Losses of potassium from grazed dairy pastures

Abstract

A simple model was used to estimate losses of potassium (K) which occur from a Mid- Canterbury dairy farm. Analysis of the results shows the role of the dairy cow in causing losses of K from the farm. The results from this study could be used to refine the estimates of animalinduced losses of K in the model used by MAF Technology to predict fertiliser recommendations. Such refinements include the incorporation of information on the time that cows spend off the pasture (in the dairy shed, raceway and on feedpads) and the amount of K lost from urinations. The study suggests that savings in K fertiliser requirements through reduced losses from dairy farms are best achieved by minimising the time that dairy cows spend off the pasture and avoiding excessive K concentrations in herbage through heavy rates of K fertiliser. Keywords potassium, model, potassium cycling, potassium losses, dairy cattle