Tuesday, March 31, 2015

Spring fertilizer application

    Spring has arrived a little later than normal this year. I've been checking pecan buds for several weeks now and have only recently seen signs of spring bud growth (photo at right). When the outer scales of primary buds split I know its time to spread some fertilizer. With light rain showers in the forecast, today was a great day to make our regular spring time fertilizer application.
    We have been following the same fertilizer program for over fifteen years and have had good results--higher yields and more consistent nut production. Remember, we make two fertilizer applications per year on our bearing pecan trees--Early spring and mid October. Today, we applied 69 lbs. N/acre and 60 lbs. K/acre. This fall, we'll spread another 46 lbs. N/acre.

   For today's fertilizer application, we used urea as our nitrogen source and potassium chloride (Potash) as our potassium source. We had our local fertilizer dealer mix 3 parts urea and 2 parts potash (by weight) and then used a rented fertilizer buggy to spread 250 lbs. of the mixture per acre (photo at left).

Thursday, March 26, 2015

Tree thinning: Sticking to the plan

    Over the past several years we have been thinning a block of Kanza trees. Yesterday we continued that process by removing several more trees (photo at right).
    Four years ago I laid out a tree thinning plan  that maps out which trees will be removed and which will stay.  At that time, only trees in the northeast corner of the block were actually starting to crowd so I decided to starting removing trees on a as-needed basis. Each year we measure tree diameter then use that information to determine which areas within the orchard might need thinning next. We have been removing 5 to 7 trees per year since 2012. Yesterday we cut down 7 trees.
      In the map at right, the diameter of each tree in the orchard is represented by a green ball. The larger the ball, the larger the diameter. Trees marked out by a black dot are the trees we cut down yesterday. This map also gives you a good idea of the progress we've made in thinning the entire orchard. As of this year, we've removed 25 of the 72 trees slated for removal in the original thinning plan.
    Thinning a pecan orchard over a period of several years offers several real advantages over thinning the entire planting at one time.
  • the impact of tree removal on total orchard  yield is minimized.
  • tree removal costs are spread out over time.
  • trees are removed before overcrowding can cause limb loss and yield reduction.

Friday, March 13, 2015

Dormant pruning last year's bark graft.

   Last spring I showed you how I top-worked a young Jayhawk tree. Then last summer I showed you how I trained and pruned this tree to create a new central leader from the sprouted scion. Now its time to revisit this same tree for some dormant pruning.
    In the photo at right, the bark graft I applied last year is painted white. I trained a single shoot from the scion to form a new central leader securing it to an eight foot long wooden stake to prevent wind damage. The graft grew an amazing 6 feet tall in a single summer.
    Last summer, I spent a lot of time pinching off stalked buds from this tree.  In a close up photo (at left) of the new shoot, you can  clearly see the stubs left behind where I clipped off  stalked buds. But, you can also see that I have some nice secondary buds that should break out this spring to form wide-angled lateral branches.
   Further up the stem I found some stalked buds that developed later in the summer. I used my clippers to carefully remove all stalked buds along the stem (photo at right). I surely don't want narrow-angled limbs developing about seven feet off the ground.
    One of the disadvantages of top-working a larger tree is that you end up doing a lot of detailed pruning several rungs up a ladder. It a good thing I've got an eight foot orchard ladder at the ready.
    At the very top of this tree the central leader totally breaks down (photo at left). Since I've got a tall enough ladder, I pruned the top of the tree to a single shoot. This meant removing all competing lateral branches to leave the strongest growing shoot.
   This spring, I'll make directive pruning cuts to preserve the central leader one more time. It won't be long before this tree grows too tall for easily accessible detailed pruning cuts. But that's OK. I'll be able to spend more time on younger trees and new grafts.    

Tuesday, March 10, 2015

Dormant pruning a young pecan graft

    This week's spring-like weather gave me the opportunity to get outside to trim some newly grafted trees. My first stop was at a small tree that had made an impressive 4 feet of new growth last summer. In the photo at right, note that the graft union is painted white and the scion is supported by a bamboo stake. The fence post is in place to hold a deer cage that protected the tree from browsing and buck rub (cage removed for the photo).
    As you can see, I made a good start on developing a strong central leader tree but the tree developed several branches near the top of the tree that, if left to grow this year, would create problems for maintaining a single dominant tree trunk. Let's take a closer look.
    Just above the graft union, some small lateral limbs have developed (photo at left). I'll be leaving these branches alone for now to help build greater leaf area on this tree. With more leaves along the lower portion of the trunk the tree develop a thicker and stronger central leader.
    My main objective in pruning this three is to define the clear central leader at the top of the tree. In the photo below you can see that the top of this tree is divided into 4 major shoots. Three of those shoots actually developed from stalked buds that sprouted into branches late last summer. I took a close up photo of two of those 3 branches (circled in red) so you can see that bark inclusions were already starting to form (yellow arrows). I pruned out all 3 branches that had formed from stalked buds.
   After pruning out the 3 side branches, I noticed that the central leader was still cover with stalked buds (photo at right). The longer shoot I pruned out with my clippers but I could snap off the shorter stalked buds with my fingers. With all stalked buds removed I was left with a central leader with prominent secondary buds.
    The photo above gives a before and after look at pruning this young grafted tree. I carved out a single central leader, removed all stalked buds, and allowed lateral branches to develop on the lower portion of the trunk (above the graft union).
    I'll need to come back to this tree  after the buds break to make directive pruning cuts to maintain a strong central leader.

Tuesday, March 3, 2015

Kernel color changes over time

   Most pecan lovers know that pecan kernels will turn reddish-brown if they are kept at room temperature for an extended period of time. The other day, we were discarding nut samples collected back in the fall of 2013 from our pecan breeding project. While most kernels had turned dark with age, I was surprised that one sample had retained a lighter color. In the photo above, I've placed kernels from this year's Kanza nuts next to one-year-old kernels harvested from three trees in our breeding plot. The straw-colored kernels of fresh Kanza nuts are the gold standard for fresh pecans. Without refrigeration, the majority of one-year-old kernels had turned dark and looked much the same as the kernels pictured above from trees KT214 and KT334. However, the kernels from tree KT342 stood apart from all other samples as having kernels that retained a fresh-looking appearance.

    With my curiosity peaked, I dug through our 2014 nut samples to find the sample from tree KT342 so I could compare it to the year-old nuts I already had in hand. The photo at left reveals that kernels from this tree do not change color even after a year in room temperature storage. Unfortunately, fungi had infested the 2013 kernels from tree KT342 so I wasn't able to perform a taste test to see if the the kernel had developed any rancidity in a year's time.
    Now we have another cultivar attribute to study in our breeding project--kernel color and shelf life. And for all those interested, KT342 resulted from a cross of Pawnee and Greenriver.