U.S. Standard sieves No. 10 (2 mm) and 20 (841 µm). Sieves are used to determine particle separate size fractions for material quality and mechanical properties evaluation and classification.
Granted, the last two AJ dispatches were heavy hitting on the technical side of things. And apologies to all who skipped reading them which I’m sure is most of you. Now, how about sharing something a little more down to earth for a change? What I had in mind was a recent encounter with that humble, often neglected but ever so useful soil conditioner, lime. Comes a time in the course of one’s daily rounds when something happens that recalls a basic truth, self-evident, incontestable it would seem, yet worthy of relearning. This moment came to me back in November while applying lime to a field that had, according to a certain soil test, gone quite acid with a measured pH of 5.3. The same test came with a recommendation to apply 1 ton/acre agricultural limestone to move the pH back up to where it should be, a mildly acidic 6.0 to 6.2. The telltale moment struck when I realized that the hopper on my Gandy drop spreader was running out much faster than it should have, which was set to run the last calibration I had marked for this particular brand of pelletized lime. Something wasn’t right, so I stopped to investigate. Continue reading
If you’ve just landed here for the first time, this is a continuation of my October 17 grand opus Interrogating Plant Status in the Key of F where I pontificated, eruditely I hope, on the phenomenon of fluorescence emission induction in plants. If fluorescence induction sounds Greek to you, I strongly urge that you go back and read through that blog post before proceeding. If you’re an expert at PAM fluorometry then everything that follows should be old hat, except for perhaps the fluorescence emission data which is the grist of this second go-round. Continue reading
If plants could communicate with their tenders, what would they have to say?
This isn’t the preposterous hypothetical question it appears because plants do in fact, speak a language, though no human ear can perceive it. The language of plants is embedded in a complex of biochemical signals that are constantly venting off in fragments of cryptic semaphore, day and night, without surcease until the very end. Scientists have devised numerous ways of interrogating a plant’s vital signs via semiconductor devices, optical sensors and microchips and converting the signals to quantitative information about plant status: a data stream language, if you will. Photosynthesis is perhaps the most familiar trait distinguishing plants; it is, without exaggerating, the engine powering twenty-first century society, for example: providing our daily sustenance, food, and the oxygen we breathe; energy production needed to heat our homes, cook our food, broadcast the internet, and fuel our modes of transportation. Human knowledge of photosynthesis dates back 350 years; yet our ability to elicit phenomenological and biophysical information about its inner mechanisms has only emerged, gradually, since the 1930s. Chlorophyll fluorescence induction, or “F” as it’s known by plant scientists, is one powerful technique used to probe the performance and well-being of photosynthesis. Continue reading
A pumpkin fit for Linus. This behemoth weighed 2,624.6 pounds (1,190.5 kg), claiming a new world record October 9, 2016 for Belgian grower Mathias Willemijns at the Giant Pumpkin European Championship in Ludwigsburg, Germany. How much further up can humans push the yield curve? Image credit: Thomas Kienzle/Agence France-Presse/Getty Images
An article in AgFunder News published February 1, 2018 reported that a bag of corn had a yield potential of about 500 bushels per acre. In 2017, the US average corn grain yield hovered around 176 bushels per acre, 2 bushels above 2016 and far away from the AgFunder News report. Meanwhile, in 2015 David Hula of Charles City, Virginia produced 532 bushels per acre; the year before, Randy Dowdy of Valdosta, Georgia marked 504 bushels per acre. This caught many experts off guard, sending them back to their research plots to figure out what they were doing. Some even criticized the yield figures as faked. In fact, the biophysical limit for corn grain yield was estimated by Matthijs Tollenaar in 1985 at ~1,320 bushels per acre using optimized, yet realistic, levels of quantum efficiency, grain fill duration, harvest and leaf area index parameters. At the time Tollenaar published his estimates, Herman Warsaw had just produced a (then) record-breaking 370 bushels per acre on his Illinois farm. Continue reading
|Yukina savoy (Brassica rapa variety). Photo taken January 2018 after several nights down to 16o F (-9o C).
Across a broad swath of North America, January isn’t prime time for outdoor plants, nor for those veteran dirt hogs dreaming of tilling the soil, sowing seed, and coddling the various tribes of the vegetable kingdom. North Carolina is not exempt from this seasonal hiatus despite the usually mild winters. Witness January 2018: opening with an icy blast of polar vortex strong enough to spawn what is being called a bomb cyclone (!) further north, thankfully far removed from my perch. Still, poignant traces of leafy green bolt skyward here in the winter garden undaunted, longing to capture the sun’s rarefied gleam. One such leafy green is yukina savoy, a relatively obscure, hardy Asian vegetable that can hold its own against freezing temperatures every bit the equal of southern mainstays like collards and kale. Continue reading