Yes, the amount of loss of color. Yes, the control could be a clear container that allows full sunlight during the entire investigation. Since the other areas are covered by a container, thus restricting air flow, the control area must also be covered. Yes, controlled variables are such things as the same type of materials used to cover the grass and the same weather conditions, such as temperature and moisture of the soil. V. Data Data is the only way that a judge has to determine whether or not you did an experiment.
Judges like to see tables, charts, or graphs of the measured results.
Any project that has data generally gets an automatic second look by judges. If there is no data, judges start to look for the reason why, and they usually conclude that the student doesn't understand what an experiment is or how to do one. Once you have decided on your project question, your hypothesis, and basically how you are going to test your hypothesis experimentally and record your data, then start your project by designing the experiment step by step. Do perform the experiment four or more times. For the chlorosis project, this would be done by having four or more cups for each time segment.