Effect of Multi-Year Protection of Grapevines with Copper Pesticides on the Content of Heavy Metals in Soil, Leaves, and Fruit

Abstract

This study evaluates the impact of multi-year protection of grapevines using copper-based pesticides on heavy metal content in soil, leaves, and fruit under organic and conventional cultivation methods. Conducted on Solaris, Hibernal, and Muscaris grapevine varieties in north-western Poland, the research highlights significant differences between the two cultivation approaches. In organic vineyards, copper content in soil averaged 10.25 mg/kg, significantly higher than the 9.05 mg/kg found in conventional soils. Manganese levels were also elevated in organic soils (223 mg/kg) compared to conventional ones (299 mg/kg). Conversely, conventional vineyards exhibited higher zinc and lead concentrations, averaging 47.10 mg/kg and 20.34 mg/kg, respectively, versus 43.50 mg/kg and 11.22 mg/kg in organic soils. The organic soils also had higher salinity (46.50 mg/kg) than conventional ones (30.50 mg/kg). The fruits of grapevines in organic cultivation showed higher copper and zinc levels, with the Solaris variety containing 15.01 mg/kg of copper and the Muscaris variety having 11.43 mg/kg of zinc. These levels exceed the commonly encountered ranges of <1 to 10 mg/kg. Lead content in fruits was higher in organic cultivation (2.19 mg/kg) than in conventional cultivation (1.18 mg/kg), occasionally surpassing the critical value for consumable plants (1 mg/kg). Leaves of grapevines from organic vineyards had significantly higher copper and manganese content than those from conventional vineyards, with the Hibernal variety showing the highest levels. These findings underscore the necessity for monitoring and managing heavy metal content in vineyard soils to ensure fruit quality and safety.

1. Introduction

In Poland, many small vineyards have been established over the past two decades. These vineyards now cover approximately 1000 ha in total, with each vineyard averaging 1.4 ha. There has been a notable annual growth, with the total vineyard area doubling over the last ten years. Most of these vineyards are located in the southern and western regions of the country [1]. Owing to a lack of traditional viticulture and a well-developed wine production infrastructure, the establishment of conventional vineyards predominates. Organic vineyards, in contrast, are scarce. Organic wine production is notably labor-intensive and expensive, necessitating specialized, frequent agrotechnical and protective interventions, employing only substances approved for such cultivation. Given the relatively recent establishment of vineyards in Poland, the influence of specific climatic and soil conditions on the quality of both the fruit and the resulting wine has yet to be extensively characterized [2]. In Poland, the climate differs from that of southern and western European countries, characterized by lower temperatures and sunlight exposure, different precipitation and frost patterns, etc., as well as distinct soil properties, mainly lower soil pH, generally below 7.0 [3,4].

In the short- and medium-term perspective, grapevine cultivation in Poland will remain economically insignificant. However, due to climate change, it may become a significant sector in the long term [5,6]. The climate, soil properties, and agronomic practices shape the quality of the grapes and the wine produced from them [7,8]. Often, the chemical composition of wine can reveal the region (soil, climate) in which it was produced [9,10,11]. Moreover, another significant factor affecting the quality of grapes and wine is their anthropogenic contamination with heavy metals. Artificial fertilizers and plant protection products are particularly significant sources of heavy metals in soil, grapes, and wine [7,8,9,10,12,13]. Copper-based fungicides, commonly used in vineyards to combat fungal diseases such as downy mildew, play a particular role in the contamination with copper but also with other heavy metals, such as Pb and Zn. Grapevine fruits in Poland mature mainly in September. During this time, heavy rainfall often occurs, causing the grapes to crack and rot. This forces producers to increase the chemical protection of the grapes, which can lead to increased contamination of the soil and fruit [14].

Among agricultural crops, the highest concentration of Cu is found in permanent crops such as orchards and vineyards. European agricultural soils often exceed the permissible content of this element [15,16], which reduces soil fertility [17]. Exceeding normative amounts of heavy metals in the soil causes a series of adverse environmental changes, including a reduction in the availability of certain plant nutrients, soil microbial activity, and the transformation of organic matter [18,19,20].

From polluted soil, plants absorb excessive phytotoxic quantities of heavy metals, which disrupt their metabolism, inhibit the growth of roots and above-ground parts, and degrade the quality of grapes [21,22,23]. Among cultivated plants, Vitis vinifera L. has a high tolerance to stress induced by heavy metals, and even at high concentrations in leaves and grapes, phytotoxic symptoms are not observed [24,25]. However, the excess of heavy metals in grapes is problematic in the process of wine production and preservation. Metal ions play an important role in redox reactions, forming complexes with polyphenols, anthocyanins, tannins, proteins, amino acids, and phosphoric acids, causing the browning of wine, cloudiness, astringency, changes in aroma and taste, as well as precipitation of sediments and tannins [9,26,27,28,29,30]. Furthermore, heavy metals in wine can affect human health. Wine is an important source of microelements but also toxic metals in the human diet [31]. The problem of heavy metal contamination in wines, especially Cu, affects many wines. The average Cu level ranges from 0.08 mg/L in Bulgarian wines to 0.81 mg/L in Turkish wines. The highest measured level of this element was found in Herzegovinian wine at 5.76 mg/L [32]. In Polish wines, the level of heavy metal contamination was low, as none of the tested wines exceeded toxic levels of heavy metals [33]. Excessive residues of copper in grapes can raise concerns about food safety. Consuming grapes with high levels of copper can pose a health risk, especially if they are consumed in large quantities or over a prolonged period. Copper toxicity can lead to gastrointestinal problems, liver damage, and other health issues.

