Transformation of ex-arable land to permanent grassland promotes pore rigidity and mechanical soil resilience

The conversion of degraded arable land to permanent grassland is widely presumed to be amendatory and is therefore proposed as a climate-smart agriculture strategy, which may rapidly restore soil quality. However, the rate and extent of soil repair will largely depend, on the management practices, deployed in the permanent grassland. In this study, our objective was to assess the effects of no-till and no-renovation management, on aggregation, internal soil strength parameters and pore system dynamics of permanent grassland, established from degraded arable land. Also, we analysed the time dependence of these changes on the some functions of the soil. Undisturbed samples were collected at 3 depths: 0-10 cm, 10-25 cm and 25-40 cm, from permanent grassland, aged 1, 8 and 19-years, and were used to determine water retention and saturated hydraulic conductivity for each sward age. Moreover, compression properties and shear stress parameters at these depths and sward-ages were determined. The results indicated remarkable improvement in pore structure in relation to the age of each sward, which resulted in improved water retention, air and water fluxes with the age of the grassland. The shear parameters and precompression stress data showed differences in the structural recovery timeline at the various depths, highlighting the difference in ecological engineering processes as a function of the time since the grassland was established and the depth considered. Our results indicate that permanent grassland management will contribute to a substantial recovery of pore functions, coinciding with enhanced pore rigidity and increased soil strength which may also influence sequestration potential in the grassland. (C) 2016 Elsevier B.V. All rights reserved.