Stone and Soil Changes in the Harvest Orchard

Changes Near the Harvest Path

During apple harvest, Ms. Alvarez's class studied a sloping path beside an orchard. The path crossed a low stone border and ended near a collection cloth. Students looked at the same area after different kinds of weather. They recorded whether Earth materials broke apart or moved to a new place.

After a heavy rain, muddy water ran down the path. The collection cloth at the lower end held 42 grams of fine soil. The upper part of the path had a shallow groove that had not been there before the rain. Some small stones from the border were also found lower on the path.

The class examined a crack in a stone border. Water had entered the crack before winter. In late fall, the crack measured 2 millimeters wide. During winter, the water in the crack froze and thawed many times. By spring, the crack measured 5 millimeters wide, and small stone chips lay beside it. No one had moved the stone.

On a dry, windy afternoon, the class placed a cloth east of a small bare patch of soil. The wind blew from west to east. The cloth caught 18 grams of dry soil. The class saw loose soil on the cloth, but no new groove in the ground. There had been no rain that day.

The students also observed an apple tree root growing through a crack in another stone. The crack measured 3 millimeters in spring and 7 millimeters in fall. A few fresh chips were beside the stone. Nearby grass roots spread through the soil, and less loose soil was found under the grass than beside the bare patch.

To model the orchard, the class used matching trays with the same slope and 100 grams of soil in each. One tray was bare, and one had a thin layer of dry leaves. They poured the same amount of water on each tray. The bare tray's catcher held 28 grams of soil; the leaf-covered tray's catcher held 9 grams. Each setup was tested twice, and these numbers were the averages.