Measuring Light
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Spectrum Technologies - "To Measure Is To Know" Measuring Light 4 LIGHT HAS ECONOMIC VALUE As the driving force for photosynthesis, light is fundamentally important to crop production. Plant growth and development is significantly influenced by both the quantity and the quality of light. Light energy is relevant to other factors too. The ET calculation (evapotranspiration) for irrigation scheduling uses solar radiation as a key variable. Leaf wetness periods or high humidity, which affect disease pressure, can be mitigated with sunny days versus cloudy days. It is essential that growers understand this important variable in order to efficiently produce quality plants.

How Does Light Affect My Plant Growth? HUMAN EYE PERCEPTION (500-600nm) Foot Candle or Lux meters measure light similar to how the human eye perceives brightness: strongest in the 500-600nm range. Though this is desirable for photography and interior design, plants react to light differently. “Measuring DLI inside the greenhouse can be very revealing, since growers usually rely on their eyes to determine the light levels and the human eye is a terrible light sensor because it is so effective at adjusting to different light environments.” James E. Faust Associate Professor of Horticulture...

Spectrum Technologies – “To Measure Is To Know” LIGHT METERS SOLAR RADIATION (300-1100nm) The sun radiates a broad range of light from 300-1100nm. In agriculture, this total radiation is needed primarily to calculate Evapotranspiration (ET). ET is the amount of moisture leaving the ground through evaporation (from the ground) and transpiration (from the leaves), and is dependent upon light, wind speed, temperature, and relative humidity. UV (200-400nm) Plants can suffer from sunburn; exposure to radiation in the mid-ultraviolet part of the electromagnetic spectrum (UV-B) triggers stress...

Spectrum Technologies – “To Measure Is To Know” Measuring Light Individual light sensors, available individually or as a bar of 3 or 6 sensors, allow you to measure site-specific areas. These hand-held sensors feature cosine correction, built-in levels, and mounting brackets for stationary measurements. Light Bars are frequently used when measuring across a greenhouse bench. 3415FX 3668I 3668I3 3668I6 3676I 3670I FieldScout External Light Sensor Meter Quantum Light Sensor Quantum Light 3 Sensor Bar Quantum Light 6 Sensor Bar UV Light Sensor Silicon Pyranometer Sensor LEAF AREA INDEX Leaf...