Soil Wars: A Look at Soil Composition, Fertilizer, and Plant Production

This topic submitted by Mark Cerny, Jenny Gallow, Kyle Gibson, Diana Maikut (gallowj2@miamioh.edu) at 10:37 AM on 12/3/02. Additions were last made on Wednesday, May 7, 2014. Section: Cummins

Natural Systems 1 Fall, 2002 -Western Program-Miami University


Soil Wars: A Look at Soil Composition, Fertilizer, and Plant Production

ABSTRACT

"Soil quality is a concept based on the premise that management can deteriorate, stabilize, or improve soil ecosystem functions." (Franzluebbars, 2001) Soil management can be accomplished through irrigation, fertilization, protection from compaction, and by covering the soil to protect it from erosion. Since soil is dynamic and undergoing constant change, the methods of management affect its properties significantly. "Management that enhances soil quality will benefit cropland, rangeland, and woodland productivity. Enhanced soil quality can help to reduce the onsite and offsite costs of soil erosion, improve water and nutrient use efficiencies, and ensure that the resource is sustained for future use." (Soil Quality Institute, 2001) Different types of soil, for example clay, sand, and topsoil, will respond differently to various methods of management. Some of the concerns most notably relevant regarding soil quality include loss to erosion, compaction near the surface, crusting, and excessive wetness (Soil Quality Institute, 2001). Erosion takes away valuable nutrients and reduces the stability of the soil. Compaction reduces the amount of space between particles that increases the density of the soil (National Soil Survey Center, 1996). This restricts the rooting depth because there are less nutrients and amounts of water available to the plant. The soil temperature also decreases. Sand is especially susceptible to compaction. Indicators of this condition include greater penetration resistance, higher bulk density, and flattened, stubby plant roots. Crusting and excessive wetness are both signs that the soil is not able to handle the amount of water that it is receiving (either too much or not enough). It cannot be efficiently and effectively distributed throughout the soil.

INTRODUCTION

The basis for our experiment will be to test various soil types and their quality. For our research we define soil as dynamic matter with chemical, biological, and physical properties that can be managed. Is functions include exchanging water, nutrients, and air with plant life that it supports. Soil quality is defined as "capacity of a specific kind of soil to function, within natural or managed ecosystem boundaries, to sustain plant and animal productivity, maintain or exchange water and air quality, and support human health and habitation." (Soil Quality Institute, 2001) One of the major soil quality indicators that we will study will be the amount of organic material, humus. in the soil samples. "Soil organic material... improves tilth in the surface horizons, reduces crusting, increases the rate of water infiltration, reduces runoff, and facilitates penetration of plant roots." (National Soil Survey Center, 1996) The humus can be identified as a dark brown, porous, almost sponge like material within the soil. It usually accounts for 5% of the volume of a sample. It improves soil quality by reducing erosion, storing and transporting water, disallowing compaction, and storing nitrogen, phosphorus, and sulfur. This counteracts many of the concerns that threaten soil quality. Additionally, we will manage the soil quality by adding fertilizers, both chemical and organic. "Experiments on the silty clay loam soil at Rothamsted and the sandy loam at Waburn are now showing benefits where soil contains extra soil organic material" (ICQ). In our experiment, manure will be the soil organic material. Large quantities must be applied regularly to have an effect. Also, MiracleGro will be used to increase the amount of Nitrogen in the soil and test its effectiveness. "The amount of N-fertilizes increases vegetable yield" (ICQ).

The intent behind our research is to find out which type of soil provides the best growing conditions for bean plants. We chose bean plants because of their potential for rapid growth, 57 days until harvest (University of Illinois, unlisted), which works well for a short lab study. Also, we will be growing these plants in a greenhouse so that we can control growing conditions and because of their susceptibility to frost . Before conducting any formal type of research, we hypothesize that an organic-rich topsoil soil type will work best. It will be composed of roughly 5% humus. Our sample soil types will be taken from various areas accessible from the Miami University campus. We suspect that the mixture closest to the type listed above will yield the bean plant that scores the highest on various testing scales, therefore proving that the soil has the best characteristics for plant growth. According to the Mississippi State University Extension Service (2002), "the ideal garden soil is deep. loose, fertile, well drained, has plenty of organic material, and is free of weeds and disease. "

Soil quality became the subject for this project because of its stability and controllability. We chose a medium that was interesting and dynamic yet easy to work with. Also, the effects that soil has on our lives are numerous and quite significant. So much of the food that we eat comes from the ground that it is interesting to see what conditions favor this life-supporting process. Questioning which areas around campus provide the best conditions tells a great deal about the vegetation that the area supports. We can see why some areas have lush vegetation while others barely support sucker trees. Furthermore, by introducing the variable of fertilizers into the experiment we can justify the practice of using or not using these sources of nutrients. Carrying this one step further, we will see whether organic or chemical fertilizers help the plants significantly more or less than the other.

