Between and within paddock soil chemical variability and forage production gradients in grazed dairy pastures

Soil chemical properties are likely to be unevenly distributed within grazed dairy farms. Paddocks that dairy cows graze more frequently, or parts of paddocks that they regularly visit potentially have elevated nutrient levels due to the excreta returned by the herd. We measured the between and within paddock distribution of a range of agronomic soil chemical properties on four commercial dairy farms. Between paddock spatial variability was high for most properties and varied between the farms (range in CV of 13-127 %). Aluminium had the widest range in CV (50-127 %) while oxidisable organic C was similar between farms (22-25 %). Only plant available K was greater at the front than at the back of the paddocks on these farms, with a trend towards higher levels at the front observed for the strip grazed farms. The impact of strip grazing on within paddock soil nutrient and pasture growth distribution was further investigated in an experimental farmlet study. Significantly greater Colwell K, EC and increased pasture production were observed in the front of strip grazed paddocks compared with the back, while soil pH and KCl-S levels were similar at both ends. The gradient of nutrients from the front to the back of these paddocks was greater in the more intensive (higher stocking rate and P fertiliser rate) systems. Soil sampling and fertiliser application strategies are needed that address nutrient variability between and within paddocks, as influenced by differences in paddock management and animal excreta distribution.