This research focused on evaluating the impact of fertilization and protection methods in organic and conventional cultivation on soil properties and the fruit quality of three grapevine cultivars, as well how the long-term use of copper-based pesticides can affect the environment.

2. Materials and Methods

2.1. Characteristics of the Area of Research and Plant Material

Vitis vinifera L. cultivars Solaris, Hibernal and Muscaris were used for the study (Figure 1).

Fruit was taken from an organic and conventional plantation located near Szczecin in north-western Poland (53°21′09.8″ N 14°26′23.3″ E) (Figure 2). In the area of Szczecin and in the nearby northern region, minimal temperatures range from −12 °C to −15 °C, which corresponds to values typical of zone 7B. The average temperature during the growing season (May–October) between 1951 and 2019 was 15.4 °C, and rainfall was approximately 350 mm [4].

During 2020–2022, major changes in the weather were observed. In July and August, temperatures exceeded 30 °C for several days and did not fall below 20 °C at night—a phenomenon of tropical nights. There were prolonged periods of drought—2020: 35 days without rainfall; 2021—32 days without rainfall; 2022—46 days without rainfall. This period was followed by heavy/intense rainfall exceeding 100 mm per day. September was characterized by weather typical of the period and similar to that of many years (data obtained from the Meteorological Experimental Station in Lipnik, Poland 53°20′35″ N 14°58′10″ E).

2.2. Cultivation Scheme

Grapevines were planted in 2016 at a spacing of 1.01 × 2.28 m (Figure 3). Pruning was carried out in January–February. The grapevines were pruned with a Guyot (one arm) training system and vertically positioned with eight shoots with two clusters per each. On both plantations in the rows, weeds were removed with a mechanical weeder. In the inter-rows, mixtures were used to improve the soil structure and enrich it with organic matter (lucerne, red clover, oil radish). During the growing season, shoots and excess leaves from the cluster zone were removed mechanically.

During the growing season (May–October), the following was applied for crop protection (in pure component per hectare):

• In the organic plantation (Figure 4):

Sulfur—12.5 kg/ha;

Copper (copper oxychloride and copper hydroxide)—1.75 kg/ha;

Potassium carbonate—17.5 kg/ha;

Potassium grey soap—4 kg/ha.

• In a conventional plantation:

Metalaxyl-M (a compound of the phenylacetamide group 3.8%) and mancozeb (a compound of the dithiocarbamate group 64%)—2.25 kg/ha;

Cyflufenamid (a compound of the phenylacetamide group 5.32%)—0.3 kg/ha;

Cyprodinil (a compound of the anilinopyrimidine group 37.5%) and fludioxonil (a compound of the phenylpyrrole group 25%)—1.2 kg/ha.

On the organic and conventional plantations, a green manure mix of red clover, white clover, and alfalfa was sown for plowing. Every four years, magnesium lime was applied at a rate of 2 tons per ha.

On the conventional plantation, urea was applied annually at a rate of 30 kg N/ha, along with ammonium nitrate at the same rate. Due to the soil’s richness in phosphorus and potassium, fertilization with these elements was not practiced.

Collection samples from the organic and conventional field (three containers of 5 kg fruit each) were taken in late September/early October, in sterile containers. Each bulk sample collected from 10 vine bushes came from a different location within the field. After transport to the laboratory, juice was pressed from the fruit and analyses were performed. And the copper and sulfur contents were checked in the wine as well (results in preparation for publication).

The material for the study (leaves and fruits) was collected from pre-selected plants—from 10 grapevines growing next to each other in one row (2 spans) from three locations (different rows) in the central part of the plot. No material was collected from the 2 edge rows adjacent to another variety. Leaves were collected at the end of July (7 days after the last spraying with copper and sulfur-containing agents), with 2 leaves taken from the middle part of each shoot: 8 shoots × 2 leaves × 10 grapevines = 160 leaves × 3 repetitions per variety. Grapes were collected from the same plants. Grapes from each variety in both the organic and conventional fields were harvested on the same day in late September/early October (depending on the variety) into sterile containers. All fruits from the designated 10 shrubs in the three locations were collected and samples of approximately 5 kg each were prepared.

2.3. Soil

In the soil material, the following determinations were made: the granulometric composition of the soil was determined using the method Casagrandea in Prószyński’s modification, available phosphorus and potassium in the soil were determined using the Egner–Riehm method, available magnesium using the Schachtschabel method, total C, N and S contents by elementary analysis (Costech Elementary Analyzer ECS 4010, Milano, Italy), pH in H₂O and pH in 1 mol/L KCl was determined potentiometrically, salinity by conductometry, content of available Zn, Cu, Fe and Mn was by extracting in 0.5 mol/L HCl, and the content of total forms Zn, Cu, Fe, Mn, Pb and Ni were determined after mineralization in HNO₃ and HClO₄ in a ratio of soil 1:1 with flame atomic absorption spectroscopy using iCE 3000 Series. The limits of detection (mg/kg) were as follows: Cu 0.005; Zn 0.003; Fe 0.004; and Mn 0.002. Assessments of the accuracy and precision of the analytical methods and procedures used were determined using certified reference material: CRM036–050 Loamy Sand 4 (CRM 036-050 produced by Resource Technology Corporation, State College, PA, USA). The effectiveness of the process was validated with 90–95% efficiency. The results shown are the average of three measurements, working standards made from Merck standards with a concentration of 1000 mg/dm³.

