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Accepted: 25 August 2023
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Published: 28 August 2023
(This article belongs to the Section Weed Science and Weed Management)
Abstract
:Synthetic herbicides have negatively impacted biological organisms and human health. Thus, nonsynthetic herbicides for weed control are needed in organic and conventional agriculture. Nonsynthetic products such as vinegar and detergents are increasingly becoming popular in crop disease treatment, as well as controlling insects and weeds. Therefore, the objective of this study was to determine the herbicidal efficacy of various nonsynthetic products using different application methods. Various nonsynthetic products were applied to grass and broadleaf weeds at 1%, 3%, 5%, and 10% concentrations to test their herbicidal efficacy, and two plant extracts were used as adjuvants. In addition, the inhibitory effects of selected brown rice vinegar and effective microorganisms (EM) powder soap on grass and broadleaf weeds were compared to the inhibitory effects of other vinegars and EM powder soaps. Of the nine various natural products tested, brown rice vinegar and EM powder soap at 5% concentrations were the only applications to completely control grass and broadleaf weeds in Petri dish bioassays. In greenhouse conditions, the shoot fresh weight of Eclipta prostrata, Solanum nigrum, Persicaria hydropier, and Portulaca oleracea was completely inhibited when soil applications of EM powder soap at 10% concentrations were used. EM powder soap was more effective in controlling grass and broadleaf weeds than brown rice vinegar. In addition, brown rice vinegar and EM powder soap did not appear to last long in soil. Two-time application methods were more effective in controlling all weed species than one-time application methods. However, no synergism effects were observed when brown rice vinegar and EM powder soap were combined with other natural products. Brown rice vinegar and EM powder soap did not show adjuvant effects when combined with plant extracts, which can sometimes create better contact with or penetration of the weeds. Thus, weeds growing alongside transplanted vegetable crops can be effectively controlled with brown rice vinegar and EM powder soap by using soil applications in row, either individually or combined together and with either one or two applications.
1. Introduction
Weed management poses a significant challenge for organic farmers [1]. In a survey of organic vegetable growers, weeds were identified as the most significant pest group [2]. Weeds are widespread and cost the world billions of dollars to control each year in crop losses totaling billions of dollars [3]. Currently, weeds are controlled by chemical herbicides that are synthetic [4]. Advantages of synthetic herbicides include their effectiveness in rapidly controlling weeds, which produces time and labor savings, cost-effectiveness for large-scale agriculture, and the ability to choose from various modes of action [5]. However, the use of synthetic herbicides causes significant risks including weed resistance, environmental problems, and health hazards [6,7]. In addition to damaging the ecosystem, synthetic herbicides have an adverse effect on biological diversity and accumulate in soil and water [4]. Recently, many natural weed killers such as essential oils have been discovered, and the substances have been reviewed and approved for use in certified organic cultivation by the Organic Materials Review Institute [8,9,10]. However, few organically compliant herbicides exist, and even fewer have been tested adequately [11,12]. Organic herbicides can vary in terms of their active ingredients, formulation, and mode of action.
Use of natural herbicides for organic weed control might increase interest in sustainable agriculture practices [13]. Natural herbicides often have lower toxicity and degrade more rapidly compared to synthetic herbicides. This minimizes harm to soil and water and maintains ecosystem balance and biodiversity. Natural chemicals can be used to generate biochemical organic herbicides based on the structure of natural phytotoxins because of their structural variety and developed biological activity [14]. Furthermore, natural substances known as essential oils are commonly mentioned for their herbicidal properties, which are linked to their allochemical components [15,16,17,18]. Acetic acid, an organic acid created through the natural fermentation of plant sources containing sugars, is present in vinegar as a solution. Typically, household vinegar has 5% acetic acid. Acetic acid quickly decomposes and releases water as a byproduct; hence, it does not last long in the environment [19].
Previous research has assessed the effectiveness of vinegar and other natural products to control weeds in vegetable crops and other agricultural production systems [20,21,22], in addition to the effects that natural products have on desired crops [23,24,25,26,27]. Abouziena et al. [28] and Brainard et al. [29] investigated natural controls for weeds at two growth phases and the efficacy of vinegar and clove oil sprayed at various temperatures, relative humidity, and weed growth stages. The effects of vinegar on several common broadleaf weeds, including hairy vetch, were investigated [26]. Acetic acid, as a contact herbicide, should be more effective on seedlings and annuals than on mature plants and perennials [19]. Vinegar has little residual activity and offers the greatest weed control one day after application [25].
Natural herbicides can be applied either as formulation without carrier or mixed with different volumes of carriers in the spray solution [30]. The effectiveness of herbicides differs depending on the stage of weed development and the herbicide concentration in the spray solution [20,31]. Since herbicides only kill the parts of the plant where they come into contact with, it is difficult for them to control grassy weeds because of their thick cuticles and narrow and erect leaves [32]. Adjuvants can significantly improve the efficiency of a spray solution’s capacity to control weeds, as well as the herbicide’s safety and efficacy during application and protection of nontarget plants [19]. Adjuvants are frequently used for post-emergence herbicides [19,32]. To improve herbicidal activity, we used natural plant extracts to obtain adjuvants effects. Evidence suggests that acetic acid possesses nematocidal, herbicidal, and antibacterial effects [33,34,35]. Additionally, it has been demonstrated that detergents have little negative effects on mammals while having powerful insecticidal, fungicidal, and herbicidal effects on some pests and plants [36,37]. Thus, natural products like vinegar and plant oils are increasingly popular for crop development and insect control, especially in organic agriculture [38]. Therefore, the objectives of this study were to determine the herbicidal efficacy of various natural products with different application methods for control of problematic weeds in agricultural fields.
2. Materials and Methods
2.1. Plant Materials
Broadleaf weed species (Ivpomoea hederacea and Chenopodium album) and grass weed species (Echinochloa crus-galli and Digitaria ciliaris) were used as test plants that are commonly problematic in agriculture across several countries. Weed seed samples were collected from fields at Sunchon National University’s research farms in South Korea in the fall of 2020. The seeds were refrigerated at 4 °C until use.
2.2. Natural Products
Brown rice vinegar serves as an herbicidal agent because of its acetic acid content [19,25]. Other natural products such as effective microorganisms (EM) powder soap and oils can suppress weed growth indirectly. Thus, nine various natural products, natural emulsifier-A and B, loess sulfur, lime sulfur, brown rice vinegar, effective microorganisms (EM) powder soap, soybean oil, citrus lemon oil, and citrus grapefruit oil were evaluated in this study to determine their herbicidal effects on broadleaf and grass weeds. Loess sulfur contained 250 g sulfur, 5 g red clay powder, 15 g bay salt, 5 g phyllite powder, 5 g calcium powder, 200 g NaOH, and 500 mL distilled water per 1 L of product. The final concentration of sulfur was 37%. Lime sulfur was a mixture of calcium hydroxide and sulfur. Natural emulsifier-A contained 32 g KOH, 180 mL canola oil, and 788 mL distilled water per 1 L of product. Natural emulsifier-B was purchased from Sugar Bubble Inc. (Seoul, Republic of Korea). Brown rice vinegar was purchased from Natural Food Inc. (Jeonju, Republic of Korea). The brown rice vinegar was produced through the aerobic bacterial oxidation of ethanol in fermented brown rice (80 g per liter) and contained 7% acetic acid. The EM powder soap, purchased from EMbio Inc. (Gunpo, Republic of Korea), was composed of natural vegetable fats and oils, NaOH, and EM-fermented liquor in a ratio of 77:17:6. Soybean oil was purchased from Natural Food Inc. (Seoul, Republic of Korea). Citrus lemon oil and citrus grapefruit oil were purchased from nowfood.com/essential-oils (accessed on 7 June 2022) packaged in the USA (Seoul, Republic of Korea) [39].
2.3. Control Effects of Various Natural Products on Broadleaf and Grass Weeds in Petri Dish Bioassay
The selected weed seeds were soaked in sterilized water for 24 h, and then, they were placed in Petri dishes with 9 cm diameters lined with two sheets of filter paper (Whatman #1). In each Petri dish, 10 seeds were combined with 10 mL of each natural product at 1, 3, and 5% concentrations. In control treatments, seeds were combined with 10 mL of distilled water. The Petri dishes were incubated in a germination cabinet for 2 days in the dark and 5 days under lights (100 μmol m2 s−1) at 25 °C. Germination rates were recorded 1, 3, 5, and 7 days after treatment, and shoot and root lengths were measured 7 days after treatment. The selected light intensity (100 μmol m2 s−1) and the specific time intervals (1, 3, 5, and 7 days) for recording measurements in Petri dish bioassays were chosen based on previous experiments that used the same or similar parameters.
