Test and Feed the Soil
CONTENT OBJECTIVE: Conduct a soil test and determine what needs to be done to increase the nutrient level in the soil.
LIFE SKILL OBJECTIVES: Critical thinking, problem solving, decision making
INDICATOR: Successfully complete a soil test and make decisions regarding fertilizing the soil in different situations.
- 2 quart-sized Ziplock plastic bags
- Clean one- or two-gallon bucket
- Permanent marker
- Soil Sample Information Sheet for Horticulture Crops (Download the ISU Extension Publication from http://www.extension.iastate.edu/Publications/ST11.pdf)
How do you feel when you haven't eaten for a while?
You may feel tired, have no energy, and have a stomachache or headache.
What happens to your energy and how does that affect your physical and mental activity?
Your body has used up the food sources that produce energy so you may feel like you don't want to move much or do much activity.
Because your body lacks nutrients and you feel hungry, it's harder to concentrate, remember, make good decisions, and so on.
What do you do to feel better and get more energy?
What are some examples of foods that make you feel better?
When we feel or see symptoms that show something is wrong we assess the situation and determine what needs to be done.
It's pretty easy to tell when plants are thirsty, but can plants get hungry, too?
How can you tell when a plant is hungry?
It is not growing well or it shows abnormal symptoms that are not caused by insects or diseases.
Where do plants get nutrients such as vitamins and minerals?
From the soil. Water helps deliver the nutrients into the roots, up the stems, and into the leaves.
What are some places where it would be particularly important to make sure the soil contains enough nutrients to grow healthy plants?
Farm fields, gardens, lawns, golf courses, and even soil in pots in greenhouses.
How can farmers and gardeners find out if the soil is fertile enough, or contains enough nutrients to grow healthy plants?
He/she has the soil tested.
What would happen if farmers and gardeners thought that "if a little does some good, a lot will do a lot of good" and applied too much fertilizer to the soil?
It may burn the plants' roots and stunt its growth or kill the plants.
Many land-grant universities and several private laboratories test soil for its nutrient content or nutrient availability to plants. Iowa State University's Soil Testing Laboratory will test soil for several nutrients. The standard test determines the phosphorus and potassium needs of the soil as well as the soil pH. The cost of this test is $7.00 per sample. Download the ISU Extension Publication, Soil Sample Information Sheet for Horticulture Crops, from the internet http://www.extension.iastate.edu/Publications/ST11.pdf
When can you conduct a soil test?
Soil tests can be done anytime the ground isn't frozen. The best time however is in the fall, after the crops have been harvested. This also gives gardeners and farmers plenty of time to receive the test results and determine their fertilizer needs. If samples are taken in the spring, it may take longer to get the results back and may delay planting time.
Where could we take a soil test?
You need to select two or three locations to take soil samples. Think about where you might want to help plants grow better. Possibilities around the schoolyard could include bare spots in the lawn, around trees, under shrubs, next to the building, or in gardens.
Take the class outside on the school ground with two quart-sized Ziplock plastic bags, a clean one- or two-gallon bucket, a trowel, and a permanent marker. Go to two or three of the places you discussed in the classroom. Scrape away any debris, such as twigs, dead grass, mulch or leaves. Using the trowel, dig down 3 inches below the sod in lawns, 12 inches for trees and shrubs, and 6 inches for gardens. Remove a trowel full of soil and put it in the bucket. Go to about ten nearby locations in the same area, such as a different place in the lawn, and get other samples. Mix them together in the bucket. Remove any roots, twigs or leaves that may have been mixed in.
Put about 1 cup of the soil in a Ziplock bag and seal it. Discard the extra soil back where you took a sample. Label the bag as to the location where the samples were taken. This will be one sample.
You may want to take another sample from another part of the school ground. Label it sample 2 and write where it was taken.
Go back to the classroom and complete the soil sample information sheet. Send the samples and $7 per sample to the Iowa State University Soil Testing Laboratory. You should receive the soil test results within two weeks.
Why did we take soil from more than one area for our sample?
To get a good representation of the soil in the area we are sampling, whether it be a lawn, under a tree, or in a cornfield.
Why is it a good idea to take soil samples in the late fall or before the ground is frozen?
The testing labs are not as busy and you will get the results back faster.
Will the soil fertility level change during the winter?
If any changes occur, they will be very minimal. The only nutrient that would change is nitrogen because it is very mobile in the soil.
That is why the standard soil test does not test for nitrogen content.
Based on the plant life near where you took the samples, what do you think we'll find out from the test?
