Fig. 6. Influence of average N nutrition index (NNI) on average (A) areal leaf N content (N_LA; g m^-2), (B) leaf N concentration ([N]; g kg^-1), and (C) leaf area duration of potato at about 52 d after emergence (DAE) in 1997 and 47 DAE in 1998. Influence of NNI on (D) thermal time till 50% intercepted photosynthecially active radiation (PAR) at start of the season and (E) maximum leaf area index (LAI) of potato. Points are for individual replicates. Lines are regression lines for each cultivar and year separately. Parameter estimates of lines are in Table 6.