It’s been a good week for productivity I feel. The Blumat drippers are installed in the growth chamber, only not quite calibrated. I only have one tensiometer, so that takes a while to install at each plant point and then manually adjust the Blumat valve to get the proper water tension setting. But this is something that I should only have to do once. The tomato seedlings are doing well, ready to transplant into the soil tomorrow. The growth chamber controls have been working well.
One of my objectives is to measure water use. A scale under each plant, or lysimeter would be the ideal way to do this, however making a big enough soil pot for each plant seemed to hard. My plan is to simply measure how much water is used daily by weighing the water reservoirs for each plant daily. If the water tension remains roughly constant and soil drying is minimal, this should give me about the same information. Water use is closely coupled to absorbed radiation, so higher water use is another indication the plants nearest the south wall are able to use that additional light.
I’ve also gone back to my ray tracing project. I was unable to find a forward ray tracer that would work for my needs, so I wrote on myself in c++. This is close to finished, but this week I went back to simplify the code and add documentation. This will be released as open source eventually. The final project is to add the proper functions for diffusion of reflected and refracted light. A preliminary 3D scan of one of my little tomato plants worked quite well so I think that is doable. The trick with this is that the scans will get progressively harder as plants grow bigger.
Finally, I was able to clear the brush on the field south of the test greenhouse and get setup for measuring albedo. My earlier calculations didn’t indicate that albedo is very important, but I’d like to measure it all the same. Adding a reflective sheet on the south side of the greenhouse in the winter, increasing albedo, is realistic option if it adds light. Especially in my locale where snow cover is often minimal.
Sun Aquasystems 