Calcium and Potassium Foliar Sprays Affect Fruit Skin Color, Quality Attributes, and Mineral Nutrient Concentrations of ‘Red Delicious’ Apples

Figures & data

Table 1. Soil physical and chemical analyses at the experimental orchard.

	Soil texture
	Sand	Silt	Clay	Cu	Mn	Zn	Fe	K	P	N^z	OC^y	TNV^x	SP^w
Soil depth (cm)	%			(ppm)						(%)				pH	EC (ds/m)
0–30	50	32	18	0.3	0.8	2.1	0.9	250	45	0.2	2.14	40	29	7.39	2.58
30–60	50	30	20	0.6	7	1.3	5.3	261	26	0.12	1.36	45	30	7.46	1.09

Note. Soil samples were taken at 0–30 and 30–60 cm depth.

^zTotal nitrogen; ^yOrganic carbon; ^xTotal neutralizing value; ^wSaturation percentage.

Table 2. Leaf chemical composition of the experimental orchard.^z

(ppm)					(% dry weight)
B	Cu	Mn	Zn	Fe	K	P	N
65	5	37	10	73	1.13	0.12	1.63

Note. ^zSamples of 50 leaves were collected in mid-August in the year before start of the experiment from mid-terminal and new year extension growth around the trees.

Table 3. Effect of foliar application of CaCl₂, K sources, and their combinations on fruit physical properties of ‘Red Delicious’ apple over two cropping years (2013 and 2014).

	Fruit length (cm)		Fruit diameter (cm)		Length to diameter ratio		Fruit weight (g)		Firmness (N)		Bruise volume (cm^3)
Treatments	2013	2014	2013	2014	2013	2014	2013	2014	2013	2014	2013	2014
T1:Control	6.44b	6.34b	6.90b	7.36ab	0.93a	0.86a	148.65c	145.20b	39.98d	44.30c	3.77bc	3.25b
T2:CaCl2	6.68a	6.32b	7.06b	7.20ab	0.95a	0.89a	160.32b	148.37a	44.50a	46.70a	3.60c	3.07b
T3:KNO3	6.67a	6.60a	7.05b	7.53ab	0.94a	0.87a	159.30b	148.56a	39.92cd	45.20abc	4.03ab	3.39b
T4:K2SO4	6.62ab	6.33b	7.03b	7.09b	0.94a	0.89a	158.70b	148.14a	40.65bcd	44.40bc	3.63c	3.24b
T5:KCl	6.63ab	6.29b	7.01b	7.20ab	0.95a	0.87a	160.07b	148.15a	42.18bc	46.30ab	4.13a	4.01a
T6:KNO3+CaCl2	6.67a	6.68a	6.92b	7.54ab	0.96a	0.89a	166.15a	149.57a	43.50ab	47.10 a	4.06ab	2.88bc
T7:K2SO4+CaCl2	6.72a	6.61a	7.07ab	7.40ab	0.95a	0.89a	164.55a	149.60a	44.63a	46.51a	3.68c	3.14b
T8:KCl+CaCl2	6.84a	6.82a	7.31a	7.70a	0.94a	0.89a	166.17a	149.16a	43.54ab	46.54a	3.72c	3.18b

Note. Values within each column followed by the same letter are not significantly different according to LSD test (p ≤ 0.05). Data are means of four replicates (n = 4).

Table 4. Concentrations of K and Ca, and K/Ca ratio in ‘Red Delicious’ apple fruits harvested in 2013 and 2014.

	Potassium (mg.Kg^–1 DW)		Calcium (mg.Kg^–1 DW)		K/Ca ratio
Treatments	2013	2014	2013	2014	2013	2014
T1:Control	7451.5c	7686.5c	276.48c	321.50c	27ab	24ab
T2:CaCl2	7671.0b	7971.0b	374.05ab	408.55b	21c	20c
T3:KNO3	7793.0ab	8147.0ab	271.98c	313.98c	29a	26a
T4:K2SO4	7978.8a	8120.3ab	290.33c	305.33c	28ab	28a
T5:KCl	7870.3ab	8278.8a	371.43ab	412.43b	22bc	21bc
T6:KNO3+CaCl2	7774.5ab	8074.5b	366.40b	556.40a	21bc	15d
T7:K2SO4+CaCl2	7767.5ab	7977.5b	382.63ab	398.83b	20c	20bc
T8:KCl+CaCl2	7809.0ab	8139.0ab	405.43a	444.93b	19c	19cd

Note. Values within each column followed by the same letter are not significantly different according to LSD test (p ≤ 0.05). Data are means of four replicates (n = 4). DW: dry weight.

Table 5. Pearson correlation between fruit mineral concentrations and fruit quality attributes of ‘Red Delicious’ apples harvest in 2013 and 2014.

	‘r’ value (2013)			‘r’ value (2014)
Fruit properties	K	Ca	K/Ca	K	Ca	K/Ca
Anthocyanin (mg.g^–1 FW)	0.82**	ns	ns	0.55*	ns	ns
Firmness (N)	ns	0.83**	–0.85**	ns	0.75**	–0.80**
Total sugar (mg.g^–1 DW)	0.76**	0.19^ns	ns	0.86*	ns	ns
TA%	0.50*	ns	ns	0.56*	ns	ns
Sugar/TA ratio	0.55*	0.36^ns	–0.24^ns	0.70**	ns	ns
Starch (mg.g^–1 DW)	ns	0.50*	–0.53*	ns	0.64*	–0.64*
Bruise volume (cm^3)	ns	ns	ns	0.22^ns	–0.10^ns	0.11^ns

Note. ns = non-significant. *Significant at 5%; **Significant at 1%. Data are means of four replicates (n = 4).

Table 6. Effect of foliar application of CaCl₂, K sources, and their combinations on fruit chemical properties of ‘Red Delicious’ apple over two cropping years (2013 and 2014).

	Anthocyanin (mg.g^–1 FW)^z		Starch (mg.g^–1 DW)^z		Total sugar (mg.g^–1 DW)		TA%^z		Flavor index
Treatments	2013	2014	2013	2014	2013	2014	2013	2014	2013	2014
T1:Control	27.20d	24.70d	39.23de	28.76cd	8.98f	10.15d	0.48c	0.56b	18.80c	18.18c
T2:CaCl2	28.75cd	27.10cd	42.60cd	33.80b	11.43e	11.70c	0.50bc	0.59ab	22.50bc	19.64bc
T3:KNO3	34.25ab	32.62ab	35.50e	31.36bc	13.65cd	12.83b	0.57ab	0.61a	24.00b	20.89b
T4:K2SO4	35.75a	31.10ab	37.07de	26.50d	14.43bcd	12.80b	0.57ab	0.63a	25.50ab	20.38b
T5:KCl	32.40abc	33.00a	38.70de	30.57bc	16.00a	14.52a	0.61a	0.61a	26.50ab	23.62a
T6:KNO3+CaCl2	32.20abc	30.20ab	50.73a	38.10a	14.80abc	12.69b	0.61a	0.63a	21.40b	20.13b
T7:K2SO4+CaCl2	32.17abc	30.50ab	44.92bc	33.02b	13.08d	12.75b	0.54abc	0.625a	24.40b	20.39b
T8:KCl+CaCl2	31.50bc	29.70bc	47.02ab	40.48a	15.30ab	12.40bc	0.51bc	0.625a	30.11a	19.80bc

Note. Values within each column followed by the same letter are not significantly different according to LSD test (p ≤ 0.05). Data are means of four replicates (n = 4).

^zFW–DW: fresh or dry weight. TA: Titratable acidity.