Research on the Culture of Cabbage and the Possibilities of Increasing the Early Production

Abstract

The main goal of vegetable growers is to obtain early and quality harvests. In this article, the experiments were carried out in the period 2005–2007, and the culture behavior of new early cabbage hybrids, the influence of plant thickness on the production of cabbage grown in greenhouses and the field and the influence of additional protection were investigated on the early production of cabbage in greenhouses and in the field. During the years 2005–2007, studies were undertaken on the culture behavior of six hybrids and an early cabbage variety, using two different planting plots and two protection systems.

1. Introduction

The studies carried out on an international and national level attest to the importance and wide use of vegetable products, which participate more and more in human nutrition, together with meat, milk, eggs, cereals, supplementing the need for proteins, which stand out for their digestibility good, of 70–75%, and through a high quality conferred by essential amino acids [1].

The analysis of the chemical composition of vegetables shows that they contain approximately 78–93% water and 7–22% dry matter. Vegetables from the onion group have the highest dry matter content (13.5% leek, 38% garlic), and the lowest in cucumbers, lettuce, lettuce [2], and according to Bielka [3] and Maier [4], vegetables are juicy food products, with a high water content and low dry matter content; being hypocaloric foods, they decrease the intake of energy substances, preventing overweight growth.

Vegetables have a high vitamin content; the vitamins needed by the human body are taken, to the greatest extent, from vegetables and fruits. Valnet [5] states that a normal life cannot be maintained if the body does not receive the vitamins it cannot synthesize [6].

In Romania, the need for fresh vegetables, especially in the cold season, is mostly covered by imports, domestic production gains ground only as the weather warms up.

According to a study by the consulting firm Visionwise, in 2006, only 15% of all the vegetables sold on the Romanian market, through large stores, were local, while 85% were brought from Turkey, Holland, Greece, Italy and Israel. These vegetables have a bland, less pleasant taste, but excel in appearance, color and size (http://www.visionwise.ro).

Obtaining extra-early production of vegetables in our country is of particular interest, especially in the regions of the Transylvanian Plateau where, due to the cooler climate, the harvesting of vegetables begins later than in the Danube Plain or the Western Plain of the country.

White cabbage (Brassica oleracea L., Alef. var. capitata f. alba D.C. - Brassicaceae family) is one of the most important species in the assortment of vegetable plants in our country, a fact demonstrated by the large cultivated area that represents 20–27% of the surface total cultivated with vegetables [7].

The main goal of vegetable growers is to obtain early and quality harvests. In order to ensure high yields of early cabbage, it is necessary to study and perfect the culture technology adapted to the specific pedoclimatic conditions.

2. The situation and prospects of white cabbage culture

Vegetables are food products of vegetable origin with an important role in nutrition, due to their special sensory properties and the valuable nutrients they contain. The high consumption of fresh vegetables was determined, on the one hand, by civilization, on the other hand, by the efforts of nutrition specialists to popularize the virtues of these products.

White cabbage is an important crop in the world vegetable economy. The economic importance of the culture results from the fact that the average productions can be very high (even around 100 t/ha), the harvest is carried out over a long period of time of the year, ensuring income, practically, from spring to autumn. Cabbage is a slightly perishable product during transport, temporary storage and utilization. The expenses per surface unit are relatively low, some works, from establishment to harvesting, can be completely mechanized [8].

In 2007, green vegetables were grown on approximately 3 million ha around the world, achieving a total production of 69,214 Mt. In Europe, 496 thousand ha were cultivated, with a total production of 12,250 Mt. As shown in Table 1, Romania ranks first in Europe in terms of the area cultivated with cabbage, with an area of about 53 thousand ha and a total production of 1120 Mt. This places it far ahead of the following rankings: Italy (17.7 thousand ha - 345.1 Mt), Germany (14.8 thousand ha - 735.5 Mt), Spain (8.2 thousand ha - 270 Mt).

