Dear List, I realize I'm entering this discussion a bit late.
Brix can be very revealing. But it is a bit more complex than just "High brix equals high sugar and good taste with insect and disease resistance." Brix is a measure of dissolved solids, not all of which are sugars by any means. Salts and amino acids enter the picture for starters. High brix in the morning generally indicates the plant has not translocated its sugars to its roots and shed them to the soil overnight, feeding the soil food web. This, believe it or not, is highly desirable. If the plant does this it gets the soil food web stoked up and cranking out highly elaborated nutrients. Probably the most important of these are complex amino acids. If the plant gets its nitrogen as amino acids instead of nitrogen salts the assembly into proteins in the cells becomes rich and full blown as there are no nitrogen salts to interfere. Then one gets plenty of long chain aminos. That's mostly where the great flavor comes in for people. But for insects with their more rudimentary digestion they greatly prefer short chain aminos and can't digest the long chain stuff. So they leave such plants alone. If you have (relatively) high brix in the morning, then this is undesirable. Almost surely it means boron deficiency, as the plant would otherwise respond with adequate boron by translocating its carbon fixings (mostly sugars) to the roots at night--what Elaine Ingam calls carbon shedding. When a plant sheds carbon compounds abundantly at its roots it really grows like gangbusters. If you can get this going well enough you can grow corn as a soil improvement crop without fertilizer while getting superior (in every way) yields. With a BD program that's really clicking this is nearly a cinch. Horn clay, however, is a must. High brix in the afternoon means your plant has been building an abundant inventory of sugars during its daytime photosynthesis. That's great stuff, of course. But take care to consider what time of day you take your reading. Also, sometimes plants will send their sugars to the roots in the afternoon if the barometer drops enough, anticipating a severe thunderstorm. If you take your reading just before such an event and get low brix, you have a healthy, with-the-program plant that has adequate boron despite the low reading in the afternoon. So use your refractometers intelligently. They are great tools, and probably the quickest way to evaluate low boron (which may be occurring in more than 70% of crops in the US). Best, Hugh Lovel
