Effect of Low Tunnels and Planting Dates on the Fruit Quality of Organic Day-Neutral Strawberries in High Tunnels in North Carolina

Figures & data

Table 1. Effect of low tunnels, planting dates, and varieties on the fruit size in 2016/2017

	Fruit length (mm)				Fruit width (mm)
Treatment	9-Mar	30-Mar	13-Apr	1-May	15-May	9-Mar	30-Mar	13-Apr	1-May	15-May
Protection method (P)
LT^a	41.4	42.9	44.0	46.1	41.3	36.6	35.3	32.5	34.4	34.8
NLT	41.1	43.3	45.5	44.2	37.0	36.1	35.9	33.2	31.9	30.8
Planting date (D)
D1	41.4	42.8	43.6	44.9	38. 7	36.6	35.0	31.9	32.0	32.5
D2	40.2	43.4	45.9	45.4	39. 7	36.1	36.2	33.8	34.3	33.2
Varieties (V)
Albion	46.1	44.3	46.8	47.2	41.6	39.1	35.7	33.1	34.1	34.6
San Andreas	36.5	41.9	42.7	43.1	36.8	33.6	35.5	32.5	32.2	31.1
Significance
P	ns	ns	ns	ns	0.005	ns	ns	ns	ns	0.0031
D	ns	ns	ns	ns	ns	ns	ns	0.0212	ns	ns
P*D	ns	ns	ns	ns	ns	ns	ns	ns	ns	ns
V	0.0002	ns	0.0052	0.0445	0.0021	0.0012	ns	ns	ns	0.0076
P*V	ns	ns	ns	ns	ns	ns	ns	ns	ns	ns
D*V	ns	ns	ns	ns	ns	ns	ns	ns	ns	ns
P*D*V	ns	ns	ns	ns	ns	ns	ns	ns	ns	ns

^aLT: low tunnels; NLT: no low tunnels; D1:  1September; D2:  29September; ns: nonsignificant (P ≥ 0.05).

Table 2. Effect of low tunnels, planting dates, and varieties on the fruit size in 2017/2018

	Fruit length (mm)			Fruit width (mm)
Treatment	5-Mar	23-Mar	6-Apr	5-Mar	23-Mar	6-Apr
Protection Method (P)
LT^a	43.9	44.1	38.0	30.9	31.9	36.1
NLT	46.5	42.6	41.2	33.7	31.9	38.2
Planting Date (D)
D1	46.8	44.0	40.7	33.1	32.6	35.7
D2	43.6	42.7	38.5	31.5	31.1	38.5
Varieties (V)
Albion	47.0	43.7	38.8	33.1	31.5	35.5
San Andreas	43.4	43.0	40.4	31.5	32.2	38.8
Significance
P	ns	ns	ns	0.0305	ns	ns
D	ns	ns	ns	0.0344	ns	ns
P*D	ns	ns	ns	ns	ns	ns
V	ns	ns	ns	ns	ns	ns
P*V	ns	ns	ns	ns	ns	ns
D*V	ns	ns	ns	ns	ns	ns
P*D*V	ns	ns	ns	ns	ns	ns

^aLT: low tunnels; NLT: no low tunnels; D1 = 9 September; D2: 10 October; ns: nonsignificant (P ≥ 0.05).

Table 3. Effect of low tunnels, planting dates, and varieties on single fruit weight (g/fruit) in the first (2016/2017) and second year (2017/2018)

	2016/17					2017/18
Treatment	9-Mar	30-Mar	13-Apr	1-May	15-May	5-Mar	23-Mar	6-Apr
Protection Method (P)
LT^a	24.2	22.3	20.1	22.4	20.8	19.7	19.1	18.0
NLT	22.9	22.9	21.5	19.2	15.9	22.8	18.2	22.0
Planting Date (D)
D1	23.7	21.4	19.4	19.3	17.8	23.2	19.5	19.4
D2	23.3	23.8	22.2	22.3	18.9	19.3	17.8	20.6
Varieties (V)
Albion	28.9	23.6	22.0	23.2	20.8	23.3	18.6	18.3
San Andreas	18.2	21.6	19.6	18.4	15.9	19.2	18.7	21.8
Significance
P	ns	ns	ns	ns	0.0033	0.0368	ns	0.0055
D	ns	ns	0.0192	ns	ns	0.0108	ns	ns
P*D	ns	ns	ns	ns	ns	ns	ns	ns
V	0.0002	ns	0.038	0.0219	0.0031	0.0078	ns	0.0126
P*V	ns	ns	ns	ns	ns	ns	0.0337	ns
D*V	ns	ns	ns	ns	ns	0.0241	ns	ns
P*D*V	ns	ns	ns	ns	ns	ns	ns	ns

^aLT: low tunnels; NLT: no low tunnels; D1: 1 September 2016 or 9 September 2017. D2: 29 September 2016 or 10 October 2017. ns: non-significant (P ≥ 0.05).

Table 4. Simple effect of planting dates (D) and varieties (V) on single fruit weight (g/fruit) on 5 March in 2017/2018

	Single fruit weight (g/fruit)
Treatment	5-Mar
Albion
D1^a	26.9
D2	19.6
p-Value	0.0016
San Andreas
D1	19.4
D2	18.9
p-Value	Ns
D1
Albion	26.9
San Andreas	19.4
p-Value	0.0012
D2
Albion	19.6
San Andreas	18.9
p-Value	ns
D*V	0.0241

^aD1 = 9 September, D2 = 10 October. ns = non-significant (p ≥ 0.05).