Brown rice vinegar and EM powder soap (Gangcheong) were selected for further study because they showed the greatest inhibitory effects on grass and broadleaf weeds. In addition, various commercial vinegars and EM powder soaps were used to confirm the herbicidal effects of similar products. This study used various commercial vinegars, including hangman vinegar (acidity 6.5–7%), ottogi vinegar (acidity 6–7%), sea tangle vinegar (acidity 5%), persimmon vinegar (acidity 2.6%), superior mature vinegar (acidity 5%), pineapple vinegar (acidity 5–7%), apple vinegar (acidity 6–7%), white vinegar (Republic of Korea, acidity 10%), white vinegar (USA, acidity 5%), and Heinz vinegar (acidity 5%). Additionally, different commercial EM powder soap products were used, such as EM powder soap (Gangcheong), Mucheong-ga EM powder soap (Gangcheong), Wow EM powder soap (Gangcheong), Natural EM powder soap (EM Eco), and EM powder soap (Hanam Disabled Vocational Rehabilitation Center). These tests followed the same procedures as those mentioned in the seed bioassay experiments.
2.4. Control Effects of Brown Rice Vinegar and EM Powder Soap with Different Application Methods on Broadleaf and Grass Weeds
For soil and foliar application experiments, the selected weed seeds were sown in plastic pots (12 × 18 × 10 cm) filled with clay loam soil from Sunchon National University’s research farms. After sowing, the pots were placed in a greenhouse (28 °C/22 °C under a 14/10 h day/night regime and relative humidity of 70/90%). In soil application experiments, 10 mL of brown rice vinegar and EM powder soap were applied on the soil surface at 1, 3, 5, and 10% concentrations 1–2 days after sowing. In foliar application experiments, 10 mL of brown rice vinegar and EM powder soap were applied on leaf surfaces at 1, 3, 5, and 10% concentrations once weeds reached the two- to three-leaf stages. The selection of specific concentrations and timing of applications in relation to weed growth stages were determined based on previous experiments. The plant height and shoot fresh weight were recorded 14 days after treatment. Data were expressed as percentage of the nontreated control.
To confirm the soil persistence of the selected natural products, brown rice vinegar and EM powder soap at 10% concentrations were applied to the soil, and test weed seeds were planted 3, 5, and 7 days after treatment. Plant height and shoot fresh weight were recorded 14 days after treatment.
2.5. Control Effects of Brown Rice Vinegar and EM Powder Soap on Other Broadleaf and Grass Weeds
To confirm the herbicidal effects of the tested solutions, brown rice vinegar and EM powder soap at 10% concentrations were applied to other weed species such as Setaria viridis, Cyperus microiria, Eclipta prostrata, Abutilon theophrasti, Solanum nigrum, Persicaria hydropier, Portulaca oleracea, and Centipeda minima. These test plants are common, problematic weeds that are often dominant in agricultural fields across several countries. The same procedures mentioned in the soil and foliar application experiments were used in these experiments. Plant height and shoot fresh weight were recorded 14 days after sowing. Data were expressed as percentages of the nontreated control.
2.6. Control Effect of Application Frequency of Brown Rice Vinegar and EM Powder Soap on Broadleaf and Grass Weeds
To confirm the rates of control on four weed species, brown rice vinegar and EM powder soap products at 1, 3, and 5% concentrations were applied once or twice with soil and foliar application methods. In tests using foliar applications, seedlings at the two- to three-leaf stage were treated once or twice in a 7-day interval with 5 mL of brown rice vinegar and EM powder soap. A 7-day interval allows observations of not only the immediate effects but also of the potential lasting impacts of the treatments. In tests using soil applications, applications were made immediately after weed seeds had been planted. Plant height and shoot fresh weight were recorded 14 days after the first treatment. Data were expressed as percentages of the nontreated control.
2.7. Control Effects of Combined Brown Rice Vinegar and EM Powder Soap Treatments with Adjuvants on Broadleaf and Grass Weeds
The rationale for choosing certain adjuvants lies in their compatibility with brown rice vinegar and EM powder soap, as well as their potential to improve the speeding, absorption, and overall effectiveness of these substances. Different adjuvants offer unique properties that can enhance the way brown rice vinegar and EM powder soap interact with weed surface and the environment. For combination experiments, the application processes were the same as described in the previous section. Treatments included brown rice vinegar (3%) combined with EM powder soap (3%), brown rice vinegar (3%) combined with citrus lemon oil (3%), EM powder soap (3%) combined with citrus lemon oil (3%), and brown rice vinegar (3%) combined with EM powder soap (3%) and citrus lemon oil (3%). Additional treatments of brown rice vinegar, EM powder soap (each at 1%, 3%, and 5%), citrus lemon oil (3%), and natural plant extracts of Houttuynia cordata and Portulaca oleracea (1%) were tested. For the plant water extracts, 50 g of each ground material (Houttuynia cordata and Portulaca oleracea) was mixed with 1000 mL of distilled water for 24 h in a shaking incubator. The resulting mixture was filtered through two layers of miracloth and filtered again through Whatman (No. 1) filter paper. Subsequently, a vacuum dryer (Hanbaek Scientific Co., Siheung, Republic of Korea) was used to reduce the supernatants to a 50% concentration. Plant height and shoot fresh weight were recorded 14 days after treatment. Data were expressed as percentages of the nontreated control.
2.8. Statistical Analysis
The experiments were conducted in a completely randomized design with three replications. Data expressed as percentage of the untreated control were subjected to analysis of variance procedure using the R program (R statistical program, Version 4.2.3, R Core Team, UOA, Auckland, New Zealand). There were significant treatments x concentrations or application methods by factorial interaction; therefore, the data was presented at a control percent [19]. To compare the means of multiple groups in this study and determine which groups are significantly different from each other, means were separated using Duncan’s multiple range test at p < 0.05.
3. Results and Discussion
3.1. Control Effects of Various Natural Products on Broadleaf and Grass Weeds in Petri Dish Bioassay
In Petri dish bioassays, among the nine various natural products tested in this study, brown rice vinegar and EM powder soap at concentrations of 3% and 5%, respectively, as well as lime sulfur and loess sulfur at 5% concentrations, completely inhibited growth of the selected grass and broadleaf weeds (Table 1). However, other treatments such as citrus lemon oil, citrus grapefruit oil, and emulsifiers A and B at 5% concentrations inhibited these weeds by 47–100%. Lower rates of weed inhibitions were observed when soybean oil at a 5% concentration was applied to weeds (0–54% inhibition). Other natural products at 3% concentrations showed lower inhibition rates than brown rice vinegar and EM powder soap. Therefore, brown rice vinegar and EM powder soap were selected for further studies. Two factors revealed highly significant interaction between the treatments and the different concentrations on weed control. Similar to this study, brown rice vinegar and EM powder soap were shown to have herbicidal effects on Rumex crispus, Taraxacum officinal, and Echinochloa crus-galli [39]. Even though many naturally occurring substances, such as acetic acid, have herbicidal properties, there is debate about whether they should be approved for organic crop production systems [40,41]. One of main components in brown rice vinegar was acetic acid, which proved to be effective as a nonsynthetic herbicide for controlling weeds [42,43]. According to Abouziena et al. [28], clove oil (45.6%), citric acid (10%), and acetic acid (5%) were efficient against broadleaf weeds.
To confirm the herbicidal effects of various commercial vinegars and EM powder soap products, additional tests were conducted following the same procedures as mentioned in the seed bioassay experiments (Table 2 and Table 3). The tested weeds were completely inhibited by most commercial vinegar products at 5% concentrations. The tested weeds were completely inhibited by brown rice vinegar and white vinegar (Republic of Korea) at 3% concentrations. Hwanman vinegar, ottogi vinegar, white vinegar (Republic of Korea), and Heinz vinegar at 3% concentrations produced complete inhibition in I. hederacea, C. album, and D. ciliaris, but the rates of inhibition were lower when applied to E. crus-galli. Overall, brown rice vinegar was the most effective weed inhibitor of all vinegar products. These tests revealed a highly significant interaction between the vinegar treatments and concentrations in terms of weed control effectiveness.
The tested weeds (except for root length of C. album) were completely inhibited by most commercial EM products at 3 and 5% concentrations. In response to EM products at 1% concentration, the tested weeds were inhibited by 46–100%. Overall, EM powder soap (Gangcheong) was the most effective weed inhibitor of all the EM products tested. Thus, brown rice vinegar and EM powder soap (Gangcheong) were selected for further studies. Just as the case with brown rice vinegar, these tests revealed a highly significant interaction between the EM powder soap treatments and concentrations in terms of weed control effectiveness.
