Influence of Long-term Application of Sewage Sludge and Compost from Garbage with Sewage Sludge on Soil Fertility Criteria

In a long-term field experiment in progress since 1962 on a luvisol derived from loess the influence of increasing amounts of sewage sludge, garbage compost and farmyard manure on the N dynamic and microbiological soil characteristics was investigated.
The following results were obtained:
The application of the organic materials over a period of 24 years resulted in an increase of the total C and total N content of the soil. The increase was mostly pronounced in the plots treated with garbage compost. The higher total N content was caused by higher contents of hydrolyzable as well as non-hydrolyzable organic N compounds. The N mineralization potential of the soil was intensified by the application of all the different organic materials, especially by garbage compost and farmyard manure.
Dehydrogenase activity and soil respiration were positively influenced by all organic treatments with the highest effect in the soils with the highest C, contents.