Unit 2- Earth‎ > ‎

Day2 (Greenhouse Effect and Energy, Soil Sampling)

Soil Exercise


Initial Soil Collection

  1. Students will obtain soil samples directly on the KCKCC campus (weather permitting).  Allow students a good 20 minutes to leave, collect, bring back, and label…and/or find their EXACT location via a computer.
  2. Instructors will receive baggies with labels – and a set of ‘mini-instructions’ inside.  The students will be ‘instructed’ to collect a small soil sample from a near-by area of their choice. 
  3. The students will use a small, metal implement or plastic spoon to ‘dig up’ their small soil sample (the sample only needs to fill bag 1/5th to 1/4th full (SMALL amount).
  4. Once the soil is collected, the students will write the following information on the label:  location (Kansas City, KS – KCKCC campus; longitude/latitude from phone/gps device or from computer search; name(s); general color/texture of soil).
  5. The sample will be sealed up in the baggie and brought back to their lab station (one of the chemistry rooms).

 

Soil Tests from Samples Collected:

  1. Bacterial & Fungal Culture of Soil Sample
  2. Weigh out 1g of soil sample and place it in a test tube.
  3. Add sterile water just above the soil ‘mark’.
  4. Shake vigorously for 1 minute to disperse the microbes.
  5. Mix by inverting the tube several times.
  6. With the lab grease-pens, label the plates on the bottom with your initials and date.   Leave these for Ms. Liz to incubate and photograph (we cannot ‘hold’ these over break – but results will be provided to student groups).
  7. Add 0.5 ml of your dilution mix to one agar plate.  Use a sterile Q-tip to spread across the plate.
  8. Plate results can be viewed during the next session.

 

 

Determine Porosity


1. Place some dried soil (about 10ml-50ml…based on what is available) in a small beaker. Tamp the soil down gently, but do not compress it.
2. Fill a small graduated cylinder with about 5-25ml (depending on amount of soil used – amt. of soil, then ½ amt. of water) of water.  Slowly pour the water onto the surface of the soil until the soil is completely saturated and water just starts to pool up on the surface. Add the water slowly enough to give the water a chance to percolate down into the pores.
3. Measure the amount of water left in the graduated cylinder. The amount used is the amount of pore space in your sample. Record volume of soil and volume of water used.
4. Calculate porosity as a percent: % = (volume water added/10ml of soil) x 100.  (IF MORE than 10ml of soil was used, replace that value with appropriate value)
5. Based on the texture and porosity data and the following tables, determine the relative permeability, water infiltration capacity, water holding capacity, nutrient holding capacity, percolation, aeration, and workability of the soil sample.
(avg permeability tables avail via web – but can be printed out)

 

 

Organic Matter


Soil color is an indication of the amount of organic material present. Dark brown and black soils contain a high amount of organic matter. Brown to yellow-brown denotes a moderate amount of organic material, and pale brown to yellow denotes a low organic content. White colors indicate the presence of salts or carbonates, mottled colors indicate poor aeration, and blue, gray or green tingled soils indicate that the soil is water logged.

1. Identify the color and relative organic content of your soil sample. What does the soil smell like?
2. Why is it important to have organic material in the soil?

 

 

Soil Fertility  (one or some of these MIGHT be used – depending on availability of ‘kits’)



Soil fertility characterizes the ability of the soil to support plant growth. In order to grow, plants require sunlight, water and essential minerals obtained from the soil. These minerals include N, P, K, Ca, Mg, S, Cl, Fe, Mn, Cu, Zn, Mb and B. Of these minerals, the 3 primary nutrients required by plants are N, P and K.

There are 4 main factors that determine soil fertility: pH, the amount of nitrogen, the amount of phosphorous, and the amount of potassium. Acidic soils typically have lower fertility than basic soils because H+ ions in the acid displace the positively charged nutrient ions. These nutrients can then be leached from the soil into the groundwater. Normal pH for soil is between pH 4 - 8, but the uptake of N, P and K occurs more readily if the pH is between pH 5.5 - 7.5. Optimum soil pH varies for different types of plants. In acidic soils (less than pH 5), plants are more likely to uptake toxic metals, such as aluminum, iron and manganese that can kill the plants. In acidic soils, applied pesticides, herbicides and fungicides will not be absorbed or held in the soil, but will have a tendency to either runoff the land with rain water or percolate into the groundwater.


Nitrates are usually stored in the soil in the organic matter. Normal levels are between 60 -175ppm. Nitrates do not bind to soil particles and thus can easily be leached from the soil into the groundwater, especially during heavy rain. Phosphates in soils tend to cling to the surface of clay particles and organic matter, and are quickly absorbed by plants. High levels of phosphates can accumulate in the top layers of soil in the form of insoluble calcium phosphate, and subsequently can runoff into surface water producing phosphate rich sediments. Normal levels are between 5 - 15ppm. Normal potassium levels are between 75 - 200ppm.

 

Instructions accompany each kit and are easy to follow.

1. Use the soil kits to test the pH, nitrogen, phosphorous and the potassium content of your soil sample. Record results.
2. Is the pH within the normal range?
3. What could you add to a soil that is too acidic? To a soil that is too basic? (Be specific)
4. Are any of the nutrients deficient in your sample? How could you increase the fertility of the soil and at the same time build the topsoil layer and quantity of humus?

 

Pollutants in the Soil


The motion of water and pollutants through soil is heavily influenced by the properties of the soil itself. Certain soils are very likely to trap and retain pollutants over long periods of time, while others provide for a great deal of vertical motion for both water and pollutants.

1. Cut the neck off of two water bottles.  Invert the neck in the bottles to act as funnels.  Plug the necks with a piece of cotton.
2. Fill the necks of two bottles with the soil sample to 1 cm from the top.
3. Add 20 ml methylene blue solution to one of the soil bottles until it just begins to pool at the surface.
4. Let the soil sit until the dye drains through to the bottom of the bottle.
5. Repeat steps 3 and 4 with the remaining bottle using an eosin y solution.
6. Record the volume and color of each filtrate.
7. Is the filtrate color lighter than the beginning color? Does it appear that the dye was filtered out by the soil?
8. Which dye was retained by the soil? Explain why one dye was retained and why one dye moved through the soil. (Hint: one dye is cationic or positively charged and the other dye is anionic or negatively charged.)
9. What would happen to nitrates (negatively charged anions) in these soils? Would they be absorbed to the soil particles or have the tendency to leach into the groundwater?
10. How would this demonstration relate to potential pollution of groundwater if excess nitrate fertilizers were applied to the land?
11. Considering what you have learned in this activity, what potential remediation qualities do soils have to buffer against chemical pollution and to act as filters for water percolating through the soil?

 


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