Litter decomposition and microbial characteristics in agricultural soils in northern, central, and southern Germany

Decomposition of litter and soil organic matter are controlled by temperature, water availability, substrate quality, and soil microbial activities. How the decomposition process and soil microbial communities interact is, however, not well understood. Therefore, litter decomposition rates were studied in situ in comparable soil units, predominantly Luvisols, at three locations in northern, central, and southern Germany and abiotic factors and microbial characteristics were concurrently investigated at four times. The ash-free mass of Triticum, Secale, and Lolium litter remaining after 180 d of field exposure in litter bags was 68, 50, and 15% respectively. For Lolium litter, the highest decomposition rate occurred at the central German site. In contrast, the refractory Secale and Triticum litter was decomposed more rapidly at the northern and southern site where inorganic N was fertilised and plants with N-2 symbiosis were predominant respectively. Rapidly degrading Lolium litter was extensively colonised by microorganisms at the early stages, by successively decreased. When looking at the whole investigation period, the microbial properties in the litter did frequently not differ significantly between the locations. However, the interactions determined between decomposition time, litter type and location indicated that microbial characteristics including metabolic-responsive biomass, carbon availability index, metabolic, and respiratory quotient varied site-specifically dependent litter quality. The refractory Triticum litter was most rapidly degraded in the microbiologically active soil, in contrast to N-rich Lolium litter.