Azolla Blue Green Algae Biofertilizer Tanika rana M
Azolla & Blue Green Algae Biofertilizer Tanika rana M. Sc Microbiology 4 th sem.
Introduction � Azolla is a branched free floating aquatic fern & naturally available mosty on moist soil, ditches marshy ponds and streams in both tropical and sub-tropical region. � It grows in fresh water.
Structure � The plants are triangular or polygonal in shape, dichotomously branched and consist of floating branched rhizome bearing small alternate overlapping bi-lobed leaves. � The bi-lobed leaf consist of a dorsal and ventral lobe. � The dorsal lobe is green or purple in colour & has a central cavity containing its symbiotic partner-a blue green algae, i. e Anabaena azollae. � The thin white or ventral lobe always remain partially submerged in water and helps the plant to float in water.
Conti…. � Roots emanating from growing branches remained suspended in water. � The plant is about 1. 5 - 3. 0 cm in length, 12 cm in breadth. � The fern is capable of fixing atmospheric nitrogen in the soil in the form of ammonia. � It becomes available as a soluble nitrogen for the wet land rice crop, which is the major cereal crop of India.
Classification � Proposed by Saunders & Fowler (1993) : Kingdom: Plantae Division : Pteridophyta Class : Pteridopsida Order : Salviniales Family : Salvinaceae Genus : Azolla Ø The genus Azolla was established by Lamarck in 1785.
Characteristics � Azolla fern is regarded as “ Live Nitrogen Manufacturing Factory” because it harbors nitrogen fixing Cyanobacteria i. e. Anabaena azollae. � Azolla is one of the fastest growing plant on the planet doubling its biomass in just 2 -3 days. � Azolla – Anabaena is the only known symbiosis in which the two organisms remain together during the plant’s reproductive cycle, & it was designated as ‘Superorganism’ by Francisco Carrapico in 2009.
Cont… Ø Tolerant to heat & cold. Ø Extensively used as biofertilizer and green manuring for rice cultivation. Ø It is rich in proteins, amino acids, vitamins and minerals. Ø Azolla dual cropping enhance rice yield by 55% and supplement nitrogen by 50%. Ø In addition to nitrogen the decomposed Azolla also provide K, P, Zn and Fe to crop.
Nitrogen fixation process � The growth of all organisms depend on the availability of nitrogen. � In order for Nitrogen to be used for growth it must be “fixed”(combined) in the form of ammonium (NH 4) or nitrate (NO 3) ions. � Azolla fixes atmospheric nitrogen due to presence of the Cyanobacteria - Anabaena azollae , in its dorsal leaf cavities. � Although Azolla can absorb nitrates from the water, it can also absorb ammonia secreted by Anabaena within the leaf cavities. � The alga develops heterocyst and starts nitogen – fixation. � Azolla fixes 40 -60 kg N/ha/year in rice crop.
Anabaena & nitrogen fixation � Azolla leaf consist of – a thick, greenish dorsal lobe and a thinner, translucent ventral lobe emersed in water. � It is the upper dorsal lobe that has an ovoid central cavity, “living quarters” for filaments of Anabaena. � The easiest way to observe Anabaena is to remove a dorsal leaf lobe and place it on a clean slide with a drop of water. � Then apply a cover slip with sufficient pressure to mash the leaf fragment. � Under 400 X magnification the filaments of Anabaena with larger, oval heterocyst should be visible around the crushed fern leaf.
cont… The thick walled heterocysts often appear more transparent and have distinctive “polar nodules” at each end of the cell. � The polar nodules may be the same composition as cyanophycin granules. � These may serve as a nitrogen storage product. � The larger oval cells are heterocysts, the site of nitrogen – fixation where atmospheric nitrogen is converted into ammonia. � Polar nodules are visible in some of the heterocysts. �
Mass cultivation of Azolla � Microplots (20 m 2) are prepared in nurseries in which sufficient water (5 -10 cm) is added. � For good growth of Azolla, 4 -20 Kg P 2 O 5/ha is also amended. � Optimum p. H (8. 0) and temperature (14 -30°C) should be maintained. Finally, microplots are inoculated with fresh Azolla (0. 5 to 0. 4 Kg/ m 2). � After three, week of growth mat formed by Azolla is harvested and the same microplot is inoculated with fresh Azolla to repeat the cultivation. � Azolla mat is harvested and dried to use as green manure.
Uses of Azolla � In rice field as dual cropping and green manuring. � Used as cattle feed. � Used as bio- fertilizer in organic farming. � Food for fishes. � Food for pig, goat, poultry and other livestock.
Favourable condition for higher efficacy of Azolla � Water : 10 -15 cm fresh current water is necessary in multiplication pond. � Temperature : The day/night temp. ranging between 32°C and 20°C have found to be most favourable. The optimum temp. for luxurious growth of Azolla is 25°-30°C. � Light : Azolla prefers to grow well under partial shade. As dual cropping Azolla gets partial shade from rice plant. � Soil p. H : Azolla grows well in slightly acidic soil having 5. 2 - 5. 8 p. H � Nutrition : Being an N fixing fern Azolla does not require nitrogenous fertilizer for its growth. Phosphorous is desirable for good bio- mass production.
