Response of maize leaf decomposition in litterbags and soil bags to different tillage intensities in a long-term field trial

In a long-term tillage field trial under practical farming conditions in Central Germany, the decomposition of maize (Zea maize L.) leaf litter was monitored for 8 months in litterbags and soil bags, where non-decomposed litter was mixed into soil and recovered as particulate organic matter (POM). The objective was to determine which methodological approach is more suitable to reflect tillage effects on litter decomposition and microbial turnover in no-tillage and grubber (15 cm), i.e. a rigid tine cultivator, treatments in comparison with mould-board ploughing (25 cm). Under no-tillage, CO2-C efflux monitored for 22.5 months was lowest, although this soil contained the highest soil organic C and microbial biomass C contents at 0-5 cm depth. One reason is the slow warming in spring due to the highest volumetric water content, leading to the lowest mean soil temperature. Maize leaf litter was more rapidly decomposed in the soil bags, with a mean mass loss rate constant k = 0.0108 d(-1), than in the litterbags, with k = 0.0063 d(-1). This difference mainly occurred during the initial 3-month period after burying. In the soil bags, the mass loss rate constant for maize leaf litter was significantly higher in the no-tillage than in the plough treatment. In contrast, the mean microbial C use efficiency of the maize leaf litter of 0.27 in the soil bags was not affected by the tillage treatments. Although both methods are in principle suitable for monitoring decomposition processes, the soil bag method has advantages, as initial accessibility to decomposing microorganisms is facilitated.