Answering these questions through scientific research will provide background information for anyone who wishes to try and grow plants. Although we are only using bean plants, our results should be relevant for most similar crops. This way green thumbs, gardeners, and farmers alike can see how to develop and nourish their soil in a way that will help their harvest the most. Additionally, one may want to take soil samples of an area of land to see the composition of the soil before investing time, money, and effort into the plot. One could compare the results of his soil testing to the data that we collect on the specific soil types to see the potential in the area.

Finally, this research has interest because of its familiarity to everyone. However, so many people take the soil around them for granted that they have no idea what is going on below the grass, weeds, and leaves. We will show the significance of what is below the surface so that others can understand this common material better.

RELEVANCE

In the past, groups have worked on projects that dealt with the difference in plant growth and the variety of different soils used for each plant. Some other groups have worked on projects that dealt with different fertilizers and which fertilizer had the better results of plant growth. Our project is a combination of both of these previous ideas. For our original idea we were going to observe the difference in growth just by the variety of soil used. We then decided to add either organic, chemical, or no fertilizer to our plants and soil. A group from the past Natural Systems class did a project just focusing on the fertilizer and not the type of soil too. Therefore, we are using the combination of past projects to begin our project of observation in plant growth.

Our research project can help answer many questions referring to how to grow a plant to its fullest. This question can range from people who are growing plants at home to landscapers putting in plants for people. If someone would want a plant to grow to their fullest, they are going to need to know what kind of soil is more nutritious and what kind of fertilizers work the best. We can also find out how fast a bush bean plant can grow if someone wanted to grow them. Through our experiment, our group will become pretty well aware of what type of soil and fertilizer is needed for a plant to grow to its fullest. This will give more people the time to actually do work that needs to be done instead of messing around with a plant because it won't grow.

MATERIALS & METHODS

120 bean seeds
12 rectangular flats
3 different soil types from the Miami Campus
1 bagged soil for a control (Metro Mix)
Organic fertilizer
Chemical fertilizer
Water
Trowels
Ruler
Balance
Camera
pH test
Greenhouse space

In order to discover the effects soils have on plant growth, four different soil samples will be used in a controlled study. The samples will vary in consistency, texture, color, location, moisture, and contact with human life to ensure that the samples are representative of a broad group. We hope to use a sandy soil, clay based soil, soil from an area not traveled by humans, and then a bagged soil metro mix. Once gathered, the samples will be examined in the science laboratory to determine its pH, a factor that will be used to ensure that the samples differ.

In order to determine how well plants grow in the varying soil types, we will grow bush bean plants in the greenhouse for a number of weeks while observing the growth of the plant. Each soil type will be observed under three varying circumstances the use of organic, chemical, and no fertilizer. "Natural organic fertilizers are typically slow releasing (delivering nutrient over a period of time) because decomposition of the organic matter occurs slowly. "(Johnson, 1998) We will grow 10 plants per soil per growing circumstance (10 plants in sandy soil with no fertilizer, 10 plants in sandy soil with chemical fertilizer, 10 plants in sandy soil with organic fertilizer, etc.). The bush bean plants will be grown in labeled flats that all receive comparable amounts of sunlight, water, and stimulation. Every other day a group member will check on the plants to ensure that they are receiving proper amounts of water.

Twice a week, the plants will have their height measured, be rated on a scale from 0-5 based on health, and photographed so that results can be monitored throughout the growing process. At the end of the growing period, each plant, and its root system, will be weighed on a triple-beam balance to establish another variable to compare when establishing the soils success.

At the end of the experiment, the plants overall progression and growth will be compared to establish if a certain soil type and growing condition (i.e. fertilizer) affects the plants growth either positively or negatively.


Pictured above is an example of a plant we would have rated as a 1 on our 5-point scale.


Pictured above is an example of a plant we would have rated as a 3 on our 5-point scale.


Pictured above is an example of a plant we would have rated as a 5 on our 5-point scale.

STUDENT INVOLVEMENT

Although the growing process with the beans is fairly easy, we will need the classes help to collect and compare data. Towards the end of the 7-8 week growing period we will need the class, in four groups, to examine one of the soil types with one of our group members. The groups will be given the previously collected data concerning that soil type and will be asked to use the soil information, height, mass, photographs, and physical descriptions to draw a final conclusion concerning that soil type. How has the plant changed based on the photographs? How has the size of the plant changed? How have the pots containing fertilizers progressed in comparison to the pot without fertilizer?

At the end of this short observation and conclusion period the class will reconvene and talk about their findings. We will compare the numerical and physical values the groups found (overall growth in mass and size / foliage, stability) to decide which soil, and under what circumstances, had the most obvious growth. A data chart will be completed as this process progresses.

