Spatial variation of soil nutrients in dairy pasture paddocks

Eight paddocks under perennial pasture were sampled on six commercial dairy farms in Tasmania, Australia on a grid with 32 to 40 topsoil samples taken from each paddock at 0-100 mm depth. The samples were analysed for soil pH and the plant available nutrients of phosphorus, potassium and sulfur. Soil nutrient levels were highly variable within paddocks due to livestock concentration and fodder management. There was a decreasing trend in nutrient concentration with increasing distance from the gate in most of the paddocks. Significant step changes occurred in the data at 0.178, 0.172 and 0.178 of total paddock length for P, K and S respectively. The implications are that no P or K fertiliser can be applied within approximately 20% of the length of the paddock from the gateway without compromising pasture productivity, as nutrients are well in excess of optimum.