Continent/Country	Harvested area (1000 ha)
	Year
	2003	2004	2005	2006	2007
World	3186	3079	3136	3082	3088
Africa	86	114	119	102	103
North America	149	39	38	38	38
South America	60	25	26	13	13
Asia	2265	2359	2410	2387	2396
Europe	250	515	516	505	496
Romania	42	42.5	54.6	45.7	53
Spain	8	7.9	7.7	8	8.2
Italy	24	17.2	18.5	17.1	17.7
Denmark	1	1.1	1.7	7.4	7.5
Austria	2	1.8	1.7	1.6	1.7
Germany	14	16	14.4	14.7	14.8
Ireland	1	0.8	0.8	0.9	0.9
Oceania	3	0.9	0.8	0.9	0.9

Table 1.

Area harvested with cabbage and other brassicas, in the world, in 2003–2007 period.

In 2005, in Cluj county, the area cultivated with cabbage was 1780 ha (Table 1), a relatively small area compared to the rest of the country’s counties. The total production recorded in Cluj County was 40.5 Mt., of which 40.3 Mt. was realized in private properties.

3. The importance of culture

White cabbage is grown for chefs who have a wide use in the culinary art, being used raw or pickled, with or without meat, dehydrated or frozen [9] in different ways, in an assortment of dishes much appreciated by consumers. It is also a very important raw material in the canned food industry and especially vitamin juice, usually mixed with carrot juice. Having a high resistance to low temperatures, its fresh consumption can be greatly extended in winter (4–5 months) by keeping it cold (cold storage) or in the field (in improvised shelters) in quantities necessary for consumption, from November to March. We should also not forget the preservation by pickling, a simple, effective and so frequent and traditional measure for the Romanian peasant for consumption during the winter, used as a salad or prepared in various ways, among which the sarmal cabbage or “á la Cluj” cabbage [10].

During the winter, sauerkraut is an important source of vitamins and minerals due to the fact that through lactic fermentation, they are mostly preserved without significant degradation [11]. Cabbage juice is an excellent detoxifier, being effective in gastric disorders (ulcers, gastritis, intestinal inflammation). Because it produces bloating, due to the decomposition of waste from the digestive tract, it is recommended to use it after an apple and carrot juice cure, being thus administered by oncology clinics in Germany.

Due to the high content of vitamins, cabbage is revitalizing, antiscorbutic, general rebalancing, and due to its carbohydrate and protein content, it is energetic.

4. Therapeutic value

White cabbage, apart from the fact that it is a food in demand throughout the year, is equally appreciated for its therapeutic value. Being low in fat and rich in fiber, it is used in diets, helping to keep the level of calories and fat to a minimum.

Research carried out in the last 20 years has confirmed that a regular consumption of cabbage has a beneficial effect in the prevention of colon, stomach, lung and esophagus cancer (research carried out at the University of Minnesota and J. Hopkins from the USA, in Greece, Israel, Japan, Norway).

Research has revealed that people who consume vegetables from the Brassicaceae family, cabbage in particular, are much less exposed than others to colon cancer (studies conducted by the American National Cancer Institute).

Sauerkraut has a high content of vitamin C and the group of B vitamins, which stimulate the body’s defense system. Finnish nutritionists have recently discovered that isothiocyanates stop the evolution of cancer, and they are also maintained during lactic fermentation [12].

5. Plastics used in protected vegetable cultivation

Our country has favorable pedo-climatic conditions for the cultivation of numerous vegetable species, but the natural conditions for outdoor crops are favorable only in certain periods of the year, therefore there are interruptions in the supply of fresh products to the market. Supplementing the daily ration with a varied assortment throughout the year and not only in certain periods is of particular interest. To reduce deficit periods, vegetable growers resort to certain crop protection measures [13].

