How Does Mulch Effect Weed Plant Density Compared to a Location With No Mulch?




Introduction: How Does Mulch Effect Weed Plant Density Compared to a Location With No Mulch?

At some point in the year, everyone at some point smells mulch that had been laid down at some point during that day, but does one think why people lay mulch down anyways. Is it for the color, to add texture, or just because it looks good. Well mulch is used for all those reasons, but there is a better reasoning to add new mulch every year. People say if one lays a layer of mulch every year ones flower bed will have reduced soil erosion, it will keep the soil moist, and yes even suppress weed growth in that location. People have done research that says mulch suppresses weed density( Less weeds in the location where the mulch is). Well, I plan to put that to the test. From data collected through the lab, I will determine if Mulch really suppresses weed plant density compared to a location with no mulch. I believe, from the research that is collected, that the mulch bed selected will have a lower average weed plant density than that of the location with no mulch.

Teacher Notes

Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.

Step 1: Variables

Independent Variables-
1. The Mulch that was placed in the specific location earlier that year.

Dependent Variables-
1. The weeds that are growing in the locations used during the experiment.

Controlled Variables-
1. The grid used during the experiment has to be controlled. For both locations the grid has to be the same dimensions for the collection of data to be accurate.
2. The grid must be framed accurately into an even rectangle so it can be referred to as controlled. In other words, the rectangles have to look like a rectangles when they are made into a grid so one gets the correct amount of data for each location.
3.The locations used have to match the locations being tested. When collecting data for the mulch bed all the data(the weeds) has to be located in Mulch, not dirt or grass. The location used must be all mulch or all dirt in order to collect accurate data.
4. The data collected must only be weeds, no plants, in order to collect sufficient data. The weeds only can be added into the data collection to answer the question.

Step 2: Materials

Materials used in the Lab Experiment-
1. String
2. A tape measurer
3. Something to hold the string together( Wooden Stakes)
4. Something to record ones data( A pen/pencil and paper)
5. A Calculator( If needed)
6. A Mulch bed location, and a dirt bed location
7. Something to mark where the wooden stakes will be placed( Spray paint)
8. A Hammer to hit the wooden stakes into the ground

Step 3: How You Can Do It

The question is, Does mulch really affect the plant density of weeds in a population compared to somewhere without mulch? Well, in this lab that question is going to be put to the test. First one needs to collect and have the materials listed above in order to start this lab. Remember, when choosing the locations they have to be all mulch or all dirt to keep the data accurate. Now after one collects the data one has to set up a grid on each of the locations one has chosen. Grids have to be squared out evenly.

Each grid has to be the same in order to have accurate data. In order to do this please use the grid above for both locations.The grids are the most important parts to your lab. They have to be accurate in order to collect sufficient data. The grids have to be measured correctly, and need to look like rectangles when completed. To make these grids one will use the wooden stakes, the tape measurer, the spray paint, the hammer and the string one gathered. There are many ways to do this, but here is an easy way. One may need someone to help them with this part of the lab. First ,with the tape measure, measure out one side of the rectangle with the dimensions for that side listed in the sketch on the previous page. At the end of the tape measurer spray a dot of spray paint where the wooden stake will be placed in the ground then spray another dot of spray paint at the other end of the tape measurer on the ground. This should give one the end point and the starting point of that line. This should be repeated for each dimension in the grid listed on the previous page. After one has this completed it should just look like a bunch of dots. In each of those dots hammer a wooden stake into it. After that one will use the string collected to connect the stakes together. When doing this follow the grid on the previous page, but remember in the end one wants this to look like a rectangle, so make sure the lines are straight and tight. If this stage of the process is messed up than the data recorded will not be accurate when collected. Now that one has their grids marked it is time to count the density in each of the squares. One will need their material to record their data for this step in the lab. The order one counts the weeds in each square is located in the grid on the previous page. When counting the weed density make sure one is counting weeds not actual plants. If one adds a plant into their weed density data then ones data will be inaccurate. After one has collected the data then one needs to find the average and the standard deviation for both the mulch and dirt weed plant densities.
The average should give a clear result of one’s research. The standard deviation would be used, along with the average to create a graph. Compare results. What did one find out? What one thought would happen did it really happen?

Step 4: My Conclusions

As I stated earlier, I believed that the mulch bed would have a lower average weed plant density compared to a dirt bed. From the data collected my hypothesis was correct. The average weed plant density for the mulch bed that I used was 2.625 ,or 3, weeds per 3 square feet. The average weed plant density for the dirt bed used was 7 weeds per 3 square feet. The Oregon State University Extension Service, Lynn Ocone and the Cornell gardening resources were also right saying that mulch helps suppress weeds. If I extended this lab for a longer period of time I would have to keep up the grid and set up a plan where I would count the weed plant density every other week or so. I would need to go into further research for that like how long does a weed take to grow in order to get sufficient data. This is not relevant though and does not relate to this lab procedure. The results do show the hypothesis stated was correct, but the experiment could have been better if…
-there was more data. I could have did more than just one grid in each location. If I did that I could have had more data that could have made this lab a little more accurate and maybe change the data collected.
-there were more independent variables. For the mulch I could have collected data from more than one kind of mulch like black mulch, red mulch and so on.
-I had more time. I could have extended this lab. For example, I could have counted the weeds in those grids, and then came back a week later and counted the weed plant density in the same area. I would of course leave the grid where it was placed so that controlled variable is not affected.
If I wanted to do this same experiment again I would follow the text above and maybe get better data than I had in this experiment.

Scientific Method Contest

Participated in the
Scientific Method Contest

Gardening & Homesteading Contest

Participated in the
Gardening & Homesteading Contest

Spring's Coming Contest

Participated in the
Spring's Coming Contest

Be the First to Share


    • Trash to Treasure Contest

      Trash to Treasure Contest
    • Wearables Contest

      Wearables Contest
    • Fix It Contest

      Fix It Contest

    3 Discussions


    5 years ago on Introduction

    Ultra poor sandy soil (topsoil stripped by builder), I'm finding the soil's greatly improved 1) where the mulch was dumped and I didn't get to it for a while and 2) greatly improved around the shrubs I put in.


    5 years ago

    I always wondered if all that time I spent mulching was to any aval. Thanks for sharing.