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Correlations between soil physico-chemical properties and plant nutrient concentrations in bulb onion grown in paddy soil
Scientia Horticulturae 179 (2014) 158–162
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Correlations between soil physico-chemical properties and plant nutrient concentrations in bulb onion grown in paddy soil Jongtae Lee ∗ , Seongtae Lee Onion Research Institute, Gyeongnam Provincial Agricultural Research and Extension Services, Changnyeong 635-821, Republic of Korea
a r t i c l e
i n f o
Article history: Received 27 September 2013 Received in revised form 28 July 2014 Accepted 9 September 2014 Keywords: Fertilization Soil fertility Sustainable production Intermediate-day onion Allium cepa L.
a b s t r a c t This study was carried out to evaluate the correlations between soil physico-chemical properties and onion (Allium cepa L.) plant nutrients in a long-term onion producing area over 30 years, during the growing season of 2010–2011. Soil and plant samples were collected from 16 onion growing fields. Each mineral content of onion plants showed different trends in conversion from the initial bulbing stage to harvest. Nutrient uptakes of leaf tissue decreased from the initial bulbing to harvest, while nutrient uptakes of onion bulb substantially increased. In soil, water content, nitrate-nitrogen (NO3 N), and electric conductivity with high mobility decreased from the initial bulbing to harvest, but available phosphorus (av. P) or exchangeable cations with highly accumulated content did not change significantly. At the initial bulbing, soil N or NO3 N and ex. K content were not positively correlated with each counterpart in leaf tissue, while av. P content was positively related with leaf P content. However, bulb N, P and K were not significantly correlated with each counterpart in the soil. Soil N or NO3 N at the initial bulbing were negatively associated with bulb nutrients at harvest, especially Mg or soluble solid content. Soil av. P content at the initial bulbing showed strongly negative correlation with dry matter (DM), carbon (C), calcium (Ca), magnesium (Mg) and iron (Fe) at harvest. Soil ex. K content at the initial bulbing was solely positively related with the counterpart in bulb at harvest. Meanwhile, soil bulk density at the initial bulbing was positively correlated with DM, C, Ca, Mg, etc., in the bulb at harvest. In conclusion, the accumulated soil nutrients in a long-term onion growing area could negatively affect the bulb weight or mineral contents in bulb at harvest. Therefore, a new fertilizer recommendation program will be necessary for sustainable onion production. © 2014 Elsevier B.V. All rights reserved.
1. Introduction Onion (Allium cepa L.) is one of the most important vegetable crops grown in Korea, with 20,965 ha of production producing 1.20 million ton (Korean Statistical Information Service (KOSIS), 2012), and consumption has been increasing, due to awareness of the health benefits of onions. Intermediate-day onions planted in the fall have been introduced to temperate environments in the southern parts of Korea since the 1950s. The Korean onion has been producing more than 50 t ha−1 of bulb yield since 1989, and obtained the highest productivity all over the world (Food and Agriculture Organization (FAO), 2012). Onion productivity has been sustained by intensified cultural practices, including the use of transplants, high-density planting, polyethylene film mulches, and increased use of fertilizer, compost and synthetic chemicals.
∗ Corresponding author. Tel.: +82 10 6604 2893; fax: +82 55 254 1519. E-mail addresses: [email protected], [email protected] (J. Lee). http://dx.doi.org/10.1016/j.scienta.2014.09.019 0304-4238/© 2014 Elsevier B.V. All rights reserved.
However, recently onion growers have been worried about various physiological disorders or diseases, and bulb yield reduction or deteriorated bulb quality of onions harvested or stored in historical onion growing areas. Onion nutrient contents and bulb mineral uptakes were examined, to determine the nutritional status for optimum yield (Fink et al., 1999; Zink, 1966). Bosch Serra (1999) reported that the equilibrium N:P:K:Ca:Mg for bulb nutrient uptakes was 8:1:9:2:0.3 in bulb dry-matter yields around 11–13 t ha−1 . Many researchers contributed to determining N, P, and K fertilizer application rates suitable for optimum yield with minimum cost. Nitrogen fertilization was of great importance for onion production, but also, higher N rates did not accompany higher bulb yield (Boyhan et al., 2007; Halvorson et al., 2008). Phosphorus or K fertilizer applied to onions provided a slightly positive effect, or frequently no effects on bulb yield (Amin et al., 2007; Boyhan et al., 2007; Laughlin, 1989; Lee et al., 2011). In a paddy soil having 46.3 g kg−1 organic matter (OM) and 728 mg kg−1 available phosphorus (P), increased fertilizer beyond the recommended rates and delayed split application
J. Lee, S. Lee / Scientia Horticulturae 179 (2014) 158–162
timings decreased bulb yield and accumulated soil electric conductivity (EC), OM, exchangeable potassium (K), and nitrate nitrogen (NO3 N) in soil at harvest (Lee et al., 2012). Long-term excessive application of chemical fertilizer accumulates nutrients in soil, which may result in increased susceptibility of onion root to high soil moisture content or water deficiency. Moreover, applied fertilizer or high soil nutrients content could not work, or could depress nutrient uptakes, as well as crop growth or yield. Therefore, this study was undertaken to evaluate the nutrient contents and uptake, soil mineral contents, and interrelationships between soil physic-chemical properties and plant nutrients in a long-term onion grown area. 2. Materials and methods 2.1. Field experiment The present experiment was conducted in Changnyeong county (35◦ N, 128◦ E), in southeastern Korea, in 2010–2011 growing season. In the county, onions were grown on a total of 1152 ha (KOSTAT, 2012). Experimental sites came from 16 long-term onion growing fields. Fourteen F1 hybrid onion cultivars (Turbo, E-joeun, Premium gold, etc.) and two open-pollinated cultivars (Changnyeongjunggo, Chunjujunggo) were intermediate-day onions in bulb development, and mid or late maturing type in maturity. The onion seeds were sown from late August to mid September, transplanted from late October to early November at a plant density of 33.3 ± 2.3 individuals m−2 , and onion bulb were harvested from 3 to 9 June, when 80–100% of the plant tops had broken over at the neck. 2.2. Plant and soil sampling Samplings for onion growth, plant nutrients and soil chemical analysis were performed from 26 to 28 April (at the initial bulbing stage), and from 3 to 9 June (at harvest). Ten plants were pulled at 3 replications from each field at the initial bulbing stage, and fifty plants were pulled at three replications at harvest. Soil samples were collected from the surface soil (0–20 cm) and the subsoil (20–40 cm), at the same site and date as the plant sampling. 2.3. Plant nutrient content and nutrient uptake analysis All samples were separated into the bulb and green leaves, followed by the measurement of fresh weight (g/plant) and bulb weight (g/plant). Five representative bulbs and leaves were chopped into pieces approximately 2 cm square, and dried to a constant weight during 2 h at 105 ◦ C, and 22 h at 60 ◦ C. The dried samples were used to analyze dry matter and inorganic contents. Five other bulbs at harvest were selected, to analyze the soluble solid content (SSC), pyruvic acid (PA), and total phenolic compound (TP) of onion bulbs. Each bulb was cut longitudinally, and one half was immediately chopped into pieces approximately 2 cm square, and homogenized without water for 1 min in a blender (Food mix HMR-505, Hanil). The puree was poured into a filter paper (No. 6, Advantec), and placed in a plastic beaker, and allowed to filter. After approximately 60 min, the sample was stored in 15 ml cupped vial at −20 ◦ C, until analyzed. The dried samples were ground, weighed and dissolved in concentrated H2 SO4 and concentrated H2 O2 . Carbon (C), nitrogen (N) and sulfur (S) was measured by elemental analyzer (vario Max, Elementar, Germany) using the ground samples. Atomic absorption spectrophotometer (novAA 300, analytikjena, Germany) was used to determine the K, Ca, Mg and Na content (Slavin, 1968). Phosphorus was measured colorimetrically with the
