Hydroponics: A greener way to grow
Discovery Place Science
Much like we need to eat certain things to grow and be healthy, plants need certain things to grow and survive as well. What comes to mind when we think of how plants grow? Sun, soil and water, right? You may have heard of the term photosynthesis, which is a process performed by plants to take water, sunlight and atmospheric gases to make food for themselves. To perform photosynthesis, plants need sunlight, water and carbon dioxide
For healthy growth, plants need nutrients just like we do, but they can’t always get that from the soil they live in. Areas where there is nutrient-rich soil can be limited. If a field has been overplanted, the nutrients can be depleted, and future plants will have a hard time growing there. So, if we need space and healthy areas to grow food and plants, what can we do to plant efficiently without overplanting and stripping the earth of its nutrients? Farmers and scientists are turning toward a practice called hydroponics, where plants can be grown without huge fields to plant in, and sometimes even without soil.
In hydroponics, plant roots are given nutrient-rich water comprised of what they would find in healthy soil: nitrogen, calcium and phosphorus. These nutrients, along with sunlight, allow the plants to grow quickly and in much less space than traditional growing fields. To have a plant grow in a hydroponic system all that is needed is a container where the roots can be exposed to the nutrient-rich water, a growing medium to support the roots and sunlight.
Hydroponic systems have been found to use less water, less space, and allow for higher crop numbers since they take up less space (can be grown in vertical systems) and the nutrients can be measured in a way to promote better growth.
In this activity, we will make our own hydroponic system using recycled materials as we explore what nutrients plants need to grow and learn about hydroponics. In our build, we will be using a ‘wick’ hydroponics system. The plant will grow in a medium that allows nutrients and oxygen to reach the roots—nutrient-rich water is brought up to the roots from a reservoir below through capillary action.
It will take about 5 minutes to prepare for this activity and we’ll have about 10 minutes of learning time. This project is best suited for children in elementary school grades.
- Plastic bottle (2-liter, single-serve water bottle, etc.)
- Growing medium (soil, clay pellets, small pebbles) This needs to be a material that can keep plant upright and hold moisture but not too much to waterlog roots.
- Thick cotton string (or old T-shirt strips, shoelaces with aglets cut off)
- Plant or seedling (needs to have developed roots system)
1. Find a plastic container that can house your plant’s size. Cut it in half. You’ll be using the top half to hold the plant, and the bottom to hold the water.
2. Turn the top part upside down and place in bottom to see how they fit. If the top is too small and falls in you may need to wrap the edge of the bottom part in aluminum foil so the top part sits on edge and doesn’t fall in.
3. Cut your cotton string so that it is long enough to touch the bottom of your container and has about 6 inches (or more) left in the top part of your container.
4. Prepare your plant: Carefully remove your plant from pot and gently remove most of the soil from around roots.
5. Carefully wrap one end of your cotton string loosely around the roots, and place plant in top part of planter, making sure that there is enough string left free to reach to bottom of the planter.
6. Fill in around your plant with your medium. Don’t pack it too tightly, you want oxygen to be able to get to the roots, but enough to hold the plant upright.
7. Place your top piece onto your bottom and fill with water until just below your medium. The cotton string will use capillary action to draw water up and to the roots. You can use regular water, but plant food mixed into water will provide better nutrients for better growth of your plant.
And we’re done! You now have a hydroponic planter that takes up minimal space in the windowsill and only needs to be watered when the bottom reservoir is empty.
How to adjust for younger and older learners
For younger learners start out focusing on seeds that germinate, or sprout, very quickly. They are a great way for young learners to see something grow from seed to sprout in just a few days. Beans can start sprouting in as little as three days! Check your pantry for dried bags of beans, take one and wrap it in a damp sheet of paper towel. If you have plastic sandwich bags you can place your damp wrapped seed into it. Keep an eye on your seed and wet it a little if needed. Make sure to transplant it and place it in a sunny spot for it to continue to grow.
For older learners, take the activity further by experimenting to see how plants grow in normal potted conditions compared to a hydroponic system. This works best if you have two similar plants so the only variable you change is the way it receives nutrients. Every day, or week if you are recording at the same time for every reading, measure the height of each plant from its tallest tip to where it meets the soil, and record those measurements. Keep track of what days you had to water the plants and see after a month how growth compared.
To learn more about hydroponics and different ways to build hydroponic systems visit https://www.nps.gov/articles/hydroponics.htm