Spot the difference

It is now a month since we started to grow the baby salad leaves in the new polytunnel and using the LED lights to supplement daylight hours and we are certainly starting to see the difference. To try to ensure that we are operating as efficiently as possible we are trialling the use of the lights when the light is insufficient for growing and to extend the day.

We are currently monitoring the daily light integral, which is the cumulative amount of light received by the plants during a 24-hour period. We have a number of data loggers that provide a reading every 4 seconds and so when we see the light levels drop below a certain reading we know to switch the lights on.

The results have been very encouraging, with the leaves not only growing faster, but in a way that we have never seen before. The trays are fuller, brighter, more vibrant in colour and the leaves are of an amazing quality.

When compared with trays of the same age, grown in the main polytunnel without the use of lights the results are unrecognisable.

Despite being grown at the same density the trays are much denser and the leaves far more erect. In the main polytunnel the plants are more leggy as they look for light (on the right below), whereas under the lights the plants (on the left below), are putting their effort into leaf growth rather than stretching for light.

The colours are intense in the trays under lights and the leaves are far more succulent, seen on the left below:

The rate of growth is also very different between the two growing conditions, with the leaves developing much faster under the lights.

And when you look closely the difference is very clear, with far more advanced leaf growth (above in the photo below).

As for taste - the leaves are succulent, fresh and crisp. Cut daily for some of our local eating establishments, such as The Sheppey Inn and The Bocabar, they provide a rather unique addition to a variety of dishes, from speciality salads to high-end burgers.

All the results so far have been observed on trays that are placed on the floor so 171cm beneath the lights, however through the simulations undertaken by GN UK the manufacturers, it is recommended that the trays should be 145cm from the lights.

As a result, we are experimenting with trays at different heights and monitoring their daily progress, once they reach maturity we can then establish at which height the staging to support the trays needs to be. 

We now wait and eagerly watch with keen interest and excitement.