Effects of no-tillage on chemical gradients and topsoil acidification

No-tillage is an increasing way of management for agricultural soils. The objective of this study was to identify in which extent the chemical properties of a loamy soil could be affected by no-tillage under temperate conditions. Soil chemical properties were investigated on a field subjected to either conventional or no-tillage management of maize (Zea mays L.) and wheat (Triticum aestivum L.) with identical fertilization practices and no lime supply since 1970. On no-tilled soil, maize was cropped exactly on the same line every other year, which enabled soil sampling under the row and under the interrow. Tilled soil had an homogeneous ploughed horizon, whereas soil under no-tillage exhibited strong vertical gradients of pH, exchangeable cations and organic C. No-tilled soil had 11.4% greater organic C than tilled soil, and the difference was concentrated in the upper 5 cm. The proportion of exchangeable cations was highest in the interrow of no-tilled soil and lowest in tilled soil. Tilled soil contained much lower exchangeable K than no-tilled soil, indicating a difference in retention capacity of this cation. The pH of the upper 5 cm of no-tilled soil was low, probably because of surface accumulation of organic residues. Whatever the tillage system, exchangeable Al was significantly related to pH according to the relation: Alex = 76441 × 10−0.99 pH (r2 = 0.96; p < 0.001). An expected complexing effect of organic matter on Al was not observed, probably hidden by the influence of pH. Since yields were not negatively affected by long-term no-tillage and organic C content was higher, no-tillage appears to be a cost-saving choice for maize and wheat production under these temperate environmental conditions, as well as a way for C sequestration.