A Review of Azolla spp. as a Potential Resource for Sustainable Agriculture in Sri Lanka: A New Effort for the Green Agriculture among Sri Lankan Farmers
Indika Subhashini Wijeysingha and Sajeewani Rajika Amarasinghe
Abstract
The present economic crisis in Sri Lanka has limited the usage of inorganic fertilizers in agriculture sector. Furthermore, animal husbandry, the other branch of agriculture has problems due to high prices of animal feed and unavailability. The concept of using Azolla spp. as a multifaceted resource for sustainable agriculture, which facilitates the environment-friendly green concept, is receiving great attention in the present crisis. Azolla is a small floating, fast-growing aquatic fern distributed globally. Because of its growth habitat, high biomass production and nitrogen-fixing ability, it has acquired substantial value in the agriculture sector, especially as a nitrogen supplier to plants. Besides its usage as a fertilizer, Azolla can be used as a nutrient provision for animals, human food, phyto-remediating agent, weed controller, mosquito controller, medicinal plant, and a substrate for biogas production. It is a feed rich in protein, which can be used to feed farm animals, poultry, and fish. As well, it is found to be a more affordable additional feed supplement for the animals. The nitrogen-fixing ability of Azolla with the aid of a symbiotic cyanobacterium Anabaena azollae has led to the exploitation of Azolla as an effective nitrogen fertilizer and a protein supplier. Also, it helps to conserve water, sequestrate carbon, and appropriate for integrated farming systems. Azolla is grown in many countries for the aforementioned uses and its cultivation aligns with the goals of sustainable and environmentally conscious agriculture. Azolla can be easily grown in containers, soil pits or cement tanks that hold water. The required conditions should be supplied, including optimum light intensity, relative humidity, pH, salinity macro and micronutrients, etc. This review addresses the morphology of Azolla, its symbiotic relationship, and the potential usages for sustainable agriculture as a new effort for the green agriculture among Sri Lankan farmers.
Keywords: Azolla spp., Biofertilizer, Green Manure, Nitrogen Fixation, Sustainable Agriculture