The balance of solar radiation and photosynthetically active radiation in rice plant community
1990
Lee, J.T. | Yun, S.H. | Im, J.N. (Rural Development Administration, Suwon (Korea Republic). Agricultural Sciences Institute) | Kim, D.U. (Kyungpook National Univ., Taegu (Korea Republic). Coll. of Agriculture)
Radiation balance within the canopy of two rice cultivars, Chuneongbyeo (japonica) and Samgangbyeo (Tongil type), was studied in terms of total solar radiation (TSR) and photosynthetically active radiation (PAR). Light transmission rate (LTR) decreased as an exponential function of leaf area index (LAI), where LTR was underestimated above LAI 5.0. Light extinction coefficients (k) of TSR were 0.382 within the canopy of Chucheongbyeo, and 0.318 of Samgangbyeo, while k of PAR were 0.516 of Chuncheongbyeo and 0.499 of Samgangbyeo, respectively. The reflection ratio of PAR above rice canopy decreased from 9 % at transplanting to 3 % at later growth stage, while that of STR increased to 20 % as LAI increased. The reflectivity can be estimated from the exponential function of LAI, Y=r-e-(r-e-r-o) EXP (-k.LAI) without any significant differences between two cultivars. Light interception ratio was increased, as growth advanced, to 67 % in TSR and 90 % in PAR, respectively. The reflectivities of TSR were greater than those of PAR within all canopy strata of both cultivars. Light penetration rates were higher in Samganbyeo than those in Chucheongbyeo at upper strata of the canopy, but were similar at about 40cm above ground, resulting in lower absorption rates of Samgangbyeo than those in Samgangbyeo at all canopy strata, only except those of PAR at 40-60 cm statum above ground
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