Crack formation in a mediterranean rainfed Vertisol: Effects of tillage and crop rotation

- The soil compaction was greater in no-tillage compared to conventional tillage in the surface layer.
- The surface and volume of the cracks were greater in conventional tillage than in no-tillage.
- The soil water content at harvest measured at the surface was negatively correlated with the depth of cracks.
- The soil crack perimeter was greater in the wheat monoculture plots.

The frequency, size and development rate of Vertisols cracks influence the water, solute and heat dynamics and hence on the crop productivity. The aim of this study was to evaluate the effect of the tillage system and crop rotation on the behaviour of cracks and soil compaction in a long-term experiment that was initiated in 1986 on a Mediterranean rainfed Vertisol in southern Spain. The treatments studied were conventional tillage (CT) vs. no-tillage (NT) for five crop rotations: wheat (Triticum aestivum L.) - chickpea (Cicer arietinum L.), wheat - sunflower (Helianthus annuus L.), wheat - faba bean (Vicia faba L.), wheat - bare fallow and continuous wheat. The following parameters were measured: penetration resistance, water content at harvest, and perimeter, depth and width of crack. Soil compaction was greater in NT compared to CT in the top 10 cm of soil, with the opposite occurring between 10 and 40 cm. The surface area and volume of cracks was significantly greater in CT than in NT. The perimeter of the cracks was greater in wheat monoculture plots but with smaller crack width and depth in relation to the other studied biannual rotations. The water content at harvest recorded in the first 30 cm of soil was negatively correlated with the depth of cracks. The characterization of the cracks in Vertisols is very important for estimating losses or recharging the water in the soil profile as well as for evaluating its compaction and stability.