Testing For Natural Herbicide, Eliminating The WeedsFabian Ho Kai Bin(Leader) , Benson Quah , Myra Koh, Amelia Jane Lim and Lee

Hui xinPasir Ris secondary school

The purpose of this experiment is about finding out the best household chemical that can act as a good herbicide. Household item is tested is to prevent use of artificial herbicides, 2-4,d. Herbicide is substance that has 2,4-Dichlorophenoxyacetic acid which is used to kill unwanted plants but research has shown that one of the most widely used herbicides, Atrazine, which contain 2,4-d, has been linked to cancers in humans, and sexual deformities in frogs so chemicals that are used are a combination of household and convenience item as they are less harmful to the environment as compared to artificial herbicides. The materials used are household item like distilled white vinegar, citrus oil, salt solution, coke, lime, rootbeer, clove oil, half-boiled egg, boiled water, tap water, soap, toothpaste, bleach, juglans which is commonly known as walnut and corn gluten meal which is also known as cornflakes. Tap water is used for as the control for this experiment. The other measuring materials are 100 milliliters of measuring cylinder, 200 milliliters of beaker, filter funnel, filter paper, soil, electronic balance, universal indicator, lighter, styrofoam cups and the weeds, Phyllantus Urinaria L. The hypothesis made is that coke is the best household item that can act as herbicides while the other substance that can act as herbicides are distilled white vinegar, clove oil and lime. For alkali, soap and toothpaste are the one thought to be acting as herbicides. As alkaline stuff had not been proven as herbicides, this became one of the aims of this experiment. When the clove oil was substituted as the herbicide, the weeds used took no longer than 30 minutes for it to fully become discolored, before dying. This same result occurred for other similar tests conducted on the clove oil. Several factors had been taken into consideration, such as cost, eco-friendliness and the speed which the plant is killed. While bleach, half boiled egg, clove oil, citrus oil, salt solution and toothpaste can all kill weeds, the item that is concluded as the best herbicide is the clove oil.

The purpose of this experiment is about finding out the best household chemical that can act as a good herbicide. The reasons for the purpose are as listed. Firstly, household items are tested is because it is inexpensive, commonly found and it also serve as an alternative for artificial herbicides. Secondly, household item is tested is to prevent use of artificial herbicides, 2-4,d. Herbicide is substance that has 2,4-Dichlorophenoxyacetic acid which is used to kill unwanted plants but research

has shown that one of the most widely used herbicides, Atrazine, which contain 2,4-d, has been linked to cancers in humans, and sexual deformities in frogs so chemicals that are used are a combination of household and convenience item as they are less harmful to the environment as compared to artificial herbicides. Thirdly, preventing the use of “ugly” herbicides. Glyphosate, the ingredient in Roundup, is toxic to amphibians. Glyphosate is safe for use near mammals, but there is

some debate as to whether it is an endocrine disruptor. Monsanto Corporation, makers of roundup, created a genetically modified canola. The modified canola is resistant to roundup, making it easier to treat weeds. This genetically modified canola can cross pollinate with weeds, making them resistant to roundup. No one knows the possible effects of genetically modified food crops intermingling with native plants. As well, Monsanto sued a Canadian farmer whose canola field was

contaminated with the Monsanto genetically modified canola blown in by the wind. According to the Monsanto patent, farmers who use their canola seed must buy it every year. They cannot store seed. The chemical will be tested on a weed named Phyllanthus Urinaria L, also known as Meniran. Phyllanthus Urinaria L is a kind of weeds that has small alternate leaves resembling those of the mimosa tree, disposed in two ranges. The leaves are large at the tip and smaller towards the petiole.

Material and Methods

The materials used are household item like distilled white vinegar, citrus oil, salt solution, coke, lime, rootbeer, clove oil, half-boiled egg, boiled water, tap water, soap, toothpaste, bleach, juglans which is commonly known as walnut and corn gluten meal which is also known as cornflakes. Tap water is used for as the control for this experiment. The other measuring materials are 100 milliliters of measuring cylinder, 200 milliliters of beaker, filter funnel, filter paper, soil, electronic balance, universal indicator, lighter, styrofoam cups and the weeds, Phyllantus Urinaria L.