2.4. Plants

The content of elements in fruit and vine leaves were determined: Cu, Zn, Fe, Mn, Pb and Ni were measured after wet mineralization in H₂SO₄ and HClO₄ in a ratio 3:1. The content of elements was measured with atomic absorption spectroscopy using iCE 3000 Series. The efficiency of the process was validated with 90–95% success using certified reference materials, namely, tea leaves (INCT-TL-1) and a mixture of Polish herbs (INCT-MPH-2), both produced by the Institute of Nuclear Chemistry and Technology, Warsaw, Poland. All tests were performed in three replications.

2.5. Must Quality

The total soluble solid content (SSC) (°Bx) in samples was measured at 20 °C by a digital refractometer (PAL-1, Atago, Tokyo, Japan). Total acidity (calculated on tartaric acid) was determined by titration of aqueous extract with 0.1 N NaOH to an end point with pH 8.1 (Elmetron CX-732, Zabrze, Poland), according to the PN-90/A-75101/04 standard.

The must’s turbidity was measured using a Lovibond TB211IR working on the principle of measuring scattered light in the 400–600 nm range.

YAN was quantified using the enzymatic method; readings were taken in an automatic wine analyzer using the spectrophotometric method.

2.6. Statistical Analysis

All statistical analyses were performed with Statistica 12.5 (StatSoft Polska, Cracow, Poland). The data were subjected to one-factor variance analysis (ANOVA). Mean comparisons were performed using Tukey’s least significant difference (LSD) test; significance was set at p < 0.05.

3. Results and Discussion

3.1. Basic Soil Properties

Numerous studies conducted in vineyards indicate that heavy metals are absorbed and accumulated in grapevines [13,34,35]. Their uptake by plants depends on many factors, primarily their content in the soil, the content of humus and clay minerals, soil pH, the presence of other macro and microelements as well as toxic elements in the soil, pollution emissions, and the physiological conditions of grapevine species [11,35,36,37]. Especially in young vineyards under Polish conditions, these dependencies are poorly understood.

The vineyard was established on Luvisols soil, which was loamy (sand—40%, silt—40%, clay—20%), non-saline, rich in humus and macroelements, and ranging from acidic to slightly acidic in reaction. Phosphorus levels in conventional soils were significantly higher than in organic soils, but both were within acceptable agricultural norms. Both organic and conventional soils had potassium levels within the normal range, with conventional soils showing a slight but not significant increase. Magnesium levels in conventional soils were significantly higher than in organic soils but remained within acceptable agricultural norms. These are some of the main soil types in Poland with an average agricultural value, most commonly cultivated with demanding agricultural plants (wheat, rapeseed) and orchards. The identified properties of these soils (

Table 1. Comparison of soil properties by cultivation method and soil layer.

Cultivation Method	Soil Layer		Mean
	0–20 cm	20–40 cm
	C total (%)
organic	1.45 c *	1.12 a	1.28 A
conventional	1.54 d	1.23 b	1.38 A
mean	1.49 B	1.17 A
	N total (%)
organic	0.15 bc	0.12 a	0.14 A
conventional	0.17 c	0.13 ab	0.15 A
mean	0.16 B	0.13 A
	P (mg/100 g)
organic	0.13 ab	0.12 a	0.13 A
conventional	0.18 c	0.15 b	0.17 B
mean	0.16 A	0.14 A
	K (mg/100 g)
organic	0.48 b	0.42 a	0.45 A
conventional	0.50 bc	0.53 c	0.52 A
mean	0.49 A	0.48 A
	Mg (mg/100 g)
organic	0.23 a	0.21 a	0.22 A
conventional	0.28 b	0.29 b	0.29 B
mean	0.26 A	0.25 A
	S total
organic	0.04 b	0.02 a	0.3 B
conventional	0.02 a	0.01 a	0.1 A
mean	0.03 B	0.01 A
	pH H2O
organic	6.44 a	6.65 a	6.55 A
conventional	6.95 b	6.73 ab	6.84 B
mean	6.70 A	6.69 A
	pH KCl
organic	5.77 a	5.79 a	5.78 A
conventional	6.36 b	6.27 b	6.32 B
mean	6.07 A	6.03 A
	Salinity
organic	51 c	42 b	46.50 B
conventional	34 a	27 a	30.50 A
mean	42.50 B	34.50 A

* mean values in column denoted by the same uppercase or lowercase letters do not differ statistically significantly at 0.05 according to Tukey test.

) favor the binding of heavy metals in the top layer of the soil and their solubility and availability to plants due to the acidic and slightly acidic reaction. The properties of soils, as well as organic and conventional cultivation systems, affect the quality parameters of the fruit and the content of heavy metals in the leaves and fruit of grapevines.

3.2. Parameters and Chemical Composition of the Grapes

Based on the presented data (

Table 2. Comparison of grape yield and quality metrics by cultivation method and cultivars.

Cultivation Method	Solaris	Hibernal	Muscaris	Mean
	Yield/plant (kg)
organic	2.38 c *	1.75 a	2.10 b	2.08 A
conventional	2.56 d	2.07 b	2.28 c	2.30 B
mean	2.47 C	1.91 A	2.19 B
	Weight of 100 grape berries (g)
organic	113 b	89 a	136 c	113 A
conventional	134 c	95 a	142 c	124 A
mean	123 B	92 A	139 C
	Cluster weight (g)
organic	132 bc	98 a	139 c	123 A
conventional	147 cd	117 b	164 d	143 B
mean	140 B	108 A	152 C
	SSC (°Brix)
organic	25.8 e	22.0 b	24.9 d	24.2 B
conventional	24.5 cd	20.9 a	23.7 c	23.0 A
mean	25.2 B	21.5 A	24.3 B
	Total acidity (g tartaric acid/L)
organic	7.4 b	8.5 c	6.7 a	7.5 A
conventional	8.3 c	9.1 d	7.2 ab	8.2 B
mean	7.9 B	8.8 C	7.0 A
	Turbidity of must (NTU)
organic	1025 b	884 a	2045 d	1318 A
conventional	1414 c	903 a	2261 e	1526 B
mean	1220 B	894 A	2153 C
	YAN—Yeast Assimilable Nitrogen (mg/L)
organic	125 a	136 ab	134 a	132 A
conventional	162 c	158 c	149 bc	156 B
mean	144 A	147 A	142 A

* mean values in column denoted by the same uppercase or lowercase letters do not differ statistically significantly at 0.05 according to Tukey test.

