Application of digested sludge for improving eroded soil caused by SO₂

The soil affected by SO₂ is acidic, low in nutrients and contains a large portion of coarse particles due to the destruction of the vegetation by SO₂ released by the acid manufacturing plant, and soil erosion occurred as a consequence. Fine particles have been washed away and the coarse particles were left behind. 

The up-grading of the soil was confirmed by a green house trial planting two species of grass, Agropyron smithii and Buchole dactyloides with sludge-treated and untreated soil. There was a positive growth response to the application of sludge on the crops tested. It can be concluded that the properties of the eroded soil were improved, demonstrated by their higher crop yield. 

Although the present experiment has proved that it is possible to improve the soil affected by SO₂ by applying sludge, difficulties may be encountered in the practice of applying and maintaining the sludge on a large scale outdoors. However, land application of sludge in this context not only has potentiality in improving the eroded area but will also solve part of the disposal problem in a small and densely populated area such as Hong Kong. Copyright © 1978 Informa UK Limited.