Germination and seedling growth of vegetable crops in fly ash-amended soils

The soil amendment effects of fly ash, a by-product of coal-powered energy production, were examined during germination tests of two vegetable species. Fly ash samples contained a high total content of various trace elements including Cd, Pb and other metals such as Co, Cu, Fe, Mn, Mo, Ni and Zn. However, the extractable content (by DTPA) of these elements was comparatively low. Fly ash was applied at rates of 0, 3, 6, 12 and 30% (on a dry weight basis) to a sandy soil and a sandy loam. 

After application of fly ash, germination of Brassica parachinensis and B. chinensis seeds in 3 and 6% treated sandy soil was enhanced, while those in 12 and 30% treated sandy soil and 30% treated sandy loam showed a significant (P = 0.059) reduction. Values of EC₅₀ (effective concentration that reduced seed germination by 50%) of fly ash for both plants on seed germination were higher in sandy soil than in sandy loam. In general, the dry weight productions of crops were enhanced and the length of first leaves, shoots and cotyledons were longer in the 3% amendment but reduced in 12 and 30% amendment for both soil types. The results indicated that low ash amendment at 3% improved young seedling growth of both crops, but high ash amendment (12 and 30%) produced adverse effects on growth. 

The electrical conductivity and pH of both recipient soils were raised, but more so for the sandy soil. The increase in electrical conductivity may limit the availability of soil water because of the high osmotic pressure, and the increased pH would alter the availability of micro-elements to plants. Copyright © 1989 Published by Elsevier B.V.