Sunlight availability and nut production after thinning of pecan trees (Carya illinoensis K. Koch)
The volume of a well-illuminated canopy is one of the main factors in the productivity of pecan trees. When mature pecan orchards with high densities (at least 100 trees per hectare) become overcrowded, photosynthetic active radiation penetration within the tree canopy and between trees, growth and nut production are adversely affected. Little research has been done to determine the effect of pecan tree thinning on available sunlight and productivity of the orchard. The objective of this experiment was to determine the effect of tree thinning on photosynthetic active radiation (PAR) available between and within permanent pecan trees, shoot growth, foliage density, nut production and nut quality. This study was carried out in a mature pecan orchard thinned at different stages from 25 to 50 % during the 1995-1997 period. Available PAR between and within pecan trees, shoot growth, foliage density and nut production per tree were affected by thinning treatments; however nut quality (kernel percentage) per tree during the three year period of the study was not significantly affected. The results of this study indicate that gradual orchard thinning at the appropriate time, in terms of orchard age, must be done to avoid drastic reduction in nut production.