Dear Frits Besides the recorded phenology stages in field, I calculated that dimensionless DVS used by Wagenningen group, through accumulated temperature devision to the whole needed to a special stage. but the problem is still on, It seems to me that to have a comparision of simulated phenology with observation, one has to have an anatomical recording phenology sampling. Terminal spikelet is not a sort of shape that we walk in the field and say we are at this stage or not, but it is more easy to find that how many true leaves we have on a plant scale. I wonder if anybody else faced such a problem and found a way? Regards Mohammad