Question

Small scale experiments of growing plants

Answer 1

Plant Growth Experiments

The instructions below outline a protocol for conducting plant growth experiments in the laboratory. You may want to make adaptations for use in a greenhouse or outdoors.

Purpose: To determine the effect of compost on plant germination and growth.

Materials

pots or planting trayscompostsoilseedslight source (sunlight or artificial lighting)

Procedure

1. Design your own experiment. There are many possibilities--a few ideas are listed here, but the variations are endless:

Test various combinations of soil and compost on plant growth. For example, you might wish to dig a soil sample from your school yard and mix it with various amounts of finished compost for planting experiments. (Natural soil is better than prepackaged potting soils for experiments such as this because the potting mixes are formulated for optimal plant growth and already contain significant amounts of compost or humus.)
Another possibility is to mix your own potting soil by using vermiculite, sand, and compost. Creating several mixtures using the same percentages but different types of compost is a good way of comparing the influence of the various types of compost on plant growth. For example, you could compare compost at various levels of maturity, compost created using different mixtures of organic wastes, or vermicompost versus compost created in a thermophilic system. 
If you are interested in investigating the effects of compost tea on plant growth, you could fill the pots with a sandy soil or potting medium such as vermiculite, then use compost extracts for watering.

2. Whatever type of experiment you choose, make sure that you design your experiment to include replicates of the various treatments.

Plant your seeds, water them, and place them in a well-lit location. Many type of seeds will work, but radish or lettuce are often chosen because they grow quickly. Melon seeds are sensitive to fungal diseases, and thus they provide a sensitive indicator of whether fungi have been killed through heating or curing of the compost.

4. Keep all the pots in the same setting to minimize any variation in temperature, lighting, pests, and other environmental factors. Even when the environmental conditions are kept as constant as possible, it is a good idea to randomize the grouping of plants rather than placing all the plants that are receiving the same treatment together in one group. This helps to further minimize the effect of any environmental differences.

5. Record on a daily basis the number of seeds that have germinated, plant growth, and observations about plant health such as color, vigor, or damage due to pests and diseases. You can decide what measurements to use as indicators of plant growth; possibilities include plant height, number and size of leaves, and dry weight of the entire plant at the end of the experiment. (For dry weight, weigh the plant after drying in a 105C oven for 24 hours.)