Dursun EŞIYOK¹, M Kadri BOZOKALFA¹, Bülent YAGMUR², Atnan UGUR^1
1Department of Horticulture, Faculty of Agriculture University of Ege 35100 Bornova/Izmir Turkey (contact e-mail: esiyok@ziraat.ege.edu.tr) ²Department of Soil Science, Faculty of Agriculture University of Ege 35100 Bornova/Izmir Turkey

Introduction

Turkey has a suitable ecological condition for vegetable production. Vegetable used for food source because of their high fiber, vitamins and mineral matter contents. Consumption preference determines the type of vegetables. Endive is member of Astaraceae family and used for fresh salads or cooked. Endive is a warm weather vegetable and grown autumn and spring seasons in Turkey climate. In the winter, early high temperatures increase early flowering incidence. In many countries, growers use more fertilizer than needed to increase the yield. This causes some unfavorable soil conditions as salinity or pollution of underground water. Nitrogen is a very important nutrient element especially for green leafy vegetables. Excessive use of nitrogen reduces plant carbohydrate content and destroys carbohydrate-nitrogen balance. The high nitrogen content of soil or plant causes the sour taste of green vegetables. Because of this nitrogen fertilization is very important for leafy green vegetables.

Material and methods

This investigation was carried out in the experimental fields of Faculty of Agriculture, Ege University in 2002-2003 growing seasons. The soil characteristics were given in table 1.

Table 1. Some physical and chemical properties of the experimental soil

In the experiment White curled Endive variety used. The nitrogen doses were 0-60-120-180 kg/ha N. Experimental design was randomized complete blocks with tree replications. Seeds were sown in multicells (45 ml volume) filled with torf and perlite mixture (1:1). Seedling transplanted in soil 60*35 cm distance and 150 kg/ha K₂O and 100 kg/ha P₂O₅ fertilizer were entirely incorporated to soil preplanting under disc-harrow. Usual cultural practices were followed during the growing season. Soil samples are analyzed according to international rules. Plant circumference, plant diameter, plant weight, root weight and length and color was determined measured with tristimulus colorimeter (Model CR-300 Minolta Japan) as CIE L hue and chroma and dry matter content analyzed were determined in randomly chosen 20 plants in each plot. The data were evaluated statistical packet programmed.

Results and discussion

Nitrogen doses did not have statistically significant effects on plant circumference, and plant diameter of endive, but harvest period is affect on circumference and diameter. Delay the harvesting period increase the circumference and diameter(Table 2).

Circumference was changed between 24.03 and 25.75 cm and diameter 6.79?7.20 cm. Plant weight of endive was affected by nitrogen. Increasing the application doses of nitrogen linearly increased the plant weight and the highest plant weight 297.6 g obtained from 180 kg/ha nitrogen application (Figure 1). Delaying the harvest also increased the average plant weight. Nitrogen doses and harvest period were significantly affected endive root weight. Root length was not affected by nitrogen doses statistically and changed between 15.61-14.89 cm. Lightness of endive was not affected by nitrogen applications, but delayed harvest increased the lightness values, i.e. leaf color was lighter. Nitrogen doses and harvest period statistically influenced the hue of the color. Nitrogen application caused a greener leaf color, and on the second harvest the leaves were greener. Dry matter content was not affected by nitrogen doses and changed between 6.29-6.40 %. Harvesting period had a significant effect on dry matter, delaying the harvest increased the dry matter content of endive leaves.

Figure 1. Effect of nitrogen doses yield of Endive