Estimates for the half-saturation co-efficient, hN (Eqs. (4) and (6)) were obtained from
the relationships between water nitrogen concentration and plant growth rate (Fig. 2A and
B) and between water nitrogen concentration as a measure of plant nutrient concentration
(Fig. 4A and B). In the first year of the study by Aoyama et al. (1986), hN was determined
to be 0.202 0.077 (95% CI) and 0.072 0.040 (using plant growth rate and plant
nutrient concentration, respectively). In the second year of their study, hN was determined
to be 0.074 0.073 and 0.027 0.014, respectively. In summary, their experiment
suggests hN is 0.1 (range 0.01–0.3). However, hN is higher in other studies (0.902 0.302
from Fig. 2B and 1.10 0.85 from Fig. 4B). As an initial estimate, we set the value for
hN to be 0.2.