Monday, January 8, 2018

Yields from a young pecan orchard

Harvesting a young orchard
   Frequent questions new pecan growers have usually revolve around questions of when and how much young pecan trees start to bear nut crops. Back in 2002 we planted one-year-old Colby pecan seedlings to start a new block of trees. Most of these trees were grafted in 2005, with every tree in the planting successfully grafted by 2007. We grafted three cultivars; Faith, Gardner and Lakota. The trees produced a handful of nuts by 2010 and as the trees grew larger nut production steadily increased.
   By harvest time 2017, the trees in this orchard averaged over 7 inches in diameter and were producing a full crop of nuts. Lets take a look at this year's yield data.

    This field of young trees contained 32 trees of each cultivar. We harvested each cultivar separately and then calculated yield per tree. In the chart at right, I list the average yield per tree and present a measure of the variation in yield observed between trees grafted to the same cultivar (mean yield +/- standard deviation).
 Twelve to fourteen pounds of pecans per tree doesn't sound like a lot of pecans but, when added up on a per acre basis, the income generated by these young trees is significant.
   The trees in this orchard were planted at a density of 27 trees per acre. This means that Gardner produced 327 lbs/acre, Faith produced 378 lbs/acre, and Lakota 359 lbs/acre. I sold these nuts for $3.00 per pound which translated to a gross return that ranged from $981 to $1134 per acre depending on cultivar. That's not bad for a 15-year-old pecan orchard.

Friday, January 5, 2018

Native pecan yield 2017

    Every year I learn something new about native pecans. This past summer (2017), the branches of our native trees were hanging low with, what I thought, was a heavy nut crop. However, this past year our native trees fooled me. The limbs were weighted down with a huge leaf crop that hid a below average nut crop.
    It was only when we began shaking trees, that we discovered the true nature of the 2017 native crop.

     For 37 years we have be recording the yields from 6, one-half-acre plots of native pecans. The 2017 yields are presented in the table above (numbers listed in Lbs.). The half-acre plots are labeled A thru F.  We always harvest each plot twice; the first time in mid November and then again in late December. The weight of nuts collected at each harvest time is listed above.
    The 37 yield average yield/acre for these plots is 1150 lbs. The 2017 crop averaged 798 lbs./acre or 30% below average. What was interesting about the 2017 harvest was that we harvested almost one third of the crop (32%) during the second harvest. Prior to 2017, second harvest yielded 15% to 20% of the total crop. Why the difference in 2017?
    I blame the heavy leaf crop. During the first harvest, our pecan harvester had a tough time digesting all those leaves. A lot of nuts ended up riding on a stream of leaves and getting blown out of the back of the machine. When we went back for the second harvest, the leaves had been chopped up and partially broken down by our first harvest operation. During the second pass over the field, the harvester could easily process the ground up leaves and orchard floor was swept clean of nuts.  
   A below-average nut crop and an above-average leaf crop in 2017 is a sure sign that the potential for the 2018 native crop will be huge.

Sunday, December 31, 2017

Stuart in the north

Stuart nuts at shuck-split

     Stuart is one of the oldest and most widely know pecan cultivars. The tree had its origins in a seedling orchard planted in 1874 outside of Pascagoula, Mississippi  using nuts procured from Mobile, Alabama. The tree gained local notoriety for excellent nut production. In 1893, a severe storm blew the original tree down. Fortunately, the tree re-emerged from a root sprout and the tree began bearing nuts again by 1902.  
     The first attempt to graft Stuart was largely a failure. In 1886, sixty grafts were attempted but only one grew successfully. Graft failure was all too common during the late 1800's as nurserymen used grafting techniques commonly used for fruit trees when trying to propagate pecans. However, by the early 1900's,  grafting techniques specifically developed for pecan improved success rates dramatically. From the 1920's to the 1950's Stuart quickly became the  dominant cultivar planted across the southeastern United States.
Stuart grown in SE Kansas 2017
    But how did Stuart migrate northwards? The popularity of Stuart in the south was largely driven by outstanding yields and scab resistance. Every pecan nursery began propagating Stuart and trees became so widely available that they were ultimately promoted for planting outside traditional southern pecan growing areas.  For a tree from the deep south, Stuart has excellent cold hardiness enabling Stuart trees to grow and thrive in northern pecan areas. However, it was soon discovered that northern climates do not provide a long enough growing season to properly mature nuts. Our 2017 crop of Stuart nuts contained roughly 50% stick-tights (photo above).

