Litter quality, temperature, and soil water content as drivers of decomposition and respiration in a long-term tillage trial

For sugar beet cultivation in most parts of central Europe especially water erosion is a serious problem, as for in the beginning of the growing season in late spring inherent to the cultivation system large soil areas of bare soil are left poorly protected up to the time when the plants are closing in the rows (beginning of crop covering; phenological growth stages of BBCH 31 - 39) (Koch et al., 2009). Non-inversion tillage systems are an effective measure for reducing erosion risks by diminishing soil compaction and increasing the water infiltration rate and cumulative seepage. However, a serious drawback is the considerable reduction of these systems in terms of sugar beet yield production, especially in the no-tillage treatment (Koch et al., 2009; Murugan et al., 2014). To investigate the effects of tillage intensity on all relevant aspects for sugar beet cultivation the German sugar industry in collaboration with the Institute for Sugar Beet Research (Göttingen/Germany) established a series of on-farm long-term tillage trials in the early 1990s at initially ten loessial study sites typical for sugar beet cultivation in southern and eastern Germany (Jacobs et al., 2015; Koch et al., 2009). The three tillage intensities were (1) annual mouldboard ploughing (25-30 cm depth), (2) grubber (10-15 cm), i.e. a rigid tine field cultivator, and (3) no-tillage, in a winter wheat - winter wheat - sugar beet crop rotation. In order to improve sugar beet establishment the seedbed of the no-tillage treatment was prepared to a depth of 3-5 cm before sugar beet sowing.