), the results indicate a relationship between the cultivation method (organic or conventional) and several quality parameters and components of grapes as well as their processing into wine.

The cultivation method has a significant impact on the quality and composition of grapes. Conventional cultivation resulted in higher yields per plant compared to organic cultivation. Grape berries and clusters harvested from conventionally grown grapevines were also larger.

In particular, organic cultivation tends to result in higher soluble solids content and lower total acidity (calculated on tartaric acid), which can positively affect the taste and balance of the wine. This may be due to lower plant stress and smaller fruit size. Conversely, conventional cultivation is characterized by higher turbidity and higher YAN (yeast assimilable nitrogen) levels, which can influence the fermentation process and the quality of the final product. The higher YAN levels may be due to higher nitrogen content in the soil (Figure 5).

The studied varieties differ significantly in terms of technological parameters of the must, which can influence the final quality and sensory profile of the wine. The choice of variety and cultivation method should be tailored to the desired characteristics of the final product. Solaris shows the highest yield and soluble solids content, allowing for wines with varying characteristics and relatively low acidity. Hibernal is characterized by the highest acidity and the lowest fruit weight, which may contribute to a more pronounced wine flavor but lower yield. Muscaris stands out for the largest fruit and cluster weight but also has the highest must turbidity, which can affect the clarity of the final product.

The analysis of data presented in Figure 5 and

Table 3. Correlation coefficients between soil, leaves, grapes, and YAN for organic and conventional cultivation methods.

N	Organic				Conventional
	Soil	Leaves	Grapes	YAN	Soil	Leaves	Grapes	YAN
soil	1.00	−0.37	−0.35	−0.58	1.00	0.37	0.35	0.48
leaves	−0.37	1.00	0.42	0.43	0.37	1.00	−0.22	0.60
grapes	−0.35	0.42	1.00	0.77 *	0.35	0.22	1.00	0.86 *
YAN	−0.58	0.43	0.77 *	1.00	0.48	0.60	0.86 *	1.00

* correlation significance at the level of 0.05.

indicates relationships between nitrogen content in the soil, leaves, and fruits of grapevines grown in organic and conventional systems. Soils in conventional cultivation contained higher amounts of nitrogen compared to organic cultivation, suggesting more intensive use and better utilization of nitrogen fertilizers in the conventional system. Leaves and grapes of conventionally grown grapevines also showed higher nitrogen content than those from organic cultivation. High nitrogen content in indicator parts may result from better nitrogen supply to plants in the conventional system. Higher nitrogen content in the soil, leaves, and grapes of conventionally grown grapevines can improve conditions for plant growth and fruiting, as well as the quality of the final product, which is wine. This is supported by the results describing fruit quality and higher YAN levels.

The correlation coefficients between nitrogen content in the soil from conventional cultivation and other parameters (Table 3) indicate moderately strong negative relationships with its content in leaves (−0.37), grapes (−0.35), and YAN in must (−0.58).

There is, however, a moderately positive correlation between nitrogen content in the leaves and nitrogen content in the grapes (0.42) as well as YAN (0.43). Additionally, a strong positive correlation exists between nitrogen content in the grapes and YAN (0.77).

In conventional cultivation, a moderately positive correlation was found between nitrogen content in the leaves (0.37), grapes (0.35), and YAN (0.48). There is a negative correlation between nitrogen content in the leaves and grapes (−0.22) but a moderately positive correlation with YAN (0.60). Similar to organic cultivation, a very strong positive correlation exists between nitrogen content in the grapes and YAN (0.86).

The analysis of correlation coefficients shows differences in nitrogen distribution in various parts of the grapevine and must depending on the cultivation method. In organic cultivation, there is a stronger negative correlation between soil nitrogen and other variables, which may suggest more complex interactions in the organic cultivation system. In conventional cultivation, these relationships are generally more positive, particularly between nitrogen in the grapes and YAN, indicating a more direct influence of fertilization on must quality and the fermentation process.

3.3. Heavy Metals in Soils, Leaves and Grapes

3.3.1. Copper

The harmful threshold for copper in soil is 100 mg/kg [17]. Globally, copper levels in soils range from 1 to 140 mg/kg [38], with European levels typically between 5 and 20 mg/kg [16]. In Poland, the average copper content is 6.5 mg/kg [16,38]. Copper binds to clay minerals and humus [39,40], and its solubility depends on soil pH, element interactions, redox properties, and climate [20,38,41,42,43].

Agricultural soils may have elevated copper due to plant protection products and fertilization [16,42,44,45]. Although Poland uses relatively less copper-based fungicides compared to other European countries [16], the rise of organic farming has increased their use, especially in vineyards.

In Poland, small vineyards, including organic ones, have been commonly established in recent years, where copper-based products are the main plant protection agents. The excessive use of these in Polish conditions has not yet been adequately researched. The conducted research showed that the soil in the organic plantation was richer in exchangeable copper by an average of 21% and in total copper by 13% compared to the conventional plantation (

Table 4. Total element content in soil by cultivation method and soil layer (mg/1000 g).