Previous research proved that broadleaf weeds including Morrenia odorada (strangler vine), Solanum nigrum (black nightshade), and Abutilon theophrasti (velvet leaf) can be efficiently controlled using household vinegar with 5% acetic acid, particularly in the early growth stage [19,28]. According to earlier research by Radhakrishnan et al. [22], herbaceous weeds treated with various acetic acid solutions and concentrations of less than 10% killed weeds within 2 weeks of emergence. Another effective solution is wood vinegar with acetic acid as the primary component. When applied at a rate of 4000 L/ha, it can produce inhibition rates of 82–100% in field conditions with broadleaf weeds of Perilla frutescens, Oxalis corniculata, and Geranium carolinianum [44].
3.2. Control Effects of Brown Rice Vinegar and EM Powder Soap with Different Application Methods on Broadleaf and Grass Weeds
To confirm the herbicidal effect of selected brown rice vinegar and EM powder soap, soil and foliar application methods were used (Table 4 and Table 5). In soil applications tests in greenhouse conditions, the selected brown rice vinegar and EM powder soap were less effective at controlling the four selected weeds than they were in Petri dish conditions. In addition, the inhibiting effectiveness on weeds was increased with increasing concentrations (1, 3, 5, and 10%) of brown rice vinegar and EM powder soap. At 10% concentrations, brown rice vinegar inhibited I. hederacea, C. album, E. crus-galli, and D. ciliaris shoot fresh weight by 88.2%, 89.4%, 79.3%, and 85.6%, respectively. Similar to brown rice vinegar, EM powder soap at 10% concentrations inhibited shoot fresh weight of I. hederacea, C. album, E. crus-galli, and D. ciliaris by 86.8%, 100.0%, 87.5%, and 87.7%, respectively.
In tests using foliar applications, the selected brown rice vinegar and EM powder soap in greenhouse conditions produced lower rates of inhibition on the four selected weeds than in Petri dish conditions. Inhibition effectiveness on the weeds was higher as concentrations increased (1, 3, 5, and 10%). In general, soil and foliar application tests of brown rice vinegar and EM powder soap produced higher rates of inhibition of shoot fresh weight than plant height. Additionally, EM powder soap was a more effective inhibitor than brown rice vinegar. Rates of weed inhibition were highest when brown rice vinegar and EM powder soap were applied using soil applications rather than foliar applications. However, the inhibiting effectiveness on tested weeds was consistent across broadleaf and grass weeds. In another greenhouse study, vinegar with acetic acid at concentrations of 5.0, 10.5, 15.3, and 20.2% killed Chenopodium album, Setaria faberii, Abutilon theophrasti, Amaranthus hybridus, and Cirsium arvense weed species [19]. In the above study, soil application was better than foliar application for controlling weeds. Research has shown that using vinegar to kill weeds that are small in size will maximize control [21,24,28]. In addition, it has been observed that killing older plants requires a larger dosage of acetic acid [45].
To test the persistence, the selected natural products in the soil brown rice vinegar and EM powder soap at 10% concentrations were applied to the soil 3, 5, 7, and 14 days before the four selected weeds were sown (Figure 1). With brown rice vinegar and EM powder soap, weed control efficacy on the four tested weed species decreased as time after soil treatment increased. However, brown rice vinegar was less efficient as an inhibitor than EM powder soap. These tests indicate that weed control efficacy is lowest at 14 days after treatment. Thus, brown rice vinegar and EM powder do not appear to last long in soil. Acetic acid is a contact herbicide that only kills aboveground vegetation [10]. Additionally, acetic acid treatments (5%, 20%, and 30%) initially eliminated weeds quickly but weeds were able to regrow [46]. Several authors have indicated that acetic acid is most effective on small weeds [22,28], and Smith [31] noted that weed control with clove oil was most effective on small weeds with one to two leaves. Additionally, Evans et al. [25] observed that vinegar effectively controlled weeds that were in the cotyledon to six-leaf stage at the time of application within the first day of treatment.
3.3. Effects of Brown Rice Vinegar and EM Powder Soap on Other Various Broadleaf and Grass Weeds in a Greenhouse
To confirm herbicidal effects on different weeds, vinegar and EM powder soap products at 10% concentrations were applied with soil and foliar application methods (Figure 2). In soil application, E. prostrata, S. nigrum, P. hydropier, and P. oleracea were completely inhibited by EM powder soap at 10% concentrations. However, brown rice vinegar at 10% concentrations inhibited 72–90% of E. prostrata, S. nigrum, P. hydropier, and P. oleracea. Brown rice vinegar and EM powder soap at 10% concentrations inhibited 66–92% of other weeds such as S. viridis, C. microiria, A. theophrasti, and C. minima. Generally, tested weeds except S. viridis were more effectively inhibited in EM powder soap than in brown rice vinegar treatments.
In foliar application, S. viridis, E. prostrata, S. nigrum, and P. hydropier were more inhibited in brown rice vinegar than in EM powder soap. In contrast, P. oleracea was more inhibited in EM powder soap than in brown rice vinegar. The inhibition rates of other weeds such as C. microiria, A. theophrasti, and C. minima were similar in brown rice vinegar and EM powder soap treatments. Overall, soil application was more effective in controlling weeds than foliar application in brown rice vinegar and EM powder soap. In this study, we only used D. ciliaris, E. crus-galli, and S. viridis for grass weeds with eight broadleaf weeds. Thus, it was not easy to determine the difference in control levels between broadleaf and grass weeds. However, natural contact herbicides using acetic acid or vinegar were more successful in suppressing broadleaf weeds than grassy weed species [19]. In another study, vinegar could control small annual broadleaf weeds when applied in a concentration and volume sufficient for the weeds [21,24,28]. Although the acetic concentrations used were higher than those in this study, acetic solutions of 10, 15, and 20% provided 80–100% of certain annual weeds (foxital, lambsquarters, pigweed, and velvetleaf) from greenhouse and field studies [47].
3.4. Effects of Application Frequency on Control Efficiency of Brown Rice Vinegar and EM Powder Soap on Broadleaf and Grass Weeds
To confirm the rates of control on the four weed species, brown rice vinegar and EM powder soap products at 1%, 3%, and 5% concentrations were applied once or twice with soil and foliar application methods (Table 6 and Table 7). In tests using soil applications, brown rice vinegar and EM powder soap were more effective when applications were made twice. In tests with one or two applications, weed inhibition effectiveness of brown rice vinegar and EM powder soap increased as concentrations of treatments increased (1, 3, and 5%).
In tests using foliar applications, brown rice vinegar and EM powder soap were more effective inhibitors when applications were made twice. In tests with one or two applications of brown rice vinegar and EM powder soap, weed inhibition effectiveness of brown rice vinegar and EM powder soap increased as concentrations of treatments increased (1, 3, and 5%).
In tests using one and two applications, weeds were more effectively controlled by brown rice vinegar and EM powder soap when soil applications were used. In general, weeds were more effectively inhibited when treated with EM powder soap than brown rice vinegar, regardless of the application method. As mentioned in the previous section, neither brown rice vinegar nor EM powder soap persisted in soils for long. In many cases, although weeds were suppressed by the first application, they often began to regrow later on. Thus, weeds should receive a second application to ensure complete weed control. According to Jang and Kuk [48], the results showed that plants treated with two applications of the extracts performed better than plants treated with a single application. Natural product herbicides must be sprayed at the appropriate time for several reasons, the most important of which is that they are most effective on small weeds and must be applied as soon as the weeds grow [21]. Radhakrishnan et al. [22] observed that acetic concentrations below 10% achieved complete weed elimination when sprayed within 2 weeks of weed emergence. Radhakrishnan et al. [22] and Moran [49] reported similar results, finding that increasing the concentration of acetic acid from 5% to 20% led to more effective weed control, obtaining rates of 80% to 100% across different weed species.
3.5. Control Effects of Combined Brown Rice Vinegar and EM Powder Soap Treatments with Adjuvants on Broadleaf and Grass Weeds
This study examined the effects of combining citrus lemon oil as an adjuvant with brown rice vinegar and EM powder soap, as well as using a combination of all the three and combinations of brown rice vinegar and EM powder soap (Table 8). In general, tests that used soil and foliar application methods of combined treatments were most effective when weeds received three applications. In particular, when brown rice vinegar (3%), EM powder soap (3%), and citrus lemon oil (3%) were combined, they produced the highest overall rates of weed inhibition. Similarly, weeds were more effectively inhibited when two applications were made as opposed to just one, regardless of which combination was being used. In tests using soil and foliar application methods, brown rice vinegar and EM powder soap were more effective weed inhibitors when combined with citrus lemon oil and less effective when combined with one another.