The materials that are acidic are distilled white vinegar, citrus oil, clove oil, walnut, coke, lime, rootbeer, cornflakes. The materials that are alkali are soap, toothpaste and soap. Salt, boiled water and tap water are neutral substance. Most of the substances are either in powdery form, diluting it with water or it is a solution.

The pH-value of the items listed is also tested and the values respectively are as listed below. Distilled white

vinegar is 2.86, citrus oil is 4.36, salt solution is 7.00, coke is 2.54, lime is 2.66, rootbeer is 4.75, clove oil is 6.12, half-boiled egg is 7.90, boiled water is 7.00, tap water is also 7.00, soap is 6.74, toothpaste solution is 6.84, bleach solution is 9.76, walnut is 6.31 in is powdery form, diluting with water and cornflakes is 5.55 in its powder form after diluting with water.

The pH-value of the soap, toothpaste and the half-boiled egg will be discussed later. The method used is applying the household item to the weeds after putting the weeds in cups. This means that five grams of the respective chemical will be poured into the cup that is labelled with the chemical name.

The procedure for the experiment goes. Firstly, hypothesis is created before anything is done to have a rough idea of what the result of the experiment would be like. The hypothesis made is that coke is the best household item that can act as herbicides while the other substance that can act as herbicides are distilled white vinegar, clove oil and Lime. For alkali, soap and toothpaste are

the one thought to be acting as herbicides. As alkaline stuff had not been proven as herbicides, this became one of the aims of this experiment. Secondly, one hundred gram of mixed burnt soil is poured into cups of 15. This is to ensure that the amount of soil is the same to ensure that the experiment would not be affected thus having a fair test is needed.

Thirdly, one Household chemical is pour into each cup with each cup having the same amount of chemical. This ensures that the experiment would be a fair one. Fourthly, the cups are left for three days facing the window at the science lab. This is to make sure the

weeds could photosynthesise thus light is not the factor why the weeds died.

Fifthly, the weeds are watered at a frequency of two days as the weeds need it to stay alive also making sure water is not one of the factor why the weeds dead. Observations of the weed are recorded before and after the three days as to see the differences thus having a clear eye of the changes. Last but not least, the results are recorded on a small booklet to have a reference of the result. As to minimise the experimental errors that is made, the experiment is repeated for four times using the same procedures repeatedly, taking the average results in the end of the experiment.

substances Initial length of weeds

End length of weeds

pH of soil(acidic /alkaline)

Did the plant die?

Half boiled egg

5.0 cm 4.5 cm 7.90 No

Clove oil 5.7 cm 4.9 cm 6.12 YesCitrus oil 5.5 cm 6.5 cm 4.36 YesCornflakes 6.5 cm 4.9 cm 5.55 NoWalnuts 5.5 cm 5.7 cm 6.31 NoToothpaste 5.1 cm 6.1 cm 6.84 Yeslime 4.9 cm 3.2 cm 2.66 NoCoke 4.9 cm 4.9 cm 2.54 NoBoiled water 6.2 cm 6.7 cm 7.00 NoTap water 5.5 cm 3.9 cm 7.00 NoSalt solution 4.5 cm 5.0 cm 7.00 YesBleach 4.5 cm 5.6 cm 9.76 YesRootbeer 4.9 cm 3.2 cm 4.75 NoDistilled White Vinegar

5.2 cm 5.5 cm 2.86 Yes

Lemon flavored soap

4.5 cm 4.7 cm 6.74 Yes

Table 1

ResultsThis table is formed from the average result of all the experiment done. The results collected have shown that there are some convenience items that can also be used as effective herbicides, such as salt and toothpaste. It also shows that some items have positive effects on the growth of the plant. All of the carbonated drinks used in this experiment aid the growth of plant , also cornflakes and walnuts are also agents that promotes growth of the plant. With half boiled egg as the herbicide, the weed died once out of three experiments and mould can also be seen growing on the egg. The clove oil kills the weed quickly and the weed that died leaves of a deep brown colour.