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ammonium–vanadate–molybdate method (Gericke and Kurmies, 1952). The SSC was determined with a hand reflectometer, and expressed as % Brix. The PA content was measured by the method of Yoo et al. (1995) and Yoo and Pike (1999). The concentration of PA was calculated from a standard sodium pyruvate curve. TP content was determined with the Folin–Ciocalteau assay (Singleton and Rossi, 1965). The content was expressed as mg gallic acid equivalents (GAE) kg−1 at the fresh weight basis. 2.4. Soil chemical analysis The bulk density (BD) and water content (WC) were measured by gravimetric method, using a 100 ml sampling core. Fresh soil samples were analyzed for NO3 N, and air-dried soil samples were analyzed for pH, electric conductivity (EC), organic matter (OM), nitrogen (N), sulfur (S), available phosphorus (av. P), and exchangeable cations. Organic matter, N and S contents were measured by elemental analyzer (vario Max, Elementar, Germany), and NO3 N was identified by reflectometry (RQ plus, Merck). Soils for analyzing P and ex. cations were extracted using Morgan extractant (McIntosh, 1969). The extracted soil P was analyzed by spectrophotometer, and ex. cations were measured by atomic absorption spectrophotometer. Soil pH was determined using a 5:1 DI water:soil ratio, and the EC was measured by conductivity meter. 2.5. Data analysis Statistical analyses were performed using XLSTAT Pro 2013.1.01 (Addinsoft, USA). To assess the correlations between soil physicochemical contents and bulb nutrients values, the Pearson coefficient (r) was calculated, and presented in a rectangular correlation matrix. 3. Results and discussion 3.1. Plant mineral contents and uptakes Fresh weight, P and S concentrations decreased in leaf tissue and increased in bulb at harvest, compared with the initial bulbing stage (Table 1). In contrast, Mg, Na and Fe concentrations increased in leaf tissue and decreased in bulb at harvest, from the initial bulbing stage. The yield, and N, P, K, S uptakes decreased in leaf tissue, while all elements in bulb increased at harvest, compared with the initial bulbing stage (Table 2). Total leaf-plus-bulb uptakes at final harvest were 119.8 kg ha−1 in K, 116.7 kg ha−1 in N, 32.7 kg ha−1 in S, 32.5 kg ha−1 in Ca, followed by 16.0 kg ha−1 in P, 11.6 kg ha−1 in Mg, 3.3 kg ha−1 in Na. The nutrient ratios of bulb to bulb plus leaf were 91.8% in P, 87.2% in S, 79.5% in N, 78.0% in K and 72.6% in Fe, and lower than 70% in other elements. The nutrient concentrations and uptakes depend on day length-induced cultivar type, maturity, soil fertility or fertilization methods (Lee et al., 2009; Salo et al., 2002; Yoldas et al., 2011; Zink, 1966). Zink (1966) reported that Southport White onions, spring-direct seeded cultivar removed 159.2 kg ha−1 of N, 28.0 kg ha−1 of P, 142.4 kg ha−1 of K, 89.7 kg ha−1 of Ca, 13.5 kg ha−1 of Mg, and 10.1 kg ha−1 of Na in 260 g of fresh weight, with 145 g kg−1 of dry matter at harvest. The higher N, K and Ca uptakes than our findings resulted from higher fresh weight and dry matter. Fink et al. (1999) summarized from studies related to nutrient contents that 60 t ha−1 of onion bulb took up 108.0 kg ha−1 of N, 21.0 kg ha−1 of P, 120.0 kg ha−1 of K and 9.0 kg ha−1 of Mg, while 5.0 t of harvest residues removed 15.0 kg ha−1 of N, 1.0 kg ha−1 of P, 9.0 kg ha−1 of K and 1.0 kg ha−1 Mg, which were similar to our studies.
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Table 1 Fresh weight, dry matter and mineral contents of onion plants at the initial bulbing stage and at harvest in onion growers’ fields on a fresh weight basis (n = 16). Parts
Sampling time
Dry matter (g kg−1 )
Fresh weight (g plant−1 )
Mineral content Cz
N −1
(g kg Leaf
Bulb
Initial bulbing stagey Harvestx Probabilities Initial bulbing stage Harvest Probabilities
72.1
85.3
P
K
S
Ca
Mg
Na
Fe
Mn −1
)
(mg kg
36.7
2.46
0.19
2.28
0.48
0.65
0.17
0.07
25.6
) 5.08
43.9 <0.001 34.5
105.5 0.114 91.8
41.2 0.359 35.7
2.03 0.093 1.26
0.11 <0.001 0.13
2.30 0.963 1.46
0.36 0.042 0.25
1.14 0.015 0.30
0.37 <0.001 0.13
0.13 0.002 0.07
58.6 <0.001 60.5
8.25 <0.081 4.06
227.8 <0.001
103.2 <0.001
42.0 <0.001
1.33 0.404
0.21 <0.001
1.35 0.051
0.41 <0.001
0.29 0.683
0.11 0.009
0.03 <0.001
26.4 <0.001
3.02 0.317
z C is the carbon, N is the nitrogen, P is the phosphorus, K is the potassium, S is the sulfur, Ca is the calcium, Mg is the magnesium, Na is the sodium, Fe is the iron, Mn is the manganese. y Samples were collected from 26 to 28 April in 2010. x Samples were harvested from 3 to 9 June in 2010.
Table 2 Nutrient uptake of onion plants at the Initial bulbing stage and harvest in onion growers’ fields (n = 16). Parts
Sampling time
Yield (Mg ha−1 )
Nz
P
K
S
Ca
Mg
Na
Fe
Mn
4.11 1.28 <0.001 1.32 14.7 <0.001
49.8 26.4 <0.001 15.2 93.3 <0.001
10.1 4.17 <0.001 2.65 28.4 <0.001
14.1 12.2 0.123 3.08 20.1 <0.001
3.66 4.04 0.303 1.27 7.42 <0.001
1.54 1.41 0.403 0.72 1.81 <0.001
0.55 0.70 0.069 0.58 1.84 <0.001
0.10 0.09 0.724 0.03 0.21 <0.001
kg ha−1 Leaf
Bulb
z y x
Initial bulbing stagey Harvesty Probabilities Initial bulbing stagex Harvest Probabilities
22.2 13.9 <0.001 10.7 68.5 <0.001
53.2 23.9 <0.001 12.4 92.8 <0.001
N is the nitrogen, P is the phosphorus, K is the potassium, S is the sulfur, Ca is the calcium, Mg is the magnesium, Na is the sodium, Fe is the iron, Mn is the manganese. Samples were collected from 26 to 28 April in 2010. Samples were harvested from 3 to 9 June in 2010.
3.2. Soil physical and chemical properties Significant differences between the soils at the initial bulbing stage and harvest were found in WC, EC, N, NO3 N and exchangeable Ca values in surface soil (Table 3). Significant differences of soil properties in subsoil were the same as in surface soil. The WC, EC, N and NO3 N content decreased at harvest, compared with the initial bulbing stage in surface soil and subsoil, while exchangeable Ca content increased in surface soil, but decreased in subsoil at harvest. Other exchangeable cations, S and available P content also showed the same tendency as Ca content, although the values were not significant. Lower WC, EC, N and NO3 N content at harvest in surface soil can be explained by their removal into plant tissues and nutrient leaching loss. However, because onion plant absorbed Ca significantly less than N or K (Table 2), and Ca moved to surface soil from the subsoil, the exchangeable Ca content might increase
in the surface soil at harvest. In Korea, most crops have ranges of pH, OM and several main elements in soil for their production (Lee et al., 2006). The range for onion crop production includes 6.0–6.5 of pH, <2.0 dS m−1 of EC, 25–35 mg kg−1 of OM, 129–168 mg kg−1 of P, and 0.39–0.50, 5.8–6.7, 2.1–2.7 cmolc kg−1 of Ex. K, Ca and Mg, respectively. At the initial bulbing stage in surface soil, the av. P content was 3 times higher than the optimum range, and ex. K and Ca was 0.67 and 1.72 cmolc kg−1 higher than the optimum range. The soil OM or EC content were not high as compared with the range, but were considerably accumulated, relative to common paddy soil in Korea. Bernstein and Ayers (1953) reported that initial yield decline started at a threshold EC of 1.4 dS m−1 , and 50% yield reduction was at 4.1 dS m−1 . Lee et al. (2011) found that NO3 N content in the range of 7 to 42 mg kg−1 soil over the growing season resulted in the same bulb yield as at least 100% higher NO3 N content.