Vegetable cultivation under plastic or plastic culture, due to its specificity and particularities, is an exclusively intensive branch and cannot be conceived without the judicious use of the land in the constructions intended for the cultivation of different types of vegetables in the cold period of the year. From the data of the specialized literature, it follows that crop successions ensure an earlier appearance of production in the spring and an extension of it in the autumn [14].

The plastics used in vegetable cultivation are of various types and present multiple improvements. The first experiments regarding the use of plastic masses, in the culture of vegetables, were made in 1929, at the University of Kentucky - USA. The experiments were carried out using cellophane, under which lettuce was grown. In 1932, at the Institute of Agricultural Physics in Leningrad-Feinberg, research was initiated with cellophane shelters on a radish crop. The experiments were resumed in 1948, but with a wider application in vegetable cultivation: 1950 in Japan, 1954 in Russia and the USA, 1956 in England and France.

6. Other materials used in direct crop cover

Advances in science have allowed the improvement of culture technologies for some vegetable plants, with high yield methods being developed [15]. Thus, the use of non-woven textiles in horticulture occupies an important role in modern technologies.

Non-woven textiles are part of the group of materials used in horticulture, generically called agrotextiles. These materials are made by a specific technology from polymer fibers of a polyolefinic nature, such as polypropylene, polyesters or polyamides. In horticulture, these materials are used in various forms, such as mulch and as covering material in the blanket system.

Polypropylene was first introduced in 1957 by an Italian company Montecatini (chemical compound) and proved to be a cheaper material than polyethylene. It has a thickness of 10–30 microns, representing a very high transparency, very good dimensional stability, mechanical and chemical resistance, against oils, acids, bases.

Non-woven textiles are presented as a “fabric” in which the constituent fibers are not woven but are overlapped, by bonding, in a layer of variable thickness (0.1–0.2 mm). It is a heat-resistant polymer used in the pre-packaging of vegetable products, making textiles, ropes, reusable containers.

The manufacturing technology of these materials provides for the random arrangement of fibers in the same plane in a layer uniform in thickness and composition, followed by pressing and thermoadhesive bonding between two rolls, a process called calendering [16].

AGRYL P19 (Figure 1) - is a light and resistant material, has a weight of 19 g/m², protects against bad weather (cold, wind) and insects, improves yield and quality of early production; creates a favorable microclimate for plant growth; it has a light flux transmissivity capacity of 85% [17, 18, 19, 20, 21].

Figure 1.

Agryl P-19 coating material.

7. Solar culture technology

The experimental culture was established in the greenhouse covered with double polyethylene film.

The land was prepared in the fall, it was fertilized with 40 t/ha of manure, which was incorporated with the motor cultivator. In early spring (17.03.2005, 15.03.2006, 07.03.2007) the solarium was covered with durable polyethylene film TVK.

The land was modeled in layers of 140 cm. The seedlings were produced in the heated greenhouse, the sowing was carried out on 14.01.2005, 11.01.2006 and 10.01.2007 respectively. On 28.01.2005, 30.01.2006 and 26.01.2007 the seedlings were transplanted into nutrient cubes of 5×5 cm.

The seedlings were planted on 24.03.2005, 20.03.2006 and 9.03.2007, when temperature 8°C were recorded in the soil of the greenhouse. The planting distances were as follows: 40 cm between rows and 35 cm between plants per row, thus resulting in a plot of 71,500 plants/ha, respectively 40 cm between rows and 40 cm between plants per row, achieving a plot of 62,500 plants/ha. Immediately after planting, the double-protected varieties were coated with Agryl P-19.

In the experimental year 2005, 1 week after planting, the gaps were filled with seedlings from the same hybrid, then on 04/03/2005, facial fertilization was done with Complex III 250 kg/ha. On 16.05.2005, another foliar fertilization with Fertitell 1.5 l/ha was carried out.

In the experimental year 2006, fertilization with Complex III was carried out on 29.03, and in the experimental year 2007, fertilization was carried out on 21.03.2007.

