Soil quality in vegetable cropping systems is seriously threatened by intensive tillage and fertilization
practices and by limited crop rotations. Inclusion of cover crops, compost application and reduced tillage
may help to sustain soil quality. A three-year field trial was set up on horticultural land to explore the
combined effects of compost amendment at three rates (0, 15 and 45 Mg ha1 year1
) and tillage practices
(reduced tillage versus conventional ploughing) on soil quality. Cover crop was not a factor in the
experiment, but cover crops were included in the rotation for reasons of good agricultural practice. The
highest compost dose supported the initial level of total organic carbon in the arable layer. The decrease
in pH in the arable layer was considerably limited by compost application, irrespective of the dose
applied. Reduced tillage resulted in a favorable stratification for different soil quality indicators both by
placement of organic inputs near the soil surface and by a reduction of leaching of base cations and
organic carbon compounds. Differences between tillage practices and compost doses were most striking
in the 0–10 cm soil layer. Compost application at the highest rate enhanced organic C content by 16%
compared to the contentin the non-amended soil. Reduced tillage induced a 13% higher organic C content
in the 0–10 cm soil layer than that in the underlying 10–30 cm layer. Combining reduced tillage and
recurrent compost application resulted in a different soil microbial community structure in the 0–10 cm
surface layer, as revealed by phospholipid fatty acids analysis. Total microbial biomass was 44% higher
under reduced compared to conventional tillage and increased by 27% due to compost application at a
rate of 45 Mg ha1 year1
. Fungal biomass doubled in the surface layer by reduced tillage. Actinomycetes
and arbuscular mycorrhizal fungi were favored by both reduced tillage and compost application.
Conversion to reduced tillage allowed for sustaining crop production in this intensive vegetable cropping
system. Compost application and reduced tillage counteracted soil degradation.