Dredging of lake and application of sapropel for improvement of light soil properties

Abstract

Approx. 1.5 billion m3 of sapropel are accumulated in silty Lithuanian lakes. Sapropel is a valuable organic and limy matter, which can be used for fertilisation and soil improvement. Silted lakes usually require mechanical cleaning, i.e. removal of lake sapropel. Such cleaning was carried out in one of the lakes of Lithuanian – Lake Ilgutis: using a dredge, sapropel was extracted, dried in sediment bowls to 80–85% of humidity, carried to a field and insert into the soil. Summarised results of the long-term experiment showed that calcareous sapropel can reduce soil acidity and increase the amount of exchangeable bases (Ca+Mg). Under the influence of sapropel, the contents of organic carbon and total nitrogen increased as well. The results of investigations demonstrated that by the end of the second (after 12 years), third (after 18 years) and fourth (after 24 years) rotation, the effect of sapropel on soil chemical properties was positive. Compared with limestone, calcareous sapropel improved physical characteristics of the soil to a greater extent.