Saturday, October 17, 2020

Fertilizing pecan trees in the Fall

      Long time readers of this blog will remember that I like to make two applications of fertilizer to my pecan trees each year. The first is applied in early spring when buds first show signs of swelling. The second application is made in the Fall, usually in early October. This year I delayed the Fall application until today based on soil conditions and weather predictions (photo at right). I applied a complete fertilizer containing N, P and K.

    During the first half of October, the weather has been unseasonably warm and the soil bone dry. Spreading nitrogen fertilizer under these conditions would result in massive losses of nitrogen from volatilization. So I've been waiting and closely watching the weather forecast. Today, the wind blew hard all day with the approach of a cold front that promises to drop our temperatures and give us a good chance of rain. If we get about a quarter inch of rain tomorrow, all the fertilizer I spread today should get washed in.

    One frequent question I receive concerns the fertilization of young trees. Many folks like to hand fertilizer young trees by spreading fertilizer in a circle around the tree. The thought is to fertilize just the tree and not all the ground cover between trees. On my farm, I broadcast fertilizer over the entire pecan planting (photo above) regardless of tree size. Sure, broadcasting fertilizer will stimulate the ground cover but I view that as beneficial. Every time I mow the pecan grove, I'm adding valuable organic matter to the soil. Soil organic matter increases water retention and increases the availability of essential micro-nutrients. In addition, the rotting grass clippings release significant amounts of N, P and K back into the soil (nutrient recycling). Over the long term, my objective is to develop a healthy soil environment  which promotes active pecan root growth. With healthy roots, I'll maximize the productivity of my pecan trees.

Sunday, October 11, 2020

Dry summer changes pecan appearance

     The summer of 2020 was hot and dry in S.E. Kansas. In fact, it was so dry that normal nut development was inhibited. This past week, I was collecting nut samples when I decided to see how much nut size and shape was effected by comparing nuts harvested this year with nut samples I have saved from the high rainfall year of 2019. Since most of the nut samples I've been collecting are from my breeding project, several examples pictured below are numbered selections. However, I collected Kanza nuts to illustrate the impact of dry weather on a known cultivar. You should note that all of the nuts collected in 2020 have darker shells that 2019. That is because the 2020 samples were just pulled out of the husk (at shuck-split) and are still quite wet.   

    The Kanza pecans from 2020 are visibly smaller that 2019. In addition, the 2020 nuts are shorter and more rounded. The good news for Kanza this year is that we received just enough rain in late August/early September to completely fill out the kernels inside the shell.

     Dry weather had minimal impact on the overall size of KT114. However, nut shape was effected. The 2020 nuts are not as blocky as the 2019 nuts. You can see the difference by looking at the base and apex of the nuts.

    KT217 nuts collected in 2020 illustrate two common changes in nut appearance associated dry weather. First, overall nut size is smaller. But secondly, the 2020 nuts are more tapered toward the base. Remember, all nut development processes start at the apex and work down toward the base. In the case of KT217, water became increasingly limited during nut enlargement resulting in a nut that has a much smaller diameter base.

    KT252 nuts are much smaller in 2020. The nuts are less blocky and ever show some basal taper. The overall changes in nut shape in 2020 make it hard to believe that nuts from 2019 and 2020 came from the exact same tree.

   Since irrigation is not an option for my pecan grove, yearly fluctuations in nut size and shape are to be expected. Each year, I collect nut samples from each cultivar and breeding selection in my orchard. Part of the data I collect from these samples is a photographic record of nut appearance.  As the years progress, I'll be able to see exactly how each clone reacts to variable weather conditions.