2018 ASHS Annual Conference

Close spacing is the fastest way to generate a lot of pecans in early years. With the application of much better precocious cultivars and improved horticultural technologies, high density pecan production could be achieved. Like some other fruit trees, most of the fruits bear only on the shoots with terminal growth less than 30 cm. However, young pecan trees always have vigorous vegetative growth with the terminal growth greater than 50 cm. It’s difficult to generate pecans on young trees. This experiment was carried out to: (1) evaluate the effects of paclobutrazol on inhibiting pecan vegetative growth and increasing the number of bearing branches. (2) investigate composition of different kinds of branches.

The study was conducted from 2012 through 2014 in a 6-year-old pecan orchard in Nanjing, Jiangsu, China. ‘Mahan’ trees were spaced 5×7.5 m apart. Trees appeared to be crowding as limbs began to intermesh within rows. Most newly branches grew much than 30 cm which couldn’t form flower buds. Paclobutrazol (15% a.i.) was applied to trees via soil drench (rates of 0, 30, 90, and 150 mg/cm² trunk cross-sectional area). The four treatments initially were applied in a randomized complete block design to three replications. Terminal shoot growth was measured in April 2013 and 2014, and 10 terminal shoots were selected on each of four sides of the tree at the height of maximum limbspread.

Compared with the control, the application of PBZ treatments significantly increased the number of branches (less than 30 cm) by 76.4%, 141.0%, 54.0% respectively, and decreased branches (greater than 30 cm) by 48.3%, 64.2%, 60.3% respectively. The cumulative growth of current-season shoots was significantly inhibited in comparison with the control. The chlorophyll content of leaves was significantly increased in response to paclobutrazol application.