Nova Scotia Wild Blueberry Soil and Leaf Nutrient Ranges

Abstract

Soil and leaf samples were collected from 44 wild blueberry fields throughout Nova Scotia in 1989–90 and in 1997–98, and analyzed for macro- and micronutrient content. Samples were obtained from sprout fields, in late July and early August, after terminal dieback of terminal leaf buds. Soil and tissue concentrations of P and K were increased by repeated fertilizer applications between the two sample periods, whereas soil pH was decreased. Leaf tissue concentrations of P, Cu, B, Zn and Fe were consistently lower than indicated by the Trevett standards, suggesting that a separate set of nutrient ranges should be adopted for Nova Scotia wild blueberry fields.

KEYWORDS:

• wild blueberry
• Vaccinium angustifolium Ait.
• fertilizer soil and foliar concentration
• soil and leaf analysis

INTRODUCTION

The wild blueberry (Vaccinium angustifolium Ait.) is managed through a process of regular pruning which forces it into a biennial production cycle, with maximum yields occurring in the second growing season following pruning (Hall et al., 1979; Jordan and Eaton, 1995). Regular pruning and the use of selective herbicides also maintain the blueberry as the dominant plant in commercial fields (Jensen 1986; Yarborough et al., 1986). Wild blueberry plant stands develop naturally from randomly introduced plants; thus they display great genetic variability with large numbers of diverse clones (Hepler and Yarborough, 1991).

Chemical fertilizers are a regular management practice, even though short-term plant responses are inconsistent (Eaton, 1988; Eaton, 1994; Smagula and Hepler, 1978). Some long-term studies demonstrated positive long-term effects, on the other hand. Eaton (1994) observed increased stem lengths and fruit bud numbers after repeated applications of an N-P-K fertilizer in conjunction with herbicides, but with inconsistent yield increases. Similarly, Penney and McRae (2000) showed that herbicide plus a nitrogen fertilizer significantly increased yields over 8 years in a Newfoundland study, whereas a P only fertilizer had no effect. Also, increased plant growth and yields occurred in both the first and second crops with the application of an N-P-K (17-17-17) fertilizer during a 12-year study on second cropping (Eaton and Nams, 2006).

Trevett (1972) developed a set of leaf analysis standards for lowbush blueberry, primarily for Maine, USA. The Trevett standards are still used for assessing leaf tissue levels by producers in Atlantic Canada, even though soil climatic and management conditions may vary considerably from those in Maine (Sanderson et. al., 2007). Lockhart and Langille (1962) reported ranges and means for leaf nutrients in sprout and crop plants for three fields in the Parrsboro, Nova Scotia area, but did not establish standard ranges as did Trevett (1972).

This study was initiated (1) to assess the effects of repeated fertilizer applications on soil and leaf nutrient levels in commercial wild blueberry fields in Nova Scotia, Canada, over an 8-year period and (2) to establish ranges for both soil and leaf nutrient concentration ranges commonly found in wild blueberry fields in Nova Scotia.

MATERIALS AND METHODS

This study represents a portion of a larger survey of commercial wild blueberry fields initiated in 1989, during which soil and leaf tissue samples were obtained from 75 fields in 1989 and 1990. We repeated the survey during 1998 and 1999 on 44 fields of the original 75 fields. All fields were located in Colchester (45°22’N, 63°19’W), Cumberland (45°38’N, 63°08’W), Halifax (44°70’N, 63°83’W) and Pictou (45°41’N, 62°43’W) Counties in Nova Scotia, Canada (45°22’N, 63°16’W). These four counties represent approximately 90% of the entire wild blueberry acreage in Nova Scotia.

The history of crop fertilization was obtained from producers for each field included in the survey, from the initiation of the study until the final sampling dates (1997 and 1998). All fertilizers were applied in the spring of the pruning years. Fertilizer types applied during the study include: 13-26-5 (13N-11.4P-4.2K), 9-46-0 (9N-20.2P-0K), 17-17-17 (17N-7.5P-14.1K), 18-46-0 (18N-20.2P- 0K), 0-37-0 (0N-16.2P-0K), 15-38-9 (15N-16.6P-7.5K) and 16-26-16 (16N-11.4P-13.3K) at application rates ranging from 95 to 560 kg ha⁻¹ as determined by individual producers. Fields that received three or more applications of fertilizers containing P during the 8-year span between sampling were considered to be “fertilized”; all others were considered to be unfertilized. Fourteen of the 44 fields received no fertilizer applications at all, whereas five of the “unfertilized” fields received one or two fertilizer applications.

