Soil Lab Write Up

Abstract

Around San Diego, there are a diverse amount of soil types. The environments they’re in, how the soil is tended, and numerous other factors determine soil quality. Measuring pH level and the content of the three primary soil nutrients (Nitrogen, Phosphorous, and Potassium)is one way to determine soil quality and its suitability for growing different plants.  Most soils had a low amount of nitrate, a medium amount of phosphorus, and a high amount of potassium; with mostly acidic and neutral pH levels. These trends were surprising to find considering the variety of places the soil samples were taken from.

Introduction

Most of life on earth depends on soil. It is easy to understate the necessity of testing its textural, compositional, and chemical characteristics, but it is invaluable to land ecosystems due to the fact that soil is where autotrophic land organisms (the foundation of the food chain) thrive. Our objective is to measure soil pH and nutrient content, as they are important factors in determining the quality of this complex mixture of inorganic and organic materials, microorganisms, water, and air. We will determine whether soil is acidic, neutral, or basic, and how much (if any) primary macronutrients—nitrate, phosphorous, and potassium (commonly abbreviated NPK)—it contains.

Chemical tests were performed in order to approximate the nitrogen, phosphorous, and potassium content in various soil samples collected from around San Diego by students. The tests were conducted by adding chemical testing tablets to soil “supernatant”—water poured over the soil—and results were obtained by comparing the resulting color of the solution with color charts to approximate a reading of Low, Medium, or High.

I expect the soil to have a more acidic pH since rainwater tends to be more acidic and the nitrate content should be less since most of the soil samples are from non-fertilized and unmaintained locations. Potassium and phosphorous content might be around medium since there should be decomposing and dead organic matter in most of the soil areas.

Results & Analysis

There were four measurements taken from the soil and despite the variety of samples they all followed similar trends despite the expected outliers. Look for the trends of low Nitrate content, medium Phosphorous content, and high Potassium content, and predominately acidic to neutral pH levels.

It seems that the soil samples had a lot of organic matter in order to achieve higher levels of Phosphorous and Potassium, but not as much nitrogen fixation was occuring or the plants were using up nitrates faster than they could be replenished. Although desert soil, which is native to San Diego, often has low nutrient levels and is basic, the soil samples were more acidic and neutral which might be due to the fact that they are watered by hose and rainfall has increased in the San Diego biosphere over the last century or more.

Acidic < 7                                           Neutral = 7                                          Basic >7

Reflection

This investigation explored a necessary part of our existence I had never before considered. I was happy to find there were trends in the data despite the fact that our soil came from many places around San Diego. Also, it goes to show how complex and important soil really is. I think that the investigation went great and that people had fun doing the lab and were neither frustrated nor stumped. I didn’t see many sources for error in a text like this unless the error was a mistake on the part of the person (i.e. not following instructions…). As a result, I definitely enjoyed this lab and the knowledge it had to offer. The only thing I can say, and it is a generality for many bigger assignments in Environmental Science, is that I think an assignment description and due date should always be posted on the class blog.

Conclusion

In determining the quality of various soils from around San Diego, there was a collective realization of the amazing yet underappreciated role soil plays in the circle of life. We are dependent upon it, but it is something many take for granted. Once we performed chemical tests, I was certainly surprised at the trends we found. I expected results to be erratic, but for the most part our soil had Low levels of Nitrogen, Medium levels of Phosphorous, and High levels of Potassium, with a pH hovering around neutral or just slightly acidic.

  

Short Answer Questions

Some investigations will include short answer questions that will be answered here. When answering the questions, rewrite the question first, and then provide the answer. All questions must be numbered and answers must be typed.

1.      The proportions of what three particles are used to determine soil texture? Which of these particles has the   smallest surface area? Which has the largest?

The portions of sand, silt, and clay are used to determine soil texture. Clay has the smallest surface area, whereas sand has the largest surface area.

2.      Using the soil texture triangle (Next Page), to determine the type of soils with the following particle sizes:

a.       20% silt, 10% clay, 70% sand

Sandy loam contains 20% silt, 10% clay, and 70% sand.

b.      30% sand, 10% clay, 60% silt

Silt loam contains 30% sand, 10% clay, and 60% silt.

c.       10% silt, 50% sand, 40% clay

Sandy clay contains 10% silt, 50% sand, and 40% clay.

d.      30% clay, 30% sand, 40% silt

Clay loam contains 30% clay, 30% sand, and 40% silt.

e.       40% sand, 10% silt, 50% clay

Clay contains 40% sand, 10% silt, and 50% clay.

f.       Determine the soil type for your sample based on your % volumes.

3.      Looking at the Soil Texture Triangle (Next Page), which soil type has the greatest:

a.       water retention ability?