Thirteen waterings were carried out in 2005, 11 in 2006, with quantities of 200–250 m³ of water. In 2007, six waterings were carried out with quantities of 200–250 m³ of water, and the rest of the waterings were done with the help of a drip irrigation system, with a flow rate of 2 l/hour, through intermittent applications.

During the vegetation period, three manual weedings were carried out in the period 12–28.04.2005, two in the period 04–20.04.2006 and only one manual weeding in the period 22.03–06.04.2007.

I mention that no phytosanitary treatment was done during the 3 years of experience.

The removal of the covering material, Agryl P-19 type, was done according to the climatic conditions in the place of cultivation, as follows: on 16.05.2005, 20.04.2006 and 23.04.2007. This material was kept on culture for 50 - 30 - 25 days, respectively.

The harvests were carried out between 20.05-10.06.2005, when productions varying between 62.8–75.5 t/ha were obtained, in 2006 the harvests were made between 15.05-5.06.2006 with productions between 59.1–78.0 t/ha, and in 2007, the harvesting period was between 03.05-30.05.2007, obtaining productions between 61.2–76.5 t/ha.

8. Field culture technology

The preparation of the land started already in the autumn, when it was fertilized with 25 t/ha of manure, which was incorporated with deep plowing, at 28–30 cm.

The land was modeled in layers of 140 cm. The seedlings were produced in the heated greenhouse, the sowing was carried out on 14.01.2005, 11.01.2006 and 10.01.2007 respectively. On 28.01.2005, 30.01.2006 and 26.01.2007 the seedlings were transplanted into nutrient cubes of 5 × 5 cm. The seedlings were planted on 29.03.2005, 22.03.2006, respectively on 20.03.2007 when the soil temperature reached temperature 8°C. The planting distances were as follows: 40 cm between rows and 35 cm between plants per row, thus resulting in a plot of 71,500 plants/ha, respectively 40 cm between rows and 40 cm between plants per row, making a plot of 62,500 plants/ha. Immediately after planting, the protected varieties were coated with Agryl P-19.

The covering material, type Agryl P-19, was removed, following the monitoring of the climatic conditions in the field, as follows: on 23.05.2005, 17.05.2006 and 14.05.2007. This material was kept on culture for 55 - 40 - 30 days, respectively.

In the experimental years 2005–2006, 1 week after planting, the gaps were filled with seedlings from the same hybrid and facial fertilization was done with Complex III 250 kg/ha. In 2007, after filling in the gaps, two partial fertilizations were made, one on 29.03, with 150 kg/ha of ammonium nitrate and on 20.04 with the same amount of mineral fertilizer.

Three waterings were carried out in 2005, seven waterings in 2006 and eight waterings in 2007, with quantities of 200–250 m³ of water. I mention that in 2005 there was a rainy period, for this reason no more irrigation was done until the harvest.

During the vegetation period, three manual weedings were made between 08.04–10.05.2005, two between 01.04–20.05.2006 and two between 30.03–02.05.2007. During the vegetation period, two phytosanitary treatments were carried out, one for Delia radicum L. with Fastac 0.1 l/ha and one treatment with Optimol 15 kg/ha for Deroceras agreste L. The cabbage fly attack depreciated part of the harvest unprotected, therefore the production of early cabbage from the field was lower in 2005 than in the following years of experience.

The harvests were carried out in the period 06.06–14.06.2005, when productions varying between 38.4–59.1 t/ha were obtained, in 2006 the harvests were made in the period 06.8–19.06.2006 with productions between 48.3–58.4 t/ha, and in 2007 productions varying between 53.4–61.7 t/ha were obtained, harvesting was carried out between 25.05–04.06.2007.

