ENVS 210: Introduction to Sustainable Food Systems
Fall 2018
Lab 4: Soil Nutrients
Unlike the other labs that we have done up to this point, we are going to focus on something
other than the plants themselves. Today, we look at dirt. Yes, that is not the most exciting statement,
but it is important. The soil is where plants get much of their nutrients, so we must make sure that the
soil has those nutrients before planting. Of course, since you are the best kind of students, you are
either asking how we do this or looking it up on your phones or computers. Fret not! We have
instruments! Today, we will be using these instruments to test for a variety of nutrients.
First, lets talk about dirt. When we think of dirt or soil the thought of black potting soil comes to
mind, but that is not what is below our feet. Soils come in many types and it is key to know what type of
soil you have in your yard before planting. Find a partner and take some time using your phones or
computer and find definitions for the following soil types:
Loess:
Loam:
Clay:
Silt:
Sand:
Peat:
Which type or combination of types of soils do we have in the area around Dekalb?
Now that you are all experts on soil types, let’s discuss the nutrients that plants get from the
soil. Nitrogen is important in plant nutrition since it is responsible for leaf growth and producing green
leaves. Phosphorous is key to seed development and plant maturity. It aids in the seed yield and fruit
development. It also helps build the plant’s resistance to winterkill and disease. Lastly, there’s potassium
or potash. This is an important mineral because even though it does not form any part of the plant, it is
needed as a catalyst to produce carbohydrates and conduct protein synthesis. To be clear there are
other minerals that plants derive from the soil, but these are the three we will examine. Too much or
too little of any of these nutrients can be detrimental and can stunt the plant’s growth or kill it outright.
So it is important to know how to address soils whose nutrient levels are problematic. With a partner
determine what you would do to fix the following situations:
The soil is nitrogen deficient:
The soil’s potassium level is too low:
The soil’s phosphorus level is too high:
The last thing that needs to be determined about the soil is its pH level. This is the scale that
determines whether something is acidic or basic. On the pH scale 7 is considered neutral, 0 is totally
acidic, and 14 is totally basic, because it loves pumpkin spice. Most plants tend to prefer neutral soils,
anything from 6.0 – 8.0 pH, however some can grow in more acidic conditions, like pecans and
blueberries. These plants can thrive in soils that range from 4.0 – 6.0 pH.
Well so what, this information is cool, but not very useful if we have no way to get it, but like I
said before we have tools that we can use. Today we will be a variety of meters and testing kits in order
to determine the mineral levels and pH of our soil outside. In groups read the instructions of the kit or
meter and find the following information for our soil:
pH: __________________
Nitrogen: ________________
Phosphorus: _______________
Potassium (potash): ___________________