Soil and leaf samples (one sample per field) were taken in the sprout year at all sites in 1989 through 1990, and 1997 through 1998. Leaf samples were randomly collected after stems had reached the terminal abortion stage (Hall et al., 1979), and were obtained by taking the top 5 to 10 leaves from approximately 50 stems in each field. Samples were dried at 80^oC, ground to 1 mm, ashed at 500^oC, and extracted in 2 M HCl. The extract was centrifuged and concentrations of P, K, Ca, Mg, Cu, Zn, Mn, Fe, B and S were determined in the supernatant using ICAP, using AOAC Method 968.08. The N content of plant tissue was determined by gas analysis of the combustion stream using a LECO CNS analyzer AOAC Method 990.03 (Association of the Official Analytical Chemists, 2003).

Soil samples were taken with a hand-held soil probe to a depth of 15 cm from all fields at the same time as the leaf samples. Samples were air dried at 35^oC and passed through a 2 mm sieve prior to analysis. Soil pH was determined with a 1:1 soil to water ratio. Soil nutrient concentration of P, K, Ca, Mg were extracted with Mehlich 1 in 1989–90 and Mehlich 3 in 1997–98 (Tran and Simard, 1993) and the supernatant was analyzed using ICAP, AOAC Method 990.303 (AOAC 2003). Soil nutrient concentration of Cu, Zn, B, Fe, and Mn were extracted with 0.1 N HCl in 1989–90 and with Mehlich 3 in 1997–98. During the 1989–90 time period, soil organic matter was determined using loss on ignition (450^oC for 1 h). Prior to 1997, the method differed in that the data provided by the loss on ignition was converted to % organic matter (OM) with the formula: % OM = (0.618 × LOI) + 0.69 (Donald and Harnish, 1993). Therefore, the % OM data from the 1989–90 sample period were converted to bring them in line with the 1997–98 data.

Data were analyzed using the ANOVA directive from the statistical programming language Genstat® (Release 10.2, Lawes Agricultural Trust, Rothamsted Experimental Station, 2007), using a completely randomized design to evaluate the nutrient concentrations for each year surveyed. The standard deviation (SD) across fields was determined using the residual mean squared from the ANOVA. The range of a nutrient was calculated as plus or minus one standard deviation from the grand mean. Each range was tested by classifying the fields to determine the percentage of fields within the calculated range.

RESULTS AND DISCUSSION

Levels of soil organic matter, pH, and mineral nutrients were not affected by year (data not shown) but were affected by fertilizer history (Table 1). Soil pH was reduced by repeated fertilizer applications between 1989–90 and 1997–98, whereas soil organic matter and levels of P, K and B were increased. Levels of all other soil nutrients were not affected by fertilizer applications. The fertilizers applied by producers contained several combinations of N, P, and K, but not micronutrients. Increased soil levels of P and K were observed in several long-term studies involving repeated fertilizer applications (Eaton, 1994; Eaton at al., 1997; Sanderson and Eaton, 2008), with inconsistent or no effects on production.

TABLE 1 Effect of Repeated Fertilizer Applications on Soil Organic Matter, Soil pH, and the Three Effected Blueberry Soil Nutrient Levels

	% OM	pH	P	K	B
			kg ha^−1
Fertilizer (n = 25)	9.53	4.61	85	156	0.27
No fertilizer (n = 19)	8.36	4.80	41	126	0.22
SEM	0.362	0.040	6.2	8.7	0.017
Significance	∗	∗∗∗	∗∗∗	∗	∗
All other nutrients were not affected. 44 fields were sampled in 1989–90 and again in 1997–98.
∗, ∗∗∗ Statistically significant at 0.05, 0.01 and 0.001 levels, respectively; NS, not significant (P > 0.05).

Mean tissue levels of both P and K were increased by repeated fertilizer applications, but did not differ between 1989–90 and 1997–98 (Table 2). Other studies have provided similar results (Eaton, 1994; Eaton et al., 1997, Sanderson et al., 2008). Other nutrients were not affected by fertilizer applications, but did differ between sampling periods (data not shown). Mean leaf tissue concentrations of Mg and Cu were increased from 0.16 to 0.18% and 0.7 and 1.8 mg kg⁻¹, respectively, between 1989–90 and 1997–98, whereas those of B, Zn and Fe decreased from 27 to 22, 20 to 18 and 41 to 37 mg kg⁻¹, respectively. We are unable to determine factors that might contribute to these differences, except that we obtained only one sample from each field at each sample date, and also, considerable variation in nutrient levels occurs within fields (Argall et al., 1998).

TABLE 2 Effect of Repeated Fertilizer Applications on Leaf Nutrient Concentration in Wildblueberry

	N	P	K	Ca	Mg
	%
Fertilizer (n = 25)	1.83	0.133	0.48	0.40	0.17
No fertilizer (n = 19)	1.79	0.120	0.45	0.39	0.17
SEM	0.027	0.0025	0.008	0.011	0.003
Significance	NS	∗∗∗	∗	NS	NS
44 fields were sampled in 1989–90 and again in 1997–98.
∗, ∗∗∗ Statistically significant at 0.05 and 0.001 levels, respectively; NS, not significant (P > 0.05).

