Wednesday, December 28, 2011

Pecan harvest patterns

    The pull-type picker has become the mainstay of the native pecan industry (photo at right). The other day, I drove past two native pecan groves and noticed huge differences in the pattern of leaves left on the ground after being blown out the back of the harvester.
    In the first grove, you can see a distinctive circle of brushed grass around each tree with all the tree leaves scattered around the outside of the circle (photo at right). This grower picked each tree individually, starting at the dripline of a tree and working towards the trunk in a circular path.
    In the second grove, the leaves were left in long rows, indicating the the harvesters were driven in a straight line, weaving around trees as they harvested large blocks of trees at a time (photo at right). In this case, the grove was picked much like you would mow the orchard floor. You start on the outside of the grove and work your way towards the middle of the field.
    There is not a right or wrong way to harvest nuts. Both of these harvest patterns seem to work. However, at the Experiment Field, we tend to harvest our native trees in blocks rather than individual trees. Driving around in circles tends to make the operator crazy and I feel like the harvester can capture a wider swath of ground by driving a straighter path.
   These photos also illustrate one very important difference between these two groves. Note the amount of leaves left behind after harvesting.  The grove harvested in circles had far fewer leaves on the ground than the grove harvested as a block (the grove with more leaves). These two groves are adjacent to each other but only the second grove receives annual applications of nitrogen fertilizer.  Regular nitrogen fertilization stimulates the growth of more leaves, more leaves capture more solar energy, and more energy in the tree results in more nuts.
     Before harvest you could see an obvious difference in nut production between these two groves. After harvest the leaves tell the same story.