We will then use this information to draw our own final conclusions concerning the various soil types.

TIMELINE

Week 1: 9/29 to 10/5
Thursday 10/3: Plant, water, and photograph all soils / bean plants

Week 2: 10/6 to 10/12
Tuesday 10/8: Water, measure, and photograph all bean plants
Thursday 10/10: Water, measure, and photograph all bean plants
Saturday 10/12: Greenhouse workers will water the bean plants

Week 3: 10/13 to 10/19
Tuesday 10/15: Water, measure, and photograph all bean plants
Thursday 10/17: Water, measure, and photograph all bean plants
Saturday 10/19: Greenhouse workers will water the bean plants

Week 4: 10/20 to 10/26
Tuesday 10/22: Water, measure, and photograph all bean plants
Thursday 10/24: Water, measure, and photograph all bean plants
Saturday 10/26: Greenhouse workers will water the bean plants

Week 5: 10/27 to 11/2
Tuesday 10/29: Water, measure, and photograph all bean plants
Thursday 10/30: Water, measure, and photograph all bean plants
Saturday 11/2: Greenhouse workers will water the bean plants

Week 6: 11/3 to 11/9
Tuesday 11/5: Water, measure, and photograph all bean plants
Thursday 11/7: Water, measure, and photograph all bean plants
Saturday 11/9: Greenhouse workers will water the bean plants

Week 7: 11/10 to 11/16
Tuesday 11/12: Water, measure, and photograph all bean plants
Thursday 11/14: Water, measure, and photograph all bean plants
Saturday 11/16: Greenhouse workers will water the bean plants

Week 8: 11/17 to 11/23
Tuesday 11/19: Student Involvement Water, measure, and photograph all bean plants
Thursday 11/21: Final conclusions!

RESULTS

Plant Growth Data Chart - Complete!

Student Involvement - Final Data Sheet - Complete!

These pictures were taken through the duration of the experiment.

CONCLUSIONS


This data chart provides us with basic statistical information revealing the mean, standard deviation, etc. for each soil type and fertilization combination. Notice how metro mix soil with natural fertilizer had the highest mean height, implying that it is the most successful combination. Likewise, clay-like soil with natural fertilizer was the least successful, having the lowest mean height.


This data chart provides us with basic information revealing the mean, standard deviation, etc. for each soil type and fertilization method as defined by overall health on our 5 point scale. The chart shows that nutrient-rich soil with natural fertilizer had the highest mean rating over the growing period, whereas clay-like soil with natural fertilizer had the lowest rating over the growing period.


This graph plots the health of the bean plants split by soil type over time. The progression reveals that the health of the plants was consistent and distributed evenly over the entire growing period.


This graph plots the height as a function of time.


This box plot shows the distribution of the bean heights using the soil type and fertilization method as dividing variables. The circles indicate where outliers are found, those data points that lie outside of the standard deviation.


Using 2 way t-test with soil type and fertilization method as defining variables as applied to the final bean plant height, the p-values imply that there is a significant difference between the 4 soil types (since less then alpha level .05), but not between fertilization method and bean plant height, or soil types split by fertilization method and bean plant height (since greater then alpha level .05). The box plots provide a visual representation of this information.


Using 2 way t-test with soil type and fertilization method as defining variables as applied to the final plant mass, the p-values imply that there is a significant difference between the 4 soil types and soil type split by fertilization method and bean plant mass (since less then alpha level .05), but not between fertilization method and bean plant mass (since greater then alpha level .05). The box plots provide a visual representation of this information.


Using 2 way t-test with soil type and fertilization method as defining variables as applied to the final root mass, the p-values imply that there is no significant difference between the root mass depending on the soil type, fertilization method, or both together (since all p-values are greater then alpha level .05). The box plots provide a visual representation of this information.


Using 2 way t-test with soil type and fertilization method as defining variables as applied to the final bean mass, the p-values imply that there is a significant difference between the 4 soil types (since less then alpha level .05), but not between fertilization method and bean mass, or soil types split by fertilization method and bean mass (since greater then alpha level .05). The box plots provide a visual representation of this information.


This graph plots the final height of the bean plants split by soil time and fertilization method.

Based on the data charts explained above, a number of conclusions can be drawn regarding plant growth in the four varying soil types and the three varying fertilizers. As a whole, when examining soil type alone, the Metro Mix store bought soil performed the best overall. It had the largest mean height among the four soils throughout the growing period, reaching a towering 25.035 cm while nutrient rich soil only reached 21.62 cm, clay soil only reached 12.43 cm, and sandy soil only reached 15.68 cm. When examining the final heights of the bean plants, again, the Metro Mix soil had the largest heights. Using the 5-point health index, the Metro Mix soil had the highest overall health rating over the growing period, producing an average reading of 3.595. The nutrient rich soil had an average reading of 2.947, the clay soil an average of 2.11, and the sandy soil an average of 2.75. Three different masses were recorded using the plants at the end of the growing period. The plants final mass, root mass, and bean mass were recorded. It was concluded that root mass was not significant when examining the different soil types, but with the other two measurements, Metro Mix soil squashed the others.