The rootbeer does not kill the weed but instead it helps it to grow better, at the end of the experiment, the weed did not wilt but remain healthy. The salt solution did kill the weed. The weed has wilt and dehydrated .Also some of its leaves fell off. The bleach effectively killed the weed which wilts quickly but also the bleach increase the pH value of the soil by an undesirable amount. The toothpaste killed the weeds twice out of three experiments, the weed wilt at the end of two experiments.

The vinegar changed the pH value of the soil, making it more acidic, thus creating an unfavorable environment for the germination of plant. The weed that was applied vinegar died. The weed that was applied with coke grew well and did not die at any of the experiment. The same can be said of the weed that was applied with cornflake. The citrus is proving to be an effective herbicide, it kill the weed in every experiment. The weed always wilt

at the end of the experiment .Lime, acting as herbicide, killed the weed once out of three experiment, thus it may not prove to be an effective herbicide. When soap acted as herbicide, the weed was killed in every experiment, thus it is proving to be a quite effective herbicide. The cornflake did not proved to be a good herbicide. Through all the experiments, the cornflake succeeded in kill one weed.

This table also shows that the weeds might have grown by a little before it is dead.

In conclusion, research shown that acidic substance like lime, walnut and cornflakes is not as effective as alkaline substance like toothpaste, soap and bleach. So this research shown that not all acidic substance is herbicides. The table shows that Clove oil, Citrus oil, Toothpaste, Salt Solution, Bleach, Distilled white vinegar and Lemon flavored soap are substance that killed the weeds.

Discussion

After conducting the experiment for four weeks, the results observed can be categorized into 2 different groups, namely weeds that die after 3 days, weeds that are still surviving and have grown. However through the various experiments, certain trends observed remain constant.

When the clove oil was substituted as the Herbicide, the weeds used took no longer than 30 minutes for it to fully become discolored, before dying. This same result occurred for other similar tests conducted on the clove oil.

Juglans nigra, more commonly known as walnuts have also displayed trends that remained constant through the tests conducted. The walnuts when grounded and applied on the soil shows no change at first, but 3 days later, a layer of mold and fungi can be observed at the top of this layer of juglan herbicide. This phenomenon is similar to that of the cornflakes although the cornflakes promote the growth of weed rather than stunning its growth.

The tooth paste and soap when applied on the plant caused it to wilt downwards presumably due to the weight. The same reaction happened to the plant poured with bleach. However, in both cases, it is once again possible for the 2 substances to raise the PH value of the soil to an alkalinity that the weeds are not able to survive in, causing it to wilt before dying.

The half boiled egg and citrus oil, although killed the weed several days later had also attracted an increasingly large amount of pests, hence is advisable to either use it with pesticide or avoid using it.

The salt and white distilled vinegar also caused the weed to wilt and turn brown. This could be because of the dehydrating agents found in both substances. Because water is a very vital component of what the weed needs to survive, without it, the plant would wilt. As there is a higher concentration of water present in the cell as compared to the soil contents added the salt or vinegar herbicide substitute, water from the plant cells are lost through osmosis, causing the plant cell to dehydrate and therefore become flaccid. Hence, it is

most likely the cause of the wilted look and discoloration.

When coke, root beer, lime, was added, the leaves remained green with some discoloration at the edges as it grew to an average of 10cm. it is most likely due to the nutrients added from the drink to the soil that the plant needs. As the coke and root beer are both consumer items, it could have contained more amounts of nutrients as compared to the level of acidity, hence caused more growth rather than elimination of the weeds.

As water, (control) and boiled water was substituted as herbicides, no visible signs of elimination happened, but rather it grew to an average of 9-10cm. the most likely reason is due to the fact that water has proven to be a necessary essential, and that the plant would not survive without it.

