Solar radiation and other climatic data were collected from Bangladesh Meteorological Department, which is responsible to record such type of data. Yield data was taken from the Annual Report of Bangladesh Institute of Nuclear Agriculture (BINA, 2004).
Dry matter calculation:
Dry matter production for a particular crop season was calculated as (Adapted from Ghuman and Singh, 1993):
DM = AE x Ep x Cd ................................................ (3)
Where, DM = dry-matter production, Mg/m2-day
AE = available solar energy, MJ/m2-day
Ep = photosynthetic efficiency
Cd = energy needed (MJ) to produce 1 gm dry-matter
For field crop, photosynthetic efficiency (Ep) was taken as 6.6 % (Mitsui et al., 1977), and energy needed to produce 1 gm dry-matter of field crop was taken as 4226 cal (0.01768 MJ).
The increasable production percentage (Pp) was calculated as:
Pp = 100(Production gap between potential and present drymatter )/ (Present drymatter production)
Calculation of atmospheric (extraterrestrial) radiation:
The extraterrestrial radiation was calculated following the procedure of Smith et al. (1992):
Crop season: Three crops were reported in cropping pattern for Rangpur, Jute (Mar. – June), T. aman (July – Nov.) and wheat (Nov. -Mar.) The effective growth period (for capturing solar energy) for Jute was taken as 93 days (out of 114 days life cycle), for T.aman it was taken as 108 days (out of 135 days of life cycle), and for wheat it was taken as 100 days (out of 125 days of life cycle).