EARTHWORMS AFFECT MINERALIZATION OF DIFFERENT ORGANIC AMENDMENTS IN A MICROCOSM STUDY

Abstract

The efficiency of organic amendment applications as a sustainable practice is directly related with activity of soil organisms and their interactions. Earthworms (Lumbricidae) are one of the most important group of soil organisms, which can critically affect organic matter mineralization by incorporating, decomposing and redistributing soil surface organic matter.
 To study the decomposition and mineralization of two organic amendments (i.e. barley straw and cattle manure) a number of 30 microcosms was set up using polypropylene tubes filled with soil (FAO: luvisol). Half of the microcosms were inoculated with two species of earthworms (Lumbricus terrestris and Aporrectodea caliginosa), while half remained without animals. Different lengths of 13C labelled barley straw and cattle manure were put on the surface of each column. After 45 days of incubation, the organic matter consumption was recorded and earthworm casts and soil (top 10 cm) were analysed. 
 The results showed that the organic matter consumption rate is higher in manure treatments compared with straw treatments. The amount of consumed manure was about 63% from added quantity in earthworm treatments, respectively 26% in control treatments. The straw consumption rate was far less only 19% and 20% of added straw being consumed in earthworm treatments, respectively 13% and 15% in control treatments. However, the earthworms preferred a straw length of 2.5 cm. 
 Earthworm activity stimulated microbial biomass, improved Nt and N-NO3- content of the soil and reduced C/N ratio.