During a unit on rainforests, Pat Murray's 2nd graders in Westerville, OH, wondered about what happens when forests are cut for farming, and the same food crops are grown on poor soil year after year. Their questions inspired an activity idea for their classroom GrowLab. Why not set up a classroom experiment to see what would happen if one crop was planted and harvested over and over again on the same plot of soil?
Using 3-inch by 8-inch containers with drainage holes, students planted 10 corn seeds in simulated rainforest soil-poor soil covered with a thin layer of topsoil. They made five consecutive plantings and then, as a class, brain stormed how they would observe the plant's growth: 1. By measuring the time it took the seeds to germinate; 2. By measuring the time it took them to grow to five inches; 3. By observing the quality of the leaves; and 4. By measuring how many actually germinated and grew. Students cared for, harvested, recorded observations, measured and graphed results.
Once the seedlings reached 5 inches, they were plucked from the ground and new corn seeds planted immediately. "Just as the students had predicted, based on our readings," said Pat, "the number and quality of seeds that grew significantly diminished each time we replanted them."
"Although this was a loose simulation," she added, "the impact of doing and seeing it firsthand helped the kids understand the significance of 'over farming' and area. It sparked a class discussion about how our simulation differed from real life, and about the lack of choices people in those areas may have."