In some tests, however, the application method had an effect on weed control. For example, tests on C. album using a combination of all three substances were more effective when the soil application method was used. By contrast, D. ciliaris was more effectively controlled when treated using the foliar application method. However, in tests on I. hederacea and E. crus-galli weeds, a combination of all three substances produced similar rates of inhibition regardless of whether soil or foliar applications were used. In a previous study, the most effective rates of weed inhibition were observed when 5% acetic acid, 5% salt, and 0.2% dish soap were combined and used for treatments [50]. In Thailand, combined mixtures are commonly referred to as safe and effective homemade herbicides by farmers [50]. In addition, a combination of clove oil, citric acid (10%), and garlic produced satisfactory weed control [20,51]. However, according to Johnson [52], using treatments of only citric acid (10%) and garlic weeds does not effectively control weeds. Adjuvants such as orange oil or canola oil produced little or no benefit when added to acetic acids such as vinegar spray solutions [19].
Houttuynia cordata and Portulaca oleracea extracts are emulsifiers with a viscosity well suited for use as adjuvants [53,54]. Adjuvants may be added to herbicide solutions to act as spreader-stickers, emulsifiers, drift control agents, and herbicide penetration agents [19]. To determine the adjuvant effects of Houttuynia cordata and Portulaca oleracea plant extracts on test weeds, brown rice vinegar and EM powder soap were applied with plant extracts in soil and foliar application conditions (Table 9 and Table 10). In soil application, Houttuynia cordata and Portulaca oleracea plant extracts at 1% concentration inhibited the tested weeds by 4.5–17.4%. In a previous study, aqueous extracts (1%, 2%, 4%, and 8%) made from the dried powders of Houttuynia cordata inhibited the germination and initial seedling growth of lettuce and two major weed species, Echinochloa crus-galli and Monocharia vaginalis, in Petri dish tests [54]. However, growth inhibition rates in this study were very low in tests using Houttuynia cordata extracts at 1% concentration.
The rates of growth inhibition decreased when test weeds received applications of Houttuynia cordata and Portulaca oleracea plant extracts mixture. Treatments of brown rice vinegar or EM powder soap applied alone produced higher rates of growth inhibition. Similar to soil application tests, rates of growth inhibition were very low when Houttuynia cordata or Portulaca oleracea plant extracts were used alone in foliar application tests. Furthermore, treatments using a mixture of Houttuynia cordata and Portulaca oleracea plant extracts were less effective than brown rice vinegar or EM powder soap treatments used alone. This result means that the two plant extracts tested did not show adjuvant or combination effects when combined with brown rice vinegar and EM powder soap. In a previous study, crop oil, yucca extract, or potassium salt fatty acid as adjuvants did not affect the performance of acetic acid used for weed control [21,24,26,28]. Therefore, brown rice vinegar and EM powder soap did not show adjuvant effects when combined with plant extracts that can sometimes create better contact with or penetration of the weeds.
4. Conclusions
Of the nine various natural products tested, brown rice vinegar and EM powder soap at 5% concentrations were the only applications that completely controlled grass and broadleaf weeds in Petri dish bioassays. Additionally, the tested grass and broadleaf weeds were completely inhibited in greenhouse conditions when soil and foliar applications of EM powder soap at 10% concentrations were used. However, several factors such as crop and weed diversity should be considered when extrapolating these findings to field conditions. While soil applications were more effective than foliar applications at inhibiting weed growth, several limitations and challenges such as residual impact and root uptake must be considered when deciding whether to favor soil-based approaches for weed management. EM powder soap was more effective in controlling grass and broadleaf weeds than brown rice vinegar. Moreover, two-time application methods were more effective in controlling all weed species than one-time application methods. However, no synergism effects were observed when brown rice vinegar and EM powder soap were combined with other natural products. In addition, brown rice vinegar and EM powder soap did not show adjuvant effects when combined with plant extracts that can sometimes create better contact with or penetration of the weeds. Thus, weeds growing alongside transplanted vegetable crops can be effectively controlled with brown rice vinegar and EM powder soap by using soil applications in row, either individually or combined together and with either one or two applications. The findings of this study hold significant implications for the advancement of sustainable agricultural practices and the potential enhancement of integrated weed management strategies.
Author Contributions
Data curation and writing, P.-P.W. and H.-H.P.; writing, review, and editing, Y.-I.K. All authors have read and agreed to the published version of the manuscript.
Funding
This work was supported by Sunchon National University. This paper is a part of an MS thesis for Pyae-Pyae Win.
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
Not applicable.
Conflicts of Interest
The authors declare no conflict of interest.
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Figure 1.
Effects of soil persistence of brown rice vinegar and EM powder soap at 10% concentrations on broadleaf weeds Chenopodium album (A) and Eclipta Prostrate (B) and grass weeds Echinochloa crus-galli (C) and Digitaria ciliaris (D). Means expressed error bar (±SE) with three replicates.
Figure 1.
Effects of soil persistence of brown rice vinegar and EM powder soap at 10% concentrations on broadleaf weeds Chenopodium album (A) and Eclipta Prostrate (B) and grass weeds Echinochloa crus-galli (C) and Digitaria ciliaris (D). Means expressed error bar (±SE) with three replicates.
Figure 2.
Effects of soil (A) and foliar (B) treatments of brown rice vinegar and EM powder soap at 10% concentrations on various weeds. Means expressed error bar (±SE) with three replicates.
Figure 2.
Effects of soil (A) and foliar (B) treatments of brown rice vinegar and EM powder soap at 10% concentrations on various weeds. Means expressed error bar (±SE) with three replicates.
Table 1.
Effects of various natural products on shoot and root lengths of broadleaf and grass weeds in Petri dish bioassay.
Table 1.
Effects of various natural products on shoot and root lengths of broadleaf and grass weeds in Petri dish bioassay.
| Treatment | Conc. % | Ivpomoea hederacea | Chenopodium album | Echinochloa crus-galli | Digitaria ciliaris | ||||
|---|---|---|---|---|---|---|---|---|---|
| Shoot Length | Root Length | Shoot Length | Root Length | Shoot Length | Root Length | Shoot Length | Root Length | ||
| % of Control | |||||||||
| Control | 0 q | 0 m | 0 l | 0 j | 0 m | 0 p | 0 k | 0 n | |
| Brown rice vinegar | 1 | 72.0 d | 97.4 b | 86.9 b | 92.6 b | 56.4 g | 91.7 c | 86.6 c | 93.5 b |
| 3 | 100 a | 100 a | 100 a | 100 a | 85.4 cb | 100 a | 100 a | 100 a | |
| 5 | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | |
| EM powder soap | 1 | 94.5 b | 97.9 b | 97.4 a | 94.0 b | 93.5 b | 100 a | 100 a | 100 a |
| 3 | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | |
| 5 | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | |
| Lime sulfur | 1 | 45.5 j | 86.3 d | 56.5 e | 48.2 g | 54.8 gh | 65.9 i | 53.3 g | 87.4 e |
| 3 | 93.8 b | 100 a | 87.1 b | 100 a | 78.8 ef | 100 a | 73.3 de | 100 a | |
| 5 | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | |
| Loess sulfur | 1 | 42.1 k | 88.2 c | 15.3 k | 66.4 e | 51.6 gh | 88.3 e | 35.5 h | 58.5 j |
| 3 | 97.2 a | 98.0 b | 84.6 b | 94.2 b | 83.8 de | 100 a | 73.5 de | 90.4 d | |
| 5 | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | |
| Citrus lemon oil | 1 | 42.2 k | 44.2 h | 29.4 j | 54.0 f | 50.0 h | 52.3 k | 77.7 d | 83.8 f |
| 3 | 50.8 i | 58.1 f | 41.0 gh | 69.8 de | 77.4 f | 83.2 f | 93.3 b | 91.9 c | |
| 5 | 65.9 f | 66.5 e | 47.4 f | 90.6 b | 95.1 ab | 96.2 b | 100 a | 100 a | |
| Citrus grapefruit oil | 1 | 4.7 p | 11.7 l | 55.1 e | 52.9 f | 41.9 i | 47.1 l | 77.7 d | 65.1 h |
| 3 | 30.6 l | 19.0 k | 62.8 d | 72.6 d | 77.4 f | 90.6 d | 93.3 b | 79.7 g | |
| 5 | 57.1 h | 47.4 g | 76.9 c | 82.6 c | 90.3 bc | 95.5 b | 100 a | 100 a | |
| Soybean oil | 1 | −11.5 r | −15.3 o | 0.0 q | 21.0 i | 24.1 kl | 16.8 p | 13.3 j | −11.1 o |
| 3 | −2.0 q | −4.9 n | 13.0 p | 34.0 h | 38.7 i | 20.7 n | 14.9 o | 27.0 m | |
| 5 | 20.4 l | 0.0 m | 34.8 n | 54.0 n | 43.5 i | 29.3 m | 20.0 i | 37.8 k | |
| Emulsifier A | 1 | 23.0 m | 42.0 i | 12.8 k | 52.8 f | 20.9 l | −1.8 q | 13.3 j | 34.3 l |
| 3 | 29.2 l | 58.1 f | 37.1 hi | 69.8 de | 43.5 i | 60.7 j | 40.0 h | 62.9 i | |
| 5 | 61.9 g | 67.6 e | 85.8 b | 81.6 c | 51.6 gh | 79.7 g | 68.8 ef | 100 a | |
| Emulsifier B | 1 | 14.9 o | −4.8 n | 43.5 fg | 69.8 de | 27.4 jk | 66.0 i | 64.4 f | 83.8 f |
| 3 | 69.3 e | 36.9 j | 71.7 c | 92.5 b | 32.2 j | 78.4 h | 91.1 bc | 100 a | |
| 5 | 83.6 c | 85.5 d | 100 a | 100 a | 77.4 f | 100 a | 100 a | 100 a | |
| Treatment | *** | *** | *** | *** | *** | *** | *** | *** | |
| Conc. | *** | *** | *** | *** | *** | *** | *** | *** | |
| Treatment × Conc. | *** | *** | *** | *** | *** | *** | *** | *** | |
Conc., concentration. Means followed by different letters in the same column are significantly different by Duncan’s multiple range test at 5% level. Significance: *** = p value < 0.001.
