The agrobiological efficiency of arugula cultivation in protected soil

Expanding the assortment of grown crops is one of the most actual problems of the modern vegetable production. In everyday practice many new crops for our country are introduced. At the same time, most interesting cultures intended for dietary and healthy nutrition. One of the most promising vegetable crops in this area is arugula (Erúca sativa). Arugula is widely cultivated in the Southern regions of Europe for a long time. It is especially popular in France and Italy. Back in the 90s of the last century, arugula in some of our restaurants was presented as a kind of exquisite «overseas» greens [1]. For today, State Register of Selection Achievements permitted for use in the Russian Federation included four cultivars of arugula: Pasyans, Rocket, Taganskaja Semko, and Euphoria [2]. Arugula - a culture rich in macro-and micronutrients, an important source of nutrient iodine for the population. Taking into account that the majority of Russians are living in regions of iodine deficiency, growing of iodine-rich arugula has important national economic significance [3]. Particularly acute this problem is in North Caucasian republics, including Kabardino-Balkaria. Iodine is responsible for normal thyroid function and for supporting hormonal balance; also iodine is needed for the brain function and for the maintenance the human immune system [4]. Iodine consumption rates are (as recommended by WHO): infants - 50 mcg, children from 2 to 6 years - 90 mcg, children from 7 to 12 years - 120 mcg; adolescents over 12 years - 150 mcg; pregnant and lactating women - 200 mcg. Iodine content in arugula reaches 835 mg/kg of product [5].

Therefore the object of our study was arugula salad, which rare in Russian agriculture.

MATERIALS AND METHODS OF RESEARCH

Development of the optimum technological parameters of arugula cultivation in open and protected soil in southern Russia was the purpose of work. To achieve this purpose, the following tasks were solved: explore the biological characteristics of growth and development of different arugula cultivars; determine the best sowing time when grown in the different conditions of open and protected soil; reveal the optimal schemes and nutrition area in dependence on the period of cultivation; examine growth characteristics, development and productivity of cultivars at the various terms of growing.

Investigations were carried out in 2010 - 2012, within the joint scientific research work of «horticulture and viticulture» and «cultivation and selection of agricultural plants» departments of Kabardino-Balkaria State Agrarian University named after V.M. Kokov and in the production conditions of the plastic greenhouses of the farm enterprise «Berbekov product». Production inspection of individual technology elements carried out in the glassed winter greenhouses of company «Yug-Agro» in 2011.

Seeds and plants of arugula cultivars Pasyans, Spartacus, Victoria, Poker were the material of investigations.

Investigations were carried out by setting microplot trial, modeling and laboratory experiments. Experiments carried out in accordance with conventional techniques and recommendations: «Methods of experimental work in the vegetable production and melon production», «Methodology of field experiment in vegetable production» [5, 6].

During landing of seedlings, nutrition areas of plants, which help avoid competition, were used. Landing of seedlings was carried out on 6-line ribbon, spacing of 60 cm between ribbons. Variants differ by distance between plants in a row - 10, 15, 20 cm.

Experiment variants:

• 1. S. of nutrition area = 267 cm² at planting scheme /60+(20*5)/*10cm;

• 2. S. of nutrition area = 400 cm² at planting scheme /60+(20*5)/*15cm;

• 3. S. of nutrition area = 533 cm² at planting scheme /60+(20*5)/*20cm.

Investigations were carried out against the backdrop of the cultivation of Pasyans and

Spartacus cultivars. Arugula was grown in 6 rotations throughout the year.

Planting dates (±3 days): 2010: January 11, March 4, April 20, June 5, September 9, October 28; 2011: January 11, March 4, April 20, June 5, September 9, October 28; 2012: January 11, March 4, April 20, June 5, September 9, October 28.

To ensure a stable demand for perishable green cultures, essential elements of technology are the stepwise terms of sowing and planting of plants. Experiments were carried out with the stepwise terms of planting to determine the optimal planting dates, the technological features of cultivation and the other parameters of culture. Variants also differed by distance between plants in the row and by nutrition area (Pasyans cultivar):

• 1. S. of nutrition area = 267 cm² at planting scheme /60+(20*5)/*10cm;

• 2. S. of nutrition area = 400 cm² at planting scheme /60+(20*5)/*15cm;

• 3. S. of nutrition area = 533 cm² at planting scheme /60+(20*5)/*20cm.

All experiments were repeated four times.

Comparative evaluation of arugula cultivars was performed according to "Methods of test for distinctness, uniformity and stability." Each plot and the accounting of the yield of marketable products and seeds were evaluated. The energy of germination and germination of seeds were determined [7, 8].

During the experimental part of the work was carried out:

• -    phenological observations : noted dates of sowing seeds, germination and emergence of 1 - 3 true leaves, the phase of technical maturity;

• -    biometric measurements were carried out in phases: cotyledons, 1st, 2nd leaf, 15 and 30 days after planting, the phase of technical maturity;

• -    agrochemical observations : the content of the mobile forms of phosphorus and potassium in the soil (by Machigin method), as well as acidity and humus content in the soil were determined;

• -    biochemical measurements : arugula leaves were tested for nitrate content, dry matter and ash content.

All necessary accompanying observations were carried out according to conventional techniques. Statistical processing and evaluation of the reliability of the experimental results was performed by the standard technique [9, 10].

RESULTS OF RESEARCH

Despite the increasing popularity and widespread in European countries, arugula is a rare and little-known vegetable culture in our country. High consumer characteristics and increasing demand of this valuable dietary culture among the population, causes the spread of it in modern agricultural practice [11, 12]. However, many agrobiological peculiarities of culture and agronomic requirements for arugula cultivating are still insufficiently studied.

