Is morning sun the most important for turf? It depends.

I used Storify to string together some related tweets and images over the past few years. That service is shutting down. I’ve moved a “story” about light, shade, and time of day to this Twitter moment.

Most important time of day for sun to reach turf

This is a demonstration using temperature and light data on 10 minute intervals for all of 2014 at Mobara, Japan. I chose Mobara because that weather station has the data I was looking for on 10 minute intervals, and because it is close to Habu CC (now ゴールデンクロスカントリークラブ), where I was the greenkeeper in 2000 and 2001.

My hypothesis about the most important time for sunlight to fall on a turfgrass surface, or conversely the worst time for shade to occur, goes like this:

The most important time for full sunlight to reach a turfgrass surface corresponds to the optimum temperatures for photosynthesis for that species. More specifically, the longer the duration of time at which the PPFD on the turf surface is near the maximum the grass can use, while at the same time the air temperature is close to an optimum for photosynthesis, will optimize turf performance.

More about that hypothesis in this post.