Lesson 1: Introduction to Biofertilizer Production
INTRODUCTION TO BIOFERTILIZER PRODUCTION
The following video will introduce you to the need for biofertilizers, types of component organisms and how you would test them and apply them. Further details about this topic is provided in the text matter below.
Need for Biofertilizers:
Food is a basic need, and ‘Food Security for All’, is an important goal of the United Nations. Farming provides the food required by all. Farmland used for agriculure rapidly gets depleted of nutrients leading to a loss of productivity.
Hence farmers use chemical fertilizers to supply the necessary nutrients.
Soil should be analysed for its type (sandy, silt, clay or loamy), its constituents (macro- and micro- nutrients), characteristics such as pH etc. before the selection and application of fertilizers.
The chemical fertilizers are sources of macronutrients (such as N, P and K) and micronutrients [such as boron (B), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), zinc (Zn), nickel (Ni) and chloride (Cl)].
Chemical fertilizers: are used in a combination so as to provide both NPK (Nitrogen, Phosphorus and Potassium) and micronutrients to the plants.
Composition of chemical fertilizers:
- I) Chemical fertilizers which are sources of nitrogen:
Chemical fertilizers may contain:
- nitrates: Sodium nitrate (16% N), Calcium nitrate (15.50% N); Potassium nitrate (13% N);
- salts of ammonium: Ammonium chloride (24-26% N), Ammonium sulphate (20% N), Diammonium phosphate (18% N) and
- Ammoniacal-nitrate fertilizers contain nitrogen in both forms—ammoniacal and nitrate e.g. Ammonium nitrate (33% N), Calcium ammonium nitrate (26% N) OR
- amides: Urea
- II) Phosphate fertilizers:
(a) Water soluble phosphatic fertilizers: H2PO4 in water, they are readily available to the plants e.g., Triple super phosphate (TSP: 42% phosphate), Double super phosphate (DSP: 32% phosphate); Single superphosphate (SSP: 16-18% phosphate);
(b) Citric acid soluble phosphatic fertilizers— are readily soluble in acidic water/weak acids- contain phosphorus in available form (H3PO4); e.g. Basic slag (18% phosphate) byproduct of iron and steel industries, Dicalcium phosphate.
(c) Insoluble phosphatic fertilizers— completely insoluble in water; slightly soluble in weak acids like citric acid e.g. Rock phosphates (20-40% P2O5); Bone meal.
- III) Potassium containing fertilizers:
- Potassium sulphate (K2SO4 + 50% K2O),
- Muriate of potash (KCl + 60% K2O)
- IV) Fertilizers which supply trace / micro- nutrients such as copper, zinc, molybdenum
Problems created by Chemical Fertilizers : Excessive use of chemicals fertilizers leads to an increase in the salinity of soil, change in pH (acidic or alkaline soils), heavy metal accumulation, eutrophication of water and accumulation of nitrates. Air pollution results from generation of gases containing nitrogen and sulfur and can lead to problems such as the greenhouse effect. It leads to environmental and health problems.
What is the solution?
The use of biofertilizers for making the required nutrients available to the plants can solve the issue of pollution of soil, water, environment and consequent health and environment issues.
- a) What are biofertilizers?
- A biofertilizer consists of viable (living) microorganisms which when applied to seeds or soil, promote plant growth. These organisms either get established in the rhizosphere (region in the soil around the root of the plant) or live symbiotically (their association benefits both the plant and the microorganism) within the plant (called endophytes).
- b) What is the importance of biofertilizers in sustainable agriculture practices and improvement of crop productivity?
The application of biofertilizers: composed of microorganisms with plant growth promoting properties will ensure improvement of crop productivity and at the same time promote soil health and prevent environmental pollution and the subsequent threats to human health. Thus application of biofertilizers would be in tune with the SDGs (Sustainable Development Goals) of the United Nations.
The biofertilizers are made up of microorganisms which exhibit plant growth promoting properties such as:
- they increase the supply or availability of nutrients to the plant: e.g. Nitrogen-fixing organisms (make nitrogen available), phosphate-solubilising organisms (make phosphorus available), siderophore-producing organisms (chelate iron and make it available to the plants).
- Some produce auxins/ plant growth hormones such as Indole-3-acetic acid (IAA) or giberellic acid (GA), which regulate and promote plant growth.
- Some produce lytic enzymes (e.g. chitinases, lipases) or anti-microbial compounds (e.g. HCN) which protect the plant against infection by phytopathogens.
Hence, the types of microbes which constitute potential biofertilizer candidates are: nitrogen fixers/ diazotrophs, phosphate solubilizers, plant growth hormone producers, siderophore producers. They may live independantly in the soil or may live symbiotically as endophytes within plants.
Cyanobacteria (or Blue-Green Algae) are photosynthetic bacteria. Some of them fix atmospheric N2 (by means of the heterocysts that their filaments have) and release it in the form of amino acids, proteins and growth promoting substances in their surroundings. They are good candidates for biofertilizers. They are generally applied to paddy fields where there is stagnant water exposed to sunlight, two prime requirements for the growth of cyanobacteria. Examples of cyanobacteria: Anabaena, Nostoc. In the absence of sunlight they follow heterotrophic mode of nutrition.
Image is that of grown cyanobacteria
Mycorrhizas are one more type of biofertilizer candidate: They result from a mutualistic symbiosis between some specific root – inhabiting fungi and plant roots. It leads to improved plant growth and yield, and resistance against climatic and edaphic stresses, pathogens and pests.
Carrier based biofertilizers: These biofertilizers are carrier based, ie the suspension of microorganisms is mixed with the carrier material and dried. This is done for ease of handling, long term storage with high effectiveness. Carriers are inert/ slowly degradable materials to which the microorganisms adhere and remain viable for a long period of time. Peat, cocopeat and charcoal powder are examples of carrier materials used in biofertilizer production.
- d) In further lessons we shall be seeing how such candidate microbes can be isolated and tested for their potential; how such candidate microbes can be grown in larger volumes and developed into biofertilizers using suitable carrier material.
- f) How should we apply biofertilizers in the field to yield higher crop productivity in a sustainable manner?
The selected culture, once isolated is grown in a suitable medium, its population is increased to a sufficient amount, a saline suspension of the culture is prepared and then it is mixed with sterile carrier material. It is then dried. Standards laid down by National Institutes are followed with respect to the purity, functionality and density of culture suspension prepared as well as the ratio of suspension to carrier material used.
The biofertilizer is then maintained/ stored in a cool place.
There are various ways of application of the biofertilizer:
- It is directly applied to the field/ soil in the vicinity of the planted seeds.
- The bioinoculant is mixed with water and the slurry thus produced is sprayed or used as water for irrigation.
- Seeds are coated with the biofertilizer and then the seeds are sowed.
- The explants (cut stems/ pieces of planting material) are dipped in a slurry of the biofertilizer for 30 min, dried in the shade and then planted.
- Savci Serpil. ‘An Agricultural Pollutant: Chemical Fertilizer’. International Journal of Environmental Science and Development, February 2012. 3 (1): 77-80.