Farming for soil health: assessing the impact of agricultural management systems of soil biodiversity and functioning

This thesis investigated the effects of agricultural management systems on soil health in temperate grasslands. Three major gaps in knowledge were identified: (1) What impacts, if any, do different agricultural management systems (conventional intensive, organic, and extensive) have on physical and chemical health in grassland soils? (2) Does biological soil health differ between management systems? (3) Will the intensity of management, as measured by stocking rate, within these systems create a gradient of soil health in which functional trade-offs will occur? Physical health was not affected by managements system as all sites were well drained and of similar soil types meaning they had similar physical characteristics. Chemical health was influenced by managements systems. Conventional (CON) systems had excesses of nutrients like P and K according to the Teagasc soil indexes, thus requiring other nutrient inputs (e.g. Cu, Mg), to balance chemical health. Extensive (EXT) and organic (ORG) systems had significantly lower pH, P and K than conventional systems but ORG systems were within the optimum soil index ranges while EXT systems were not. Biological health was affected by management systems with increased nitrification gene abundance in CON systems compared to ORG and EXT systems. Fungal gene abundance was increased in EXT systems at depth (15-30 cm) compared to CON systems. Alpha diversity was reduced in EXT systems for both prokaryotes (compared to CON) and fungi (compared to ORG). Beta diversity showed significant differences between systems and this was driven mainly by soil fertility (pH, P and K levels), indicating that nutrient deficiencies as well as excesses affected microbial communities. Functional trade-offs occurred across the systems, however, contrary to the hypothesis it was not a gradient of management intensity, as ORG systems had the best balance of functionality, however they did have slightly reduced soil carbon stocks compared to CON systems.

Funder

Teagasc Walsh Scholar Programme

Publisher

University of Galway

Rights

CC BY-NC-ND

cbn

Collections

University of Galway Theses (Research Masters Theses)