Spatial patterns of soil biological and physical properties in a ridge tilled and a ploughed Luvisol

The present study was conducted to determine the spatial heterogeneity of bulk density, soil moisture, inorganic N, microbial biomass C, and microbial biomass N in the ridge tillage system of Turiel compared to conventional mouldboard ploughing on three sampling dates in May, July, and August. The soil sampling was carried out under vegetation representing the ridge in a high spatial resolution down the soil profile. Bulk density increased with depth and ranged from 1.3 g cm−3 at 10 cm depth to 1.6 g cm−3 at 35 cm in ploughed plots and from 1.0 g m−3 at 5 cm to 1.4 g m−3 at 35 cm in the ridges. In the ploughed plots, the contents of microbial biomass C and microbial biomass N remained roughly constant at 215 and 33 μg g−1 soil, respectively, throughout the experimental period. The microbial biomass C/N ratio varied in a small range around 6.4. In the ridged plots, the contents of microbial biomass C and microbial biomass N were 5% and 6% higher compared to the ploughed plots. Highest microbial biomass C contents of roughly 300 μg g−1 soil were always measured in the crowns in July. The lowest contents of microbial biomass C of 85–137 μg g−1 soil were measured in the furrows. The ridges showed strong spatial heterogeneity in bulk density, soil water content, inorganic nitrogen and microbial biomass.