ENGLISH VERSION

Marzena Błażewicz-Woźniak
The effect of agrotechnical factors on the growth and yielding of fennell(Foeniculum vulgare var. azoricum Mill.)

A field experiment with the cultivation of fennel (Foeniculum vulgare var.azoricum Mill.) was done on grey brown podzolic soil in the years 1997-2003 at the Experimental Station in Felin at the Agricultural University of Lublin. Two research series were performed, including 4 experiments.

The purpose of the paper was to study the possibility of obtaining a satisfactory yield from a field cultivation of fennel in less favourable climatic-soil conditions which are created for this plant in the central-eastern region of Poland .

The studies considered the following factors: method of cultivation: from seedlings, from sowing directly to the field; manner of producing the seedlings: in plastic and peat pots; date of sowing (March, April, May, June); the use of covers: covering the soil with black polyethylene foil PE, covering the soil with black unwoven polypropylene fibre PP50, flat covering the plants with white polypropylene unwoven fibre PP17; date of collecting the bulbs (after 10, 12 and 14 weeks of vegetation); nitrogen fertilization: N1 – 80 kg N .ha -1 pre-sowing; N2 – 160 kg N .ha -1 pre-sowing; N3 – 80 kg N .ha pre-sowing + 80 kg N .ha -1 to-dressing. The studies included 2 cultivars of fennel: "Rudy F 1" and "Zefa Fino". Besides, the dynamics of the growth of plants and bulbs was analyzed with the aim of determining the optimum date of collecting fennel bulbs, and the changes taking place in the nutrient value were established depending on their weight, applied agrotechnical treatments and the way of storing.

The seedlings produced in plastic pots from the sowing in April and May were the basis to obtain a high yield of bulbs with good quality features. The production of seedlings in peat pots and the sowing in June did not ensure the seedlings with the required parameters.

All the applied covers had a positive effect on the growth of fennel. Mulching the soil with black unwoven fibre PP50 and PE foil increased the total and marketable yields of fennel bulbs and had a good effect on the yield structure. The highest total and marketable yields were collected after mulching the soil with black unwoven fibre PP50. The highest proportion of bulbs of class I was obtained from the objects mulched with black foil.

The emergences of plants in the field were very poor. Fennel emerged most numerously from April seeding, while the worst from the sowing in June. Cultivar "Zefa Fino" sprouted better in the field than cultivar "Rudy F 1". The highest total yield of fennel bulbs was obtained from the sowing in April and May, while the lowest – in June. The growth dynamics of fennel bulbs significantly depended on the course of the weather in successive years of studies. Cold periods in spring and droughts in August limited the growth of the bulbs from April and June sowing. Plants from May sowing formed the bulbs with marketable features already after 10 weeks of vegetation. Both the total and marketable yields of "Zefa Fino" cv. were higher than in the case of "Rudy F 1" cv.

It was found out that the best date of collecting fennel bulbs was the harvest after 12 weeks of vegetation, when the optimum weight of the bulbs was assumed at 200-350 g, independently of the sowing date and the cultivar. The harvest after 10 weeks of vegetation was too early, especially with April sowing. With the sowing in June it is possible to delay the collection of bulbs up to the 14 th week of vegetation. Taking no account of the minimum weight of 200 g for the marketable yield made it possible to obtain the bulbs with satisfactory morphological features already after 10 weeks of vegetation and increase the marketable yield of the bulbs by 8.6 t .ha -1, on average.

The application of nitric fertilization in a dose of 160 kg N . ha -1, regardless of the date, caused a significant increase of the content of nitrates in fennel bulbs as compared to the dose of 80 kg N .ha -1 used pre-sowing. An especially big amount of nitrates was gathered in the bulbs with the weight of < 200 g (>2300 ppm N 3 -), and at least with the weight > 350 g .

During the storage in a fridge, an increase of the level of dry weight and a decrease of the content of vitamin C, reducing sugars and total sugars in fennel bulbs were found out. A higher nutrient value was kept by the bulbs stored loose as compared to those stored in perforated foil, but they lost the fresh weight faster and hence they should be stored shorter. It was shown that fennel bulbs should not be stored in a fridge for longer than 2 weeks, and the minimum weight of the bulbs should be bigger than 200 g .

It was found out on the basis of the obtained results that both studied cultivars, i.e. "Rudy F 1" and "Zefa Fino", are perfectly suitable for the cultivation in the central-eastern region of Poland from the sowing in the field between April 20 and June 20, and from seedlings between May and June. They gave a high yield of good quality bulbs, and the effect of the yielding probably depended on the course of the weather with the shortage of water in the period of emergence and the formation and growth of the bulb as the determining factors.