The agent can be split into two groups, the one that promote growth or the one that stunt growth. In between these two groups, it can be split into smaller groups to further understand what is common in the ingredient that causing the chemical to fell into the category after research and comparison.

Firstly, the one that promotes growth. Nitrogen (N) , phosphorus (P) , potassium (K) , calcium (Ca) , magnesium (Mg) , sulphur (S) , boron (B) , copper (Cu) , iron (Fe) , chloride (Cl) , manganese (Mn) , molybdenum (Mo) and zinc (Zn) are the nutrients found in soil needed for a plant to grow well. But firstly, it must be noted that the 13 nutrients which come from the soil, are dissolved in water, and absorbed through the roots. However, there are

mostly insufficient amounts of these nutrients. This is also the reason why most farmers and gardeners use fertilizers to add nutrients to the soil.

The mineral nutrients can be divided into 2 groups, macronutrients and micronutrients.

Macronutrients can then be further subdivided into 2 more groups, known as primary and secondary nutrients. The primary nutrients, consisting of nitrogen, phosphorus and potassium, are major nutrients that lack the first as large amounts of it is used by plants for survival and growth.

The secondary nutrients, consisting of calcium, magnesium and sulphur, are much more abundant as compared to the primary nutrients. Because it can replenish itself through natural and non harmful ways, it is not necessary to add fertilizers. Through liming, calcium and magnesium are largely produced. Sulphur is produced during the slow decomposition of soil organic matter.

Micronutrients are the elements essential to a plants growth although it is only used in small quantities as its name (micro) suggests. The remainder of the nutrients fell under this category. It is also produced by recycling grass clippings or tree leaves.

From the previous statement, it can be concluded that not all acids are able to kill weeds such as coke and rootbeer. 11 grams of phosphoric acid, And 30 grams of lime juice can be found on the ingredients used to make coke. Modern rootbeer has also shown common components as coke.

Other chemical such as lime which also has acidic properties is instead used in maintaining the soil’s PH value. When a soil has too much acidity, maybe due to fertilizers, irrigation of acidic water or decomposition of soil organic matter, liming is a common garden term to reduce the PH value of the soil. It is necessary as nutrients, needed by plants to grow well lessens as the PH value of the soil drops below 6.0 on the PH scale. Some of these nutrients include nitrogen, phosphorus, potassium, sulphur, calcium, magnesium and molybdenum. As the amount of these nutrients decrease, the plant will be affected in terms of its colour, vigour, and ability to resist and recover from heat, drought and traffic stress. By adding lime to increase the PH value above 6.0, the amount of these nutrients is also, in turn, increased. However do note that an excessive amount of lime can cause high alkaline PH in the soil. If the soil PH exceeds 8.0, important nutrients such as nitrogen, phosphorus, iron, manganese, boron, copper and zinc becomes lesser, resulting in an unhealthy less vigorous plant.

In addition, by just looking at the components in a raw lime juice, traces of calcium (14mg) , copper (0.027mg) , iron (0.09mg) , manganese (0.018mg) , magnesium (8mg) , phosphorus (14mg) , potassium (0.1mg) and zinc (0.08mg) which is needed for plants to grow can be found.

According to researches, water has proven to be a necessary need for plants to survive, let alone grow. As water acts as a solvent for minerals and food, as it cannot be absorbed by the plant in a solid form. Another reason is

that the Water is used to transport the metabolic products from one part to the other where they are needed. Thirdly, for the plant to photosynthesize, water is one of the raw materials that are needed. And water lost through the stomata through transpiration actually helps to cool the plant, in a similar way that humans do through perspiration. This evaporation process also helps the stomata to remain open for the intake of carbon dioxide. Finally, water also helps the plant cells to remain turgid rather than flaccid, resulting in a healthy upright plant look rather than a wilted look.

Cornflakes on the other hand have been known to contain iron, another essential mineral that plants require to grow.