From looking at the Soil Texture Triangle, Clay has the greatest water retention ability.

b.      water percolation rate?

From looking at the Soil Texture Triangle, Sand has the greatest water percolation rate.

4.      What role does humus play in soil fertility?

Humus makes for fertile soil due to the fact that it is organic matter that has decomposed until it cannot break down any longer. Thus, the nutrients from this material are readily available to plants in need of them. Plant fertility is dependent upon a number of variables, but without organic matter in the soil, not only do plants not have a source of the nutrients they need to grow and reproduce, but the other living things within soil cannot thrive without humus either.

5.      Why is pH such an important aspect of soil fertility?

Soil fertility refers to the amount of nutrients and the overall ‘health’ of the soil. Therefore, the less nutrients there are, the less fertile the soil is. Certain nutrients are more readily available in certain pH levels than others. For instance, microorganisms synthesize nitrogen and sulfur better at a slightly acidic pH, creating an abundance of nitrates and sulfates for plant use. If the pH is too acidic, less nutrients will be available, which means soil fertility is negatively impacted.

6.      What are some natural sources of the nitrogen, potassium and phosphorous found in soil?

We intake more Nitrogen than Oxygen every time we breathe in since earth’s atmosphere is rich in N. As a result, most nitrates in the soil originally come from the air. Potassium comes from organic materials, especially decomposed organisms, which are rich in the K that the soil absorbs. Similarly, phosphorous also comes from decomposed organisms, like bone meal. From these examples, it becomes evident how important humus is once again.

7.      How are the three primary plant nutrients used by living organisms?

Plants use the three primary plant nutrients in photosynthesis, growth, and the formation of various cell and system parts. Living organisms use Nitrogen to produce complex organic molecules; Phosphorous is essential for nucleic acids and cell energy (ATP), and plays a role in all the nervous and circulatory systems; and Potassium is vital to neurological/nervous system function.

8.      By what process is atmospheric molecular nitrogen (N2) converted into a form that plants can readily absorb through their roots? What form of nitrogen is this?

Atmospheric molecular nitrogen (N2) is converted into ammonia (NH2) through a process called Nitrogen Fixation.

9.      What are some possible sources of error in this experiment?

Some possible sources of error in the experiment are that the soil was left uncovered and it is possible that organic/inorganic material was added or lost. Even pH could be affected by moisture in the room. Also, results (which are determined by visual color comparison) could be tainted by how well the soil sample settled.

10.  Evaluate the fertility of the soil used in this lab activity based upon your results.

11.  What types of vegetation does soil of the type and pH you sampled best support?

What is the Omnivore's Dilemma?

Pollan paints a gripping picture of the many different social, political, agricultural, and historical elements that play a role in the omnivore's dilemma--that is, the age old question of what to eat for dinner. The focus of this book is the modern American civilization food culture and how it is detached from the source of food through processed and packaged goods. It's purpose is to disillusion the modern omnivore by showing him or her that the food we buy and eat is the product of an illogical, unreasonable, greedy, and powerful industrial complex that encompasses even Whole Foods and most organic/free-range/drug-free/all-natural foods. With no purity or transparency in our convoluted food business complex, the conscious omnivore does have a dilemma indeed.

Thus, the Omnivore's Dilemma in the 21st Century is one based on ignorance. Society is easily swayed by this and that new food trend--fads that have had a wide range of detrimental effects not only to our health, but to our concept of what is good and bad to eat. Ironically enough, when you get to the root of America's food source, you find Zea mays, Corn, and all of the problems it brings, literally, to the table. No doubt, corn is relatively easy and cheap to grow, and we use it for every element of food--as a grain to feed us, to feed the livestock we eat, to make plastic from, to sweeten just about everything. There are a plethora of uses for it, but these easy calories and uses lead to a monoculture of corn, corn, corn. They lead to dietary consequences like Diabetes, obesity, heart disease. They lead to a ridiculous dependence on a single plant. As Pollan says in the book:

"Of all the species that have figured out how to thrive in a world dominated by Homo sapiens, surely no other has succeeded more spectacularly--has colonized more acres and bodies--than Zea mays, the grass that domesticated its domesticator."

And that is the crux of our dilemma. What do we eat for dinner? And the answer, in the Western world at least, is easily "corn." It might not compose all of our diet, but you'd be hard set to find a meal without some corn derivative in it.

