Evaluation the Effect of Water Hyacinth and Humic Acid Compost on some Morphophysiological and Biochemical Properties of Gerbera (Gerbera jamesonii Bolus. cv. Artist)

Water hyacinth (Eichornia crassipes) is one of the world’s most prevalent invasive aquatic plants. Due to the environmental and economic concerns associated with the water hyacinth spread, control of this plant seems will be necessary. Composting is promising techniques for controlling water hyacinth. Humic acid is the fraction of naturally occurring organic materials, which derive from the decomposition of plant and animal residues. Humic acid plays important roles in plants through stimulation of root growth and increase of water and nutrient uptake by plants. In this study, we evaluated the effect of water hyacinth compost and humic acid on the vegetative and reproductive characteristics of gerbera flowers

The present study was conducted as a factorial experiment in a completely randomized design with three replications. The first factor was water hyacinth compost (0, 25, 50, 75 and 100% v/v) and the second factor was humic acid (0, 250 and 500 mg L-1). The peat moss + perlite (2:1 v/v) was considered as a control treatment. To prepare water hyacinth compost, the water hyacinth was collected from a river in Sari, Mazandaran, Iran. Water hyacinth leaves were exposed to direct sunlight for eight hours to wither then chopped to fine pieces and eventually was spread on the surface. The thickness of leaves is five-centimeter. One centimeter thickness of animal manure was added on top of the water hyacinth leaves and then a layer of ash and lime respectively added. This step was repeated until the height of the layer reached to one meter, finally the top layer was covered with dry leaves of native trees and black polyethylene sheets. The mass was mixed up every 15 days to get a better result (uniform decomposition). Finally, after three months, the compost was prepared. Gerbera (cv. Artist) seedlings with uniform size (15 cm) were planted in plastic pots at different levels of compost. Humic acid was used once every ten days. The average day and night temperature in the greenhouse during the experiment was 17±2 and 23±2ºC, respectively, and the average greenhouse humidity was 65 to 75%. Flowering time, number of flowers, number of leaves, stem length, flower stem diameter, flower disk diameter, fresh and dry weight of shoots and roots, phenol content, total chlorophyll and carotenoids, concentrations of nitrogen, phosphorus, potassium and calcium in the leaves, ion leakage of petals and vase life were evaluated.

According to the results of the effect of compost, humic acid and their interaction on most of the studied characteristics were significant. The highest number of flowers with 117% increase compared to the control treatment was related to 50% compost + 500 mg L-1 humic acid. In this treatment, the time of flower emergence occurred 40 days earlier than the control. The highest chlorophyll content with 155.52% increase compared to control was observed in 25% compost + 500% humic acid. Mineral elements in the leaf of the Gerbera plant were significantly affected by growth media and humic acid. The highest nitrogen content was found in 50% compost + 500 mg L-1 humic acid (a 50% increase compared to control). The highest potassium content was observed in 50% compost + 250 mg L-1 humic acid. The highest concentrations of calcium were found in the leaves of plants grown in 50% compost + 500 mg L-1 humic acid. The highest vase life with a 71.67% increase compared to the control treatment was related to plants that were grown in 25% or 50% compost+ 500 mg L-1 humic acid. The lowest ion leakage was recorded in 50% compost + 500% humic acid with 56.79% decrease compared to the control. In the present study, most of the growth media and humic acid significantly affected most of the Gerbera plant parameters. The best results were obtained from 25% and 50% compost +250, 500 mg L-1 humic acid. Due to proper drainage, increased water retention, a pseudo hormonal compound such as auxin and increased absorption of elements, compost improve the chemical and physical structure of growing media. Also, high leaf nitrogen content was observed in most compost-containing substrates. This element plays a key role in vegetative growth. The concentration of nitrogen and phosphorus in compost is usually 5 to 11 times higher than soil which is gradually delivered to the plant and increases the growth and flowering of the plant. Humic acid plays important roles in plants through stimulation of root growth and increase of water and nutrient uptake by plants. In our study the application of humic acid at 250 and 500 mg L-1 significantly increased concentration of nitrogen, phosphorus, calcium and potassium as compared with control. It has also been reported that humic acid provides growth regulators to regulate and control hormone levels in plants and stimulates the production of plant enzymes and hormones, which ultimately increases the vegetative and reproductive growth of the plant.

The results of this study showed that water hyacinth compost with humic acid due to improving the root environment and increasing the absorption of nutrients, increased quantitative, qualitative and vase life characteristics of Gerbera in comparison with control (peat + perlite). 50% compost was introduced as the best treatment in combination with concentrations of 250 and 500 mg L-1 of humic acid.