Passage VI

Three studies examined the effects of adding fly ash (fine-grained ash from burning coal) to a sandy soil. In the studies, 4 samples were analyzed: Sample 1 was pure sandy soil, Samples 2 and 3 each had a different amount of fly ash thoroughly mixed with sandy soil, and Sample 4 was pure fly ash.

Study 1

To determine the relative water-holding capacity of the 4 samples, the percent by mass of sand-size, silt-size, and clay-size particles in each sample was measured (see Table 1) . As the total percent by mass of silt-size and clay-size particles in a sample increases, the water-holding capacity of the sample increases.

Study 2

Sample 1 was analyzed for boron (B), an element that inhibits plant growth. Next, 4 kg of Sample 1 was placed in each of 3 identical pots. Eight corn seeds were planted in each pot. Identical amounts of water were added to the pots regularly. Fifty-five days after planting, the corn plants in each pot were harvested, dried completely, and weighed. These procedures were repeated with Samples 2 and 3 (see Table 2) .

Study 3

Equal-volume portions of Samples 1-3 were leached by running an amount of water equivalent to 100 cm of rainfall through them to reduce the B content. (The B compounds that were present are water-soluble.) Then, all the procedures of Study 2 were repeated with those leached portions (see Table 3).

Tables adapted from M. Ghodrati et al., “Enhancing the Benefits of Fly Ash as a Soil Amendment by Pre-Leaching." ©1995 by Williams and Wilkins.