Table 2.
Effects of various vinegar products on shoot and root lengths of broadleaf and grass weeds in Petri dish bioassay.
Table 2.
Effects of various vinegar products on shoot and root lengths of broadleaf and grass weeds in Petri dish bioassay.
| Treatment | Conc. % | Ivpomoea hederacea | Chenopodium album | Echinochloa crus-galli | Digitaria ciliaris | ||||
|---|---|---|---|---|---|---|---|---|---|
| Shoot Length | Root Length | Shoot Length | Root Length | Shoot Length | Root Length | Shoot Length | Root Length | ||
| % of Control | |||||||||
| Control | 0 n | 0 j | 0 j | 0 g | 0 u | 0 k | 0 i | 0 g | |
| Brown rice vinegar | 1 | 92.2 b | 98.8 a | 88.2 cd | 91.9 b | 66.6 e | 97.5 b | 94.7 b | 100 a |
| 3 | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | |
| 5 | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | |
| Hwanman vinegar | 1 | 76.6 d | 82.6 d | 73.5 g | 85.3 c | 31.7 jk | 80.0 f | 92.8 b | 100 a |
| 3 | 100 a | 100 a | 100 a | 100 a | 50.7 h | 90.0 d | 100 a | 100 a | |
| 5 | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | |
| Ottogi vinegar | 1 | 88.3 c | 88.4 c | 79.4 efg | 78.0 d | 33.3 ijk | 30.0 j | 84.2 cd | 94.3 b |
| 3 | 100 a | 100 a | 100 a | 100 a | 52.3 gh | 85.0 e | 100 a | 100 a | |
| 5 | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | |
| Sea tangle vinegar | 1 | 51.9 g | 82.6 d | 76.4 fg | 78.0 d | 36.5 ij | 85.0 e | 68.4 e | 83.3 d |
| 3 | 100 a | 100 a | 97.0 ab | 98.1 a | 47.6 h | 90.0 d | 100 a | 100 a | |
| 5 | 100 a | 100 a | 100 a | 100 a | 80.9 c | 100 a | 100 a | 100 a | |
| Persimmon vinegar | 1 | 23.3 j | 23.6 i | 38.2 i | 60.9 f | 19.0 l | 31.6 j | 35.0 h | 55.8 f |
| 3 | 74.0 e | 76.9 e | 85.2 cde | 91.2 b | 38.1 i | 75.0 g | 100 a | 100 a | |
| 5 | 100 a | 100 a | 100 a | 100 a | 57.1 fg | 100 a | 100 a | 100 a | |
| Superior mature vinegar | 1 | 14.2 l | 61.5 h | 47.0 h | 70.7 e | 28.5 k | 30.0 j | 36.8 h | 57.5 e |
| 3 | 32.4 i | 71.1 f | 100 a | 100 a | 47.6 h | 85.0 e | 100 a | 100 a | |
| 5 | 100 a | 100 a | 100 a | 100 a | 74.6 d | 100 a | 100 a | 100 a | |
| Pineapple vinegar | 1 | 10.3 m | 65.3 g | 52.9 h | 63.4 f | 14.2 m | 70.0 h | 56.1 g | 86.2 c |
| 3 | 92.2 b | 88.4 c | 100 a | 100 a | 66.6 e | 89.5 d | 100 a | 100 a | |
| 5 | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | |
| Apple vinegar | 1 | 53.2 f | 71.1 f | 82.3 def | 63.4 g | 12.6 m | 74.6 g | 82.4 d | 86.1 c |
| 3 | 100 a | 100 a | 85.2 cde | 78.0 d | 60.3 f | 93.3 c | 100 a | 100 a | |
| 5 | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | |
| White vinegar (Korea) | 1 | 92.2 b | 94.2 b | 82.3 def | 70.7 e | 61.9 ef | 81.6 f | 82.6 d | 94.2 b |
| 3 | 100 a | 100 a | 100 a | 100 a | 80.9 c | 100 a | 100 a | 100 a | |
| 5 | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | |
| White vinegar (USA) | 1 | 18.1 k | 65.3 g | 91.1 bc | 79.3 d | 9.5 m | 55.0 i | 85.9 c | 100 a |
| 3 | 46.1 h | 82.6 d | 100 a | 100 a | 28.5 k | 74.6 g | 100 a | 100 a | |
| 5 | 100 a | 100 a | 100 a | 100 a | 93.6 b | 100 a | 100 a | 100 a | |
| Heinz vinegar | 1 | 92.2 b | 93.0 b | 85.2 cde | 78.2 d | 0.0 n | 54.8 i | 63.1 f | 94.5 b |
| 3 | 100 a | 100 a | 100 a | 100 a | 57.1 fg | 85.0 e | 100 a | 100 a | |
| 5 | 100 a | 100 a | 100 a | 100 a | 79.3 c | 100 a | 100 a | 100 a | |
| Treatment | *** | *** | *** | *** | *** | *** | *** | *** | |
| Conc. | *** | *** | *** | *** | *** | *** | *** | *** | |
| Treatment × Conc. | *** | *** | *** | *** | *** | *** | *** | *** | |
Conc., concentration. Means followed by different letters in the same column are significantly different by Duncan’s multiple range test at 5% level. Significance: ***= p value < 0.001.
Table 3.
Effects of various EM powder soap products on shoot and root lengths of broadleaf and grass weeds in Petri dish bioassay.
Table 3.
Effects of various EM powder soap products on shoot and root lengths of broadleaf and grass weeds in Petri dish bioassay.
| Treatment | Conc. % | Ivpomoea hederacea | Chenopodium album | Echinochloa crus-galli | Digitaria ciliaris | ||||
|---|---|---|---|---|---|---|---|---|---|
| Shoot Length | Root Length | Shoot Length | Root Length | Shoot Length | Root Length | Shoot Length | Root Length | ||
| % of Control | |||||||||
| Control | 0 g | 0 e | 0 f | 0 i | 0 h | 0 f | 0 e | 0 e | |
| EM-1 | 1 | 95.0 b | 96.3 b | 100 a | 90.9 c | 93.5 b | 100 a | 100 a | 100 a |
| 3 | 100 a | 100 a | 100 a | 96.8 b | 100 a | 100 a | 100 a | 100 a | |
| 5 | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | |
| EM-2 | 1 | 72.1 e | 91.1 c | 78.6 d | 80.9 f | 82.9 e | 87.0 d | 92.6 b | 86.2 d |
| 3 | 100 a | 100 a | 100 a | 87.1 d | 86.6 d | 93.4 b | 100 a | 100 a | |
| 5 | 100 a | 100 a | 100 a | 100 a | 95.5 b | 100 a | 100 a | 100 a | |
| EM-3 | 1 | 91.6 c | 90.5 c | 81.7 c | 83.5 e | 90.4 c | 90.5 c | 100 a | 100 a |
| 3 | 100 a | 100 a | 100 a | 81.9 e | 100 a | 100 a | 100 a | 100 a | |
| 5 | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | |
| EM-4 | 1 | 89.8 d | 90.0 c | 90.8 b | 67.8 g | 54.8 g | 90.4 c | 88.0 c | 96.5 b |
| 3 | 100 a | 100 a | 100 a | 87.1 d | 100 a | 100 a | 100 a | 100 a | |
| 5 | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | |
| EM-5 | 1 | 55.9 f | 80.8 d | 46.0 e | 62.0 h | 66.1 f | 73.8 e | 85.7 d | 92.4 c |
| 3 | 92.1 c | 100 a | 100 a | 90.1 c | 100 a | 100 a | 100 a | 100 a | |
| 5 | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | 100 a | |
| Treatment | *** | *** | *** | *** | *** | *** | *** | *** | |
| Conc. | *** | *** | *** | *** | *** | *** | *** | *** | |
| Treatment × Conc. | *** | *** | *** | *** | *** | *** | *** | *** | |
Conc., concentration; EM-1, EM powder soap (Gangcheong); EM-2, Mucheong-ga EM powder soap (Gangcheong); EM-3, Wow EM powder soap (Gangcheong); EM-4, Natural EM powder soap (EM Eco); EM-5, EM powder soap (Hanam Disabled Vocational Rehabilitation Center). Means followed by different letters in the same column are significantly different by Duncan’s multiple range test at 5% level. Significance: *** = p value < 0.001.
