This study investigates the efficiency of seaweed liquid fertilizer (SLF) prepared from combinations of different seaweeds (Sargassum polyphyllum, Turbinaria ornata, Gelidiopsis sp., Padina tetrastomatica, Gracilaria corticata) as a stimulant for the growth of Vigna radiata (Mung) as well as its antagonistic activity against fungal pathogens (Alternaria solani, Rhizoctonia solani., Sarocladium oryzae). 100% SLF was prepared, which was further diluted to 60%, 40%, and 20%. Seeds were soaked in four different concentrations of the SLF (20%, 40%, 60%, and 100%) for 12 hr and planted. After 60 d, the root and shoot length were increased by 14% and 16%, respectively, with SLF (100%). The carbohydrate and protein concentrations were also increased by 70% and 86%, respectively, at 100% SLF. The concentration of chlorophyll a, chlorophyll b, and carotenoids were found to be increased by 20%, 43%, and 28%, respectively, with 100% SLF.
SLF was prepared from 25 g powdered seaweeds viz S.pollyphyllum, T. ornata, Gelidiopsis sp., P. tetrastomatica, G. corticata were taken in equal quantity (i.e. 5 g each) and mixed in 50 mL of water. The final volume was prepared to 350 ml by adding another 300 ml of water. This was autoclaved for 60 min and the concentrate was separated through a cheese fabric cloth and allowed to cool. The filtrate was collected and centrifuged for 30 min at 10,000 rpm at 4°C. Supernatant was gathered and taken as 100% SLF. The SLF was then diluted in distilled water to make different concentrations, for example, 20%, 40%, and 60%.
Seeds of Vigna radiate (Green gram) were soaked in distinctive grouping of SLFs (20%, 40%, 60%, and 100% of SLF concentration) for 12 hr. Five seeds from the different SLF concentrations were sown in distinctive pots along with two pots for chemical fertilizer (Urea 46.0, Mangalore Chemicals Pvt. Ltd.) treatment and control (without any treatment), respectively.
The seeds of 1st group were planted without any additional substances, which served as the control. The 2nd group included seeds with chemical fertilizer (Urea 46.0, Mangalore Chemicals Pvt. Ltd.) available commercially. Seeds of the 3rd, 4th, 5th, and 6th groups were soaked with 20% SLF, 40% SLF, 60% SLF, and 100% SLF, respectively. Seeds of all the groups were planted in different pots. Seeds in all the experimental setups (control, chemical (synthetic) compost, 20% SLF, 40% SLF, 60% SLF, 100% SLF) were permitted to grow for 60 d, with appropriate watering and with vital measure of daylight. After the growth of 60 d, the plants were removed and the growth was inspected.
Seed germination was found to be the maximum for both 100% SLF concentration and chemical fertilizer (urea) as all the five seeds germinated on day 3. Seeds treated with 40% SLF and 60% SLF showed good germination rates with the growth of two and three seeds, respectively. Day 4, all seeds had germinated. The root and the shoot length were increased at a similar rate for the chemical fertilizer as well as the SLF when compared with that of the control. The control plants had a mean root length of 6 cm and the mean shoot length is 21 cm. Maximum shoot length was found to be 25 cm for 100% SLF and maximum root length of 6.8 cm was found in chemical fertilizers. However, 100% concentration of SLF also showed notable root length of 6.5 cm which is nearly equivalent to the chemical fertilizers (6.8 cm). Minimum shoot length of 20 cm was observed in 20% SLF treated plants while both 40% and 60% SLF treated plants have grown 23 cm. The minimum root length of 3 cm was observed for both 20% and 40% SLF treated plants while the 60% SLF treated plants have a mean root length of 4 cm.
Protein content was found to be highest for 100% SLF treated plant. The mean of the concentrations was 6.8 mg/g. The minimum concentration of 0.9 mg/g was found in control plant. Other concentrations of SLF treated seeds also showed significant protein content. Chlorophyll a, chlorophyll b, and carotenoids were found to be the highest in chemical fertilizer and 100% SLF treated plants. The concentration increased by 20%, 43%, and 28%, respectively, when compared with the control.
Activity of SLF against three fungal pathogens A. solani, S. oryzae, and R. solani was checked. Zones of inhibition were observed different for different concentrations of SLF against the pathogen A. solani. It was observed that the 100% SLF showed the mean zone of inhibition value of 46 mm.
Discussion
The combinations of seaweed extracts can be used as an environmentally friendly method of plant disease control and can be used in organic farming and for vegetable cropping systems, where use of synthetic chemicals or fungicides needs to be controlled. These extracts were proved to be significant biostimulants and fungicides. Thus, research is being done in the field of bioactive compounds from these seaweeds that could be used as potential biofungicide.
Conclusion
The use of seaweed and its products have increased due to its effect on productivity of various crops. The use of SLF should be encouraged to avoid environmental pollution due to high concentrations of chemical fertilizer in the soil. SLF has a positive effect on the leaves (size and pigment content), root length, and even on carbohydrate and protein content of the plants. Plants also showed increased resistance to fungal pathogens. Moreover, the abundance of seaweeds has made them a very good choice to be used as a potential alternative for chemical fertilizers. However the mechanism due to which the seaweed increases productivity is still unknown. It could be due to the macronutrients present in the algae. In the experiment performed, seeds of V. radiate treated with 100% SLF concentration showed maximum carbohydrate, protein, and pigment content. It also showed 100% seed germination on day 3, as well as a high root and shoot length. The SLF was also able to successfully inhibit the growth of A. solani at both 60% and 100% concentration.
Reference:
Sarkar, G., Jatar, N., Goswami, P., Cyriac, R., Suthindhiran, K. and Jayasri, M.A., 2018. Combination of different marine algal extracts as biostimulant and biofungicide. Journal of Plant Nutrition, 41(9), pp.1163-1171.
