All agronomic
practices in this experiment were similar to normal farming
practices of the region and fertilizer nitrogen supply was at a rate
of 50 kg/ha which is considered to be adequate for prevailing
growing conditions. Accumulated growing degree days (GDD)
were calculated by summing daily degree days according to Darroch
and Baker (1990). Daily degree days were calculated as
Tn = (Tmax + Tmin)/2 Tb, where Tmax and Tmin are the maximum
and minimum daily temperatures, respectively, and Tb is the base
temperature (5 C).