DePauw Stories

Students work together to balance the wheelbarrow and move heavy sandbags used to hold down the tarps used for solarization.

The large tarps used by Ullem Farm warm the soil to promote weed germination* while cutting off light so that weeds can’t grow; this is an organic process of weed control called solarization. However, the large tarps are heavy and difficult to move without the students’ coordinated teamwork.

*Basically, the tarps warm the soil, which causes the seeds to open and start the growth process; this always happens underground in the dark, so it doesn’t require sunlight. Rather, the seeds contain enough stored energy to support plant growth for a little while (the amount of time depends on the plants; FYI – this is why seeds and nuts are so nutritious!). However, once the shoots emerge, the plant metabolism switches over to photosynthesis. So, by the tarps blocking the light, that process can’t occur, and the plants die. This duel process – promoting germination (aka the start of the process) but blocking light (preventing photosynthesis) is what makes them so effective because, without the heat, the seeds would just lie dormant until the tarp is removed, and then start to grow when the crops are planted, which interferes with crop growth. This whole process is called “solarization.”

Ullem Farm manager Catherine Fisher explains the hydro-phobic properties of soil while a student slowly mixes water with the planting material to moisten it before planting.

Literally getting their hands dirty, students plant spinach, chard, kale and salad mix for a fall harvest.

Tiny seeds must be carefully placed to a soil depth of a half-inch to ensure that they have the right conditions for growth.