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August 26

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August 26

 

 

 

 

General view Aug 26, 2003Our field is looking a bit ragged.  The leaves are starting to senescence or die. Our field is at physiological maturity (R9), which means the seeds are as big and heavy as they are going to be and we're just waiting for harvest.  So, if it were to rain, it wouldn't really help the plants. Now, before we can harvest this field the seeds will have to dry down or lose moisture that's in them and the stalks will have to dry, too.

Drought stressThe heat and drought have speeded up the plants' maturation process. The leaves are yellowing and drying up.  It's been 14 days since we've had a rain and that rain was just a sprinkle.  The hottest day so far in August was on August 21st when it reached 106 F.  That's hot!


Front R9 plantThis is the front of an R9 plant.  The dried floral parts have stuck to the head the whole summer. The head is starting to dry down to a harvestable moisture content.  You know, if you stare at that head long enough, you can almost make out eyes and it starts to look like a space alien!  What do you think? Sorry, I've been out in the sun too long.


Back head of R9 plantThis is the back side of the previous head.  It has a nice buttery-yellow color and the bracts have turned brown.  The rest of the head will eventually turn brown. 


Cross sectionThis is the cross section of the same head. Like most of the heads we've observed lately, this one has the brownish areas indicating head moth larvae activity.  There's a little bit of Rhizopus head rot visible, but it doesn't appear to be too bad.  


Large outer seedThe small, shriveled seeds are from the center of the head, while the larger seeds are from the outside edge. 
This is what I've been worried about for a couple weeks. This is an example of drought stress and it will have a serious impact on yields. 


KernelThis is a seed that is physiologically mature. Notice its color is more grayish than when we looked at a seed a
couple weeks ago.  It still has too much moisture inside it to be harvested and stored in a grain bin.  The seeds and sunflower heads have to be dry enough that seeds can be separated from the heads in the harvesting process. 


Stalk lodgingAt this point in the season we'll start to see things, such as this stem that has lodged or broken over, that we
haven't seen throughout the growing season. This damage is due to the stem weevil that we've talked about before.  As the plants mature and dry down we'll see more stalk lodging.  Farmers don't like to see lodged plants because these lodged plants won't be able to be harvested. 


Large head bent stalkWe've talked about sunflower heads being too large and this one is a good example.  This plant didn't have other
plants very close, so it compensated for that extra space by developing a very large head. This head was so heavy that it broke the stem -you can see the brown break-line about ten inches below Dale's hand.  This head will probably hang on and make it to harvest, but the seeds will likely be shriveled. 


Headless purple plantWe thought this was an interesting plant. Notice, it doesn't have a head and its leaves and leaf petioles (stems) are purple.  I don't know why the head is missing, but the reason the leaves are purple is because the head is gone. In a healthy plant, sugars that are made in the leaves through the process of photosynthesis are transported and deposited into the seeds, but because this plant's head is gone, there's no place for the sugars to go. So, the leaves are purple.  


Golf ballWell, there's the same golf ball we saw when we were looking for emerged seedlings in May.  It was easy to see with the leaves starting to die.