The influence of crop residues type on their decomposition rate in the soil: a litterbag study

Abstract

The aim of the study was to evaluate the effect of crop residue type, chemical composition and amount of microorganisms on residue decomposition rate in the soil. Different residues types of winter and spring oilseed rape, winter wheat and red clover were incorporated into the soil in a field experiment. The decomposition rates of crop residues incorporated into the soil were found to depend on plant species, residue type, and chemical composition; the most important indicators were proved to be the C:N ratio and lignin concentration. The research findings showed that winter and spring oilseed rape threshing remains as well as stubble of winter wheat and red clover decomposed very intensively within the first 2.5 months after their incorporation into the soil. Decomposition of these crops roots and oilseed rape stubble was more intensive later on (2.5–26 months). Multiple regression analysis indicated that the decomposition rate of crop residues depended on the complex of their chemical composition: C:N ratio, N and lignin concentration. Decomposition rate correlated with the amount of micro-organisms only during the initial stages of decomposition up to 14.5 months; later on (14.5–26 months) no significant correlation was estimated. Growth of different groups of micro-organisms (mineral N assimilators, ammonificators, micromycetes, and cellulose degraders) depended on the decomposing substrate and period of crop residues incubation in the soil. Threshing remains of winter and spring rape and also stubble and roots of red clover were a more favourable substrate for growth of the investigated groups of micro-organisms than stubble and roots of winter and spring rape, and winter wheat.