Cultivation Method	Soil Layer		Mean
	0–20 cm	20–40 cm
	Fe
organic	13,729 c *	18,252 d	15,990 B
conventional	10,225 a	11,236 b	10,730 A
mean	11,977 A	14,744 B
	Mn
organic	246 b	200 a	223 A
conventional	321 d	278 c	299 B
mean	283 B	239 A
	Cu
organic	10.27 c	10.22 c	10.25 B
conventional	9.34 b	8.75 a	9.05 A
mean	9.81 A	9.49 A
	Zn
organic	45.4 c	41.6 b	43.50 A
conventional	58.4 d	35.8 a	47.10 B
mean	51.90 B	38.70 A
	Pb
organic	14.1 b	8.33 a	11.22 A
conventional	23.4 d	17.27 c	20.34 B
mean	18.75 B	12.80 A
	Ni
organic	18.20 a	25.50 b	21.85 A
conventional	33.30 cc	35.80	34.55 B
mean	25.75 A	30.65 B

* mean values in column denoted by the same uppercase or lowercase letters do not differ statistically significantly at 0.05 according to Tukey test.

and

Table 5. Bioavailable element content in soil by cultivation method and soil layer (mg/1000 g).

Cultivation Method	Soil Layer		Mean
	0–20 cm	20–40 cm
	Fe
organic	2304 d *	1816 c	2060.00 B
conventional	1573 b	1311 a	1442.00 A
mean	1938.50 B	1563.50 A
	Mn
organic	160.5 d	99.7 c	130.10 B
conventional	77.8 b	64.5 a	71.15 A
mean	119.15 B	82.10 A
	Cu
organic	4.48 d	3.39 b	3.94 B
conventional	3.63 c	2.89 a	3.26 A
mean	4.06 B	3.14 A
	Zn
organic	10.02 b	6.63 a	8.33 A
conventional	19.4 d	14.5 c	16.95 B
mean	14.71 B	10.57 A

* mean values in column denoted by the same uppercase or lowercase letters do not differ statistically significantly at 0.05 according to Tukey test.

).

Exchangeable copper constituted about 27% of total copper, with the 0–20 cm soil layer richer in copper than the 20–40 cm layer. According to Polish standards [46], exchangeable copper levels were medium, and soils did not require copper fertilization. Total copper content in soils from both organic and conventional vineyards was typical for uncontaminated agricultural soils, ranging from 4 to 36 mg/kg [38]. The total copper levels in these soils were nearly five times lower than the average in European vineyard soils [16] but similar to those in Hungary and Ukraine [47].

High copper contamination in European vineyard soils is significant, with 14.6% of soils exceeding the 100 mg/kg threshold [16,42,44,48]. Especially high levels are found in France, Italy, Portugal, and Romania [48,49], and in some Australian vineyards, levels reach up to 250 mg/kg [50]. Old vineyards can have copper levels between 200 and 500 mg/kg, posing environmental threats and affecting plant growth and fruit quality [13,42,47,51,52,53].

Copper uptake by grapevines depends on soil concentration and pH, with grapevines showing resistance to high soil copper levels [35,48]. Copper content in grapes from both organic and conventional vineyards was similar, averaging 12.78 and 12.87 mg/kg, respectively.

The highest copper content was found in the Solaris variety (15.01 mg/kg dry matter) and the lowest in Hibernal (10.29 mg/kg dry matter). These Cu levels in grapes were higher than the common range of <1 to 10 mg/kg but similar to other studies and lower than those in contaminated areas. Elevated copper in grapes from both organic and conventional vineyards results from frequent use of copper-based preparations, negatively impacting fruit quality [39]. High copper levels in wine can cause browning, loss of freshness, and sediment formation [15,54]. In Poland, the acceptable copper level in food products is 20 mg/kg [55].

Leaves of the studied grapevine varieties contained more copper than grapes (

Table 6. Analysis of mineral content in grapes from organic and conventional cultivation (mg/1000 g).

Cultivation Method	Solaris	Hibernal	Muscaris	Mean
	Fe
organic	23.78 a *	27.38 c	24.05 a	25.07 A
conventional	26.01 b	26.14 b	32.06 d	28.07 B
mean	24.90 A	26.76 AB	28.06 B
	Mn
organic	3.08 a	6.40 d	5.35 c	4.94 A
conventional	3.73 b	7.58 e	7.49 e	6.27 B
mean	3.40 A	6.99 B	6.42 B
	Cu
organic	14.48 c	12.10 b	11.78 b	12.78 A
conventional	15.55 e	8.49 a	14.57 d	12.87 A
mean	15.01 C	10.29 A	13.18 B
	Zn
organic	10.47 b	10.46 b	11.49 d	10.80 A
conventional	9.90 a	10.88 c	13.51 e	11.43 A
mean	10.18 A	10.67 A	12.50 B
	Pb
organic	2.62 c	3.87 d	0.10 a	2.19 B
conventional	2.79 c	0.31 b	0.45 b	1.18 A
mean	2.70 B	2.09 B	0.27 A
	Ni
organic	1.38 a	1.59 ab	1.92 c	1.63 A
conventional	1.79 bc	1.72 b	2.30 d	1.94 B
mean	1.58 A	1.65 A	2.11 B

* mean values in column denoted by the same uppercase or lowercase letters do not differ statistically significantly at 0.05 according to Tukey test.

and

Table 7. Analysis of mineral content in grapevine leaves from organic and conventional cultivation (mg/1000 g).

