Wednesday, March 16, 2011

Fertilizing pecans

    Today we are fertilizing our pecan groves (photo at right). For our spring time fertilizer,  we spread 150 lbs/acre of urea (69 lbs N/ acre) and 100 lbs/acre potash (60 lbs K/acre).
    The cost of fertilizer has increased dramatically with the recent spike in energy costs. Today's fertilizer application cost $62.50 per acre, which represents the largest single-day expense we'll incur all season long. However,  fertilizer application is still the best investment you can make in managing your pecans. Annual fertilizer applications increase pecan yield by over 600 lbs/ acre.
   Come this fall, we will apply and additional 100 lbs of urea per acre (46 lbs. N/acre) sometime during the month of October. If fertilizer prices remain constant (which they won't), the fall nitrogen application would add $22.25/acre to our fertilizer costs. For the year, we will end up applying 115 lbs. N/acre and 60 lbs. K/ acre.
  Over the years, I've been recommending March 1 as the date to fertilize pecans. But recently, I've realized that we should let the trees tell us when it is time to fertilize rather than the calender. The first outward sign that spring growth has begun is something called outer scale split. In the photo above,  you can see two primary buds. The right-hand bud is still covered by the outer scale but you can see a crack (or split) has developed in the protective outer layer. In contrast, the outer scale of the left-hand bud has cracked and fallen off, revealing silver-colored inner scales. Outer scale split is an indication that the sap is flowing, the buds are swelling, and the roots are growing. Applied nutrients are most efficiently taken up by pecan trees during periods of active root growth. Timing your spring fertilizer application by watching bud development is one way to optimize nutrient uptake and ensuring you are getter the most out of your fertilizer investment.