Study the agrobiological properties of arugula, conducted against the background of growing cultivars (Pasyans, Poker, Spartacus and Victoria) showed the prospect of its cultivation under greenhouses in southern Russia.

High precocity of culture confirmed by phenological observations made during the years of the study (2010-2012) [12, 13]. At the same time, the shoots of culture were observed already after 2-3 days from the date of sowing in the most favorable periods for plant growth (early April - end of September) - see Table 1.

Phenological observations of arugula cultivars (Pasyans, Poker, Spartacus, Victoria) did not show significant differences of these indicators between the cultivars. In view of this and for the convenience of presentation materials, data on the Pasyans cultivar presented in Table 1.

Table 1 - Phenological observations of arugula plants seedlings (Pasyans cultivar, the average for 2010-2012)

Date of seeding	Dates, days from seeding
	Sprouting	Planting seedlings to a permanent place
January 2	5,1	8,1
February 25	4,3	7,2
March 27	3,1	6,1
May 1	2,1	5,2
June 29	3,1	6,1
September 17	3,3	6,2
November 4	4,1	8,2
November 19	5,2	8,1

During biometric studies, the influence of different terms and schemes of cultivation on the formation of the root system and aerial parts of arugula has been determined. Found that the plants had the following basic biometric characteristics at the time of cutting: height - 11,6 - 19,8 cm, number of leaves - 10,4 - 17,9; mass of the root system - 10,7 - 16,6 g.

Plants grown in the autumn-winter period (November - February) had a small height (11,6 - 19,6 cm) and diameter of the main stem (3,4 - 4,4 mm). Similar biometric characteristics in the summer were: 16,1 - 19,8 cm and 5,4 - 6,2 mm, respectively. However, the arugula plants of winter-autumn cultivation period are characterized by a high degree of leaves coverage. As expected, the timing of planting culture had a significant impact on the duration of the vegetation period and beginning of generative organs formation [14]. Being a long-day plant, arugula moves quickly to the generative stage of development with increasing duration of the light period. That, in turn, led to reducing time before cutting plant with 38 - 46 days (photoperiod 9 - 12 hours) to 32 - 38 days (photoperiod over 12 hours).

Different microclimatic conditions, emerging under stepwise dates of cultivation culture, cause the necessity of the selection of optimum planting schemes and the nutrition areas of plants [12, 14, 15]. Analysis of the experimental data showed that the highest specific productive weight of plants was marked at thinned planting schemes (distance in a row of 20 cm) - more than 69 g/plant. This regularity is not dependent on the timing of cultivation. However, productivity of variants with different dates of landing fluctuated a much larger at thickened planting scheme (distance between plants in a row - 10 cm and nutrition area - 267 cm²): 47,1 - 49,3 g/plant in the winter-spring period and 40,2 - 41,8 g/plant in the period from April to September months. Conducted on specially left model plants, account of dates flowering confirmed our assumptions.

Plants, grown with photoperiod longer than 12 hours, begin to bloom at 41- 48 days after planting, while the plants that have been formed with a shorter photoperiod - at 50-54 day.

Table 2 - Arugula yield (kg/m²) depending on the schemes and dates of planting (Pasyans cultivar, the average for 2010-2012)

Date of planting	Distance between plants in the row (cm)
	10	15	20
January 10	1,680	1,568	1,171
March 3	1,630	1,530	1,186
April 19	1,452	1,502	1,107
June 6	1,470	1,435	1,044
July 5	1,398	1,397	1,161
September 23	1,592	1,440	1,185
October 27	1,613	1,474	1,167
November 27	1,721	1,565	1,171

НСР 05 А = 0,08 kg/m² НСР 05 В = 0,05 kg/m² НСР 05 А+В = 0,082 kg/m²

Yield is an integrated index of the effectiveness of crop production. The studies found that the highest yield was obtained at thickened planting scheme (nutrition area = 267 cm², planting scheme /60+(20*5)/*10 cm;) despite the higher specific productivity in variant with a larger nutrition area of plants. The maximum yield at short photoperiod observed in variants with planting dates from October to March - 1,6-1,72 kg/m², while in variants with other cultivation dates yield was 1,4-1,48 kg/m² (table 2). With the increase of nutrition area to 440 cm² (distance between plants in the row 15 cm) yield decreased to 1,47-1,6 kg/m² compared to the thickened planting scheme when grown in short photoperiod. In variants with the summer period of cultivation, yield did not significantly differ depending on the location plants in a row (10 or 15 cm). The highest yield was at planting scheme /60+20(*5)/10 cm regardless of the period of culture cultivation – 1,6-1,7 kg/m².

The agrobiological efficiency of studied agricultural methods was also confirmed at film greenhouses in the 2011-2012 against the background of arugula cultivation Poker, Pasyans cultivars.

CONCLUSIONS

• 1.    The peculiarities of growth, development and productivity of arugula cultivars at the various terms of cultivation have been studied. Found that the phase of technical maturity of the studied cultivars begins at the 42nd day in the winter period, at 39th day in the spring, at 34th day in the summer, and at 38th day in the fall period (±3 days) when grown under conditions of Kabardino-Balkaria.

• 2.    The stimulating effect of increasing the length of photoperiod on the speed of passing the phenological stages of plant confirmed. Grown at photoperiod to 12 hours, plants starts flowering at 41st - 48th day from planting date, while plants formed under shorter photoperiod - at 50th - 54th day.

• 3.    In dependence on the period of cultivation, the optimal schemes and nutrition areas have been revealed. Found that the maximum yield of greens provided by thickened planting scheme /60+(20*5)/*10 cm at cultivation the Pasyans cultivar of arugula in early February – 1,68 kg/m². However, the largest specific weight of single plant was observed in growing Pasyans cultivar at planting scheme /60+(20*5)/*20 cm – 62,9 g/plant.