Relationships of photosynthetically active radiation and shortwave irradiance

✍ Scribed by C.M. Britton; J.D. Dodd

• Publisher: Elsevier Science
• Year: 1976
• Weight: 369 KB
• Volume: 17
• Category: Article
• ISSN: 0002-1571
• DOI: 10.1016/0002-1571(76)90080-7

✦ Synopsis

Measurements of photosynthetically active radiation (400--700 nm) and shortwave irradiance (ca. 300--2,000 nm) were made over a 14-month period at College Station, Texas. The proportion of photosynthetically active radiation changed with intensity of incident irradiance and length of photoperiod. For the period April 21 to August 21, long photoperiod days, the proportion varied from a high of 58% for the 0--5 MJ m -2 d -1 irradiance class to a low of 47% for the 25--30 MJ m-d-class. From October 21 to February 21, short photoperiod days, the proportion varied from a high of 50% for the 2 1 2 1 0--5 MJ m-d-class to a low of 45% for the 15--20 MJ m-d-class. Comparing the longest photoperiod day to the shortest photoperiod day, under clear conditions, the proportion changed from 46% to 44%, respectively. Equations are presented for estimation of photosynthetically active radiation by shortwave irradiance classes and bimonthly periods.