Figure 4.4 (a) A field experiment investigating the effectiveness with which a grass buffer strip prevents nutrients applied to the arable field beyond from reaching the stream. In the foreground the V-notch weir is being used to monitor flow, and the small shed houses automatic equipment to sample and assess water quality at regular intervals. (b) Results from such experiments indicate that the majority of the dissolved nitrogen entering the buffer strip is either retained or volatilized, with little reaching the stream even at relatively high loading rates.