Sampling schemes for estimating root density distribution in cropped fields

In discussions on root research methods, so far the choice of sampling schemes seems to have been a neglected topic.In this paper sampling schemes are discussed for various situations.It is shown that the schemes used traditionally for row crops such as cereals may give a bias of about 30 % in total root dry weight.More reliable sampling schemes are presented, as well as possibilities for correction of data from traditional sampling.Available data on variation in root mass per auger sample are summarized to cal culate the number of replicate samples required to detect differences (of given mag nitude) between two means.The coefficient of variation of root weight per auger sample seems to be fairly constant at around 40 % in grassland, with slightly higher values for deeper layers of soil.A method is described by which slices of a root system, obtained by the pinboard method, can be used to estimate the total size of the root system of a single plant.As an example results are discussed for a potato experiment.A related technique is presented for calculations on profile wall observations.