Influence of Zinc and Humic Acid on Growth, Yield and Essential Oil Percentage of Fennel (Foeniculum Vulgare Mill.) Plants

Abstract

The current study was carried out to study the growth, yield and essential oil percentage of fennel as influenced by different concentrations of zinc and humic acid. The treatments were comprised of foliar application of zinc at three rates (0, 100 and 200 ppm) and soil drench of humic acid at four rates (0, 500, 750 and 1000 ppm), as well as their interactions. The results revealed that zinc treatment at 100 ppm significantly increased the number of branches/plant, number of umbels/plant, herb fresh and dry weights/plant, fruit yield/fed and essential oil %. However, raising zinc concentration to 200 ppm revealed a significant decrease in fruit yield/fed. Soil application of humic acid at the moderate level (750 ppm) scored the highest values compared to the other levels on all parameters except for plant height and herb fresh weight. The interaction effect was statistically significant on all examined parameters. In this connection, combined zinc treatment at 100 ppm and humic acid at 750 ppm proved superior in all measured parameters except for plant height. Thus, our study provides valuable information about the possibility of improving the growth and productivity of fennel plants using a combined treatment of zinc and humic acid.