Soil Additives Science Fair Projects

Soil Additives

A soil additive is anything that is added to a basic potting soil. Some soil additives are used to accelerate the growth of helpful microorganisms, while others are used to kill harmful microorganisms. If you are developing an organic soil science fair project then you will want to focus on natural soil additives instead of chemical ones.

Objective

Materials Needed

Strategy

One (1) bouillon cube is to be dissolved in 250 ml of very warm water. As the cube is dissolving, add 1 t of salt to the test tube labeled "salt"; 1 t vinegar in the test tube labeled "vinegar". Pour equal amounts of the bouillon into the test tubes. The salt may NOT dissolve quickly, but leave it alone-if you try to stir it in, you may remove some of the salt, or "blurp" it, losing some of the liquid, or contaminate another container by using the stirrer more than once.

With the test tubes arranged in the rack, LEAVE ALONE, uncovered for 2-3 days. This can take place over a weekend. Spores will drop into the tubes from the air. Perhaps a duplication of Pasteur's experiment would be helpful at the same time: put bouillon into 2 containers, one open to the air straight up, and one open to the air, but the opening is off to the side so that things could not "drop" into the container. Compare these two containers to show that things "dropped" in from the air, and did not spontaneously grow in the containers.

Students are to examine and record their findings.

Discussion. Most will find the control tube to be very cloudy and the other two will be less so. Both salt and vinegar inhibit the growth of micro- organisms.

Performance Assessment

The outcomes of each student should indicate that the directions were followed, therefore PASS. Any other outcome will be a fail for the first objective, that of following written directions. Teacher may use discretion in allowing a repeat of the experiment for half credit; 3/4 credit for a 2-3 paragraph identifying the cause of the different outcomes. 3rd party contributor