The Omnivore's Dilemma: Author

After looking up Michael Pollan's background, I think that he has the experience and the communication skills necessary to convey a notable opinion to the public, but he does not have the technical credential's to speak as an expert on the subject of food. Pollan is not a dietician, nutritionist, doctor, or scientist, and critics use that fact as a reason for not agreeing with his non-professional opinion. However, I think he deserves more than a little credibility due to his experience as an investigative journalist, who doesn't have degrees in the subjects he's investigating, but who obtains professional opinions on the subject from people who do. In addition, his arguments are based mostly on observation, not on conjecture or speculation like "maybe this..." or "it might...". Especially in The Omnivore's Dilemma, Pollan is exploring the socio-political implications of what we eat for dinner and the food chain in modern Western civilization in addition to analyzing dietary practices. Thus, his book encompasses a wider range of issues than diet and nutrition.

Pollan might not have any obvious biases, per say, but is just very opinionated about the things he has come to believe in. Of course, his critique of other diet and nutrition plans and even organic stores is definitely biased by what has been described as a "purist" approach by people like the CEO of Whole Foods, who wants to have as many people turn to organic, natural food as possible instead of reserving the experience only for total purists. The fact that he is somewhat of a celebrity and a known entity, a communicator to the public on important food issues, makes many overlook the fact that he is under qualified. Nonetheless, I think that his work deserves credit for being sincere and written with integrity, although his approach to the issue of food as a black and white subject is indeed faulty. The processes, availability, and affordability of food include many gray areas and one size does not fit all, which is the true omnivore's dilemma in my mind.

Photosynthesis Review Question Responses

1) After Thanksgiving break you return to the HTHMA garden to find that your crops have not been watered in over two weeks. Most of your plants are dead and those that are alive are barely hanging on.  In relation to the process of photosynthesis, describe what has happened to your plants.

Water is a reactant in photosynthesis. Without it, the photosynthetic systems in the plant's chloroplasts cannot synthesize glucose. The significant lack of H2O starved the plants of energy.

2) Upon microscopic inspection of the underside of your plant’s leaves, you notice that in an attempt to conserve water the stomata (aka stomates) are closed. Explain in detail how this impacts the light independent reactions of photosynthesis.

Since gas flow is regulated through the stomates, if the stomates close up then the plant can't absorb CO2 for the light independent stage of photosynthesis or release O2, the byproduct. This means that the plant can perform the light dependent stages of photosynthesis with the conserved water to create ATP, but cannot synthesize glucose because of the lack of CO2/O2 flow that the Calvin Cycle needs.

The Future of Seeds

Everyday, millions upon millions of people go about their lives oblivious to the fact that the very basis of the existence of life on earth—autotrophs, better known to the laymen as plants—are slowly becoming extinct and less biodiverse. But who would care that a species shrivels up and dies if it isn't on Facebook? Who notices if it isn't worth tweeting? Why even take time out of our lives to consider the consequences of plant extinction? Because the future of the human race depends on the future—whether positive or negative—of the more than 380,000 plant species known to exist today. And the fate of just a handful of those plants could determine mankind's future or lack of one.


A recent study by researchers at Kew Gardens in London conservatively estimates that 22% of all the world's plant species are at risk of extinction. That means about one in five plants could cease to exist within the next few decades. Even if it might be something as insignificant as a small pink flower, such plants could have medical or other applications directly applicable to humanity that makes them invaluable. The Madagascan periwinkle, for example, was thought unimportant until it was found to contain compounds used in cancer medications. Thousands of other plant species contain numerous genes that could be used for numerous different purposes. A gene from a tomato could save maize in Africa, an obscure sub-Saharan shrub could be the answer to cancer—the possibilities are endless if we preserve the plants we have.


However, that's the problem: how do we preserve our remaining plants, the precious foundations of life on earth? The answer is in seed banks. Originally, this entailed private stores of certain seeds maintained by farmers or hobbyists, but the new generation of seed banks aims at preserving all wild plant-life or all crops in deep freezers that are heavily secured and guarded against any possible disaster. When you consider the fact that everything else needs those seeds and their subsequent plants to survive, then the reason for seed banks is self-explanatory. Seed banks provide a way to survive climate change, any other man-induced disaster, or natural threats against our food supply. Need there even be an argument?


What could be said in opposition? That those paltry millions (the United States only volunteered $6.5 million [not even billion] to the Svalbard Seed Vault) go to wars and foreign aid instead? By preserving seeds, you preserve the future. Whatever life there is on earth 20, more or less 200 years from now, it will need food and energy to survive. Just as Cary Fowler said in a TED Talk in 2009, in 20 years we'll be seeing food shortages and mass starvation in countries like South Africa due to climate change, inadequate crop species, and population increase. Collecting, saving, and storing seeds, and subsequently researching them is the only way that we can insure the future of mankind. 

Final Plants

For my final plants, I'm still going to be growing German Chamomile and Lavender. I'm less sure about going ahead with Peppermint for the sole reason that it has a very invasive nature. You can read more in depth about the specifications of these plants in the post below.