Technical Issues
There were some technical issues that resulted in only a partial data set for November, 2024 and January, 2025. Data from December, 2024 is not available. The technical issues have been resolved and more complete datasets will be available moving forward.
Background
Daily light integral (DLI) and photosynthetic photon flux density (PPFD) data is important to greenhouse production because they measure the amount of light that is available to the crop. This data can be used to adjust the growing environment, such as irrigation and carbon dioxide levels, to optimize photosynthesis and crop yield.
DLI is the total amount of light within the photosynthetically active radiation (PAR) spectrum (light wavelengths of 400-700 nm) that impacts a surface in a day. It is measured in moles per metre squared per day (mol/m2/day).
PPFD is the total amount of light within the PAR spectrum that impacts a surface every second. It is measured in micromoles per metre squared per second (µmol/m2/second).
Objectives
The DLI and PPFD Data section of this blog provides greenhouse producers in southwestern Ontario with outdoor light levels on a regular basis year-round. It is meant to serve as a record of the amount of light this location received on a daily basis throughout the year.
Each blog post in this section contains tables with the available data for a one month period and and Excel file with data from previous months.
NOTE: This data is provided for information purposes and does not represent the amount of light at any specific location. It is an approximation and does not represent exact values.
Materials and Methods
The data was collected using a DLI-600 sensor from Apogee Instruments. It measured the extended PAR (ePAR) spectrum (400-760 nm), which includes far red light. The sensor was placed 90 cm off the ground outside of a greenhouse near the Leamington-Kingsville border in Ontario.
A NanoLambda light meter was also used to measure irradiance (W/m2 for 340-1010 nm) and PPFD (µmol/m2/second for 400-700 nm) at a specific date and time. It was placed beside the Apogee light meter when measurements were taken.
Available DLI data is presented for each month (Table 1), for each day (24 hr period) of the current month (Table 2) and the available DLI and PPFD data is presented in the attached Excel sheet in the last section.
DLI Data
Table 1: Monthly DLI data for Leamington-Kingsville.
| Month and Year (number of days of data) | DLI (mol/m2/day) (average ± standard deviation) |
| January, 2025 (15 days) | 19 (± 5) |
| November, 2024 (8 days) | 10 (± 5) |
| October, 2024 (13 days) | 34 (± 10) |
| September, 2024 (29 days) | 39 (± 14) |
| August, 2024 (27 days) | 49 (± 12) |
| July, 2024 (25 days) | 56 (± 12) |
| June, 2024 (22 days) | 59 (± 12) |
Table 2: Daily (24 hr period) DLI data for Leamington-Kingsville for January, 2025.
| Date (day/month/year) | DLI (mol/m2/day) |
| 16-Jan-25 | 8.9 |
| 17-Jan-25 | 24.4 |
| 18-Jan-25 | 8.7 |
| 19-Jan-25 | 15.7 |
| 20-Jan-25 | 22.7 |
| 21-Jan-25 | 20.9 |
| 22-Jan-25 | 16 |
| 23-Jan-25 | 15.8 |
| 24-Jan-25 | 18.4 |
| 25-Jan-25 | 21.8 |
| 26-Jan-25 | 22.3 |
| 27-Jan-25 | 28.4 |
| 28-Jan-25 | 18.3 |
| 29-Jan-25 | 21 |
| 30-Jan-25 | 24 |
| January, 2025 DLI average ± standard deviation | 19 ± 5 |