Fig. 2. Potassium, Ca, P, S, and N concentrations as a function of dry matter (DM) yield of timothy fertilized with different N treatments in spring. Dotted lines are data from one N fertilization treatment; solid and dashed lines indicate the stages of development at sampling. Values are based on the average of 2 yr, 2001 and 2002. Standard error of the mean are presented in Table 2.