In conclusion to these comparisons, it is possible to conclude that water is the most important factor for a plant’s growth but lime actually provides the plant with the most nutrients it requires to grow.

However, anti-growth means that it does not provide growth for the weed thus making it a good herbicide. The following groups are those that are anti-growth- Soap, bleach and toothpaste, vinegar and salt, half-boiled egg and walnut, lastly, clove oil and citrus oil.

For soap, bleach and toothpaste, they all contain a common ingredient of sodium hydroxide also known as caustic soda or lye. Sodium hydroxide is a register herbicide which helps to control tree roots in sewage system which in turn will kill the plant. Preparation of soap through a process called saponification, where fatty acid reacts with sodium

hydroxide creating soap and glycerol. For bleach, chlorine gas is passed into sodium hydroxide for the bleaching of clothing. As for toothpaste, sodium hydroxide is use as a tooth whitening agent.

Soap itself is a good herbicide because it will destroy the weeds surface which will not allow the plant to photosynthesis and thus killing it. It also helps to control weeds due to the potassium salt of fatty acidFrom the research, it says that fluometuron; an aryl fluoride herbicide is use to kill weeds in grain and cotton fields. Therefore, it is inferable that fluoride which is found in toothpaste can also be named as a weed killer. As for bleach, due to it being highly alkaline it will detoriate the soil condition and thus resulting in the death of the weeds.

From an article, it says that using of bleach as an herbicide is not a good idea. It is sodium hypochlorite and that its pH is 11.When bleach is added, it will increase the pH value of the soil on the PH scale, and add sodium in to the soil through the run-offs. In fact, it will be providing an undesirable condition for plant to germinate.

Also another common ingredient found in soap, bleach and toothpaste is sodium lauryl sulphate which is able to kill weeds. In most commercial herbicide, this is usually one of the active ingredients used.

Salt and vinegar are also commonly seen as a cheap and abundant herbicide in households. As commercial vinegar contains about 5% acidity, the acid present there affects the weed growth. The acetic acid, found in vinegar, is not

absorbed into root systems, hence vinegar will eliminate surface growth, but perennial plants (plants that live for more than two years) will reshoot. Note though, that commercial vinegar does not exceed 5% acidity whereas vinegars sold as herbicides have at least 10% acidity. The disadvantage of having vinegar as herbicide is that vinegar can indirectly kill the plants that are desirable. It is also not a hundred percent control over the weeds.

One of the reasons why salt is used as an herbicide is due to the fact that the cells of plants contain a certain amount of water and other dissolved substances. When surrounded by water that contains a larger amount of salt, there is a general rule, called osmosis, which water will try to move through the plasma membrane to make the concentration of dissolved substances equal. Hence, if there is a higher concentration of salt outside the cell, water from the cell is lost to its surroundings through osmosis. This same theory applies to how salt can be substituted as an herbicide.

Another reason can be due to dehydration. Salt, applied to the ground around the weed will soak in and the salt will interact with the roots. Water will be drawn out to equalize the osmotic pressure, and the plants will die of dehydration.

However, the disadvantage is that it can remain in the soil as run-offs and affect distant plant. It also affects the growth of desirable plant other than the weeds that should be eliminated. Salt also defeats the purpose of developing a healthy soil.

Next for the group of clove oil and citrus oil, they are both known as essential oil. For clove oil, it contains eugenol which is a type of biocide. It is also a type of phenol which is found in citrus oil too. Therefore, the similar substance is phenol.

Clove oil kills weed by desiccating the plant shoot, also from a research it states that since it does not move into perennial weeds, none of the substances will directly kill the root system. Another source says that due to the presence of eugenol it will kill weeds by disrupting cell membranes and thus causing content like electrolyte to leak out resulting in the cell death. As for the citrus oil, in most organic based herbicide there will be a certain concentration of citrus oil being added to it. An example is the combination of vinegar and citrus oil. As this product tends to be foliar spray which kills most broad leaf weed on contact and many other well established weeds that may need a stronger formula like the combination of vinegar and citrus oil.

