Long-term impacts of different tillage intensities on the C and N dynamics of a Haplic Luvisol

Abstract

The objectives of the study were to quantify the effects of 40 years of conventional tillage (CT) and reduced tillage (RT, maximum tillage depth of 8 cm) on C and N dynamics in the surface (0–5 cm) and subsurface (5–25, 25–40 cm) soils of a silty Luvisol in a long-term trial at Garte Süd, Germany (temperate climate). Stocks of C and N and contents of microbial biomass C and N were significantly higher in the surface soil of the RT treatment than in the CT treatment. However, over the entire profile (0–40 cm), C and N stocks did not differ significantly. Cumulative net N mineralization (determined in a laboratory incubation at 13.7°C and 60% water holding capacity) was significantly higher in the surface soil of RT (58.6 mg kg⁻¹) than that of CT (26.7 mg kg⁻¹), whereas in the subsurface soil depths, cumulative N mineralization was higher in the CT treatment. By contrast, gross N mineralization rates did not generally differ significantly between the treatments. Overall, different tillage intensities affected C and N dynamics only slightly in the entire profile because increases in C and N stocks and N mineralization rates in the surface soil of RT were counterbalanced at greater depths.

Keywords:

• tillage
• organic matter
• incubation
• N mineralization
• ¹⁵N pool dilution
• microbial biomass
• passive pool