MODELING WEATHER EFFECTS ON NUTRITIONAL-VALUE OF GRASS-CLOVER LEYS .2. ESTIMATION AND VALIDATION OF PARAMETERS IN A MODEL FOR CHANGES IN CRUDE PROTEIN-CONTENT
B. Fagerberg et P. Nyman, MODELING WEATHER EFFECTS ON NUTRITIONAL-VALUE OF GRASS-CLOVER LEYS .2. ESTIMATION AND VALIDATION OF PARAMETERS IN A MODEL FOR CHANGES IN CRUDE PROTEIN-CONTENT, Swedish Journal of Agricultural Research, 25(1), 1995, pp. 3-12
Three parameters were optimized in a simulation model for weather affe
cted change in protein content (CP) of grass and red clover. Two param
eters determine the shape of the change rate function and one sets the
protein content at the onset of growth. The parameters were optimized
from field experiment data obtained during 1985-1988 at six sites in
central and southern Sweden. The model was validated on data from mixe
d Jeys. The results of the optimization and validation show that the m
odel gave more reliable results than time regressions, but individual
values of the starting value of protein content (max) must be derived
for each situation because of the nitrogen dynamics in the soil. There
fore, CP prediction in a particular field cannot be made without calib
ration sampling.