The Porosity of Different Types of Soil. Mrs. Weber, Homeroom 201

Purpose The purpose of this experiment is to determine which type of soil can hold the most water based upon how large the pore space is between each particle that makes up the soil. This is an important idea for a person to understand because it can be used when deciding which type of soil to use in potting plants or even looking at the soil for their landscaping. On a grander scale, knowing this information could be used to help determine the best type of soil to use in sand bags because the particles size in the soil could be used to compact the bags closer.

Hypothesis Given that most soils are composed of mineral types, like sand, silt or clay, and organic matter, the pore space is determined by knowing the soil type and the percentage of sand, clay and silt within the soil. It is important to also remember that as the soil particle size increases, the pore size also increases. The opposite situation also occurs. Given all of these factors, I believe that the soil sample size from the suburban yard will displace the most water because the suburban yard must absorb a lot of water from rainfall, melting of snow/ice, watering vegetation, water runoff, etc. I believe that the suburban park and city park will be next in absorbing the most water because the parks should contain similar amounts of mineral given that they are both used in parks. Since parks also have areas that are designed for different fields to play sports, the compositions of the soil are a little more versatile in mineral compositions, which means it will not absorb as much water, but keep it on top of the soil to be evaporated into the atmosphere to keep those fields dryer. Finally, the city lakefront will absorb the least amount of water because the amount of water it is exposed to yields a soil that must allow most of the water to run-off back into the lake.

Materials · Five 600 ml beakers: Used as testing containers.  5000 ml of distilled water: Liquid to pour in soil samples.  One measuring cup: Used to collect soil samples and to measure out trial testing amount.  Five different types of soil from different areas: suburban front lawn, suburban park, city park, city lakefront, potting soil mls of each soil. Material with which porosity is being tested.  Five clear plastic (3200 ml) storage containers: Used to collect initial soil samples.  Foldable shovel: Used to collect soil samples from the ground.  Spoon: Used to dispense soil into the beakers from the storage containers.

Procedure 1. First, you will need to find your soil sample. You will want 3-5 different soil samples. 2. Fill each clear plastic container with 600 ml each of your samples. Label each container with the soil sample type. 3. Fill each beaker with 200 ml of each soil sample. 4. Fill your metric measuring cup with water to the 300 mL mark. Place a screen on top of the beaker to keep organic matter from floating out as you pour the water into the cup. 5. Pour water into the first sample until it reaches 300 ml. Pour slowly and gently so you do not spill water out of the measuring cup, as this will cause error in your measurement. 6. Record the amount of water left in the measuring cup. It should be less than 300 mL. Write your result in a data table:

Procedure Continued 7. Now calculate the amount of empty space in the sample by subtracting the amount of water you measured from 300 mL. 8. Then calculate the percentage of soil space by dividing the remaining amount of water by the initial amount of water. 9. Repeat steps 2-6 for each sample four times. 10. Make a graph of your data to compare your results.

Trial #1 Data Table Soil TypeWater Before (ml)Water Remaining (ml) Volume Remaining (ml) Soil Space (%) Suburban Front Yard 300 ml150 ml 150/300 = 50% Suburban Park300 ml200 ml100 ml100/300 = 33% City Park300 ml100 ml200 ml200/300 = 67% City Lakefront300 ml200 ml225 ml100/300 = 33% Potting Soil300 ml75 ml225 ml225/300 = 75%

Trial # 2 Data Table Soil TypeWater Before (ml)Water After (ml)Volume Remaining (ml) Soil Space (%) Suburban Front Yard 300 ml200 ml100 ml100/300 = 0.33 = 33% Suburban Park300 ml155 ml145 ml145/300 = 0.48 = 48% City Park300 ml125 ml175 ml175/300 = 0.58 = 58% City Lakefront300 ml175 ml125 ml125/300 = 0.42 = 42% Potting Soil300 ml60 ml240 ml240/300 = 0.80 = 80%

Trial #3 Data Table Soil TypeWater Before (ml) Water After (ml) Volume Remaining Soil Space (%) Suburban Front Yard 300 ml165 ml135 ml135/300 = 0.45 = 45% Suburban Park300 ml175 ml125 ml125/300 = 0.42 = 42% City Park300 ml110 ml190 ml190/300 = 0.63 = 63% City Lakefront300 ml175 ml125 ml125/300 = 0.42 = 42% Potting Soil300 ml65 ml235 ml235/300 = 0.78 = 78%

Data Analysis The graph shows that the potting soil had the highest percentage of soil space because potting soil is geared specifically to provide plants with their necessary amount of minerals. The potting soil had the highest percentage of soil space with an average of seventy-eight percent. The suburban yard and the suburban park appear to have very similar compositions of minerals within the soil because the average percentage of soil space is right around forty percent. The city lakefront had the least percentage of soil space with an average percent of thirty-nine percent.

Conclusion My hypothesis was incorrect because the order of absorption that I thought was not right for the suburban yard, suburban park, potting soil or city yard. I was correct in thinking that the city lakefront would have the lowest absorption rate because of all the sand present. If the experimenter were to perform this experiment again, then she would find the time to analyze the soil samples to discover exactly what the soil is composed of and in what percentage, because knowing this may help to explain the results better. In this experiment, the type of error experienced would be experimental error. In this experiment, the experimenter used a plastic measuring cup to measure out the water level used in testing the soil porosity. Since it was a white colored plastic measuring cup, it was hard to distinguish if the meniscus of the water sample were truly at 300 ml each time in each trial. Also, the measuring cup had large divisions of the milliliters on the side. The soil was dried and some of it was in large chunks, there may have been some soil cups with a little less or even a little more than 200 ml when each trial was completed. This could have affected how much water was displaced because of the different starting amounts of soil. Furthermore, since some of the soil samples were in large chunks, while other samples were much more compact, this could cause some discrepancy in the true amount of space within the soil.