Table 4.
Effects of soil treatment of brown rice vinegar and EM powder soap concentrations on broadleaf and grass weeds.
Table 4.
Effects of soil treatment of brown rice vinegar and EM powder soap concentrations on broadleaf and grass weeds.
| Treatment | Conc. % | Ivpomoea hederacea | Chenopodium album | Echinochloa crus-galli | Digitaria ciliaris | ||||
|---|---|---|---|---|---|---|---|---|---|
| Plant Height | Shoot Fresh Weight | Plant Height | Shoot Fresh Weight | Plant Height | Shoot Fresh Weight | Plant Height | Shoot Fresh Weight | ||
| % of Control | |||||||||
| Control | 0 i | 0 g | 0 h | 0 i | 0 h | 0 i | 0 i | 0 h | |
| Brown rice vinegar | 1 | 10.1 h | 20.0 f | 32.6 g | 44.2 h | 11.7 g | 32.4 h | 23.3 g | 39.1 g |
| 3 | 16.5 g | 40.7 e | 55.3 e | 65.6 f | 33.7 f | 56.2 f | 29.5 f | 50.9 e | |
| 5 | 37.4 d | 56.7 c | 73.0 c | 84.1 d | 63.0 d | 66.7 e | 51.3 e | 77.2 c | |
| 10 | 73.0 b | 88.2 a | 87.1 b | 89.4 b | 77.7 b | 79.3 c | 76.8 ab | 85.6 a | |
| EM powder soap | 1 | 19.1 f | 39.0 e | 41.8 f | 56.9 g | 34.6 f | 35.2 g | 48.8 e | 47.6 f |
| 3 | 25.3 e | 52.5 d | 63.1 d | 70.5 e | 57.2 e | 69.5 d | 54.6 d | 67.2 d | |
| 5 | 41.2 c | 61.3 b | 75.1 c | 86.6 c | 73.7 c | 84.1 b | 72.6 c | 80.7 b | |
| 10 | 75.8 a | 86.8 a | 100 a | 100 a | 81.1 a | 87.5 a | 82.8 a | 87.7 a | |
| Treatment | *** | *** | *** | *** | *** | *** | *** | *** | |
| Conc. | *** | *** | *** | *** | *** | *** | *** | *** | |
| Treatment × Conc. | *** | *** | ** | *** | *** | *** | *** | *** | |
Conc., concentration. Means followed by different letters in the same column are significantly different by Duncan’s multiple range test at 5% level. Significance: *** = p value < 0.001; ** = p value < 0.01.
Table 5.
Effects of foliar treatment of brown rice vinegar and EM powder soap concentrations on broadleaf and grass weeds.
Table 5.
Effects of foliar treatment of brown rice vinegar and EM powder soap concentrations on broadleaf and grass weeds.
| Treatment | Conc. % | Ivpomoea hederacea | Chenopodium album | Echinochloa crus-galli | Digitaria ciliaris | ||||
|---|---|---|---|---|---|---|---|---|---|
| Plant Height | Shoot Fresh Weight | Plant Height | Shoot Fresh Weight | Plant Height | Shoot Fresh Weight | Plant Height | Shoot Fresh Weight | ||
| % of Control | |||||||||
| Control | 0 h | 0 h | 0 h | 0 i | 0 i | 0 h | 0 h | 0 h | |
| Brown rice vinegar | 1 | 8.4 g | 22.8 f | 10.9 g | 22.6 g | 6.0 h | 15.0 g | 10.4 g | 20.3 g |
| 3 | 15.6 f | 34.8 e | 25.7 e | 30.7 f | 18.2 g | 25.1 f | 24.0 e | 26.9 f | |
| 5 | 32.4 d | 50.0 d | 37.6 d | 49.5 d | 31.5 e | 51.5 d | 34.6 d | 45.7 d | |
| 10 | 59.4 b | 69.9 c | 60.9 b | 71.7 b | 56.5 b | 67.6 b | 59.8 b | 68.7 b | |
| EM powder soap | 1 | 14.9 f | 19.9 g | 13.7 f | 18.7 h | 22.3 f | 24.1 f | 16.1 f | 19.3 g |
| 3 | 22.8 e | 36.6 e | 39.0 d | 39.6 e | 35.1 d | 37.5 e | 35.5 d | 37.6 e | |
| 5 | 46.3 c | 59.2 c | 59.1 c | 60.9 c | 41.2 c | 61.1 c | 45.2 c | 60.3 c | |
| 10 | 88.4 e | 96.5 a | 90.5 a | 97.6 a | 62.2 a | 78.4 a | 79.9 a | 83.9 a | |
| Treatment | *** | *** | *** | *** | *** | *** | *** | *** | |
| Conc. | *** | *** | *** | *** | *** | *** | *** | *** | |
| Treatment × Conc. | *** | *** | ** | *** | *** | ** | *** | *** | |
Conc., concentration. Means followed by different letters in the same column are significantly different by Duncan’s multiple range test at 5% level. Significance: *** = p value < 0.001; ** = p value < 0.01.
Table 6.
Effect of soil treatment application frequency of brown rice vinegar and EM powder soap on broadleaf and grass weeds.
Table 6.
Effect of soil treatment application frequency of brown rice vinegar and EM powder soap on broadleaf and grass weeds.
| Treatment | Application Frequency | Ivpomoea hederacea | Chenopodium album | Echinochloa crus-galli | Digitaria ciliaris | ||||
|---|---|---|---|---|---|---|---|---|---|
| Plant Height | Shoot Fresh Weight | Plant Height | Shoot Fresh Weight | Plant Height | Shoot Fresh Weight | Plant Height | Shoot Fresh Weight | ||
| % of Control | |||||||||
| Control | 0 h | 0 h | 0 h | 0 g | 0 j | 0 g | 0 h | 0 h | |
| BRV 1% | Once | 11.5 g | 24.7 g | 29.0 g | 43.2 f | 10.1 i | 27.8 f | 20.2 g | 33.4 g |
| Twice | 21.0 f | 32.7 f | 44.6 f | 56.6 e | 24.7 h | 40.4 d | 31.2 f | 43.6 f | |
| BRV 3% | Once | 23.0 f | 41.2 e | 53.6 e | 64.0 d | 30.7 g | 52.2 c | 26.8 fg | 48.4 f |
| Twice | 34.5 de | 49.1 d | 64.5 d | 73.6 c | 59.8 de | 63.0 b | 57.7 c | 68.9 de | |
| BRV 5% | Once | 39.3 de | 60.0 c | 72.4 c | 81.8 c | 60.7 d | 63.9 b | 50.2 d | 73.0 cd |
| Twice | 65.4 b | 77.3 a | 84.6 ab | 90.1 a | 74.6 ab | 78.0 a | 74.0 ab | 80.7 ab | |
| EM 1% | Once | 25.0 f | 37.1 ef | 41.8 f | 53.7 e | 32.7 g | 33.9 e | 43.1 e | 45.7 f |
| Twice | 37.9 de | 49.0 d | 53.9 e | 69.4 cd | 39.7 f | 51.5 c | 55.5 cd | 50.6 f | |
| EM 3% | Once | 33.2 e | 50.5 d | 62.4 d | 69.3 cd | 55.4 e | 65.5 b | 52.4 cd | 63.7 e |
| Twice | 51.9 c | 69.8 b | 79.6 bc | 85.4 ab | 67.2 c | 75.3 a | 67.9 b | 76.1 bc | |
| EM 5% | Once | 41.2 d | 58.8 c | 73.7 c | 82.1 b | 73.2 b | 76.3 a | 72.6 b | 76.8 abc |
| Twice | 73.3 a | 81.9 a | 88.5 a | 90.4 a | 79.0 a | 80.2 a | 79.8 a | 83.6 a | |
| Treatment | *** | *** | *** | *** | *** | *** | *** | *** | |
| Application frequency | *** | *** | *** | *** | *** | *** | *** | *** | |
| Treatment × Application frequency | *** | ** | ns | * | *** | ** | *** | ** | |
BRV, brown rice vinegar; EM, EM powder soap. Means followed by different letters in the same column are significantly different by Duncan’s multiple range test at 5% level. Significance: *** = p value < 0.001; ** = p value < 0.01; * = p value < 0.05; ns = p value > 0.1.
