Pruning Strategies for Young ‘Nadorcott’ Mandarin Trees Planted in High Density Orchards in South Africa

Figures & data

Figure 1. Tree forms used for pruning experiment. A) Control; B) Open Center and C) Pyramid form

Table 1. Effect of pruning treatments on removed biomass, trunk cross-sectional area (TCSA), and canopy volume of young ‘Nadorcott’ trees between 2014 and 2017

Parameter	Treatment	2014/15	2015/16	2016/17	3-year mean per treatment
Removed biomass (kg/tree)^x	Control	0.0 ± 0.0 b	2.8 ± 0.3 a	3.7 ± 0.4 a	2.2 ± 0.2 b
	Open Center	2.3 ± 0.3 a	3.9 ± 0.3 a	3.5 ± 0.4 a	3.2 ± 0.3 ab
	Pyramid	3.1 ± 0.5 a	3.8 ± 0.8 a	4.0 ± 0.4 a	3.6 ± 0.5 a
TCSA (cm^2)	Control	27.1 ± 1.1 a	35.4 ± 1.9 a	37.5 ± 1.8 a	33.2 ± 1.3 a
	Open Center	24.7 ± 0.9 a	31.9 ± 1.1 a	35.3 ± 1.2 a	30.6 ± 1.0 a
	Pyramid	25.8 ± 1.8 a	31.6 ± 1.6 a	34.8 ± 2.0 a	30.7 ± 1.2 a
Canopy volume (m^3)	Control	1.2 ± 0.3 a	2.7 ± 0.6 a	2.8 ± 0.6 a	2.2 ± 0.1 a
	Open Center	1.1 ± 0.3 b	2.5 ± 0.3 b	2.6 ± 0.3 b	2.1 ± 0.1 b
	Pyramid	0.8 ± 0.2 c	1.8 ± 0.4 c	1.7 ± 0.3 c	1.4 ± 0.1 c

Data are means ± SE (n = 10). Treatment means per year and 3-year means followed by different letters within a column and for each variable differ significantly at p = .05 according to Tukey’s Studentized Range test.

^xJuly pruning and January water shoot thinning combined per season.

Table 2. Effect of pruning treatments on yield, production efficiency (PE) and fruit diameter of young ‘Nadorcott’ trees between 2014 and 2017

Parameter	Treatment	2014/15	2015/16	2016/17	3-year mean per treatment
Yield (kg/tree)	Control	45.4 ± 1.8 a	37.0 ± 5.4 a	51.7 ± 4.1 a	45.3 ± 2.8 a
	Open Center	30.0 ± 3.4 b	33.0 ± 3.6 a	44.8 ± 3.3 a	36.0 ± 2.1 b
	Pyramid	29.2 ± 3.7 b	39.3 ± 4.0 a	49.5 ± 2.8 a	39.3 ± 2.5 ab
PE1 (yield/TCSA)	Control	1.7 ± 0.1 a	1.1 ± 0.2 a	1.4 ± 0.1 a	1.4 ± 0.1 a
	Open Center	1.2 ± 0.2 b	1.0 ± 0.1 a	1.3 ± 0.1 a	1.2 ± 0.1 a
	Pyramid	1.2 ± 0.2 b	1.3 ± 0.1 a	1.4 ± 0.1 a	1.3 ± 0.1 a
PE2 (yield/canopy volume)	Control	37.9 ± 1.3 a	13.6 ± 2.0 b	18.5 ± 1.4 b	23.7 ± 2.2 b
	Open Center	28.1 ± 3.6 a	13.0 ± 1.5 b	17.3 ± 1.3 b	19.5 ± 1.8 b
	Pyramid	39.0 ± 5.2 a	21.9 ± 2.2 a	28.0 ± 1.7 a	29.6 ± 2.3 a
Fruit size (diameter in mm)	Control	61.1 ± 0.8 b	76.8 ± 1.7 a	63.4 ± 1.1 a	66.5 ± 0.8 b
	Open Center	68.8 ± 1.4 a	75.6 ± 1.2 a	65.8 ± 0.9 a	70.1 ± 0.5 a
	Pyramid	68.5 ± 1.4 a	74.9 ± 1.4 a	64.5 ± 1.0 a	69.3 ± 0.9 a

Data are means ± SE (n = 10). Treatment means per year and 3-year means followed by different letters within a column and for each variable differ significantly at p = .05 according to Tukey’s Studentized Range test.

Table 3. Pearson’s correlation coefficients (r-values) for removed biomass and canopy volume correlated with various yield-related parameters (3 years of data combined)

Treatment	Parameter	Removed biomass	TCSA	Yield
Control	Removed biomass^a	1	0.78478***	0.05972ns
	Canopy volume	0.87039***	0.73337***	0.01576ns
Open Center	Removed biomass	1	0.58351***	0.06118ns
	Canopy volume	0.58785***	0.78829***	0.35033ns
Pyramid	Removed biomass	1	0.75025***	−0.02917ns
	Canopy volume	0.27020ns	0.59391***	0.51672**

^aJuly pruning and January water shoot thinning combined per season

* significant at p < 0.05; ** significant at p < 0.01; *** significant at p < 0.001

Figure 2. Effect of pruning treatments on biomass removal of young ‘Nadorcott’ trees for the entire trial period for: A) pruning after harvest in July and B) water shoot thinning in January. Bars indicate mean values ± SE (n = 10). Different letters above columns indicate significant differences among treatments and pruning times at p = .05 according to Tukey’s Studentized Range test

Table 4. Pearson’s correlation coefficients and significance levels of various tree parameters between 2015 and 2017

Correlation coefficients /Significance level	Yield June ‘15 / Leaf starch June ‘15	Yield July ‘16/Leaf starch July ‘16	Yield July ‘17/Leaf starch July ‘17	Fruit size June ‘15/Leaf starch June ‘15
r-value	−0.84012	−0.44646	−0.62295	0.65188
p-value	<0.0001	0.0152	0.0003	0.0001

Figure 3. Effect of pruning treatments on percentage leaf starch content of young ‘Nadorcott’ trees at various phenological growth stage between June 2015 and July 2017. Columns indicate mean values ± SE (n = 10). Statistical significance at p = .05 is indicated as a HSD bar according to Tukey’s Studentized Range test