Table 3 Soil bulk density, water content, organic matter and mineral contents in onion growers’ fields on a dry weight basis (n = 16). Soil depth
Sampling time
BDz (g l−1 )
WC (g kg−1 )
pH
EC (dS m−1 )
OM (g kg−1 )
N (g kg−1 )
NO3 N (mg kg−1 )
S (mg kg−1 )
Av. P (mg kg−1 )
Ex. cation, (cmolc kg−1 ) K
Surface soil
Subsoil
Initial bulbing stagez Harvesty Probabilities Initial bulbing stagez Harvesty Probabilities
1.15
36.8
6.11
1.37
37.8
2.77
1.10 0.191 –
29.7 0.001 –
6.41 0.127 6.74
0.84 0.004 0.94
38.7 0.792 29.5
2.36 0.022 –
41.8 0.007 63.9
6.87 0.604
0.62 0.003
26.6 0.159
– –
17.7 <0.001
– –
– –
101.4
Ca
255
485.1
1.17
293 0.189 –
504.3 0.815 289.3
1.39 0.286 0.76
10.9 0.009 7.84
2.48 0.716 2.54
253.4 0.523
0.59 0.213
5.57 <0.001
2.22 0.084
– –
8.42
Mg 2.41
z BD is the bulk density, WC is the water content, EC is the electrical conductivity, OM is the organic matter, N is the nitrate, NO3 N is the nitrate nitrogen, S is the sulfur, Av. P is the available phosphorus, Ex Cations is the exchangeable cations, K is the potassium, Ca is the calcium, Mg is the magnesium. y Samples were collected from 26 to 28 April in 2010. x Samples were harvested from 3 to 9 June in 2010.
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Table 4 Correlation coefficient between soil physico-chemical properties and leaf nutrients at the initial bulbing stage (n = 16). Soil properties
BD WC pH OM N NO3 N S Ava. P Ex. K Ex. Ca Ex. Mg EC
Leaf nutrients FWz
DM
C
N
S
P
K
Ca
Mg
Fe
Mn
−0.242 0.372 −0.059 0.445 0.122 −0.379 −0.284 0.111 0.550* −0.178 0.110 −0.351
−0.521* −0.147 −0.275 0.126 0.467 0.032 0.255 0.376 0.213 0.148 0.076 −0.073
−0.572* −0.102 −0.260 0.194 0.541* 0.072 0.121 0.415 0.274 0.176 0.075 −0.040
−0.321 −0.213 −0.106 −0.184 0.344 0.257 0.217 0.438 −0.180 0.253 −0.113 0.162
−0.322 −0.287 −0.153 −0.017 0.417 0.237 0.317 0.466 −0.063 0.206 −0.050 0.280
−0.432 −0.118 −0.172 −0.037 0.470 −0.052 0.218 0.574* −0.033 0.161 −0.085 −0.096
−0.384 −0.219 −0.280 −0.049 0.366 −0.106 0.364 0.544* −0.029 0.045 −0.187 −0.216
−0.076 −0.516* −0.043 0.142 0.362 0.117 0.326 0.076 −0.069 0.182 0.154 0.152
0.045 0.270 0.611* −0.268 −0.033 −0.157 0.099 −0.013 −0.196 0.477 0.316 −0.054
0.341 −0.229 0.087 −0.329 −0.147 −0.228 0.140 −0.156 −0.268 −0.030 −0.111 −0.125
0.076 −0.478 −0.642* −0.267 0.072 0.025 0.231 0.267 −0.402 −0.432 −0.560* −0.065
z FW is the fresh weight, DM is the dry matter, C is the carbon, N is the nitrogen, S is the sulfur, P is the phosphorus, K is the potassium, Ca is the calcium, Mg is the magnesium, Fe is the iron, Mn is the manganese, BD is the bulk density, WC is the water content, NO3 is the nitrate, Ava is the available, Ex is the exchangeable, EC is the electric conductivity. Asterisks indicate significance at p < 0.05 (*) for correlations.
Table 5 Correlation coefficient between soil physical-chemical properties and bulb nutrients at the initial bulbing stage (n = 16). Soil properties
BD WC pH OM N NO3 N S Ava. P Ex. K Ex. Ca Ex. Mg EC
Bulb nutrients FWz
DM
C
N
S
P
K
Ca
Mg
Fe
Mn
−0.267 0.488 −0.027 0.382 0.180 −0.166 −0.164 −0.126 0.414 −0.050 0.272 −0.223
−0.111 −0.172 −0.344 0.031 0.198 0.243 0.212 −0.052 0.101 −0.163 0.038 0.076
−0.194 −0.090 −0.295 0.133 0.257 0.195 0.194 −0.002 0.200 −0.135 0.098 0.043
0.024 −0.295 −0.211 −0.374 −0.027 0.284 0.251 0.297 −0.422 −0.045 −0.386 0.145
0.034 0.098 0.254 −0.207 −0.042 0.557* 0.088 −0.166 0.050 0.398 0.336 0.617*
0.145 0.073 0.234 −0.092 0.166 −0.391 0.097 0.032 0.238 0.200 0.185 −0.255
0.109 −0.219 −0.009 −0.148 0.173 −0.149 −0.109 0.192 −0.017 0.058 −0.132 −0.181
−0.087 −0.252 0.283 0.161 0.151 0.170 −0.151 0.079 0.044 0.451 0.241 0.216
0.533* −0.257 0.227 −0.533* −0.338 0.107 −0.077 −0.178 −0.525* 0.088 −0.227 0.135
0.554* −0.333 −0.049 −0.597* −0.408 0.251 0.003 −0.325 −0.625** −0.085 −0.345 0.183
0.271 −0.340 −0.528* −0.351 −0.038 0.185 0.070 0.062 −0.459 −0.411 −0.509* 0.099
z FW is the fresh weight, DM is the dry matter, C is the carbon, N is the nitrogen, S is the sulfur, P is the phosphorus, K is the potassium, Ca is the calcium, Mg is the magnesium, Fe is the iron, Mn is the manganese. BD is the bulk density, WC is the water content, NO3 is the nitrate, Ava is the available, Ex is the exchangeable, EC is the electric condutivity. Asterisks indicate significance at p < 0.05 (*) and p < 0.01 (**) for correlations.
