Cricket Field Edges: Compare the Designs

Three Small Models

A community cricket club wanted to improve a worn strip beside its practice field. During rain, brown water sometimes crossed the strip and reached a walkway. On dry, windy afternoons, loose soil sometimes blew from the strip onto the walkway. The grounds crew considered three surfaces: bare soil, a layer of pebbles over soil, and living grass rooted in soil. Before choosing, a visiting science class compared small models of these surfaces.

The class used trays of the same size, each with a drain opening at its lower end. Each tray held the same depth and type of soil. The trays rested at the same gentle slope. Students changed the surface cover. They began with equally moist soil and slowly poured 200 milliliters of room-temperature water onto each tray. They used the same pouring height, pouring time, and pattern. Cups caught water leaving the lower ends. The class repeated the comparison three times with matching trays and calculated the average runoff for each surface. The graph shows these classroom results.

Students also kept observation notes. Runoff from bare soil looked muddy. Pebble runoff looked less muddy, and grass runoff looked clearest. At the end, soil beneath each cover was wetter than before the pour. Along a clear tray wall, students could see grass roots branching through the soil. They did not measure how much water entered the roots or how much stayed between soil particles.

The class made a separate observation about grass and air. Students placed identical clear bags over dry grass blades and over a space without plants. They covered the soil beneath both bags so soil moisture could not enter them. Both bags began with the same air and stayed in the same light shade. Later, many more drops appeared inside the grass bag than inside the bag without plants. Water vapor is invisible water in air. It can become liquid drops when it cools. The students used their notes and data to develop a model of the field edge.