Table 7.
Effect of foliar treatment application frequency of brown rice vinegar and EM powder soap on broadleaf and grass weeds.
Table 7.
Effect of foliar treatment application frequency of brown rice vinegar and EM powder soap on broadleaf and grass weeds.
| Treatment | Application Frequency | Ivpomoea hederacea | Chenopodium album | Echinochloa crus-galli | Digitaria ciliaris | ||||
|---|---|---|---|---|---|---|---|---|---|
| Plant Height | Shoot Fresh Weight | Plant Height | Shoot Fresh Weight | Plant Height | Shoot Fresh Weight | Plant Height | Shoot Fresh Weight | ||
| % of Control | |||||||||
| Control | 0 g | 0 g | 0 i | 0 i | 0 i | 0 g | 0 i | 0 g | |
| BRV 1% | Once | 11.1 f | 20.9 f | 16.9 h | 24.6 h | 7.9 h | 14.2 f | 10.2 h | 17.7 f |
| Twice | 20.4 e | 27.9 ef | 25.7 g | 29.5 g | 14.8 g | 25.6 e | 16.2 g | 24.5 ef | |
| BRV 3% | Once | 18.5 ef | 33.0 de | 28.1 fg | 34.7 f | 18.4 fg | 24.2 e | 21.8 f | 27.0 e |
| Twice | 29.9 cd | 39.9 d | 33.4 ef | 40.6 e | 24.5 e | 37.6 d | 28.3 e | 39.3 d | |
| BRV 5% | Once | 37.6 c | 54.2 c | 41.9 d | 52.3 d | 33.2 d | 54.8 c | 34.9 d | 46.9 c |
| Twice | 59.1 b | 66.9 b | 58.9 bc | 73.4 b | 58.2 b | 64.8 b | 55.4 b | 63.8 b | |
| EM 1% | Once | 18.5 ef | 24.8 f | 17.2 h | 25.1 h | 20.9 ef | 25.5 e | 16.8 g | 21.5 ef |
| Twice | 26.7 de | 37.1 d | 27.8 fg | 38.6 ef | 31.9 d | 34.6 d | 31.5 de | 35.4 d | |
| EM 3% | Once | 27.5 de | 40.1 d | 36.6 de | 42.0 e | 34.5 d | 37.7 d | 35.6 d | 39.4 d |
| Twice | 50.6 b | 61.2 bc | 54.2 c | 64.0 c | 45.8 c | 58.8 bc | 48.8 c | 59.1 b | |
| EM 5% | Once | 53.4 b | 57.4 c | 63.3 b | 65.1 c | 45.9 c | 61.2 b | 50.0 c | 62.3 b |
| Twice | 77.6 a | 80.9 a | 82.3 a | 86.6 a | 63.3 a | 71.8 a | 66.8 a | 80.3 a | |
| Treatment | *** | *** | *** | *** | *** | *** | *** | *** | |
| Application frequency | *** | *** | *** | *** | *** | *** | *** | *** | |
| Treatment × Application frequency | ** | ** | ** | *** | *** | ** | *** | ** | |
BRV; brown rice vinegar, EM; EM powder soap. Means followed by different letters in the same column are significantly different by Duncan’s multiple range test at 5% level. Significance: *** = p value < 0.001; ** = p value < 0.01.
Table 8.
Combination effects of soil and foliar treatment of brown rice vinegar and EM powder soap with citrus lemon oil on broadleaf and grass weeds.
Table 8.
Combination effects of soil and foliar treatment of brown rice vinegar and EM powder soap with citrus lemon oil on broadleaf and grass weeds.
| Treatment | Application Method | Ivpomoea hederacea | Chenopodium album | Echinochloa crus-galli | Digitaria ciliaris | ||||
|---|---|---|---|---|---|---|---|---|---|
| Plant Height | Shoot Fresh Weight | Plant Height | Shoot Fresh Weight | Plant Height | Shoot Fresh Weight | Plant Height | Shoot Fresh Weight | ||
| % of Control | |||||||||
| Control | 0 k | 0 j | 0 m | 0 l | 0 m | 0 k | 0 l | 0 m | |
| BRV 3% | Soil | 19.2 i | 45.2 g | 52.1 h | 64.7 g | 32.0 j | 51.1 g | 29.1 j | 49.6 i |
| Foliar | 15.8 j | 34.4 i | 26.1 l | 32.5 k | 16.1 l | 29.6 j | 24.0 k | 40.8 j | |
| EM 3% | Soil | 27.1 h | 50.6 f | 61.2 g | 72.2 f | 54.6 g | 65.5 e | 53.8 g | 65.9 f |
| Foliar | 18.6 i | 35.7 i | 39.3 i | 41.4 i | 33.9 i | 34.2 h | 40.9 h | 52.4 h | |
| CLO 3% | Soil | 19.9 i | 37.6 h | 30.7 k | 50.1 h | 29.0 k | 33.3 h | 29.6 j | 31.0 l |
| Foliar | 19.8 i | 37.5 h | 32.7 j | 34.8 j | 28.4 k | 34.4 i | 31.5 i | 33.8 k | |
| BRV 3% + EM 3% | Soil | 36.6 g | 56.2 e | 75.2 e | 79.3 e | 59.2 f | 78.7 cd | 65.5 d | 73.8 e |
| Foliar | 40.8 f | 63.5 b | 60.6 g | 65.1 g | 37.3 h | 60.5 f | 55.7 g | 63.2 g | |
| BRV 3% + CLO 3% | Soil | 46.7 d | 63.3 bc | 78.0 d | 89.4 b | 66.8 c | 78.0 d | 66.7 d | 77.6 c |
| Foliar | 44.5 e | 61.1 d | 69.8 f | 79.8 e | 65.2 d | 78.7 cd | 63.6 e | 75.9 d | |
| EM 3% + CLO 3% | Soil | 51.6 c | 61.6 cd | 79.7 c | 82.9 d | 64.0 e | 80.0 bc | 70.1 c | 79.2 b |
| Foliar | 52.9 c | 64.6 b | 76.1 e | 80.9 e | 69.8 b | 80.5 b | 72.7 b | 80.0 b | |
| BRV 3% + EM 3% + CLO 3% | Soil | 63.1 a | 71.8 a | 85.4 a | 97.2 a | 69.2 b | 82.1 a | 72.2 b | 79.7 b |
| Foliar | 61.1 b | 70.9 a | 81.9 b | 85.5 c | 73.5 a | 83.1 a | 75.7 a | 82.6 a | |
| Treatment | *** | *** | *** | *** | *** | *** | *** | *** | |
| Application method | ** | *** | *** | *** | *** | *** | *** | *** | |
| Treatment × Application method | *** | *** | *** | *** | *** | *** | *** | *** | |
BRV, brown rice vinegar; EM, EM powder soap; CLO, citrus lemon oil. Means followed by different letters in the same column are significantly different by Duncan’s multiple range test at 5% level. Significance: *** = p value < 0.001; ** = p value < 0.01.
Table 9.
Effects of soil treatment of brown rice vinegar and EM powder soap with plant extracts on broadleaf and grass weeds.
Table 9.
Effects of soil treatment of brown rice vinegar and EM powder soap with plant extracts on broadleaf and grass weeds.