3.3. Correlation coefficient between soil physical–chemical properties and plant nutrients
to most of the leaf nutrients, with being significant in C content. Increase in leaf FW was associated with increases in soil WC, OM and Ex. K, but with decreases in soil NO3 –N and EC. Soil ava. P content was positively correlated with plant P and K concentration. Table 5 is a correlation matrix that shows the relations between soil tests and bulb minerals at the initial bulbing stage. Soil NO3 N and EC were positively correlated with bulb S content. Bulb Mg and
Table 4 presents a correlation matrix for relations between soil tests data and leaf mineral concentrations of onions at the initial bulbing stage, collected from 16 farmers. The soil BD was negatively correlated with most of the leaf nutrients, with being significant in DM and C content. Higher soil N related positively
Table 6 Correlation coefficient between soil physico-chemical properties at the initial bulbing stage and bulb nutrients at harvest (n = 16). Soil properties
BD WC pH OM N NO3 N S Ava. P Ex. K Ex. Ca Ex. Mg EC
Bulb nutrients FW
DM
C
N
S
P
K
Ca
Mg
Fe
Mn
SSC
PA
T P
0.063 0.260 0.012 0.200 −0.089 −0.449 −0.444 0.123 0.264 −0.193 −0.203 −0.419
0.516* −0.019 0.022 −0.153 −0.253 −0.354 −0.127 −0.554* −0.000 −0.261 0.089 −0.306
0.637** −0.046 −0.085 −0.252 −0.326 −0.326 −0.185 −0.608* −0.033 −0.329 0.054 −0.235
0.222 −0.191 −0.567* −0.407 −0.316 0.344 −0.192 0.026 −0.488 −0.639** −0.550* 0.162
0.202 −0.111 0.004 −0.202 −0.025 0.131 0.040 0.051 −0.109 −0.056 −0.120 0.150
0.355 −0.195 −0.186 −0.358 −0.156 −0.252 0.049 −0.009 −0.222 −0.234 −0.188 −0.183
−0.240 0.513* 0.200 0.394 0.441 −0.336 0.283 0.258 0.567* 0.217 0.176 −0.355
0.677** −0.227 −0.232 −0.604* −0.495 0.366 −0.279 −0.812*** −0.451 −0.168 −0.070 0.317
0.770** −0.018 0.008 −0.633** −0.514* −0.050 −0.259 −0.633* −0.454 −0.202 −0.181 −0.039
0.612* −0.037 0.282 −0.671** −0.449 0.024 −0.304 −0.626** −0.370 0.053 0.090 0.068
0.603* −0.223 −0.068 −0.378 −0.242 −0.051 −0.170 −0.510* 0.044 −0.125 0.047 0.147
0.472 −0.007 −0.218 −0.270 −0.433 −0.567* −0.194 −0.176 −0.187 −0.530* −0.405 −0.564v
−0.362 −0.347 −0.442 0.092 0.393 0.311 0.267 0.549* −0.122 −0.162 −0.243 0.292
−0.511* −0.117 −0.245 0.344 0.385 0.286 0.269 0.500* −0.107 −0.001 −0.087 0.198
FW is the fresh weight, DM is the dry matter, C is the carbon, N is the nitrogen, S is the sulfur, P is the phosphorus, K is the potassium, Ca is the calcium, Mg is the magnesium, Fe is the iron, Mn is the manganese, SSC is the soluble solid content, PA is the pyruvic acid, T-P is the total phenolic compounds, BD is the bulk density, WC is the water content, NO3 is the nitrate, Ava is the available, Ex is the exchangeable, EC is the electric conductivity. Asterisks indicate significance at p < 0.05 (*), p < 0.01 (**) and p < 0.001 (***) for correlations.
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Fe content were positively correlated with soil BD, but negatively correlated with OM and ex. K content. Numerous significant correlations existed between soil tests at the initial bulbing stage and bulb minerals at harvest (Table 6). Soil BD was significantly positively correlated with bulb DM, C, Ca, Mg, Fe and Mn content, but negatively with T P. Conversely, available P content was negatively correlated with bulb DM, C, Ca, Mg, Fe and Mn, but positively with PA and T P. Similarly, soil OM content was negatively correlated with bulb Ca, Mg and Fe content. Increases in soil pH, ex. Ca and Mg content were associated with decrease in bulb N content. Although correlations among soil tests and bulb FW were not significant, higher soil NO3 N, S and EC content related negatively to bulb FW. Nitrogen, P and K are the main fertilizers applied by onion growers before transplanting, and as side-dress fertilizer. Moreover, much compost or composted animal manure are applied preplanting, for improving soil physics, which also accumulate nutrients in soil, especially P or K, as well as OM (Bary et al., 2000). There were contradictory hypotheses on how much fertilizer should be applied to onion plants. Onion requires excessive rates of fertilizer to attain maximum bulb yield, because the onion plant has a shallow, sparsely branched root system, which result in considerable residual nutrients in soil after harvest (Brewster, 2008). However, onion is among the most sensitive crops to soil salinity, particularly at seedling emergence (Alen et al., 1998). Lee et al. (2012) reported that excessive fertilization was detrimental to the yield and quality for onion grown on high organic matter content paddy soils. Plant nutrients and leaf growth generally may increase with applied fertilization rate during the vegetative growth stage (Buwalda and Freeman, 1987; Painter, 1977; Westerveld et al., 2003). However, overfertilization including N, P, K or compost did not positively affect bulb yield or bulb nutrients at harvest (Abdelrazzag, 2002; Lee et al., 2012). In addition, fertilizer uptake efficiency decreased with higher N or K application rates (Lee et al., 2011). These literatures explain why in our results soil N and P contents had a relatively positive correlation with leaf DM, C, N, S, P and K at the initial bulbing stage, but did not have a consistent correlation with bulb nutrients, or a negative correlation with bulb nutrients at harvest. Acknowledgements The author would like to thank Prof. George Boyhan at University of Georgia for writing assistance and suggestions to improve this manuscript. The research was financed by Locally Specialized Agricultural Techniques (No. PJ00733004) from Korean Rural Development Administration (RDA), Republic of Korea. References Abdelrazzag, A., 2002. Effect of chicken manure, sheep manure and inorganic fertilizer on yield and nutrients uptake by onion. Pak. J. Biol. Sci. 5, 266–268. Alen, R.G., Pereira, R.G., Raes, D., Smith, M., 1998. Crop Evapotranspiratin- Guidelines for Computing Crop Water Requirements. FAO Irrigaion and Drainage Paper 56. Rome.
Amin, M.R., Hasan, M.K., Naher, Q., Hossain, M.A., Noor, Z.U., 2007. Response of onion to NPKS fertilizers in low Ganges flood plain soil. Int. J. Sustainable Crop Prod. 2, 11–14. Bary, A.I., Cogger, C.G., Sullivan, D.M., 2000. Fertilizing with Manure. In: Washington State Univ. Coop. Ext. Pacific Northwest Ext. Publ. Pullman, WA, pp. p.533. Bernstein, L., Ayers, A.D., 1953. Salt tolerance of five varieties of onions. Proc. Am. Soc. Hortic. Sci. 62, 367–370. Bosch Serra, A.D., 1999. Ecophysilogical basis of production (Allium cepa L.): a onriution to te imprvement of agricutral practics i the Pla d’Urgell (Lleida). Doctoratesis, University of Lleida, Spain. Boyhan, G.E., Torrance, R.L., Hill, C.R., 2007. Effects of nitrogen, phosphorus, and potassium rates and fertilizer sources on yield and leaf nutrient status of shortday onions. HortScience 42, 653–660. Brewster, J.L., 2008. Onions and Other Vegetable Alliums. CAB International, Wallingford, UK, pp. 251–261. Buwalda, J.G., Freeman, R.E., 1987. Effects of nitrogen fertilizers on growth and yield of potato (Solanum tuberosum L, ‘Ilam hrdy’), onion (Allium cepa L. ‘Pukekohe lngkeepper’), garlic (Allium sativum L. ‘Y strain’) and hybrid squash (Cucurbita maxima L. ‘delica’). Sci. Hortic. 