Lastly, it is the group of walnut. A black walnut produce a substance called juglone (5 hydroxy-1, 4-napthoquinone). Juglone kills and reduces plant growth like those found under the tree canopies. Juglone is also a toxin, which exerts its effect by inhibiting certain enzymes needed for metabolic function. In a research article, it says that plants growing near the black walnut tree exhibits systems such as foliar yellowing, wilting and eventually death. Juglone is present in all parts of the plant.

The experiment for the walnut generally did not succeed was probably

due to the fact that the walnut used was baked. But in researches it is the black walnut and not baked walnut. Being unsure of the species of walnuts used and due to unavailability of the species

for our experiment, it resulted in substituting baked walnuts as the herbicide instead.

Plants Sensitive to Juglone Plants Tolerant of Juglone

Vegetables: cabbage, eggplant, pepper, potato, tomato

Vegetables: lima beans; snap beans; beets; corn; onions; parsnips

Fruits: apple, blackberry, blueberry Fruits: cherry; black raspberry

Landscape plants: black alder (Alnus); azalea; basswood; white birches; Hopa crabapple*; hackberry; Amur honeysuckle; Japanese larch; lespedeza; lilac; saucer magnolia; silver maple; mountain laurel; loblolly pine; red pine; scotch pine; white pine; potentilla; privet; rhododendron; Norway spruce

Landscape plants: red cedar; crabapple*; elm; winged euonymus; forsythia; hawthorn; hemlock; hickories; black locust; most maples; oaks; autumn olive; pachysandra; pawpaw; persimmon; wild rose; sycamore; most viburnums; Virginia creeper

Flowers & herbaceous plants: autumn crocus (Colchichum); peony

Flowers & herbaceous plants: bluebells; Kentucky bluegrass; daffodil; daylily; ferns; fescue; iris; Jack-in-the-pulpit; liriope; narcissus; phlox; poison ivy; Shasta daisy; trillium

Field crops: alfalfa; crimson clover; tobaccoField crops: white clover; red top grass; orchard grass; soybean; timothy; wheat

Table 2

The third experiment was counted as a failure because no results of the weeds growth can be extracted and all weeds have died. It is believed that the lack of water was the essential cause for the plant to die because all the plants that are used for this experiment, even the plant used as a control had died. Another reason why lack of water was regarded as the essential reason for the plants is due to the fact that the fourth experiment, which was carried out after the third experiment was a success when the plants were watered, even though the other variables from the third experiment was left unchanged to the fourth experiment.

Water is crucial to all lives, including the plant. If there is not enough entry of water in a plant, the plant could not get the nutrients it needs to survive. Water helps a plant by transporting important nutrients through the plant. Nutrients are drawn from the soil and used by the plant. Without enough water in the cells, the plants wilt, so water helps a plant stand. Water carries the dissolved sugar and other nutrients through the plant. So without the proper balance of water, the plant not only is malnourished, but it is also physically weak and cannot support its own weight.

Photosynthesis is the process by which green plants, in the presence of chlorophyll and light energy, manufacture carbohydrates (glucose) from carbon dioxide and water. While

carbon dioxide is considered essential for this process, water is also counted as critical raw materials that are needed for photosynthesis. Without photosynthesis, plants will die.

Hence, from the third experiment, we can conclude that other than the different agents (vinegar, salt solution, distilled water, etc.) that are used to test the best herbicide; water is also an important agent that affects the growth of the plants. Particularly for this experiment, lack of water is believed to be the main cause for the plants to die and water is proved to be an important agent in order for the plants to survive.