| Treatment | Plant Extract | Ivpomoea hederacea | Chenopodium album | Echinochloa crus-galli | Digitaria ciliaris | ||||
|---|---|---|---|---|---|---|---|---|---|
| Plant Height | Shoot Fresh Weight | Plant Height | Shoot Fresh Weight | Plant Height | Shoot Fresh Weight | Plant Height | Shoot Fresh Weight | ||
| % of Control | |||||||||
| Control | 0 n | 0 j | 0 m | 0 k | 0 m | 0 j | 0 o | 0 m | |
| None | HC | −8.0 p | −2.4 k | 8.1 l | 15.5 j | −3.5 n | 10.1 i | 4.5 n | 12.3 l |
| None | PO | −3.4 o | −1.3 jk | 12.7 k | 17.4 j | −3.5 n | 11.4 i | 6.6 n | 14.6 kl |
| BRV 1% | None | 10.8 kl | 20.1 i | 32.5 hi | 44.2 h | 11.9 k | 32.4 ef | 23.5 k | 38.8 h |
| BRV 3% | None | 16.0 j | 40.7 ef | 55.8 de | 65.5 e | 33.6 g | 56.3 c | 29.5 j | 50.8 f |
| BRV 5% | None | 35.2 c | 56.6 b | 73.2 b | 84.2 a | 62.3 b | 66.8 b | 50.5 d | 75.4 b |
| BRV 1% | HC | 9.2 lm | 18.8 i | 27.9 j | 37.3 i | −3.9 n | 10.8 i | 17.0 m | 17.5 k |
| BRV 3% | HC | 12.3 k | 38.9 f | 41.8 f | 51.9 g | 15.9 j | 27.2 g | 21.5 kl | 34.3 i |
| BRV 5% | HC | 29.4 e | 51.4 c | 56.9 d | 67.9 de | 27.1 i | 42.9 d | 37.5 hi | 54.4 e |
| BRV 1% | PO | 8.3 m | 19.5 i | 30.2 ij | 39.7 i | 8.3 l | 22.2 h | 17.5 m | 22.6 j |
| BRV 3% | PO | 18.2 i | 39.7 f | 43.0 f | 57.8 f | 21.2 i | 44.2 d | 35.5 i | 44.4 g |
| BRV 5% | PO | 31.5 d | 53.1 c | 52.3 e | 75.1 b | 49.5 d | 56.7 c | 39.5 gh | 58.4 d |
| EM 1% | None | 19.1 hi | 39.1 f | 43.0 f | 56.9 f | 34.9 g | 35.4 e | 46.5 e | 48.6 f |
| EM 3% | None | 26.3 f | 52.3 c | 63.9 c | 70.5 cd | 57.5 c | 69.1 b | 54.5 c | 66.8 c |
| EM 5% | None | 42.1 a | 62.0 a | 77.9 a | 86.1 a | 74.5 a | 78.0 a | 72.5 a | 78.4 a |
| EM 1% | HC | 17.9 i | 31.8 h | 27.9 j | 37.5 i | 18.2 j | 30.4 fg | 18.5 lm | 23.3 j |
| EM 3% | HC | 20.4 h | 41.8 e | 36.0 gh | 51.4 g | 39.3 f | 54.4 c | 42.5 fg | 51.2 f |
| EM 5% | HC | 32.8 d | 51.6 c | 52.3 e | 73.2 bc | 59.7 c | 70.8 b | 65.0 b | 68.0 c |
| EM 1% | PO | 18.2 i | 35.4 g | 39.5 fg | 52.6 g | 28.3 h | 32.1 ef | 30.5 j | 36.1 hi |
| EM 3% | PO | 23.8 g | 45.3 d | 53.4 de | 60.0 f | 44.6 e | 55.7 c | 45.0 ef | 57.4 d |
| EM 5% | PO | 37.4 b | 55.9 b | 61.6 c | 77.2 b | 64.6 b | 67.5 b | 68.0 b | 73.4 b |
| Treatment | *** | *** | *** | *** | *** | *** | *** | *** | |
| Plant extract | *** | *** | *** | *** | *** | *** | *** | *** | |
| Treatment × Plant extract | *** | ** | *** | *** | *** | *** | *** | *** | |
BRV, brown rice vinegar; EM, EM powder soap; HC, Houttuynia cordata (1%); PO, Portulaca oleracea (1%). Means followed by different letters in the same column are significantly different by Duncan’s multiple range test at 5% level. Significance: *** = p value < 0.001; ** = p value < 0.01.
Table 10.
Effects of foliar treatment of brown rice vinegar and EM powder soap with plant extracts on broadleaf and grass weeds.
Table 10.
Effects of foliar treatment of brown rice vinegar and EM powder soap with plant extracts on broadleaf and grass weeds.
| Treatment | Plant Extract | Ivpomoea hederacea | Chenopodium album | Echinochloa crus-galli | Digitaria ciliaris | ||||
|---|---|---|---|---|---|---|---|---|---|
| Plant Height | Shoot Fresh Weight | Plant Height | Shoot Fresh Weight | Plant Height | Shoot Fresh Weight | Plant Height | Shoot Fresh Weight | ||
| % of Control | |||||||||
| Control | 0 n | 0 n | 0 l | 0 l | 0 k | 0 l | 0 k | 0 l | |
| None | HC | 3.2 m | 8.4 m | 7.7 k | −2.9 m | 4.1 j | 10.0 k | 3.1 j | 0.2 l |
| None | PO | 5.0 lm | 10.0 m | 8.9 k | −2.6 lm | 4.7 ij | 9.7 k | 3.3 j | 1.6 l |
| BRV 1% | None | 10.1 jk | 21.8 ij | 12.5 ij | 25.1 i | 6.0 i | 15.4 j | 11.6 i | 19.5 i |
| BRV 3% | None | 15.8 g | 34.7 f | 25.7 g | 32.7 fg | 19.2 g | 24.1 gh | 23.7 e | 27.6 g |
| BRV 5% | None | 32.8 c | 51.4 bc | 38.9 cd | 51.2 b | 31.5 c | 51.6 c | 33.5 bc | 45.9 c |
| BRV 1% | HC | 6.2 l | 13.7 l | 11.9 j | 15.5 k | 5.8 ij | 10.0 k | 10.2 i | 17.3 k |
| BRV 3% | HC | 13.4 hi | 31.7 gh | 20.3 h | 29.8 h | 13.3 h | 21.8 i | 20.2 f | 24.6 h |
| BRV 5% | HC | 26.5 e | 40.8 e | 26.3 fg | 36.6 de | 25.7 d | 45.5 d | 29.7 d | 43.0 d |
| BRV 1% | PO | 8.9 k | 19.4 jk | 12.5 ij | 15.4 k | 5.4 ij | 10.2 k | 10.9 i | 19.3 ij |
| BRV 3% | PO | 14.0 gh | 33.2 fg | 23.9 g | 31.3 gh | 14.1 h | 22.8 hi | 21.7 f | 24.6 h |
| BRV 5% | PO | 29.5 d | 47.3 d | 32.9 e | 40.3 c | 30.9 d | 46.8 d | 29.4 d | 43.8 d |
| EM 1% | None | 15.8 g | 23.0 i | 14.9 i | 18.7 j | 22.7 e | 25.1 g | 17.7 g | 19.8 i |
| EM 3% | None | 25.0 e | 42.4 e | 41.3 bc | 39.7 c | 35.7 b | 37.0 e | 34.8 b | 37.4 e |
| EM 5% | None | 46.5 a | 59.5 a | 59.8 a | 61.5 a | 40.7 a | 61.3 a | 45.8 a | 60.4 a |
| EM 1% | HC | 10.1 jk | 14.6 l | 13.7 ij | 15.7 k | 20.6 fg | 21.7 i | 14.9 h | 17.5 jk |
| EM 3% | HC | 19.1 f | 30.2 h | 28.7 f | 34.3 ef | 30.0 c | 32.6 f | 33.0 c | 35.4 f |
| EM 5% | HC | 39.4 b | 49.2 cd | 36.5 d | 49.3 b | 36.4 b | 55.8 b | 44.1 a | 51.6 b |
| EM 1% | PO | 11.6 ij | 18.8 k | 14.9 i | 16.4 jk | 21.3 ef | 21.8 i | 15.7 h | 19.6 i |
| EM 3% | PO | 20.2 f | 34.3 fg | 31.7 e | 38.3 cd | 31.6 c | 35.4 e | 32.3 c | 35.2 f |
| EM 5% | PO | 42.5 b | 52.8 b | 42.5 b | 49.2 b | 40.4 a | 57.2 b | 44.6 a | 53.4 b |
| Treatment | *** | *** | *** | *** | *** | *** | *** | *** | |
| Plant extract | *** | *** | *** | *** | *** | *** | *** | *** | |
| Treatment × Plant extract | *** | ** | *** | *** | *** | *** | *** | *** | |
BRV, brown rice vinegar; EM, EM powder soap; HC, Houttuynia cordata (1%); PO, Portulaca oleracea (1%). Means followed by different letters in the same column are significantly different by Duncan’s multiple range test at 5% level. Significance: *** = p value < 0.001; ** = p value < 0.01.
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MDPI and ACS Style
Win, P.-P.; Park, H.-H.; Kuk, Y.-I. Control Efficacy of Natural Products on Broadleaf and Grass Weeds Using Various Application Methods. Agronomy 2023, 13, 2262. https://doi.org/10.3390/agronomy13092262
AMA Style
Win P-P, Park H-H, Kuk Y-I. Control Efficacy of Natural Products on Broadleaf and Grass Weeds Using Various Application Methods. Agronomy. 2023; 13(9):2262. https://doi.org/10.3390/agronomy13092262
Chicago/Turabian StyleWin, Pyae-Pyae, Hyun-Hwa Park, and Yong-In Kuk. 2023. "Control Efficacy of Natural Products on Broadleaf and Grass Weeds Using Various Application Methods" Agronomy 13, no. 9: 2262. https://doi.org/10.3390/agronomy13092262
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