32, 161–173. Food and Agriculture Organization (FAO), 2012. FAOSTAT. Food and Agriculture Organization (FAO), http://faostat.fao.org/. Fink, M., Feller, C., Scharpf, H.C., Weier, U., Maync, A., Ziegler, J., Paschold, P.J., Strohmeyer, K., 1999. Nitrogen, phosphorus, potassium and magnesium contents of field vegetables—recent data for fertilizer recommendations and nutrient balances. J. Plant Nutr. Soil Sci. 162, 71–73. Gericke, S., Kurmies, B., 1952. The colorimetric phosphorus analysis with ammonium–vandate–molybdate and its application in plant analysis. Plant Fert. Soil 59, 235–247. Halvorson, A.D., Bartolo, M.E., Reula, C.A., Berrada, A., 2008. Nitrogen effects on onion yield under drip and furrow irrigation. Agron. J. 100, 1062–1069. Korean Statistical Information Service (KOSIS), 2012. Korean Statistical Information Service (KOSIS), http://kosis.kr/index/index.jsp. Statistics Korea (KOSTAT). 2012. Cultivated area of rice and pepper, and production of onions in 2012. http://kostat.go.kr/portal/english/news/1/10/7/infex.board Laughlin, J.C., 1989. Nutritional effects on onion (Allium cepa L.) yield and quality. Acta Hortic. 249, 211–215. Lee, G.S., Park, W.G., Jeong, B.G., Song, Y.S., Jeon, H.J., Jeong, G.S., Lee, C.S., 2006. The Standard of Fertilizer Application on Crop Species (In Korean). Rural Development Administration, Suwon, Korea. Lee, J., Song, J., Lee, S., 2012. Excessive fertilization is detrimental to yield and quality for onion grown on high organic matter content paddy soils. Int. J. Veg. Sci. 18, 235–244. Lee, J., Moon, J.S., Kim, H., Ha, I.J., 2011. Reduced nitrogen, phosphorus, and potassium rates for intermediate-day onion in paddy soil with incorporated rice straw plus manure. HortScience 46, 470–474. Lee, J.T., Ha, I.J., Kim, H.D., Moon, J.S., Lee, S.D., 2009. Times and frequencies of additional fertilization to improve nutrient efficiency of organic liquid fertilizer for organic cultivation. Korean J. Hortic. Sci. Technol. 27, 30–36. McIntosh, J.L., 1969. Bray and Morgan soil extractants modified for testing acid soils from different parent materials. Agron. J. 61, 259–265. Painter, C.G., 1977. The effect of nitrogen, phosphorus, potassium and micronutrients on yield and quality of onion seed in southwestern Idaho. Bulletin, Agricultural Experiment Station, 575. University of Idaho, Idaho, pp. 3–10, 6. Salo, T., Suojala, T., Kallela, M., 2002. The effect of fertigation on yield and nutrient uptake of cabbage, carrot and onion. In: Booij, R., Neeteson, J. (Eds.), Proc. Workshop Ecol. Fertilization Veg. Acta Horticulturae 571, pp. 235–241. Singleton, V.L., Rossi Jr., J.A., 1965. Colorimetry of total phenolics with phosphomolybdic–phosphotungtic acid reagent. Am. J. Enol. Vitic. 16, 144–158. Slavin, W., 1968. Atomic absorption spectroscopy. Chem. Anal. 25, 87–90. Westerveld, S., McKeown, A.W., Scott-Dupree, C.D., McDonald, M.R., 2003. How well do critical nitrogen concentrations work for cabbage, carrot, and onion crops? HortScience 38, 1122–1128. Yoldas, F., Ceylan, S., Mordogan, N., Esetlili, B.C., 2011. Effect of organic and inorganic fertilizers on yield and mineral content of onion (Allium cepa L.). Afr. J. Biotechnol. 10, 11488–11492. Yoo, K.S., Pike, L.M., Hamilton, B.K., 1995. A simplified pyruvic acid analysis suitable for onion breeding program. HortScience 30, 1306. Yoo, K.S., Pike, L.M., 1999. Development of an automated system for pyruvic acid analysis in onion breeding. Sci. Hortic. 82, 193–201. Zink, F.W., 1966. Studies on the growth rate and nutrient absorption of onion. Hillgardia 37, 203L 212.
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Correlations between soil physico-chemical properties and plant nutrient concentrations in bulb onion grown in paddy soil Jongtae Lee ∗ , Seongtae Lee Onion Research Institute, Gyeongnam Provincial Agricultural Research and Extension Services, Changnyeong 635-821, Republic of Korea
a r t i c l e
i n f o
Article history: Received 27 September 2013 Received in revised form 28 July 2014 Accepted 9 September 2014 Keywords: Fertilization Soil fertility Sustainable production Intermediate-day onion Allium cepa L.
a b s t r a c t This study was carried out to evaluate the correlations between soil physico-chemical properties and onion (Allium cepa L.) plant nutrients in a long-term onion producing area over 30 years, during the growing season of 2010–2011. Soil and plant samples were collected from 16 onion growing fields. Each mineral content of onion plants showed different trends in conversion from the initial bulbing stage to harvest. Nutrient uptakes of leaf tissue decreased from the initial bulbing to harvest, while nutrient uptakes of onion bulb substantially increased. In soil, water content, nitrate-nitrogen (NO3 N), and electric conductivity with high mobility decreased from the initial bulbing to harvest, but available phosphorus (av. P) or exchangeable cations with highly accumulated content did not change significantly. At the initial bulbing, soil N or NO3 N and ex. K content were not positively correlated with each counterpart in leaf tissue, while av. P content was positively related with leaf P content. However, bulb N, P and K were not significantly correlated with each counterpart in the soil. Soil N or NO3 N at the initial bulbing were negatively associated with bulb nutrients at harvest, especially Mg or soluble solid content. Soil av. P content at the initial bulbing showed strongly negative correlation with dry matter (DM), carbon (C), calcium (Ca), magnesium (Mg) and iron (Fe) at harvest. Soil ex. K content at the initial bulbing was solely positively related with the counterpart in bulb at harvest. Meanwhile, soil bulk density at the initial bulbing was positively correlated with DM, C, Ca, Mg, etc., in the bulb at harvest. In conclusion, the accumulated soil nutrients in a long-term onion growing area could negatively affect the bulb weight or mineral contents in bulb at harvest. Therefore, a new fertilizer recommendation program will be necessary for sustainable onion production. © 2014 Elsevier B.V. All rights reserved.
1. Introduction Onion (Allium cepa L.) is one of the most important vegetable crops grown in Korea, with 20,965 ha of production producing 1.20 million ton (Korean Statistical Information Service (KOSIS), 2012), and consumption has been increasing, due to awareness of the health benefits of onions. Intermediate-day onions planted in the fall have been introduced to temperate environments in the southern parts of Korea since the 1950s. The Korean onion has been producing more than 50 t ha−1 of bulb yield since 1989, and obtained the highest productivity all over the world (Food and Agriculture Organization (FAO), 2012). Onion productivity has been sustained by intensified cultural practices, including the use of transplants, high-density planting, polyethylene film mulches, and increased use of fertilizer, compost and synthetic chemicals.
∗ Corresponding author. Tel.: +82 10 6604 2893; fax: +82 55 254 1519. E-mail addresses: [email protected], [email protected] (J. Lee). http://dx.doi.org/10.1016/j.scienta.2014.09.019 0304-4238/© 2014 Elsevier B.V. All rights reserved.