Application of Azolla in rice field � The • • most common mode of application of Azolla in the field is as green manure or as a dual crop along with rice. As Green Manure : Azolla collected directly from ponds/ ditches is applied in the field. A thick mat of Azolla will be formed after application in about 2 -3 weeks time and can be incorporated in the soil. Rice can also be transplanted in the field subsequently. Single super phosphate is applied in split doses. Azolla application by this mode contributes around 20 -40 Kg N/ha.
In dual cropping : � Azolla is grown along with rice and each crop of Azolla contributes on an average 30 Kg N/ha. � After 7 -10 days of transplantation fresh inoculums of Azolla is applied in the field at the rate of 0. 50 - 1. 0 ton/ha. � Single super phosphate is applied at the rate of 20 Kg/ha in split doses. � In about 15 -20 days time a thick mat of Azolla is formed weighing 10 -20 tonnes. � Azolla thus incorporated decomposes in about 810 days time and release the fixed nitrogen.
Blue Green Algae BGA are photoautotrophic, prokaryotic algae. � They are free living creatures and also known as Cyanobacteria. � It fixes the atmospheric nitrogen in moist soils, so BGA has been recommended as a biofertilizer. � These may be unicellular ( e. g. , Chroococcus), colonial (e. g. , Nostoc) and filamentous (e. g. , Oscillatoria) � Some filamentous forms have specialized cells known as heterocysts. Eg- Nostoc, Anabaena etc. �
Characters Ø They are omnipresent, and occur in all possible kinds of habitats. Ø Their size ranges from 0. 5 to 60 micrometres, which represents the largest prokaryotic organism. Ø The flagella are absent. Ø The storage product are cyanophycean starch and protein. Ø There about 150 genera and 1500 species of fresh water, marine and terrestrial blue green algae.
Cont… � Cyanobacteria contain only one form of chlorophyll i. e. chlorophyll a, a green pigment. � In addition, they contain various yellowish carotenoids, the blue pigment phycobilin, and in some species, the red pigment phycoerythrin. � The combination of phycobilin and chlorophyll produces the characteristic Blue-Green colour from which these organisms derive their popular name
Nitogen fixation In some cyanobacteria nitrogen fixation occurs in heterocyst. Ø It is an enlarged cell and may be present terminally or intercalary in filamentous cyanophycean algae. Ø On one hand, these special cell wall layers permit the atmospheric N 2 (g) to diffuse inside, whereas on the other hand they stop the atmospheric O 2 to come inside. Ø This is a damage- control mechanism for the enzyme nitrogenase, as the nitrogenase is sensitive to O 2 and cold, and cannot function in the presence of O 2 (g). Ø BGA fix approximately 25 Kg N/ha/year. Ø It is suitable nitrogen fixer for paddy field. Ø
Mass production of BGA : � The following methods are used for mass cultivation – • • Cemented tank method Shallow metal troughs method Polythene lined method ( its most suitable for small and marginal farmers for the preparation of biofertilizers) Field method.
In polythene lined method� Prepare the cemented tank, shallow trays of iron sheets or polythene lined pits ion an open area, width of tanks or pits should not be more than 1. 5 m � Transfer 2 -3 kg soil and add 100 g super phosphate water the pit to about 10 cm height, mix lime to adjust the p. H. � Add 2 ml of insecticide to protect the culture from mosquitoes mix well and allow to settle down soil particles. � When water becomes clear, sprinkle 100 g starter culture on the surface of water.
Cont… � When temp. remains around 35 -40°C during summer, optimum growth of cyanobacteria is achieved. � The water level is always maintained about 1 cm during this period. � After drying the algal mass (mat) is separated from the soil that forms flaks. � It is collected, powdered and packed in polythene bag and supplied to the farmers after sealing the packets. � The algal flaks can be used as starter inoculum again.
Applications � Crop • • • response to BGA biofertilizer. The rice fields with ample light, water, high temp. and nutrient availability, provide a favourable environment for the growth of BGA. Paddy crop is significantly benefitted from the growth of BGA in the fields. The grains yield in paddy crop has been reported to increase from 7% - 23% over the control in agricultural ecosystem. BGA excrete vitamins and hormones, which enhances rice growth, & also enhances soil fertility. The beneficial effects of BGA inoculation have also been reported in a number of other crops such as Barley, Cotton, Maize, Oats, Sugarcane, Tomato and Wheat.
Cont… � It has been shown to be Therapeutant with regard to several diseases like night blinders, Anaemia, Glucomia, Cholesterol accumulation, pancreatis etc. � Its antioxidant properties have been attributed with cancer prevention possibilities. � Pigmentation of ornamental fishes and prawn larvae has commercial significance. � New areas of Spirullina application are with regard to extraction of valuable enzymes like phosphoglycerokinase specific for ATP determination, superoxide dismutase required genetic engineering and phycobillin used in immunodiagnostics.
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