9. Conclusions

Covering the early cabbage culture with textile tarps greatly influences the micro-climate of the culture space. The temperatures in the greenhouse and field have the highest values, in the first 10 days after planting, under the covering material. Thus, in the solar the average air temperature is higher by temperature 1.75°C at 8 o’clock and by 2.25°C at 12 o’clock, under the covering material, and in the field, the difference between the air temperature in the open and that under Agryl, shows an average of 2.15°C at 8 o’clock and 2.40°C at 12 o’clock.

Covering the early cabbage culture with agrotextiles also positively influenced the evolution of soil temperatures, with average differences of 2.15°C between the covered soil at 8 o’clock and 2.50°C at 12 o’clock, in the solar culture and of 1.37°C at 8 o’clock and 1.70°C at 12 o’clock, for field crops.

Analyzing the effect of the protective material on the atmospheric humidity, it is found that this parameter showed higher values, both in the solar and in the field. Thus, the average difference, between the two methods of protection, in terms of relative atmospheric humidity is 16.2%, at 8°° and 24.3% at 12 o’clock, and for field crops the average difference is 11.0%, was registered at 8°° and 17.4% at 12^oo.

The humidity of the soil, from the solar, evolved as follows: at a depth between 0 and 10 cm, on average, the humidity was higher by 7.82%, in the case of Agryl coating, and at a depth between 10 and 20 cm, the average difference in humidity was 3.44%, compared to the uncovered crop. In the field culture, the average difference in soil moisture was 5.1%, at a depth between 0 and 10 cm and 8.3% at a depth of 10–20 cm, in favor of the covered culture and was preserved more constant during the vegetation.

Following the observations made on the light intensity, both in the experimental culture in the greenhouse and in the field, it is highlighted that the variants covered with Agryl P-19 benefit from a lower amount of light than the uncovered ones, so that in on average, there is a daily difference of 1544 lux, at 8°° and of 2536 lux, at 12°°. With the early cabbage crop in the field, an average daily difference of 1347 lux is recorded, at 8°°, and at 12°°, between the two culture systems, an average difference of 2016 lux is found, in favor of the plants uncovered.

• Covering the early cabbage crop from planting with agrotextile tarps has favorable effects on the growth and development of the plants, so that all the morphological characters (rosette diameter, plant height, number of leaves in the rosette, head weight, leaf weight) were positively influenced and they recorded higher values, both in the greenhouse and in the field, compared to the uncovered crops. Biometric observations were made 19–28 days after planting.

In the culture established in the greenhouse, the diameter of the rosette of the leaves registers average values of 43.6 cm under the influence of the Agryl coating and only 36.6 cm, in the uncovered plants. In field crops, direct coverage increases rosette diameter to 30.4 cm compared to only 23.2 cm in the control.

The length of the stem registers a slight elongation in the covered crops, presenting an average waist of 7.4 cm, compared to 5.93 cm, in the control. This elongation is due to the lack of light, in the plants grown in the space covered with Agryl. In the field, the stem length is shorter than in the greenhouse; in those protected with Agryl, this character had an average of 4.25 cm, and in the non-coated versions an average of 3.65 cm.

Covering the plants with Agryl influences to a lesser extent the number of leaves in the rosette, in plants grown in the solar system. In the covered variants, the plants have an average of 11.9 leaves, and in the uncovered variants, a number of 10.7. In the field, the differences are greater than 13.5 leaves in the rosette, and in the uncovered variants 10.5 leaves.

Covering the early cabbage crop with Agryl has less influence on the average weight of the heads, in solar being 0.98 kg, for the covered versions and 1.02 kg, for the uncovered ones. In field culture, the average weight of the heads register values very close to 0.80 kg, for the protected variants and 0.75 kg, for the unprotected variants.

The total weight of the plant and the outer leaves are much higher in the culture covered with Agryl and reaches 1.94 kg, respectively 0.99 kg, and in the simply protected variants 1.84 kg, respectively 0.79 kg, in the culture from solar. For field crops, the values are lower than 1.46 kg, respectively 0.39 kg for the covered variants and 1.38 kg, respectively 0.38 kg, for the uncovered variants.

