Understanding and analysing spatial variability of nitrous oxide emissions from a grazed pasture

Nitrous oxide (N2O) emissions exhibit a high degree of spatial variability. Within a grazed pasture the uneven deposition of urine patches is one of the major sources of spatial variability in soil attributes and environmental conditions. Understanding the spatial variability of N2O emissions is necessary to estimate the size of the sampling errors using a given number of static chambers. In this study we measured N2O emissions for three weeks following a grazing event using 100 chambers. These chambers were divided into 4 blocks of 25 chambers arranged in a 5 m × 5 m grid so the within-block and between block variability could be compared. A known amount of urine was applied to 20% of the chambers. The behaviour of the sample mean using different numbers of chambers was investigated by randomly sub-sampling the chamber measurements from the 80 chambers to which urine was not applied.