Grassland soil carbon and nitrogen stocks under temperate livestock grazing

Abstract

Sustainable grassland management is critical to many agricultural economies because of the significant proportion of agricultural commodities derived from grass-fed livestock (milk and meat). Mismanagement will result in a cycle of soil quality deterioration and reduced productivity. This study estimated carbon (C) and nitrogen (N) stocks in relation to grazing management in Ireland, with a focus on understanding the role of management intensity derived from the interaction of stocking rate, N fertiliser rate and reseeding frequency. Soil samples were taken from depths 0–10, 10–20 and 20–30 cm. Soil physical properties, C and N concentrations, and microbial biomass C were measured. Significant increases in C and N concentrations were observed along the texture gradient: sandy loam < loam < sandy clay loam < clay loam < silty clay loam. However, there was little difference in C and N stock according to soil texture class. Soil with 10–20-year-old grass sward contained the lowest soil C and N content, indicating that proper reseeding is necessary to maintain soil C and N storage capacity. Increased chemical N fertiliser rate did not cause changes of soil C and N content, whereas intensified stocking rate caused great changes in soil C and N content by re-locating soil C and N at depth. Moderately intensive management was associated with significantly lower C and N stocks, and highly intensive management was associated with greater capacity of soil C and N, but no interaction between texture and management intensity was found.