Tuesday, November 27, 2018

Pawnee needs crop load management

    Pawnee is one of the most popular cultivars grown in our area (photo at right). The popularity of Pawnee is based on two factors; the nuts are big and they ripen early. However, Pawnee is a high maintenance cultivar. Pawnee is susceptible to pecan scab and the crop needs to be regulated to insure well filled nuts at harvest.
     Today, I collected a few Pawnee nuts from trees at the old Pecan Field Station. In previous years, I reduced the crop load of overloaded Pawnee trees by using a trunk shaker. Now that I've retired from the University, the field station has been abandoned and Pawnee was allowed to over-produce in 2018.

    I collected Pawnee nuts from two areas. The first was a mature orchard with nuts hanging from every terminal. Prior to 2018, these mature Pawnee trees received a good summer shake every year they loaded up with nuts. The second spot was in a young orchard, just starting to produce nuts. Like all young pecan trees, these Pawnee trees had not reached the age when over-cropping becomes a problem.  The young tree produced normal-sized Pawnee nuts while the over-loaded trees produced much smaller nuts (photo above). When I held those smaller nuts in my hands I could already tell the kernels inside were going to be shriveled.

    As I suspected, the kernels produced by the over-loaded Pawnee trees were smaller, poorly filled, and even darker in color. The two kernels on the far right in the photo above were so paper thin that they would be inedible.
   Pawnee is a cultivar that requires a high level of care but when treated right can produce beautiful pecans. Growing Pawnee profitably means adopting a good scab control program and shaking off nuts during the years when the trees set an over-abundant crop.     

Thursday, November 22, 2018

Thanksgiving harvest

Harvesting native pecans near Chetopa, KS

  Thanksgiving is an American Holiday with a long tradition of family gatherings and roast turkey dinners. But here in pecan country, today's bright sunshine and dry soil conditions makes it the perfect day to pick pecans. By mid-morning, I could hear the familiar drone of pecan harvesters working in the native groves near my farm. I took a quick drive around the area and found that every grower was celebrating the Thanksgiving holiday the same way,  by picking pecans. I can't think of a better way celebrate the fall harvest season. 

Sunday, November 18, 2018

Evaluating nut samples

    Last week we had a light snow fall that covered the pecan grove with about two inches of wet snow (photo at right). The snow turned out to be only .16 inches of precipitation but the cold weather that followed meant that the orchard floor stayed snow covered and wet for several days. Wet soil conditions means that I was unable to finish harvesting my pecans. So, I parked the tractors and moved inside to start cracking nut samples I had collected from the pecan breeding block.
   At shuck split, I collected at least 25 nuts from each tree. I let these nuts air dry for several weeks then began the process of measuring, weighing, and cracking nuts.
    The first step in my evaluation process is to record the diameter size class of each nut in the sample. I do this because every nut ever brought to a shelling plant is run through a nut sizer in preparation for cracking. Pecans are sized by a series of steel cages with various size slots for nut to fall through. The sizes are recorded in sixteenth of an inch increments. A size 12 pecan falls through an opening 12/16 or 3/4 of an inch wide. I use a series of end wrenches (measured in 1/16 increments) to simulate the nut sizing process (photo above). In the photo, note a nut stuck in the 15/16 wrench. This same nut passed easily between the jaws of the 16/16 wrench (1 inch) and would be classed as a number 16 diameter pecan. By measuring every nut in a sample I can develop a size profile for each clone. The sample I was processing when I snapped these pictures was 50% size 15 and 50% size 16 nuts.

    The next step in my nut evaluation process is to weigh 10 randomly selected pecans. This weight will give me an average nut weight but can also be used to calculate average nuts/pound. I use a gram scale to weight the nuts (photo at right).  This sample weighed 101.97 grams. This nut averages 10.197g per nut and if you divide the conversion factor of 453.6 by the average nut weight in grams you'll find that this particular pecan averages 44.48 nuts/lb.
    With the inshell nuts weighed, I next use a hand cracker and shelling tool to extract the kernels from the shell. In cracking the nuts, I use a light touch because I take great care in trying to extract full kernel halves from every nut.
    Once all the kernels are removed from the ten nut sample, I weight the kernels. This sample had kernels that weighed 54.91 grams. By dividing the kernel weight by the nut weight and multiplying by 100, I can calculate the percent kernel for this nut sample. In this case the math works out like this:  (54.91/101.97)*100=53.85% kernel.
    In addition to the hard numbers that I record on nut size, weight and percent kernel, I take notes on kernel color, ease of extracting full halves, adherence of shell packing material, and any glaring kernel defects.
    As I collect this information year after year, I should be able to recognize those trees that produce quality pecans every year. Hopefully, that will lead to some new cultivars.

Saturday, November 10, 2018

Hard freeze drops pecan leaves and kills green shucks

Kanza nuts right after a deep freeze
    Last night we received our first killing freeze as temperatures dropped to 15 degrees F (-9.4 C). For pecan trees, temperatures need to drop below 26 degrees F (-3.3 C) to kill green plant tissues. During the final days of Fall a hard freeze results in the hastening of leaf fall and killing still-green pecan shucks.

    Since the deep freeze forecast was made earlier in the week, I made plans to make a visual record of the impacts of sub-freezing temperatures on Kanza pecan trees. In the photo above, my Kanza tree was still holding a leaf crop up on November 9th. After a blast of cold weather, every leaf from the very same tree had dropped off by mid-afternoon.

    The photo above shows that Kanza shucks were still very green before the freeze but turned dark and water soaked after being subjected to temperatures below 26 degrees F. When green shuck tissue freezes, cell walls are destroyed by the formation of ice crystals. At first the shucks look water soaked but they will dry out and turn black in just a few days. As the shuck dries, it pulls back away from the nut and will finally open enough to allow the nut to fall free.

Wednesday, November 7, 2018

Comparing Kanza and Hark nuts

   This fall I have been taking a closer look at the performance of Hark as it compares to Kanza. Earlier this Fall I collected a nut sample from a Hark tree and an adjacent Kanza tree. I weighed out these samples and cracked the nuts to determine percent kernel.
   As you can see in the photo above, Hark produces a nut that is slightly larger than Kanza. The shell markings on the Hark nut are very similar to its Major parent. Both Major and Hark shells are covered with many small black speckles. In contrast, the Kanza nut shell is light colored and has few black markings. Even though Kanza has Major parentage the shell of Kanza is more reminisent of its other parent, Shoshoni.

    This year my Hark nuts yielded more percent kernel than my Kanza nuts (photo above). Hark kernels also appeared larger. However, Kanza kernels were lighter in color and appeared more attractive than the Hark kernels. For the first time, I noticed that the dorsal grooves on Hark kernels are narrow and can trap packing material. In fact, if you look closely at the left dorsal groove of the left Hark kernel you'll see some trapped packing material.
   Even though Kanza still remains my favorite cultivar, I plan to graft more Hark into my orchard. Hark is scab resistant and a good pollinator for Kanza.