32.6 leaves in the head were determined, for the double protected variants and 30.2 leaves, for the single protected variants.

The elongation of the inner coccine, in the covered plants, is due to the lack of light, under the covering tarpaulin, which prints a slight tendency of the stem elongation during the growth period and registers the following average values: 7.78 cm, in the double protected variants and 6.53 cm, for the simply protected variants from the solar and 5.70 cm, respectively 5.12 cm for the culture in the field.

• The degree of weeding of the cabbage crops, from the two variants of cabbage culture, both in the greenhouse and in the field, is reduced when the Agryl type cover material is used. In solar, protection reduced the number of weeds by about 50%, and in field culture, direct covering caused a lower degree of weeding by about 23.8%.

• The dynamics of early cabbage harvests in the greenhouse show that the best start of the harvests, in 2005, was recorded in the third decade of May, when a 71,500 pl./ha crop was used, with protection simple. In 2006, the earliest harvests were obtained in the second decade of May, at the rate of 62,500 pl./ha, and in 2007, benefiting from favorable climatic conditions, the harvests began in the first decade of May, for the variants with a plot of 71,500 pl./ha.

The dynamics of harvests in the field crop show that the highest productions, at the first harvests, are recorded in the variants covered with Agryl, cultivated at a plot of 71,500 pl./ha. For crops not covered with textile tarps, harvesting is delayed by 4–7 days compared to covered crops.

• Regarding the influence of the hybrid on the extra-early production, it is found that the highest productions were registered with the Surprise and Santorino hybrids, which obtained average productions of 39.63 t/ha and 39.29 t/ha, respectively.

Very good extra-season products are obtained if a planting plot of 71,500 pl./ha is used. This planting plot determined, on average, extra-early productions of 39.29 t/ha, with a very significant increase of 13.8% compared to the crop with a smaller plot.

Covering with Agryl P-19 shows its effect in the years 2006–2007, when this technological measure to increase earliness generates average extra-early productions of 35.73 t/ha with a very significant difference of 2.38 t/ha, compared to simply protected variants. These results can also be attributed to the fact that in these years the crop remained covered for a period of only 30 days from the beginning of vegetation.

• The highest total productions, per surface unit, in 2005, were obtained with the Resistor and Parel hybrids, and in 2006–2007, with very close values, with the Santorino hybrids (70.68 t/ha) and Surprise (69.03 t/ha), higher productions at a plot of 71,500 pl./ha.

The method of additional protection with Agryl tarpaulins of cabbage in the greenhouse increases the total production on average by 4.7%, determining a very significant difference in production of 3.13 t/ha, compared to the simply protected variants.

In field crops, the most productive were the hybrids Santorino (56.99 t/ha) and Surprise (56.78 t/ha), at a plot of 71,500 pl./ha, in the variants covered with agrotextiles, a period of 30–40 days. 7. The researched factors influence to a lesser or greater extent the biochemical composition of the heads of cabbage.

Thus, in crops covered with Agryl, the content of soluble dry matter is lower due to reduced light conditions, especially in solariums where it is filtered through two layers of coating.

The content of vitamin C is influenced in the same way, the highest values of 31.68 mg/100 g of fresh substance being registered in the field culture, in the version not covered with Agryl, and the lowest, in the solar culture, in the plants coated with Agryl (21.2 mg/100 g s.p.).

The Santorino hybrid stands out for its higher content of dry matter and vitamin C, compared to the other cultivars.

In general, all the biochemical characters, in the cabbage grown in the field, showed higher values than in the cabbage grown in the greenhouse, and the nitrate content was lower, compared to the heads analyzed in the greenhouse. In protected spaces, due to the conditions of lower light, cabbage accumulates higher amounts of nitrates (110.7 mg/kg), values that are found at the lower limit of the content specified in the specialized literature (30–580 mg/kg) and much below the maximum limit allowed for this food product.