Another thought. The following is a groundbreaking experiment originally conducted in Brazil in connection with tropical agriculture. It would be a good one to repeat in school because:
- it’s biology (ie., your area).
- it’s a nice simple experiment that can be done with minimal equipment.
- it illustrates the absolute basics of what science IS, especially regarding hypothesis and controls, and introduces the importance of repeating/verifying the research of others.
- it shows, in a very dramatic way, how bad science (in this case, the idea that plants need vast amounts of artificial nutrients, which arose from improperly-conducted experiments) can propagate into the wider world and have disastrous consequences.
If this is something you might like to try I can send you the original paper this was clipped from.
[quote]To illustrate the new concept, I will first describe an experiment reported in Ana Primavesi’s The
Ecological Management of the Soil. (Primavesi) In this experiment, crops were grown in four
hydroponic solutions. In the first solution, a normal concentration of nutrients for maximum maize
plant development was used, and replenished every 4 days. In the second, twice the normal
concentration was used and replenished every 4 days. In the third, the normal solution was diluted
50 times and also replenished every 4 days. And in the fourth case, the solution used was diluted
50 times the normal concentration, as in the third case, but was replenished every 2 days.
Plant growth (measured in grams of dry weight) in the second case was less than in the first. In the
third case, as either theory would predict, the growth of the plants was 28% less than in the first.
But in the fourth, quite surprisingly, the growth of the plants was slightly superior to that in the first
case. That is, even when the nutrient solution was 1/50 what the traditional Nutrient Quantity
Concept would have seen as optimal, the plants grew equally well, as long as the solution was
replaced frequently enough and the roots could access the nutrients.
That is, crop growth above a certain extremely low concentration, does not depend on the
concentration of nutrients. It depends, rather, on the constant access of plant roots to the nutrients,
even when these nutrients exist in very low concentrations. The Nutrient Quantity Concept’s
remedy of increasing the concentration of nutrients by applying large amounts of chemical fertilizer
misses the point almost entirely. What is needed is a constant supply of even a very small but wellbalanced
amount of nutrients over time, and the unobstructed access of plant roots to these nutrients.
This experiment shows that the relationship between concentrations or overall quantities of nutrients
and plant growth is, above a certain minimum concentration, altogether nonexistent. As long as
plants enjoy the right conditions of nutrient balance, accessibility to nutrients, and a constant
resupply of nutrients, the relationship between the concentration of nutrients in the soil and its
productivity is either zero (i.e. there is no relationship) or negative (i.e. more concentrated nutrients
reduce plant productivity).[/quote]
