Storke Wetland: Nutrient Cycle
Next Generation Science Standards
5-LS2-1.
Develop a model to describe the movement of matter among plants,
animals, decomposers, and the environment. [Clarification Statement: Emphasis is
on the idea that matter that is not food (air, water, decomposed materials in soil) is
changed by plants into matter that is food. Examples of systems could include
organisms, ecosystems, and the Earth.] [Assessment Boundary: Assessment does
not include molecular explanations.]
Objective: Students will identify sources of nutrients for plants. Students will
understand the concepts of photosynthesis, decomposition and nutrient cycles in
plants.
Materials: mulch, buckets, shovels, hand trowels, established plants, KIN journals
Preparation: Locate appropriate trees or other various plants that may be in need
of mulching. Have a pile or buckets of mulch on site.
Introduction: Ask students “What do plants need to grow?” Answers should be
water, sunlight, carbon dioxide, and nutrients. What are nutrients, and where do
these nutrients come from? Do plants eat dirt? The answer is no, and yes. Plants
are producers. They make their own food through photosynthesis, turning water and
carbon dioxide into sugar and oxygen with the energy from sunlight. (See page 11 of
KIN Journal) But plants need more than just water, carbon dioxide, and sunlight.
They need many other nutrients that they obtain from the soil. Carbon, hydrogen,
oxygen, nitrogen, phosphorous, and potassium are some of the most important.
Others include calcium, magnesium, sulfur, iron, copper, and several more.
How do these nutrients get into the soil? Some come from eroding rocks in
the soil, while others are recycled. When living organisms like plants and animals
die, the organic materials are broken down into simpler forms by soil invertebrate
fauna, fungus, and microbes and returned to the soil. This is called decomposition.
When nutrients are returned to the soil they can be used again by growing plants,
completing the nutrient cycle.
Fun facts:
-Nitrogen is an essential element to all life on Earth. It is a major component of
proteins and a major component of chlorophyll, which converts sunlight into plant
energy. The majority of the atmosphere around us (78%) is comprised of nitrogen,
however, it is in a form that plants are unable to use and needs to be converted.
This is called fixation.
-Some bacteria in the soil can fix nitrogen from the atmosphere, making it available
to plants. Some plants have evolved mutually beneficial relationships with these
bacteria.
-In 1648, Johannes Baptista van Helmont conducted the first known quantitative
experiment in Biology by planting a cutting of a willow tree weighing 5 lbs in a pot
of soil. Five years later, after adding only water, the tree weighed 169 lbs, yet the
weight of the soil had only decreased by two ounces. He deduced that the growth of
the tree was due solely to water. He of course was only half right as much of the
growth was also due to carbon from the atmosphere. Helmont also coined the term
“gas” and discovered carbon dioxide.
-A banana peel decomposes in 2 to10 days.
-A pair of leather shoes may take 25 to 40 years to decompose.
-There is no trash in nature. Everything is recycled. However, humans now create
materials, like plastics, that never decompose.
Procedure: Spread an even layer of mulch a few inches deep in the area
surrounding, but not touching the plant or tree.
Conclusion: Explain: By adding mulch to the soil we will be adding nutrients in the
form of organic material. Here, we don’t use the word “organic” like they might at
the grocery store. In science, “organic” is used to describe any materials consisting
of molecules made of carbon and hydrogen. The mulch you are spreading is made of
dead plant material and will decompose and release plant nutrients back into the
soil. The above ground mulch will also protect the soil from drying out, conserving
water. The mulch will also keep weeds from sprouting up.