Dear Hugh,
thanks for weighing in on this discussion.
Several Q's.
Does this rhythm, release of dissolve solids (sugars & amino acids) apply to all families of plants? i.e. do broccoli or potatoes, say, shed carbon from their roots?
Dear Mark,
In general I would say yes. Definitely broccoli and potatoes shed carbon. Different plants shed a different mix. Corn, for example, sheds a clear, jelly-like mix rich in polysaccarides, which are polymer (chain) sugars. Lettuce, which can be a vigorous carbon shedder, gives off a milky latex. Buckwheat sheds a mix that really stimulates the microorganisms that make phosphorous available, while hemp gives off a mix that stimulates those microbes that make potash available. Potatoes, need plenty of available potash but don't give off the rights stuff to make it available in a soil that is low in accessible potash. So potatoes give a much better yield following hemp--if we could only grow it in the US! But from this I guess you'll see some of the major reasons for crop rotations, cover cropping and the like.
What are the ramifications in term of C4 synthesis, in other words do C4 plants constantly hold their Brix high under high light & temperatures?
While I've heard of C4 synthesis I'm not clear at the moment on this terminology. Could you bring me up to speed?
What portion of the plant do you sample?
Any portion I choose (generally not the root) depending on what I'm looking for. Usually I would sample where I think the best photosynthesis is occurring or where I might expect sugars to be most concentrated at any particular time of day and/or growth cycle.
Are these principles continuous into flowering and fruits periods?
In general where sugars are being concentrated in fruit the plant is NOT sending these to the roots. That's only at the end of the growth cycle, and by then they aren't needed in the root zone anymore anyway. This is an example of sampling where I'd expect sugars to concentrate.
I have always read that Boron is toxic to many crops but "puts weight into hay"?
Boron tends to put weight in anything from apples and pears to radishes and beets. Without boron calcium (there's the weight) is not fully accessed by the plant. And, yes, rare though it seems to be, boron may be toxic. This is mostly a western problem where rainfall is sparse. Boron is one of the most soluble elements in the soil, and may leach easily if not tied up in living organisms. A good case in point is alfalfa, which is particularly boron sensitive. When deficient its leaves will be deformed, when toxic it's leaves will discolor.
In general one does not want nutrients to be soluble in the soil. That is a terrible misconception promulgated by the fertilizer industry. What you want is insoluble but available nutrients--which generally means keeping the microlife of the soil robust and healthy. I would call this a no-brainer, but most of modern, university level agriculture is looking for nutrient solubility in their soil tests and everywhere else. Tch, tch!
Hugh
Thanks
In Love & Light
Markess
> 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