However, recently onion growers have been worried about various physiological disorders or diseases, and bulb yield reduction or deteriorated bulb quality of onions harvested or stored in historical onion growing areas. Onion nutrient contents and bulb mineral uptakes were examined, to determine the nutritional status for optimum yield (Fink et al., 1999; Zink, 1966). Bosch Serra (1999) reported that the equilibrium N:P:K:Ca:Mg for bulb nutrient uptakes was 8:1:9:2:0.3 in bulb dry-matter yields around 11–13 t ha−1 . Many researchers contributed to determining N, P, and K fertilizer application rates suitable for optimum yield with minimum cost. Nitrogen fertilization was of great importance for onion production, but also, higher N rates did not accompany higher bulb yield (Boyhan et al., 2007; Halvorson et al., 2008). Phosphorus or K fertilizer applied to onions provided a slightly positive effect, or frequently no effects on bulb yield (Amin et al., 2007; Boyhan et al., 2007; Laughlin, 1989; Lee et al., 2011). In a paddy soil having 46.3 g kg−1 organic matter (OM) and 728 mg kg−1 available phosphorus (P), increased fertilizer beyond the recommended rates and delayed split application
J. Lee, S. Lee / Scientia Horticulturae 179 (2014) 158–162
timings decreased bulb yield and accumulated soil electric conductivity (EC), OM, exchangeable potassium (K), and nitrate nitrogen (NO3 N) in soil at harvest (Lee et al., 2012). Long-term excessive application of chemical fertilizer accumulates nutrients in soil, which may result in increased susceptibility of onion root to high soil moisture content or water deficiency. Moreover, applied fertilizer or high soil nutrients content could not work, or could depress nutrient uptakes, as well as crop growth or yield. Therefore, this study was undertaken to evaluate the nutrient contents and uptake, soil mineral contents, and interrelationships between soil physic-chemical properties and plant nutrients in a long-term onion grown area. 2. Materials and methods 2.1. Field experiment The present experiment was conducted in Changnyeong county (35◦ N, 128◦ E), in southeastern Korea, in 2010–2011 growing season. In the county, onions were grown on a total of 1152 ha (KOSTAT, 2012). Experimental sites came from 16 long-term onion growing fields. Fourteen F1 hybrid onion cultivars (Turbo, E-joeun, Premium gold, etc.) and two open-pollinated cultivars (Changnyeongjunggo, Chunjujunggo) were intermediate-day onions in bulb development, and mid or late maturing type in maturity. The onion seeds were sown from late August to mid September, transplanted from late October to early November at a plant density of 33.3 ± 2.3 individuals m−2 , and onion bulb were harvested from 3 to 9 June, when 80–100% of the plant tops had broken over at the neck. 2.2. Plant and soil sampling Samplings for onion growth, plant nutrients and soil chemical analysis were performed from 26 to 28 April (at the initial bulbing stage), and from 3 to 9 June (at harvest). Ten plants were pulled at 3 replications from each field at the initial bulbing stage, and fifty plants were pulled at three replications at harvest. Soil samples were collected from the surface soil (0–20 cm) and the subsoil (20–40 cm), at the same site and date as the plant sampling. 2.3. Plant nutrient content and nutrient uptake analysis All samples were separated into the bulb and green leaves, followed by the measurement of fresh weight (g/plant) and bulb weight (g/plant). Five representative bulbs and leaves were chopped into pieces approximately 2 cm square, and dried to a constant weight during 2 h at 105 ◦ C, and 22 h at 60 ◦ C. The dried samples were used to analyze dry matter and inorganic contents. Five other bulbs at harvest were selected, to analyze the soluble solid content (SSC), pyruvic acid (PA), and total phenolic compound (TP) of onion bulbs. Each bulb was cut longitudinally, and one half was immediately chopped into pieces approximately 2 cm square, and homogenized without water for 1 min in a blender (Food mix HMR-505, Hanil). The puree was poured into a filter paper (No. 6, Advantec), and placed in a plastic beaker, and allowed to filter. After approximately 60 min, the sample was stored in 15 ml cupped vial at −20 ◦ C, until analyzed. The dried samples were ground, weighed and dissolved in concentrated H2 SO4 and concentrated H2 O2 . Carbon (C), nitrogen (N) and sulfur (S) was measured by elemental analyzer (vario Max, Elementar, Germany) using the ground samples. Atomic absorption spectrophotometer (novAA 300, analytikjena, Germany) was used to determine the K, Ca, Mg and Na content (Slavin, 1968). Phosphorus was measured colorimetrically with the
159
ammonium–vanadate–molybdate method (Gericke and Kurmies, 1952). The SSC was determined with a hand reflectometer, and expressed as % Brix. The PA content was measured by the method of Yoo et al. (1995) and Yoo and Pike (1999). The concentration of PA was calculated from a standard sodium pyruvate curve. TP content was determined with the Folin–Ciocalteau assay (Singleton and Rossi, 1965). The content was expressed as mg gallic acid equivalents (GAE) kg−1 at the fresh weight basis. 2.4. Soil chemical analysis The bulk density (BD) and water content (WC) were measured by gravimetric method, using a 100 ml sampling core. Fresh soil samples were analyzed for NO3 N, and air-dried soil samples were analyzed for pH, electric conductivity (EC), organic matter (OM), nitrogen (N), sulfur (S), available phosphorus (av. P), and exchangeable cations. Organic matter, N and S contents were measured by elemental analyzer (vario Max, Elementar, Germany), and NO3 N was identified by reflectometry (RQ plus, Merck). Soils for analyzing P and ex. cations were extracted using Morgan extractant (McIntosh, 1969). The extracted soil P was analyzed by spectrophotometer, and ex. cations were measured by atomic absorption spectrophotometer. Soil pH was determined using a 5:1 DI water:soil ratio, and the EC was measured by conductivity meter. 2.5. Data analysis Statistical analyses were performed using XLSTAT Pro 2013.1.01 (Addinsoft, USA). To assess the correlations between soil physicochemical contents and bulb nutrients values, the Pearson coefficient (r) was calculated, and presented in a rectangular correlation matrix. 3. Results and discussion 3.1. Plant mineral contents and uptakes Fresh weight, P and S concentrations decreased in leaf tissue and increased in bulb at harvest, compared with the initial bulbing stage (Table 1). In contrast, Mg, Na and Fe concentrations increased in leaf tissue and decreased in bulb at harvest, from the initial bulbing stage. The yield, and N, P, K, S uptakes decreased in leaf tissue, while all elements in bulb increased at harvest, compared with the initial bulbing stage (Table 2). Total leaf-plus-bulb uptakes at final harvest were 119.8 kg ha−1 in K, 116.7 kg ha−1 in N, 32.7 kg ha−1 in S, 32.5 kg ha−1 in Ca, followed by 16.0 kg ha−1 in P, 11.6 kg ha−1 in Mg, 3.3 kg ha−1 in Na. The nutrient ratios of bulb to bulb plus leaf were 91.8% in P, 87.2% in S, 79.5% in N, 78.0% in K and 72.6% in Fe, and lower than 70% in other elements. The nutrient concentrations and uptakes depend on day length-induced cultivar type, maturity, soil fertility or fertilization methods (Lee et al., 2009; Salo et al., 2002; Yoldas et al., 2011; Zink, 1966). Zink (1966) reported that Southport White onions, spring-direct seeded cultivar removed 159.2 kg ha−1 of N, 28.0 kg ha−1 of P, 142.4 kg ha−1 of K, 89.7 kg ha−1 of Ca, 13.5 kg ha−1 of Mg, and 10.1 kg ha−1 of Na in 260 g of fresh weight, with 145 g kg−1 of dry matter at harvest. The higher N, K and Ca uptakes than our findings resulted from higher fresh weight and dry matter. Fink et al. (1999) summarized from studies related to nutrient contents that 60 t ha−1 of onion bulb took up 108.0 kg ha−1 of N, 21.0 kg ha−1 of P, 120.0 kg ha−1 of K and 9.0 kg ha−1 of Mg, while 5.0 t of harvest residues removed 15.0 kg ha−1 of N, 1.0 kg ha−1 of P, 9.0 kg ha−1 of K and 1.0 kg ha−1 Mg, which were similar to our studies.
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Table 1 Fresh weight, dry matter and mineral contents of onion plants at the initial bulbing stage and at harvest in onion growers’ fields on a fresh weight basis (n = 16). Parts
Sampling time
Dry matter (g kg−1 )
Fresh weight (g plant−1 )
Mineral content Cz
N −1
(g kg Leaf
Bulb
Initial bulbing stagey Harvestx Probabilities Initial bulbing stage Harvest Probabilities
72.1
85.3
P
K
S
Ca
Mg
Na
Fe
Mn −1
)
(mg kg
36.7
2.46
0.19
2.28
0.48
0.65
0.17
0.07
25.6
) 5.08
43.9 <0.001 34.5
105.5 0.114 91.8
41.2 0.359 35.7
2.03 0.093 1.26
0.11 <0.001 0.13
2.30 0.963 1.46
0.36 0.042 0.25
1.14 0.015 0.30
0.37 <0.001 0.13
0.13 0.002 0.07
58.6 <0.001 60.5
8.25 <0.081 4.06
227.8 <0.001
103.2 <0.001
42.0 <0.001
1.33 0.404
0.21 <0.001
1.35 0.051
0.41 <0.001
0.29 0.683
0.11 0.009
0.03 <0.001
26.4 <0.001
3.02 0.317
z C is the carbon, N is the nitrogen, P is the phosphorus, K is the potassium, S is the sulfur, Ca is the calcium, Mg is the magnesium, Na is the sodium, Fe is the iron, Mn is the manganese. y Samples were collected from 26 to 28 April in 2010. x Samples were harvested from 3 to 9 June in 2010.
