How do different treatments change how fast seeds sprout?
You can find out how quickly seeds sprout under different temperatures, or after being soaked for different times or in different liquids. Or, see how one kind of treatment affects different types of seeds.

What effect does seed size have on how well a crop like oats or wheat grows?
Pick out groups of seeds all of the same size. Be sure and measure the seeds before you plant them. You can define success a number of ways: how many seeds sprout, how fast the plants grow, how tall the plants get, etc.

Which way is up?
Many seeds and bulbs have a definite top and bottom. What happens if you plant them upside down or sideways? Will they still grow? Will it take longer for leaves to start showing up? You may have to dig the bulbs up to measure root growth.

What happens if you change a seed's direction once it starts to sprout?
Many seeds like beans can be sprouted in moist cotton or paper towels. What happens if you turn the seed 90 or 180 degrees from right-side-up every few days after it sprouts?

You can take it a step further by using a record player turntable (if you can find one) to simulate changing gravity's pull on seeds. You'll want to know more about the chemical auxin, which affects where roots and stems grow. Click here to learn more about using the turntable.

Does the amount of room a plant has for roots make a difference in how big a plant will grow--regardless of how much fertilizer the plant is given?
Plant seeds in a variety of different-sized containers using vermiculite or other soil-less material, so you will be able to give each plant a measured amount of fertilizer. Or plant a number of plants in the same size containers and vary the amount of fertilizer and see what happens. Be sure to use small enough containers so that root growth really will be constricted.

How do different types of fertilizers affect plant growth?
Fertilizers contain different amounts of the nutrients nitrogen, phosphorus, and potassium. Get different fertilizers from a garden shop or nursery and apply them to groups of the same plant. Do the different fertilizers change how the plants grow? You could measure height, width, number of leaves, how fast the plants grow, number of flowers, or yield.

What happens when you grow sweet potatoes next to other plants?
Compare how fast the other plants grow at different distances from sweet potatoes. Remember to grow some control plants nowhere near the sweet potato. Check out the term allelopathy.

How does soil pH (acidity) affect the pH of water that touches the soil?
A pH meter can be found at almost any garden shop or nursery. Gather different types of soil or look in a nursery for pottings for different types of plants. Put some of each type in a cup and check out the pH. Then check the pH of your water and add it to your cups, and mix. Wait for the soil to settle and measure the pH of the water. Be sure you use water from the same source for each soil. Click here to learn more about soil from ARS's Coastal Plains Soil, Water, and Plant Research Center.

Does soil type change how well crops grow?
Fill boxes with different types of soils (sandy, clay, etc.) and plant the same seeds in all the boxes. What happens to the plants? You could measure height, width, number of leaves, how fast the plants grow, number of flowers, or yield of seeds, or fruits that form.

How are different soil types affected by water running over them?
Farmers in many parts of the country have to irrigate--to water their crops rather than rely only on the rain. But water running over soil can cause it to wear away, or erode.

Here's a simple experiment: Find patches of different types of soil that are on slight slopes or hillsides (you could also look for patches of the same soil type with different amounts of plant cover, for example, bare soil and a grassy area). For each test site make a sampling container. Cut the tops off plastic bottles such as soda bottles or milk jugs. Use the same size bottle for all sites. Bury each container so the lip is even with or slightly below the soil surface.Weigh the soil that collects in the containers after each rain. Dry the soil in an oven before you weigh it; you don't want to weigh the water, just the soil. Record the differences to find out which test site had the most erosion.

Is there chemical contamination in your streams and creeks? One way to test for such contamination is with a bioassay, a type of experiment that measures the effect of a substance on a living organism, tissue, cell, or enzyme.

Of all the possible water-quality bioassay organisms, lettuce might be one of the last you would think of. Lettuce doesn't live in water, so why use it to test water quality? The reason is lettuce bioassays are inexpensive, easy to do, and the seeds are pretty sensitive to some types of contaminants in water, including heavy metals, pesticides and other organic toxins. Although any variety of lettuce may do, Lactuca sativa Buttercrunch is the standard variety recommended for bioassays by the U.S. Environmental Protection Agency, the Food and Drug Administration, and the Organization for Economic Cooperation and Development.

You might try taking a series of samples along one stream or compare streams near industry to water running though agricultural areas. Directions for conducting experiments can be found at the Cornell University's Environmental Inquiry webpage.

Do different varieties of the same fruit have the same level of vitamin C ?
What about different brands of orange juice? Or fresh juice compared to juice from frozen concentrate? Does the way a fruit is stored or how long it is stored change the level of vitamin C? Click here to learn how to test for vitamin C content.

Are there different amounts of iron in different breakfast cereals?
The iron in ready-to-eat breakfast cereals is in the form called elemental, not in combination with any other chemical compound. Iron is sprayed on the outside of cereal flakes. Click here to learn how to separate the iron with a strong magnet.

It's easy to think of all microorganisms as bad things--as germs, for example. But many microorganisms are very helpful, especially for agriculture, and some are even essential. Microorganisms are used to fight pest insects, diseases and weeds that make producing crops and raising livestock less efficient. Other microorganisms help make nutrients in the soil more available to plants.

What happens to the way plants grow if there are no microorganisms in the soil?
Take a sample of fertile soil from a field or garden and divide it into two portions. Bake one in an oven (to destroy the microorganisms). Leave the other portion alone as a control. Plant the same number of seeds in each soil sample. Remember to treat both samples the same while the plants are growing. Make sure all the plants receive the same amounts of water and light, and are kept at the same temperature. How do the plants differ as they grow?

Are different plants affected in different ways by specific microorganisms?
Some microorganisms and plants form mutually beneficial partnerships. For example, certain bacteria make a natural nitrogen fertilizer for plants in the family called legumes. Peas, alfalfa, and soybeans are legumes. The nitrogen-fixing bacteria are available from garden supply stores and by mail order. Grow both legumes and non-legume plants with and without the bacteria. Are there differences in how well the plants grow?

(NOTE: Most schools have special rules about doing any experiments that involve live animals. Be sure to check with your teacher before you decide on such an experiment.)

Can different colors and types of cloth attract or repel insects from plants? Plant a number of groups of the same type of plant near each other, but far enough apart to surround each set with several feet of fabric. Or, select several of the same kind of bush in one yard. You want to use the same type of plant in the same place, so all of the plants will have the same potential for insect damage.

Surround each group of plants with a different color fabric. Be sure water can penetrate the fabrics. At set intervals, record all the insects you can find on each plants and any signs of insect damage on the plant. It is a good idea to check reference sources for common insect problems of the type of plants you are using.

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