Table 5. Simple effect of protection methods (P) and varieties (V) on single fruit weight (g/fruit) on 23 March in the 2017/2018

	Single fruit weight (g/fruit)
Treatment	23-Mar
LT^a
Albion	17.8
San Andreas	20.5
p-Value	ns
NLT
Albion	19.4
San Andreas	17.0
p-Value	ns
Albion
LT	17.8
NLT	19.4
p-Value	Ns
San Andreas
LT	20.5
NLT	17.0
p-Value	0.0396
P*V	0.0337

^aLT: low tunnels; NLT: no low tunnels; ns = non-significant (p ≥ 0.05).

Table 6. Effect of low tunnel, planting dates, and varieties on the total soluble solid (TSS, ºBrix) in 2016/2017 and 2017/2018

	2016–17						2017–18
Treatment	16-Feb	9-Mar	30-Mar	13-Apr	1-May	15-May	5-Mar	23-Mar	6-Apr	5-May
Protection Method (P)
LT^a	8.4	6.9	6.7	7.4	7.1	9.1	6.1	7.5	8.7	9.8
NLT	8.7	8.5	6.6	7.0	7.7	9.0	6.3	7.8	7.8	9.2
Planting Date (D)
D1	7.8	7.3	6.9	7.3	7.4	9.2	6.0	7.4	8.0	n/a^b
D2	9.3	8.1	6.5	7.1	7.3	8.9	6.4	7.9	8.5	n/a
Varieties (V)
Albion	8.6	6.6	6.6	7.5	7.8	9.3	6.3	7.9	8.7	10.5
San Andreas	8.6	8.9	6.8	6.9	6.9	8.8	6.2	7.4	7.9	8.5
Significance
P	Ns	ns	ns	ns	ns	ns	ns	ns	0.0301	ns
D	0.0041	ns	ns	ns	ns	ns	ns	ns	ns	n/a
P*D	ns	ns	ns	ns	ns	ns	ns	ns	ns	n/a
V	ns	ns	ns	0.0235	0.004	ns	ns	ns	ns	ns
P*V	ns	ns	ns	ns	ns	ns	ns	ns	ns	ns
D*V	ns	ns	ns	ns	ns	ns	ns	ns	ns	n/a
P*D*V	ns	ns	ns	ns	ns	ns	ns	ns	ns	n/a

^aLT: low tunnels; NLT: no low tunnels. D1 = 1 September 2016 or 9 September 2017. D2 = 29 September 2016 or 10 October 2017. ns :non-significant (P ≥ 0.05).

^bn/a: not applicable. Fruit samples were collected only from D2 plants on 5 May 2018.

Figure 1. The total soluble solids (ºBrix) and average of maximum, mean, and minimum air temperatures (ºC) in 2017 and 2018

Each temperature data set represents a 2-week temperature average prior to the date specified (when a fruit quality test was conducted). LT: low tunnels inside a high tunnel; NLT: without low tunnels (high tunnels only)

Table 7. Effect of low tunnel, planting dates, and varieties on color, texture, and total titratable acidity (TTA) in February 2017

	Color			Texture	TTA
Treatment	L*	a*	b*	(N)	(%, w/w)	TSS/TTA
Protection Method (P)
LT^a	43.1	14.7	6.2	11.2	1.1	9.4
NLT	43.0	14.0	5.6	12.0	0.9	11.3
Planting Date (D)
D1	43.2	14.4	6.0	12.2	1.0	9.5
D2	42.9	14.3	5.8	11.0	1.0	11.2
Varieties (V)
Albion	42.8	13.0	5.3	11.5	1.0	10.8
San Andreas	43.4	15.7	6.6	11.7	1.0	9.9
Significance
P	ns	ns	ns	ns	ns	ns
D	ns	ns	ns	ns	ns	ns
P*D	ns	ns	ns	ns	ns	ns
V	ns	<0.0001	0.0007	ns	ns	ns
P*V	ns	ns	ns	ns	ns	ns
D*V	ns	ns	ns	ns	ns	ns
P*D*V	ns	ns	ns	ns	ns	ns

^aLT = Low tunnels, NLT = No Low tunnels, D1 = 9 September, D2 = 10 October, ns = Non-significant (P ≥ 0.05).

Table 8. Effect of low tunnel and varieties on color, texture, and total titratable acidity (TTA) in April 2017 and May 2018

	April 2016						May 2017
		Color		Texture	TTA	TSS/TAA		Color		Texture	TTA	TSS/TAA
Treatment	L*	a*	b*	(N)	(%, w/w)		L*	a*	b*	(N)	(%, w/w)
Protection Method (P)
LT^a	43.6	13.9	5.1	8.4	0.7	9.0	42.7	12.1	3.7	8.6	0.9	11.3
NLT	43.9	13.8	5.6	9.9	0.7	8.7	42.5	12.1	3.6	8.9	0.8	10.8
P-value	ns	ns	ns	0.0165	ns	ns	ns	ns	ns	ns	ns	ns
Varieties (V)
Albion	43.3	11.1	4.1	8.7	0.8	9.2	42.5	10.6	3.1	9.9	0.9	11.7
San Andreas	44.1	16.6	6.6	9.6	0.6	8.5	42.8	13.6	4.2	7.5	0.8	10.3
P-value	0.0097	<0.0001	0.0002	ns	0.0149	ns	ns	0.001	0.0016	0.002	0.0331	0.0101
significance
P*V	ns	ns	ns	ns	ns	ns	ns	ns	ns	ns	ns	ns

^aLT = Low tunnels, NLT = No Low tunnels. ns = Non-significant (P ≥ 0.05).