Table 2 Nutrient uptake of onion plants at the Initial bulbing stage and harvest in onion growers’ fields (n = 16). Parts
Sampling time
Yield (Mg ha−1 )
Nz
P
K
S
Ca
Mg
Na
Fe
Mn
4.11 1.28 <0.001 1.32 14.7 <0.001
49.8 26.4 <0.001 15.2 93.3 <0.001
10.1 4.17 <0.001 2.65 28.4 <0.001
14.1 12.2 0.123 3.08 20.1 <0.001
3.66 4.04 0.303 1.27 7.42 <0.001
1.54 1.41 0.403 0.72 1.81 <0.001
0.55 0.70 0.069 0.58 1.84 <0.001
0.10 0.09 0.724 0.03 0.21 <0.001
kg ha−1 Leaf
Bulb
z y x
Initial bulbing stagey Harvesty Probabilities Initial bulbing stagex Harvest Probabilities
22.2 13.9 <0.001 10.7 68.5 <0.001
53.2 23.9 <0.001 12.4 92.8 <0.001
N is the nitrogen, P is the phosphorus, K is the potassium, S is the sulfur, Ca is the calcium, Mg is the magnesium, Na is the sodium, Fe is the iron, Mn is the manganese. Samples were collected from 26 to 28 April in 2010. Samples were harvested from 3 to 9 June in 2010.
3.2. Soil physical and chemical properties Significant differences between the soils at the initial bulbing stage and harvest were found in WC, EC, N, NO3 N and exchangeable Ca values in surface soil (Table 3). Significant differences of soil properties in subsoil were the same as in surface soil. The WC, EC, N and NO3 N content decreased at harvest, compared with the initial bulbing stage in surface soil and subsoil, while exchangeable Ca content increased in surface soil, but decreased in subsoil at harvest. Other exchangeable cations, S and available P content also showed the same tendency as Ca content, although the values were not significant. Lower WC, EC, N and NO3 N content at harvest in surface soil can be explained by their removal into plant tissues and nutrient leaching loss. However, because onion plant absorbed Ca significantly less than N or K (Table 2), and Ca moved to surface soil from the subsoil, the exchangeable Ca content might increase
in the surface soil at harvest. In Korea, most crops have ranges of pH, OM and several main elements in soil for their production (Lee et al., 2006). The range for onion crop production includes 6.0–6.5 of pH, <2.0 dS m−1 of EC, 25–35 mg kg−1 of OM, 129–168 mg kg−1 of P, and 0.39–0.50, 5.8–6.7, 2.1–2.7 cmolc kg−1 of Ex. K, Ca and Mg, respectively. At the initial bulbing stage in surface soil, the av. P content was 3 times higher than the optimum range, and ex. K and Ca was 0.67 and 1.72 cmolc kg−1 higher than the optimum range. The soil OM or EC content were not high as compared with the range, but were considerably accumulated, relative to common paddy soil in Korea. Bernstein and Ayers (1953) reported that initial yield decline started at a threshold EC of 1.4 dS m−1 , and 50% yield reduction was at 4.1 dS m−1 . Lee et al. (2011) found that NO3 N content in the range of 7 to 42 mg kg−1 soil over the growing season resulted in the same bulb yield as at least 100% higher NO3 N content.
Table 3 Soil bulk density, water content, organic matter and mineral contents in onion growers’ fields on a dry weight basis (n = 16). Soil depth
Sampling time
BDz (g l−1 )
WC (g kg−1 )
pH
EC (dS m−1 )
OM (g kg−1 )
N (g kg−1 )
NO3 N (mg kg−1 )
S (mg kg−1 )
Av. P (mg kg−1 )
Ex. cation, (cmolc kg−1 ) K
Surface soil
Subsoil
Initial bulbing stagez Harvesty Probabilities Initial bulbing stagez Harvesty Probabilities
1.15
36.8
6.11
1.37
37.8
2.77
1.10 0.191 –
29.7 0.001 –
6.41 0.127 6.74
0.84 0.004 0.94
38.7 0.792 29.5
2.36 0.022 –
41.8 0.007 63.9
6.87 0.604
0.62 0.003
26.6 0.159
– –
17.7 <0.001
– –
– –
101.4
Ca
255
485.1
1.17
293 0.189 –
504.3 0.815 289.3
1.39 0.286 0.76
10.9 0.009 7.84
2.48 0.716 2.54
253.4 0.523
0.59 0.213
5.57 <0.001
2.22 0.084
– –
8.42
Mg 2.41
z BD is the bulk density, WC is the water content, EC is the electrical conductivity, OM is the organic matter, N is the nitrate, NO3 N is the nitrate nitrogen, S is the sulfur, Av. P is the available phosphorus, Ex Cations is the exchangeable cations, K is the potassium, Ca is the calcium, Mg is the magnesium. y Samples were collected from 26 to 28 April in 2010. x Samples were harvested from 3 to 9 June in 2010.
J. Lee, S. Lee / Scientia Horticulturae 179 (2014) 158–162
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Table 4 Correlation coefficient between soil physico-chemical properties and leaf nutrients at the initial bulbing stage (n = 16). Soil properties
BD WC pH OM N NO3 N S Ava. P Ex. K Ex. Ca Ex. Mg EC
Leaf nutrients FWz
DM
C
N
S
P
K
Ca
Mg
Fe
Mn
−0.242 0.372 −0.059 0.445 0.122 −0.379 −0.284 0.111 0.550* −0.178 0.110 −0.351
−0.521* −0.147 −0.275 0.126 0.467 0.032 0.255 0.376 0.213 0.148 0.076 −0.073
−0.572* −0.102 −0.260 0.194 0.541* 0.072 0.121 0.415 0.274 0.176 0.075 −0.040
−0.321 −0.213 −0.106 −0.184 0.344 0.257 0.217 0.438 −0.180 0.253 −0.113 0.162
−0.322 −0.287 −0.153 −0.017 0.417 0.237 0.317 0.466 −0.063 0.206 −0.050 0.280
−0.432 −0.118 −0.172 −0.037 0.470 −0.052 0.218 0.574* −0.033 0.161 −0.085 −0.096
−0.384 −0.219 −0.280 −0.049 0.366 −0.106 0.364 0.544* −0.029 0.045 −0.187 −0.216
−0.076 −0.516* −0.043 0.142 0.362 0.117 0.326 0.076 −0.069 0.182 0.154 0.152
0.045 0.270 0.611* −0.268 −0.033 −0.157 0.099 −0.013 −0.196 0.477 0.316 −0.054
0.341 −0.229 0.087 −0.329 −0.147 −0.228 0.140 −0.156 −0.268 −0.030 −0.111 −0.125
0.076 −0.478 −0.642* −0.267 0.072 0.025 0.231 0.267 −0.402 −0.432 −0.560* −0.065
z FW is the fresh weight, DM is the dry matter, C is the carbon, N is the nitrogen, S is the sulfur, P is the phosphorus, K is the potassium, Ca is the calcium, Mg is the magnesium, Fe is the iron, Mn is the manganese, BD is the bulk density, WC is the water content, NO3 is the nitrate, Ava is the available, Ex is the exchangeable, EC is the electric conductivity. Asterisks indicate significance at p < 0.05 (*) for correlations.