Means and ranges of soil organic matter, pH and soil nutrient levels for the 44 fields are given in Table 3. All soil values, with the exception of Ca, can be described by the mean ± 1 S.D. (67% of the total). These values could possibly be used as rough guidelines for soil levels in Nova Scotia commercial wild blueberry stands, although soil nutrient values are often not reliable as measures of the nutrient status of blueberry fields (Argall et al., 1998).

TABLE 3 Means and Ranges of % Organic Matter, Soil pH, and Soil Nutrients in 44 Fields Sampled in 1989–90 and Again in 1997–98 (Total of 88 Samples). Values of Nutrientsexcept for pH and %OM are Given as kg ha⁻¹

	Mean	Range		% accounted for by mean ± S.D.
		Minimum	Maximum
% OM	9.0	6.7	11.3	69
pH	4.7	4.4	5.0	80
P	65	18	111	77
K	143	86	200	74
Ca∗	427	187	670	66
Mg	81	33	139	76
B	0.25	0.17	0.32	70
Fe	286	184	389	75
Mn	59	14	105	91
Cu	0.9	0.5	1.4	86
Zn	3.4	2.3	4.6	70
∗All soil values are explained by the mean ± 1 S.D., except for Ca (66%).

When compared to the Trevett leaf tissue standards (1972), leaf nutrient concentrations of most Nova Scotia fields were deficient in P, Cu, B, Zn, and Fe, whereas nearly half exhibited excess Mn (Table 4). Leaf nutrient concentration of N, K, Ca and Mg were largely within the Trevett range. Analysis of the data revealed that means and ranges of all leaf tissue nutrients can be described by the mean ± 1 S.D. (67% of the total), except for P and Ca (65% of the total), suggesting that the data sets were normally distributed. Values are similar to those reported by Lockhart and Langille (1962) for sprout (vegetative) fields in the Parrsboro area of Nova Scotia. A Prince Edward Island study demonstrated that all elements except K, Ca, Mg and Mn were largely deficient in blueberry soils in the province (Sanderson et al, 2007). It appears that not all of the Trevett standards may apply to Nova Scotia blueberry fields. We suggest a set of leaf nutrient ranges for Nova Scotia (Table 5), similar to those developed for Prince Edward Island, and based on the ranges obtained during this study. Such a set of standards may better reflect the local conditions in Nova Scotia, which appear to vary considerably from those in Maine wild blueberry fields for which the Trevett standards were developed.

TABLE 4 Percentage of wild blueberry fields deficient or in excess of Trevett (1972) standards

	Trevett Standards		NS status (1989–90; 1997–98)
	Min	Max	Mean	% Deficient	% Excess
N (%)	1.6	2.0	1.8	10	6
P (%)	0.125	0.222	0.130	42	0
K (%)	0.40	0.90	0.47	12	0
Ca (%)	0.27	0.52	0.39	1	4
Mg (%)	0.13	0.25	0.17	2	1
Cu (ppm)	7	14	1.3	98	0
B (ppm)	24	60	25	48	1
Zn (ppm)	25	50	19	92	0
Fe (ppm)	50	100	39	87	0
Mn (ppm)	750	1502	1502	2	48

TABLE 5 Proposed Ranges for Wild Blueberry Leaf Nutrient Ranges in Nova Scotia, Canada

	Nova Scotia leaf nutrient ranges
	Minimum	Maximum
N (%)	1.6	2.0
P (%)	0.110	0.144
K (%)	0.41	0.52
Ca (%)	0.32	0.47
Mg (%)	0.15	0.19
Cu (ppm)	0.01	2.5
B (ppm)	19	31
Zn (ppm)	16	22
Fe (ppm)	32	46
Mn (ppm)	1169	1834

CONCLUSIONS AND GROWER BENEFITS

It is quite clear, from this study and others (Eaton et al., 1997; Sanderson and Eaton 2008), that repeated applications of phosphorus-containing fertilizers result in increased levels of Mehlich 3 extractable P in soils as well as higher levels of tissue P. In addition, this study demonstrates a similar pattern for soil K and leaf tissue K. Consistently deficient levels of leaf tissue P, Cu, B, Zn and Fe in Nova Scotia blueberry plants when compared to the Trevett standards suggest that Nova Scotia should follow the lead of Prince Edward Island and adopt leaf nutrient ranges more appropriate to the levels observed. Producers should compare their tissue analyses with the ranges suggested here. They should also consider reducing fertilizer applications to help prevent possible environmental contamination.

The authors are grateful to Michelle Richards and a number of other summer students for their assistance in obtaining the leaf and soil samples for this study and Sylvia Wyand for data formatting and editing. We also wish to thank Bragg Lumber Company, The Nova Scotia Wild Blueberry Institute and The Wild Blueberry Producers Association of Nova Scotia for financial assistance. Finally, thank you to the many commercial producers who co-operated with us during the study.