While bleach, half boiled egg, clove oil, citrus oil, salt solution and toothpaste can all kill weeds, the item that is concluded as the best herbicide is the clove oil. Several factors had been taken into consideration, such as cost, eco-friendliness and the speed which the plant is killed. Clove oil is mass manufactured; also, it can be easily bought from most shops. While salt can also be an effective herbicide, the time taken for salt to kill the plant is much longer than clove oil’s. In comparison to clove oil, the time taken for toothpaste to kill the weed is much longer. Citrus oil may be another option as the best herbicide but due to the cost, and also, it will attracts ants and other pest and thus worsen the situation of the numbers of unwanted pest present. Bleach is also another very effective herbicide, but as it is harmful human being and also it will harm the environment and affect other plants or crops by increasing the pH value of the soil, and thus creating an undesirable environment for any plant germination. Half boiled egg also can act as herbicides, but fungus will grow on

the half boiled egg thus creating another problem, to clean up the fungi. The vinegar changed the pH of the soil thus killing the weed, but it may also affect surrounding wanted plants. The soap effectiveness as an herbicide is not as good as clove oil. Thus, the conclusion that has been arrived is that clove oil, among all the other tested household item is the best herbicide. This has to be further research and proven to confirm the results.

Acknowledgements

We are thankful to Mdm Mok for helping us in the experiment. We are also grateful to Mr.Kelvin Chee and Ms.Jasmine Goh in helping us in this report and relevant matters in the experiment.

Reference9 "C J Burnsa, K K Beardb, J B

Cartmill. 2001. "Mortality in chemical workers potentially exposed to 2,4-dichlorophenoxyacetic acid (2,4-D) 1945-94: an update", Occupational and Environmental Medicine, Vol. 58: 2

13 Ethanolamine". Occupational Safety & Health Administration. http://www.osha.gov/SLTC/healthguidelines/ethanolamine/recognition.html.(accessed 23 June 2009)

10 Toni Leland. Friend or Foe? Weed Identification

http://davesgarden.com/guides/articles/view/2187/(accessed February 16, 2009)

14 http://science.jrank.org/pages/3187/Halide-Organic-Organofluorides.htmlOrganic Halide – Organofluorides Date: 22/6/2009

11 Patricia Diaz, vinegar as an organic killer Newslette http://www.moscowfood.coop/archive/VinegarKillsWeeds.html (accessed July 2002)

15 http://www.coopext.colostate.edu/4DMG/Weed/bleach.htmBy Robert Cox, Colorado State University Cooperative Extension, HorticultureBleach as a Herbicide?

12 Klaus Weissermel, Hans-Jürgen Arpe, Charlet R. Lindley, Stephen Hawkins (2003). "Chap. 7. Oxidation Products of Ethylene". Industrial Organic Chemistry. Wiley-VCH. pp. 159–161. ISBN 3527305785

16 http://asap.sustainability.uiuc.edu/org-ag/weeds/cover-thistleEvaluating Organic Herbicides, Summer Annual CoverCrops, and Mowing for Canada Thistle Control

1 Hammond, Larry. Summary of Regulatory Decisions and Expert Panel reviews of 2,4-Dhttp://www.24d.org/Presentations2/Chronology-expert-reviews-August-2007.pdf (Accessed August 2007)

5 EPA: Federal Register. 2,4-D, 2,4-DP, and 2,4-DB; Decision Not to Initiate Special Review.

Http://www.epa.gov/fedrgstr/EPA-PEST/2007/August/Day-08/p15109.htm(accessed 8 august 2007)

2 Alberta Farm Tech. Phenoxy Herbicides Value-Benefit Study for Canadian Usershttp://www.24d.org/Presentations2/Value-Benefit-Presentation-Webpage.pdf (accessed January 2007)

6 WHO, Lyon.1987. IARC monographs on the evaluation of carcinogenic risks to humans .France. An updating of IARC Monographs volumes 1 to 42. Supplement 7

3 Alberta Landscape Trades Association .Update on 2,4-D, http://www.24d.org/Presentations2/Landscape-Alberta-Update-March-2008.pdf (accessed March 2008)

7 M. A. Ibrahim, G. G. Bond, T. A. Burke, P. Cole, F. N. Dost, P. E. Enterline, M. Gough, R. S. Greenberg, W. E. Halperin, E. McConnell, I. C. Munro, J. A. Swenberg, S. H. Zahm, and J. D. Graham.1991 December, Weight of the evidence on the human carcinogenicity of 2,4-D. Environ Health Perspect. 96: 213–222.

