Saturday, April 18, 2015

Inexpensive LED Experiment

This $40 light fixture is affordable to buy, and operate as opposed to the expensive high powered grow lights.  It's rated at 36W, 3600 Lumin LED with 724nm (4000K).  This is on the edge of the optimum 610-720 nm range, but since it appears to cast a white light it's probably a fairly wide range, so I wanted to see if it would be appropriate for starting seedlings.  I hung the light about 9 inches from the top of the soil blocks.  The temperature was maintained at about 70F.

These LED light fixtures were available at Home Depot and Costco

This box is built with shinny Mylar to reflect as much light back to the plants as possible.

I used a paper shop cloth to wick moisture into the soil blocks.  This experiment turned out to be a good combination - saving the cost of plastic pots, and providing moisture without daily attention. Soil blocks also air prune the roots and avoid the problems associated with roots binding in plastic pots. Transplant shock is also minimized because the roots are not disturbed. 

After 2 weeks I'm very pleased with the results.  The seedlings are dark green and full of vigor.  .
Kale and Squash both responding well to the LED light

I initially filled the trays with water and the soil blocks soaked up too much water.  They held their shape, but they were 100% saturated. This later caused some mold to grow.  I was able to control the mold by misting with 3% hydrogen peroxide.   Next time I will take care to add water as needed.  

The LED lights will last a lifetime.  Florescent bulbs are half the cost, but they loose brightness over time.  Halide and mercury vapor bulbs are hot, expensive and consume far more power. It may be that lights designed specifically for photosynthesis will work better, but I'm growing a few vegetables -  not earning a living from my garden.  My conclusion is that these lights are adequate and affordable.

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