Published 22/05/2013

DLICALC Online Tool Helps Growers Calculate Daily Light Integral

Researchers have developed a new tool to help growers calculate supplemental daily light integrals and determine how much supplemental light is required to improve growth.

Managing all the different environmental and cultural aspects of greenhouse crop production can be an intimidating and daunting task, especially during the peak production season. But it’s necessary to produce a high-quality, salable plant. The greenhouse is full of moving targets, from root zone pH and EC to plant growth, air temperature and light. Managing each of the parameters of greenhouse crop production to consistently produce quality crops on time can be a challenge. Thankfully, the development of decision-support tools can aid greenhouse growers.

GROCALC is a suite of electronic grower decision support tools that include ALKCALC, FERTCALC and PGRCALC. These programs are useful for making calculations related to greenhouse crop culture including water acidification requirements, fertilizer solution and plant growth regulator (PGR) mixing. However, there are few or no tools available to help make calculations related to the greenhouse light environment.

Although light is frequently discussed in terms of instantaneous values such as the foot candle (f.c.) or micromole (µmol∙mˉ²·dˉ¹), the total photosynthetic light over the course of a day, known as the daily light integral or DLI, is becoming the preferred way to quantify light in a greenhouse. However, calculating DLI can be a daunting task. To continue the development of useful decision support tools, we created DLICALC (http://Extension.unh.edu/Agric/AGGHFL/dlicalc/index.cfm) as a tool to help growers manage the photosynthetic light environment.

A Solution For Growers
The inspiration for creating DLICALC came from growers’ frequent questions about using supplemental lighting to increase the DLI. Some of the most frequently heard questions were, “How much photosynthetic light are my lamps contributing to the overall DLI in my greenhouse?” and “How long should I run my lamps if I want to increase the DLI by XX mol∙mˉ²·dˉ¹?”

Since many growers still measure light in foot candles (f.c.) and, less often, micromoles (µmol∙mˉ²·dˉ¹), it is difficult to integrate those types of instantaneous light measurements into an integrated unit such as mol∙mˉ²·dˉ¹.

        

 

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DLICAL-Online-Tool

How DLICALC Works
The main function of DLICALC is to calculate the answer to two different questions:

1. “I currently have supplemental lights in my greenhouse. How long do I need to run them to achieve a target supplemental DLI?” For example, a young plant grower has high-pressure sodium (HPS) lamps that provide 70 µmol∙mmˉ²·dˉ¹ (530 f.c.) at plant height. They would like to increase their DLI by approximately 4 mol∙mˉ²·dˉ¹, but are unsure how long to operate the lamps.

2) “I am currently operating supplemental lights, what is my supplemental DLI?” For instance, a bedding plant grower has metal halide (MH) lamps operating from 6 to 11 a.m. and from 5 to 10 p.m. (10 total hours of operation) providing 50 µmol∙mˉ²·dˉ¹, but would like to know how much of their total DLI is from supplemental light.  

DLICALC is designed to answer these questions in two ways. First, it can estimate a supplemental DLI from your supplemental light source. Second, it can estimate hours of lamp operation to achieve a target supplemental DLI....

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