Cultivation Method	Solaris	Hibernal	Muscaris	Mean
	Fe
organic	103.21 a *	291.66 c	105.73 a	166.87 B
conventional	153.4 b	106.35 a	102.12 a	120.62 A
mean	128.30 B	199.00 C	103.92 A
	Mn
organic	33.24 b	66.87 e	46.74 cd	48.95 B
conventional	47.52 d	44.53 c	30.43 a	40.83 A
mean	40.38 A	55.70 B	38.58 A
	Cu
organic	41.88 b	112.52 e	79.77 d	78.06 B
conventional	31.19 a	82.43 d	66.38 c	60.00 A
mean	36.53 A	97.48 C	73.07 B
	Zn
organic	26.91 a	40.23 b	54.00 d	40.38 A
conventional	39.45 b	39.54 b	45.44 c	41.48 B
mean	33.18 A	39.88 B	49.72 C
	Pb
organic	0.47 b	0.81 c	0.80 c	0.69 A
conventional	1.42 d	1.72 e	0.06 a	1.07 B
mean	0.94 B	1.26 C	0.43 A
	Ni
organic	3.12 d	2.80 c	2.45 b	2.79 A
conventional	4.83 e	2.76 bc	2.01 a	3.20 B
mean	3.97 C	2.78 B	2.23 A

* mean values in column denoted by the same uppercase or lowercase letters do not differ statistically significantly at 0.05 according to Tukey test.

). Solaris leaves had the least (36.55 mg/kg dry matter) and Hibernal the most (97.48 mg/kg dry matter). This is due to the intensity of copper usage and physiological conditions. Leaves generally accumulate more copper due to their exposure to treatments and environmental factors.

The higher copper content in grapevine leaves compared to grapes is due to the physiological conditions of the plants [47]. Hibernal and Muscaris leaves have higher Cu levels than the typical 35–50 mg/kg found in grapevine leaves [30,35,40,56,57,58]. Grapevines generally thrive at about 35 mg/kg but can tolerate up to 80 mg/kg and even 148 mg/kg in some cases [23,57]. However, cultivated varieties show less resistance to high copper levels [57]. Some studies report copper levels in leaves ranging from 5 to 20 mg/kg [25,47,59].

The high tolerance of grapevines to copper is notable, since other plants show toxicity at 20–100 mg/kg, with deficiencies below 4 mg/kg [38]. The variation in copper content among grapevine leaves likely results from differences in copper usage intensity and deposition, as well as physiological factors. For instance, Solaris leaves contain significantly less Cu than Hibernal and Muscaris leaves, potentially due to a shorter vegetation period (30–45 days).

Despite this tolerance, excess copper can harm grapevine development, causing metabolic disorders and impairing photosynthesis. It also limits the uptake of micronutrients like Zn, Mo, Mn, and Fe, often leading to iron deficiency and leaf chlorosis despite high soil iron content [38].

3.3.2. Zinc

The average zinc content in the world’s soils ranges from 30 to 125 mg/kg, with Polish soils averaging about 40 mg/kg, and clay soils typically containing 52–80 mg/kg [38]. In Europe, agricultural soils generally do not contain excessive zinc levels [49], and zinc pollution is mostly localized [16]. In Poland, contaminated soils account for about 0.5% [45]. The main sources of zinc in agricultural soils are mineral fertilizers and plant protection products like Mancozeb [47,60]. However, zinc currently poses no significant threat to food safety in Europe, including Poland [38,47].

Soils in the organic vineyard were significantly poorer in exchangeable and total zinc compared to the conventional vineyard, with the topsoil (0–20 cm) being richer in zinc. The higher amounts of exchangeable zinc in conventional soils result from mineral fertilization and chemical plant protection. According to Polish standards [46], exchangeable zinc levels in both plantations were medium, and total zinc contents were typical for non-contaminated clay soils [55].

Plants absorb zinc based on its soil concentration, pH, and physiological conditions [35]. The average zinc content in plants ranges from 10 to 70 mg/kg, with 15–30 mg/kg in leaves sufficient for normal growth [38]. No significant differences in zinc content were found in grapes from organic and conventional cultivations, averaging 10.80 mg/kg and 11.43 mg/kg, respectively (Table 6). These levels are below the 50 mg/kg threshold for consumable plants [55]. Solaris grapes had the least zinc, while Muscaris had the most. The zinc levels were similar to those found by other studies [13,23,24,56] and significantly higher than others [30,40,47,61].

Zinc content was significantly higher in grapevine leaves (40.38 mg/kg in organic, 41.48 mg/kg in conventional), with Solaris leaves being the poorest and Muscaris the richest. These values are slightly higher than those commonly found in various plants but within the typical range for grapevines (25–200 mg/kg) [59]. Toxic levels in moderately sensitive plants are considered at 100–400 mg/kg [38]. Higher zinc levels in grapevines can increase sugar content and improve fruit firmness and storage properties [56].

3.3.3. Manganese

The manganese (Mn) content in soils ranges from 100 to 1300 mg/kg. Mn is bound by clay minerals and carbonates but poorly by organic matter. Manganese contamination is generally not quantitative, but its form can be hazardous [38]. The main sources of Mn in agricultural soils are mineral fertilizers [38,62].

Soils in both organic and conventional vineyards exhibited typical Mn levels for Polish brown clay soils, averaging 223 mg/kg in organic and 299.50 mg/kg in conventional vineyards (Table 4). Organic soils had nearly twice as much exchangeable Mn compared to conventional soils, primarily accumulating in the surface layer (Table 5). The soil pH below 7 in both plantations favors Mn uptake by grapevines [35].