You may want to have them record their guesses on a separate piece of paper to refer back to when the tests are returned. This is a very open question with several potential responses reflecting the knowledge level and experiences of the students.
COMPLETE THE REST OF THIS LESSON ONCE THE TEST RESULTS ARE RETURNED.
When the soil test results are returned, share it with the class as an overhead or write the results on the board.
What do these results show us?
Was the soil high or low in available phosphorus?
Was potassium available?
What are phosphorus and potassium? Nutrients
How do plants use nutrients? Phosphorous, potassium, and nitrogen are three vital nutrients for plant growth. They are used in large quantities by plants, and need to be replenished on a regular basis. Nitrogen stimulates leaf growth, phosphorus is important for fruits and flowers, and potassium or potash is necessary for good root growth. The plants roots absorb nutrients from the soil and they are transported up the stem and to the leaves where the food-making process called photosynthesis takes place.
What does soil fertility mean? Soil fertility refers to the abundance of nutrient resources available in the soil that make it productive or able to nourish plants.
Does the soil on the school ground have different fertility levels based on what is growing there?
What is fertilizer?
It is any material that is put on the soil to improve the quality or quantity of plant growth.
What fertilizer recommendations were given for the soil?
What should we do with this information?
You could share it with the school grounds keeper, offer to amend the soil as a classroom project, repeat the test at home, etc.
There are many types of commercial synthetic fertilizers available. They are different based on the different concentrations of the nutrients in the mix. They are formulated differently based on the fertility needs of various plants. A "complete analysis" fertilizer contains nitrogen (N), phosphorus (P), and potassium (K). Write N=nitrogen, P=phosphorus, and K=potassium on the board.
There are various formulations that are labeled with three numbers, such as 5-10-5. The first number represents the percentage of nitrogen, the second number is the phosphate content, and the third is the potash content. The nutrients, phosphorus and potassium, are formulated for the fertilizer as phosphate and potash.
Remember that nitrogen stimulates leaf growth, phosphorus is important for fruits and flowers, and potassium or potash is necessary for good root growth.
What nutrient, nitrogen, phosphorus, or potash, is more important for lawn fertilizer applied in the summer?
Nitrogen for a dark green lawn.
What would happen if you used that same fertilizer for your tomato plants?
It would produce lots of lush green foliage growth and very few fruits and flowers.
What nutrient is more important for lawn fertilizer applied in the fall?
Higher in potash for a strong root system to carry the grass through the winter.
The amount of complete analysis fertilizer to apply on a vegetable and flower garden depends on the analysis of the fertilizer.
The following is a general recommendation for vegetable and flower gardens:
For every 100 square feet of garden space:
- 2 lbs. 20-20-20
- 3 lbs. 10-10-10
- 4 lbs. 5-10-5
If 2 cups of fertilizer weighs 1 pound, how many cups of 10-10-10 fertilizer will you need for a 300 square foot garden?
For more information, download the following publications from Iowa State University Extension: http://www.extension.iastate.edu/pubs/ga.htm
Pm 1487 Modifying Soils in Lawns and Gardens
Pm-1680 Nonchemical Alternatives for the Home Lawn
Besides using commercial, manufactured, or mined fertilizers called inorganic fertilizers, what other fertilizers can gardeners and farmers use to replace soil nutrients?
Organic fertilizers can be used including animal waste or manure and other natural by-products such as blood or bone meal. The mineral or nutrient content, focusing on N. P. K. is the same. Organic fertilizers take more time to break down into a form that plants can use, so it takes longer to see the affects from them.
If you were a livestock farmer, which fertilizer would you probably use and why?
Manure, because it is available, natural, and cost-efficient. Research shows that manure can increase the quality of the soil by providing needed nutrients and improving the water- and nutrient- holding capacity therefore improving crop production. By using a good nutrient management plan, application of manure on farmland can be done without imposing an environmental risk. (J.L. Hatfield. Value of Manure as a Soil Resource: Need to Preserve Manure Nutrients. USDA-ARS National Soil Tilth Laboratory, Ames, Iowa)
If you were a gardener, could you use animal waste and byproducts?
Yes, lawn and garden stores, neighbors, local farmers, may sell or provide composted animal waste or byproducts to use on lawns and gardens.
Do you think farmers and gardeners test the soil before spreading manure?
Why do farmers and gardeners need to test the soil before spreading manure?
If they spread too little or too much, organic fertilizers like manure can cause plant damage and loss of revenue to farmers and gardeners.