4 D. Lerda, R. Rizzi .1991. Study of reproductive function in persons occupationally exposed to 2, 4-dichlorophenoxyacetic acid (2, 4-D). ,Mutation Research, Vol. 262, No. 1, 47-50

8 Zahm, Shelia Hoar; Weisenburger, Dennis D.; Babbitt, Paula A.; Saal, Robert C.; Vaught, Jimmie B.; Cantor, Kenneth P.; Blair, Aaron. Sep. 1990., "A Case-Control Study of Non-Hodgkin's Lymphoma and the Herbicide 2,4-Dichlorophenoxyacetic Acid (2,4-D) in Eastern Nebraska", Epidemiology, Vol. 1, No. 5.

17 http://www.postandcourier.com/news/2008/jul/20/organic_options48035/Organic optionsTONY BERTAUSKISunday, July 20, 2008

21 Classification of herbicides, Organic Herbicides, Application, Major herbicides in use todayCambridge encyclopedia vol 34Right DA, Payne JP (June 1962). "A clinical study of intravenous anaesthesia with a eugenol derivative, G.29.505" (abstract). British Journal of Anaesthesia 34: 379–385. doi:10.1093/bja/34.6.379. PMID 14008420

18 ucce.ucdavis.edu/files/filelibrary/2017/19351.pptEvaluation of Least-Toxic HerbicidesCheryl WilenUC Statewide IPM ProgramPhil BoiseUrban Ag Ecology

22 Schiestl FP, Roubik DW (January 2003). "Odor Compound Detection in Male Euglossine Bees". Journal of Chemical Ecology 29 (1): 253–257. doi:10.1023/A:1021932131526. PMID 12647866

19 http://www.finegardening.com/how-to/articles/vinegar-based-citrus-based-weed-killers.aspxVinegar-Based and Citrus-Based Weed Killers

23Cassandra, Truax. Natural Herbicides are Safe and Inexpensive, Natural Weed Control Averts Potential Environmental Disasters.

http://organicgardens.suite101.com/article.cfm/natural_herbicides_are_safe_and_inexpensive (accessed June 18, 2009)

20 Learn how they work, and how to use them effectivelyby Ann Lovejoyhttp://encyclopedia.stateuniversity.com/pages/9965/herbicide.html Herbicide - History, Health effects,

24 Herbi-Systems. Frequent Asked Questions. http://www.herbi-systems.com/FAQ_s/faq_s.htm (accessed June 20, 2009)

25 Herbi-Systems. Weed facts. http://www.herbi-systems.com/Weed_Facts/weed_facts.html (accessed June 20, 2009)

29 http://www.freepatentsonline.com/6756341.html (accessed June 19th, 2009)Mark. Czarnota. University of Georgia

26 Wim, Vermaas. (1998, March). Photosynthesis. The World & I. Retrieved from http://bioenergy.asu.edu/photosyn/education/photointro.htmlShari, Armstrong. How Does Water Affect Plant Growth.

30 http://georgiafaces.caes.uga.edu/getstory.cfm?storyid=2281 (Accessed 24 June 2009)

27 http://www.gardeningknowhow.com/children-in-the-garden/how-does-water-affect-plant-growth.htm (accessed June 19, 2009)Space Science Group. Ingredients for Photosynthesis

31 File Page HO-193. Purdue University Cooperative Extension Service. West Virginia university extension servicehttp://www.wvu.edu/~Agexten/hortcult/fruits/blkwalnt.htm (Accessed 24 June 2009)

28 http://www.spacesciencegroup.nsula.edu/lessons/Default.asp?Theme=plants&pagename=photosynthesisingredients (accessed on June 19, 2009)Grimm, Scott A. Natural herbicide for weed removal. http://www.freepatentsonline.com/6756341.html (accessed June 19th, 2009)