Mn plays a vital role in plant metabolism, with most plants containing 10–25 mg/kg, though some grasses can absorb up to 160 mg/kg. Toxic levels for most plants are above 400–500 mg/kg dry matter [38].

Grapes from both vineyard types contained small amounts of Mn, averaging 4.94 mg/kg in organic and 6.27 mg/kg in conventional plantations (Table 6). Solaris grapes had the lowest Mn content, while Hibernal had the highest (Table 6). These levels are within the typical range of 1.0 to 25 mg/kg [24,30,40,56,61].

Grapevine leaves were richer in Mn than grapes, averaging 48.95 mg/kg in organic and 40.83 mg/kg in conventional plantations (Table 7). Hibernal leaves contained the most Mn. These levels are consistent with other findings for grapevine leaves but lower than some reported values [25,40,56,59]. The Mn content in grapevine leaves can range widely from 15–400 mg/kg dry matter [38].

3.3.4. Iron

The iron content in soils worldwide ranges from less than 1% to several percent, with Polish soils typically containing 0.8% to 1.8% iron [38]. Iron solubility increases with acidity and the formation of organic complexes [51,63].

This study showed that soils from the organic vineyard were richer in both exchangeable and total iron compared to the conventional vineyard (Table 4 and Table 5). Both forms of iron were more abundant in the surface layer. Total iron content in the organic vineyard was about 1.6% (15,990 mg/kg) and 1.1% (10,730 mg/kg) in the conventional vineyard, typical for Polish clay soils [38]. Exchangeable iron levels were medium in both plantations [46].

Despite significant soil iron levels, plants do not absorb excessive quantities and show high tolerance. Iron deficiencies are usually due to form and interaction with Mn, Ni, Cu, Zn, Ca, K, and P rather than a lack of iron [64,65]. The studied soils had a pH between 6.05 and 6.98, favorable for iron uptake [35].

Iron in plants generally ranges from a few to several hundred mg/kg dry matter, typically not exceeding 400 mg/kg [38]. Grapes from both organic and conventional vineyards contained small amounts of iron (25.07 and 28.07 mg/kg, respectively), less than typical levels in these grapes [30,40,56] and significantly less than found by Zhu et al. [24]. Conventional grapes, especially Muscaris, had higher iron content (Table 6).

Grapevine leaves had iron contents ranging from 166.87 mg/kg in organic to 120.62 mg/kg in conventional cultivation (Table 7). These values are within the range reported by other studies (40–400 mg/kg) [25,30,35,40,56,58,59]. Muscaris leaves had the least iron, while Hibernal leaves had the most. Grape leaves are relatively rich in iron compared to other plants [35].

3.3.5. Lead

The natural content of lead in soils worldwide ranges from 25 to 40 mg/kg, while in Poland, it averages 18–24 mg/kg [38,66]. Lead in soil is strongly bound by clay minerals and does not pose an environmental threat in the EU, including Poland [62,67]. The highest concentrations are found in soils from Italy, France, Germany, and the UK [45,49]. In Poland, about 97% of agricultural soils have natural or slightly elevated lead levels, with only 0.7% being contaminated [45,49,66].

This study showed soils from the organic plantation had an average of 11.22 mg/kg dry matter lead, while conventional plantations had 20.34 mg/kg, mainly in the surface layer (0–20 cm) (Table 4). The higher lead content in conventional soils results from intensive agronomic treatments and sources like mineral fertilizers, plant protection products, and industrial emissions [38,62,67]. Despite higher lead levels, they did not exceed natural values typical for agricultural soils [38,55], and were lower than levels found in Ukrainian and Czech vineyards [47] (Table 4 and Table 5).

Lead in grapes averaged 2.19 mg/kg in organic plantations and 1.18 mg/kg in conventional ones, primarily in Solaris and Muscaris cultivars (Table 6). These amounts generally exceeded the critical value of 1 mg/kg for consumable plants [55]. Some cultivars exceeded the permissible lead content in foodstuffs (2 mg/kg dry matter) but were below critical levels for plant development (30–300 mg/kg) [38]. Lead content in grapes can vary greatly, with reported values ranging from 0.01 to 8.91 mg/kg depending on environmental contamination [13,23,24,47,61,68].

The source of lead contamination in fruits may be plant protection products like copper sulfate, which contains lead [31]. Copper sulfate is also a source of lead in wine and juice, making wine a significant dietary lead source in some countries [31].

In grapevine leaves, lead content was lower than in grapes, averaging 0.69 mg/kg in organic and 1.07 mg/kg in conventional cultivation, with the least in Muscaris leaves (Table 7). These levels are similar to those reported by Almeida and Vasconcelos [68], Chopin et al. [13], Vystavna et al. [47], and Oliveira et al. [30] but significantly lower than reported by Bravo et al. [35], Bora et al. [58], and Bora et al. [23]. Lead in leaves ranges widely, from 15 to 400 mg/kg dry matter in contaminated areas. Grape leaves bind lead in fine roots, and variations in lead content in organic and conventional vineyards suggest that plant protection treatments are a primary source. Lead mainly accumulates on plant surfaces and is minimally absorbed due to the protective cuticle and wax layer on leaves.

3.3.6. Nickel

The nickel content in soils worldwide ranges from 5 mg/kg in sands to 22 mg/kg in clays [38]. Nickel solubility is influenced by soil pH and is primarily sourced from magnesium fertilizers in agricultural soils [38,60]. In Europe, soils in Poland, Germany, and Scandinavia have the lowest nickel levels, while Mediterranean soils have the highest [49]. In Poland, nickel contamination is rare, affecting only about 0.04% of soils [45].

