Functional resistance and resilience of the pore system of an andisol exposed to different strategies of pasture improvement under sheep grazing

Abstract

In southern Chile, different strategies have been utilized to improve the production levels of degraded pastures. Due to grazing, soils are subjected to mechanical and hydraulic stresses throughout the year. The aim of the study was to evaluate the effect of different strategies to improve a degraded naturalized pasture under sheep grazing on the resistance and resilience of the pore system of an Andisol subjected to mechanical and hydraulic stresses. Undisturbed soil samples were collected from two tilled, seeded and fertilized pastures (T1-T2), a non-tilled degraded and naturalized pasture with no fertilization (T3), a fertilized pasture (T4) and a non-tilled-fertilized and ungrazed pasture (T5). Also, cylinders were filled with homogenized soil (T6). The tilled and non-tilled pastures (T1-T5) were able to maintain their functions of storage and transport of water and air as well as their mechanical properties against both stresses. No significant differences between the pasture improvement strategies were observed when evaluated during the second year after the implementation of the improvement strategies, which highlights the high resistance and resilience capacity of the Andisol. However, some tendencies (e.g. while the air capacity and permeability tended to increase following mechanical stress, plant available water increased; the opposite was observed following hydraulic stress) and significant differences (due to the simulated effect of aggregate destruction during tillage, a decrease in air capacity, and an increase in soil shrinkage capacity after compaction were assessed) were observed, which highlight the necessity for further studies to better understand the complex interactions in pasture systems.