Table 5 Correlation coefficient between soil physical-chemical properties and bulb nutrients at the initial bulbing stage (n = 16). Soil properties
BD WC pH OM N NO3 N S Ava. P Ex. K Ex. Ca Ex. Mg EC
Bulb nutrients FWz
DM
C
N
S
P
K
Ca
Mg
Fe
Mn
−0.267 0.488 −0.027 0.382 0.180 −0.166 −0.164 −0.126 0.414 −0.050 0.272 −0.223
−0.111 −0.172 −0.344 0.031 0.198 0.243 0.212 −0.052 0.101 −0.163 0.038 0.076
−0.194 −0.090 −0.295 0.133 0.257 0.195 0.194 −0.002 0.200 −0.135 0.098 0.043
0.024 −0.295 −0.211 −0.374 −0.027 0.284 0.251 0.297 −0.422 −0.045 −0.386 0.145
0.034 0.098 0.254 −0.207 −0.042 0.557* 0.088 −0.166 0.050 0.398 0.336 0.617*
0.145 0.073 0.234 −0.092 0.166 −0.391 0.097 0.032 0.238 0.200 0.185 −0.255
0.109 −0.219 −0.009 −0.148 0.173 −0.149 −0.109 0.192 −0.017 0.058 −0.132 −0.181
−0.087 −0.252 0.283 0.161 0.151 0.170 −0.151 0.079 0.044 0.451 0.241 0.216
0.533* −0.257 0.227 −0.533* −0.338 0.107 −0.077 −0.178 −0.525* 0.088 −0.227 0.135
0.554* −0.333 −0.049 −0.597* −0.408 0.251 0.003 −0.325 −0.625** −0.085 −0.345 0.183
0.271 −0.340 −0.528* −0.351 −0.038 0.185 0.070 0.062 −0.459 −0.411 −0.509* 0.099
z FW is the fresh weight, DM is the dry matter, C is the carbon, N is the nitrogen, S is the sulfur, P is the phosphorus, K is the potassium, Ca is the calcium, Mg is the magnesium, Fe is the iron, Mn is the manganese. BD is the bulk density, WC is the water content, NO3 is the nitrate, Ava is the available, Ex is the exchangeable, EC is the electric condutivity. Asterisks indicate significance at p < 0.05 (*) and p < 0.01 (**) for correlations.
3.3. Correlation coefficient between soil physical–chemical properties and plant nutrients
to most of the leaf nutrients, with being significant in C content. Increase in leaf FW was associated with increases in soil WC, OM and Ex. K, but with decreases in soil NO3 –N and EC. Soil ava. P content was positively correlated with plant P and K concentration. Table 5 is a correlation matrix that shows the relations between soil tests and bulb minerals at the initial bulbing stage. Soil NO3 N and EC were positively correlated with bulb S content. Bulb Mg and
Table 4 presents a correlation matrix for relations between soil tests data and leaf mineral concentrations of onions at the initial bulbing stage, collected from 16 farmers. The soil BD was negatively correlated with most of the leaf nutrients, with being significant in DM and C content. Higher soil N related positively
Table 6 Correlation coefficient between soil physico-chemical properties at the initial bulbing stage and bulb nutrients at harvest (n = 16). Soil properties
BD WC pH OM N NO3 N S Ava. P Ex. K Ex. Ca Ex. Mg EC
Bulb nutrients FW
DM
C
N
S
P
K
Ca
Mg
Fe
Mn
SSC
PA
T P
0.063 0.260 0.012 0.200 −0.089 −0.449 −0.444 0.123 0.264 −0.193 −0.203 −0.419
0.516* −0.019 0.022 −0.153 −0.253 −0.354 −0.127 −0.554* −0.000 −0.261 0.089 −0.306
0.637** −0.046 −0.085 −0.252 −0.326 −0.326 −0.185 −0.608* −0.033 −0.329 0.054 −0.235
0.222 −0.191 −0.567* −0.407 −0.316 0.344 −0.192 0.026 −0.488 −0.639** −0.550* 0.162
0.202 −0.111 0.004 −0.202 −0.025 0.131 0.040 0.051 −0.109 −0.056 −0.120 0.150
0.355 −0.195 −0.186 −0.358 −0.156 −0.252 0.049 −0.009 −0.222 −0.234 −0.188 −0.183
−0.240 0.513* 0.200 0.394 0.441 −0.336 0.283 0.258 0.567* 0.217 0.176 −0.355
0.677** −0.227 −0.232 −0.604* −0.495 0.366 −0.279 −0.812*** −0.451 −0.168 −0.070 0.317
0.770** −0.018 0.008 −0.633** −0.514* −0.050 −0.259 −0.633* −0.454 −0.202 −0.181 −0.039
0.612* −0.037 0.282 −0.671** −0.449 0.024 −0.304 −0.626** −0.370 0.053 0.090 0.068
0.603* −0.223 −0.068 −0.378 −0.242 −0.051 −0.170 −0.510* 0.044 −0.125 0.047 0.147
0.472 −0.007 −0.218 −0.270 −0.433 −0.567* −0.194 −0.176 −0.187 −0.530* −0.405 −0.564v
−0.362 −0.347 −0.442 0.092 0.393 0.311 0.267 0.549* −0.122 −0.162 −0.243 0.292
−0.511* −0.117 −0.245 0.344 0.385 0.286 0.269 0.500* −0.107 −0.001 −0.087 0.198
FW is the fresh weight, DM is the dry matter, C is the carbon, N is the nitrogen, S is the sulfur, P is the phosphorus, K is the potassium, Ca is the calcium, Mg is the magnesium, Fe is the iron, Mn is the manganese, SSC is the soluble solid content, PA is the pyruvic acid, T-P is the total phenolic compounds, BD is the bulk density, WC is the water content, NO3 is the nitrate, Ava is the available, Ex is the exchangeable, EC is the electric conductivity. Asterisks indicate significance at p < 0.05 (*), p < 0.01 (**) and p < 0.001 (***) for correlations.
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Fe content were positively correlated with soil BD, but negatively correlated with OM and ex. K content. Numerous significant correlations existed between soil tests at the initial bulbing stage and bulb minerals at harvest (Table 6). Soil BD was significantly positively correlated with bulb DM, C, Ca, Mg, Fe and Mn content, but negatively with T P. Conversely, available P content was negatively correlated with bulb DM, C, Ca, Mg, Fe and Mn, but positively with PA and T P. Similarly, soil OM content was negatively correlated with bulb Ca, Mg and Fe content. Increases in soil pH, ex. Ca and Mg content were associated with decrease in bulb N content. Although correlations among soil tests and bulb FW were not significant, higher soil NO3 N, S and EC content related negatively to bulb FW. Nitrogen, P and K are the main fertilizers applied by onion growers before transplanting, and as side-dress fertilizer. Moreover, much compost or composted animal manure are applied preplanting, for improving soil physics, which also accumulate nutrients in soil, especially P or K, as well as OM (Bary et al., 2000). There were contradictory hypotheses on how much fertilizer should be applied to onion plants. Onion requires excessive rates of fertilizer to attain maximum bulb yield, because the onion plant has a shallow, sparsely branched root system, which result in considerable residual nutrients in soil after harvest (Brewster, 2008). However, onion is among the most sensitive crops to soil salinity, particularly at seedling emergence (Alen et al., 1998). Lee et al. (2012) reported that excessive fertilization was detrimental to the yield and quality for onion grown on high organic matter content paddy soils. Plant nutrients and leaf growth generally may increase with applied fertilization rate during the vegetative growth stage (Buwalda and Freeman, 1987; Painter, 1977; Westerveld et al., 2003). However, overfertilization including N, P, K or compost did not positively affect bulb yield or bulb nutrients at harvest (Abdelrazzag, 2002; Lee et al., 2012). In addition, fertilizer uptake efficiency decreased with higher N or K application rates (Lee et al., 2011). These literatures explain why in our results soil N and P contents had a relatively positive correlation with leaf DM, C, N, S, P and K at the initial bulbing stage, but did not have a consistent correlation with bulb nutrients, or a negative correlation with bulb nutrients at harvest. Acknowledgements The author would like to thank Prof. George Boyhan at University of Georgia for writing assistance and suggestions to improve this manuscript. The research was financed by Locally Specialized Agricultural Techniques (No. PJ00733004) from Korean Rural Development Administration (RDA), Republic of Korea. References Abdelrazzag, A., 2002. Effect of chicken manure, sheep manure and inorganic fertilizer on yield and nutrients uptake by onion. Pak. J. Biol. Sci. 5, 266–268. Alen, R.G., Pereira, R.G., Raes, D., Smith, M., 1998. Crop Evapotranspiratin- Guidelines for Computing Crop Water Requirements. FAO Irrigaion and Drainage Paper 56. Rome.
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