Studies showed that nickel content in organic vineyard soils averaged 21.85 mg/kg dry matter, and 34.55 mg/kg in conventional vineyard soils (Table 4). These levels are typical for non-contaminated clay soils used agriculturally (<50 mg/kg dry matter) [38,55]. Nickel absorption by plants is proportional to soil content and favored by slightly acidic soils, which was the case in both plantations.

Higher nickel levels in conventional soils led to higher uptake in grapes and leaves. Nickel content in organic plantation grapes was 1.63 mg/kg dry matter, and 1.94 mg/kg in conventional plantation grapes; in leaves, it was 2.79 mg/kg and 3.20 mg/kg, respectively (Table 6). The Muscaris cultivar grapes had higher nickel levels than Solaris and Hibernal, but lower levels in leaves (Table 6). Excess nickel in wine degrades its quality [9].

Nickel levels in fruits from both plantations were similar to those reported by Zhu et al. [24] (3.70–7.17 mg/kg) and Bora et al. [23] (0.75–2.56 mg/kg). These values did not exceed permissible amounts for consumable plants [55]. Nickel content in leaves was about three times lower than reported by Bora et al. [58] and Oliveira et al. [30], and nearly ten times lower than in contaminated areas [23]. The detected nickel amounts in fruits and leaves were within the physiological norm for plants (0.1–5 mg/kg dry matter) [38] (Table 7).

3.3.7. PCA and Ward Analysis

PCA analysis revealed that the content of exchangeable forms of heavy metals in soils from both organic and conventional plantations was positively correlated with the content of organic carbon (Figure 6 and Figure 7).

It was also observed that the pH of the soil had a negative impact in the case of the less acidic conventional plantation (Figure 7). The lack of a clear relationship between the amounts of bioavailable forms of heavy metals and soil pH on the organic plantation can be attributed to the fact that these soils were more acidic and had uniform pH levels. Many authors have pointed out the significant impact of pH and organic matter content on the bioavailability of heavy metals in vineyard soils [35,63,69]. Furthermore, PCA analysis generally showed a mutual synergism of exchangeable forms of Cu, Fe, Zn, and Mn in the soils of both plantations (Figure 6 and Figure 7). No correlation was found in either plantation between the amounts of bioavailable forms of heavy metals and the amounts of their total forms in the soil (Figure 6 and Figure 7).

The quantities of exchangeable forms of Cu, Mn, and Fe in the soil had a positive impact on the uptake of these elements, mainly by grapevine leaves (Figure 6 and Figure 7). Lower soil pH favored the uptake of Cu, Zn, and Pb by the leaves (Figure 6 and Figure 7). Similar relationships were found in grapevine cultivation [13,35,47,69]. Moreover, in most cases, there were no clear correlations between the contents of heavy metals in the leaves and grapes.

Ward’s analysis, in terms of heavy metal content, distinguished two main homogeneous groups—one consisting of grapes from both organic and conventional plantations, and the other of leaves from both organic and conventional plantations (Figure 8).

Within the fruit group, two distinct subgroups emerged—grapes of the Solaris cultivar and grapes of the Hibernal cultivar (Figure 8). Meanwhile, leaves of the Solaris, Muscaris, and Hibernal cultivars from both organic and conventional plantations formed one chemically similar group.

4. Conclusions

The conducted studies on vineyards managed in organic and conventional systems revealed the following:

• Organic cultivation methods resulted in higher soluble solids content (°Brix) and lower acidity in the must, enhancing the taste and balance of the resulting wine. These findings suggest that organic practices may improve wine quality through better flavor profiles.
• Conventional cultivation yielded higher production per plant, larger fruit and cluster sizes, and greater turbidity in the must. This indicates that while conventional methods may enhance production efficiency and fruit size, they could also introduce more suspended particles into the must, potentially affecting the wine’s clarity and processing.
• This study found that conventional cultivation led to higher YAN levels in the must, crucial for yeast nutrition during fermentation. This suggests that conventional methods may better support the fermentation process due to higher nutrient availability, impacting the final wine quality.
• Soils in organic vineyards were richer in copper compared to those in conventional vineyards, attributed to the frequent use of copper-containing preparations. Conversely, soils from conventional cultivation contained more zinc, nickel, and lead, resulting from the use of mineral fertilizers and plant protection products containing these heavy metals. However, the concentration of heavy metals in the soils of both vineyard types was within the typical range for uncontaminated agricultural soils and significantly lower than levels observed in other regions of Europe and the world.
• No direct effect of soil heavy metal content on the accumulation of these elements in fruits was observed. Nevertheless, fruits from organic plantations contained less iron, manganese, and nickel, but more lead than those from conventional plantations. Similar amounts of copper and zinc were found in both, likely due to different fertilization and protection methods. It is worth noting that the amounts of copper and lead in fruits from both plantation types exceeded commonly encountered values, likely due to the intensive use of copper sulfate enriched with lead. The early ‘Solaris’ variety showed the greatest accumulation of these elements.
• Grapevine leaves showed a greater ability to absorb heavy metals from the soil, with lower soil pH favoring the accumulation of copper, zinc, and lead in the leaves. The ‘Hibernal’ variety, in particular, accumulated a significant amount of heavy metals in its leaves. At the same time, no clear correlation was found between the heavy metal content in the leaves and fruits, with fruits and leaves forming two separate, homogeneous groups in terms of heavy metal content.

In summary, these findings highlight the critical issue of soil management in vineyards, especially in the context of sustainable agriculture and ecological practices. They indicate the need for further research and the development of methods to minimize the risk of heavy metal accumulation in the soil and grapevine tissues.