Poorly formed Stuart kernels
     A more common indication that Stuart is not adapted to northern climates is the incomplete development of kernel inside the shell (photo at right). Northern-grown Stuart nuts are usually fuzzy and shriveled. In addition, kernels are hollow and lack an good oily taste.
    No additions of water or fertilizer will ever alter the fact that Stuart will never make a decent kernel in northern areas. Stuart requires a longer growing season than northern pecan areas can provide for proper kernel development.
   One of the most interesting artifacts of the popularity of Stuart is the large number of Stuart seedlings that can be found growing all over the US, even in northern areas. During the Great Depression and war years (1930's and 1940's), pecans were a popular stocking stuffer for Christmas. The majority of gift basket pecans at that time were Stuart nuts and some of those nuts found there way into backyard gardens to eventually sprouted into trees. Today, you can find massive 90+ year-old trees that produce a blocky shaped nut that looks a lot like a Stuart nut but is generally smaller in size. These seedlings also produce nuts that struggle to produce quality kernels in northern climates just like the mother Stuart tree.

Saturday, December 23, 2017

Site selection and pecan production

   On my farm, I established our pecan orchard in a field that is located within the Neosho River flood plain.  The soils in this field are mostly  Hepler silt loam  with small areas of Osage silty clay. This area of the farm is subjected to occasional flooding. However, I couldn't resist planting pecans around my home, located up the hill just a few hundred feet from the main pecan grove. The soil at the home site is a Cherokee silt loam; a soil that was formed from river-deposited silt during the melting of the last ice age. This soil (and my house) is not subject to flooding.

      By planting trees in both bottomland and upland positions in the landscape, I can see how site selection impacts pecan performance. The photos at right and above show Jayhawk and Kanza nuts collected from similar aged trees. Within each photo, the two nuts on the left  were collected from trees growing in the floodplain. The two nuts on the right were harvested from upland trees. In both photos, the nuts grown in the river bottom are visually larger than the nuts collected on the upland. Sample weights (grams/nut) confirmed what my eyes could easily see (table below).

Site       Jayhawk  Kanza
Bottomland   7.34   6.77
Upland       6.31   6.19

    I cracked out several nuts from each tree (photos at left and below). Of course, the larger nuts from the bottomland had larger kernels. However, what I was looking for was differences in kernel plumpness.

With ample rainfall falling during the kernel filling period this year (August 2017), upland pecan kernels were just as full as kernels collected in the river-bottom.
   So why the difference in nut size?   It all comes down to internal differences in soil profiles.  The surface layer of Hepler and Cherokee soils are very similar; both are described as silt loam. The important difference comes deeper in the soil profile. If your dig deep into the Hepler profile, you'll find the that the soil comes heavier (more clay) with depth. But the transition is gradual with no abrupt changes in soil texture. In contrast, the Cherokee soil has about 14 inches of silty loam topsoil which abruptly changes to a firm clay subsoil.
     An abrupt change in soil texture has major impacts on the movement of water within the soil profile. Both Hepler and Cherokee are slow to drain after periods of wet weather. However, the clay pan found in the Cherokee soil creates what is known as a perched water table. Water moves so slowly into the subsoil that it stacks up in the topsoil creating a zone of  super saturation. A perched water table causes the soil to lose vital soil oxygen which can lead to tree root death. Tree growing in soils with a perched water table typically end up developing shallow root systems and a pecan tree with shallow roots has a hard time competing for water during hot dry periods.
    An abrupt change in soil texture between the topsoil and subsoil also impacts the movement of water upwards during dry periods.  Surface evaporation and plant transpiration remove water from the upper portions of the soil. As the soil dries out, water moves by capillary action upwards through the soil. However, a prominent boundary layer, like a clay pan, will block the free flow of water by capillary action from deep in the subsoil. The result is a soil that tends to be "droughty". 
   A soil with a strong boundary between topsoil and subsoil does not provide a healthy rooting environment for pecan trees. A perched water table in the spring limits root growth while soil water is held unavailable in the subsoil during the hot summer.  Young pecan trees respond to upland soil types by producing smaller nuts. As trees on upland sites grow older,  you'll find that trees becomes stunted, upper limbs may start dying back and nut production becomes limited and erratic.
   My main pecan orchard is located in the river bottom, where pecan trees thrive. The trees around the house will never be commercially viable but that's not why I planted them. I just enjoy looking out the window every morning and seeing beautiful pecan trees.