The three different fertilization treatments, none, natural, and chemical, performed at varying rates. In regards to height, the chemical fertilizer (Miracle Gro) produced the largest mean heights among the plants, helping the plants to reach and average of 19.763 cm, while those plants treated with the natural fertilizer only reached an average height of 15.61 cm, and those treated with no fertilizer only reached an average height of 17.62 cm. Examining the 5-point health index, it is those plants treated with no fertilizer that appear to be the healthiest to the human eye. Those plants treated with no fertilizer received an average health reading of 2.828, while those treated with the natural fertilizer received an average rating of 2.59, and those treated with the chemical fertilizer received an average reading of 2.826. It should be noted that the ratings of those plants treated with no fertilizer and those treated with chemical fertilizer were very close. Despite this apparent difference among the fertilization treatments (in accordance to height and health readings), the differences were not significant when examining the final heights of the plants, final mass, root mass, and bean mass.

When looking at soil type and fertilizer together, it can be noted that the Metro Mix soil treated with natural fertilizer produced the tallest plants, while clay soil treated with natural fertilizer produced the shortest plants. There was a significant difference among the final mass readings of the plants when examining soil type and fertilizer together as well. The Metro Mix produced plants with the largest mass when treated with either natural or no fertilizer, whereas sandy soil produced plants with the largest mass when treated with chemical fertilizer.

Using this information, it can be concluded that as a whole, the Metro Mix soil offers bean plants with optimal growing conditions. When deciding which fertilization method to use on your bean plants, a chemical fertilizer would be more successful for producing tall plants, but no fertilizer produces the healthiest plants (something a farmer should keep in mind). As a whole though, there is not enough statistical information to conclude that one soil type or one fertilization treatment provides bean plants with the best growing conditions. Your purpose in growth should be considered prior to planting, for this will dictate which soils and fertilizers to use. If you are aware of the soil type in your area, this information could be implemented to know which fertilization method could help promote that soil type for growth. This data is relevant to growth, but statistics is to picky to recognize the differences observed.

DISCUSSION

In the past, groups have worked on projects dealing with the difference in plant growth over time in varying soil samples. Other groups have dealt with different fertilizers and which type works optimal plant growth. A previous Natural Systems group did a project focusing only on the fertilizer. We decided to expand on this project and combine the ideas. Our original idea involved observing the difference in plant growth just from the different soil types. Then, we decided to add more to the project by adding either chemical, natural, or no fertilizer to the soil samples.

Further research can involve using more soil types or fertilizers. Also, giving the plants a longer growing period would allow for more research. If the plants were given more time to grow, it is possible there could have been more of a difference, even between fertilizer types. To further help the plants, we would suggest planting them in individual pots to give them plenty of growing room. Sunlight and frequency of watering should be strictly regulated during further research to ensure that the plants are given an unbiased and optimal growing environment.


These are the dead plants drying out for final measurements.


OPPORTUNITIES FOR FURTHER RESEARCH

Originally, this experiment was supposed to test the effect of both soil type and fertilization method on the growth of bean plants. However, our results were inconclusive regarding the relative effectiveness of the various fertilization methods. This can be improved upon in further research by using the same soil type as a control and having more pots dedicated solely to the different fertilization methods. Also, it would help to conduct the experiment with a variety of plants, not just beans. What works for one plant type may not work best for another; however, whichever one works the best on a more consistent basis with the widest variety of plants would receive the highest ranking.

Another possibility to improve upon the base that we have started would be to test the soil types for their effectiveness over multiple growing seasons. This would be relevant for farmers and gardeners alike who desire to grow plants on the same land year after year. Testing soils in this way, one would discover which soils lose their nutrients more quickly and which ones are able to maintain for a longer period of time.

In order to appease those who wish to either establish a crop quickly or sustain one for a longer period of time, these characteristics of the various soil types could become the focus of another experiment. The researchers can observe which type produces a harvest first, and which one sustains a harvest for the longest period of time. The results would be useful for both the farmer needing a quick pay off and for the household gardener who desires a long-lasting garden to enjoy for weeks.

Finally, since we were able to determine that a store bought soil type worked best, it might be interesting to see if one type of store brand soil works better than another. The differences may only be slight, though, so a large number of samples would be needed. It might be helpful, though, to use more of a houseplant for this experiment; that is the type of plant most commonly grown in store bought soils.

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