Drought effects nut fill

     A hot dry summer has played havoc with this year's pecan crop. The dry weather during the 1st half of the summer decreased nut size dramatically. Back in early August, we received some welcomed rains that seemed to perk up our trees. But unfortunately, the rain turned off again and the 100 degree plus temperatures returned. Hot, dry weather in late August through early September has had a major impact on nut fill.
     This morning, I cut open some nuts to check on the progress of nut filling and made some interesting observations.  The first cultivar I checked was Pawnee.  I had expected Pawnee to have nut filling problems this year because of its large nut size but was pleasantly surprised when I found a fairly well packed kernel. However, our Pawnee nuts will not be perfect. In an earlier post, I mentioned that kernel filling starts at the seed coat and works inward. Note that the top of each kernel half has grown much thicker than underside of the kernel. This will mean that, at harvest, our Pawnee nuts will have a concave appearance on the bottom of each kernel half.

    Next, I cut open a Osage nut, thinking that a super, early-maturing nut may be better filled. You can see in the photo that kernel deposition was similar on both upper and lower portions of each kernel half. At this point in the season, Osage has already started the process of shuck separation from the shell and kernel deposition is effectively complete. Note that there are still obvious voids in the kernel. This type of drought damage translates into a dry, crumbly kernel at harvest.

     Lakota ripens almost 2 weeks later than Pawnee and you can see that the nut filling process is still underway. If you zoom in on the photo, you can see translucent areas where kernel is still being developed. Amazingly, we are getting some rain today, with more forecast later in the week. Will these rains help Lakota fill out their kernels? Time will tell, but I think most of our cultivars and all of our native pecans will produce nuts with much lower percent kernel than in normal years.

A ray of hope

 

     Morning light filtering through a native pecan grove quiets the soul and lifts the spirit.

Dominating the landscape

     Last week, I wrote about tree age and response to drought. When I drove into work this morning, I noticed that our soybean crop provided the perfect example of how pecan trees come to dominate the landscape. In the photo at right, note the large native pecan tree marked with a yellow bar. The roots of this tree have suppressed the growth of the adjacent bean crop (out-competed the beans for water). The red arrow points to a distinctive line in the field of soybeans that marks the extent of the pecan roots domination over the bean crop. Even 60 feet away from the tree,  the beans are struggling for water. Outside the tree's influence the beans maybe drought stressed but the plants are 30 inches tall.  It is important to note that a tree's underground influence on its environment extends far beyond the "drip line" of the tree's canopy.

Grafting success

     Over the past several years, I've been preaching the importance of waiting until a young tree tells you when its ready to be grafted.  Here's proof that waiting until the tree is ready yields great results. We used a bark graft on this tree in early May and have grown a strong, central-leader tree that's now over 6 feet tall (even in a drought year!).
   There is one thing I want you to notice on this tree. In mid-August we removed all the wrappings from the graft union and painted that area of the tree with white latex paint. The paint prevents sun scald to the graft union (just like the aluminum foil) but more importantly the white paint gives us an obvious visual cue as to which trees have been grafted and the exact location of the graft union. In a field of 140 young trees,  the white paint on successful grafts will make it easy to locate trees that still need grafting in 2012.
      Grafting is the first step in training young pecans into strong, central-leader trees. To learn more about the tree training process go my 7 post series called "Training young trees" .