Transition to conservation agriculture: how tillage intensity and covering affect soil physical parameters

Abstract. Conservation agriculture (CA) relies on the following three key practices to improve agricultural sustainability: crop rotation, reduced tillage, and cover crop usage. Despite known soil physical benefits (reduced soil compaction and strength, enhanced soil porosity, and permeability), inconsistent reports on short-term CA results have limited its adoption in the European agroecosystems. To elucidate the short-term effects, a 3-year field experiment was undertaken in the low-lying Venetian plain (northern Italy). Bulk density (BD), penetration resistance (PR), soil hydraulic saturated conductivity, and sorptivity were used to evaluate soil quality obtained by combining three tillage intensities (conventional tillage – CT; minimum tillage – MT; no tillage – NT) with three winter soil coverings (bare soil – BS; tillage radish cover crop – TR; winter wheat cover crop – WW). Among the tillage methods, CT, on average, reduced BD by 4 % (from 1.48 to 1.42 g cm−3) and PR by 3.1 % (from 1.69 to 1.64 MPa) in the 0–30 cm tilled layer. Across the soil profile, reduced tillage coupled with WW improved soil physical properties even below the tilled layer, as evidenced by root-growth-limiting condition reductions (−11 % in BD values, with BD >1.55 g cm−3, and −7 % in PR values, with PR >2.5 MPa). Soil hydraulic measurements confirmed this positive behaviour; NT combined with either BS or WW produced a soil saturated conductivity of 2.12×10-4 m s−1 (4 times that of all other treatments). Likewise, sorptivity increased in NT combined with BS vs. other treatments (3.64×10-4 m s−1 vs. an all-treatment average of 7.98×10-5 m s−1). Our results suggest that, despite the increase in BD and PR due to reduced tillage, the strategy improved soil functioning and particularly soil hydraulic conductivity. In the short term, the WW cover crop moderately increased physical soil parameters, whereas TR had negligible effects. This study demonstrates that, to quantify CA, several soil physical parameters should be monitored.