Biofertilizers

1. INTRODUCTION
 Fertilizer is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients.
 When crops are harvested, the nutrients follow the crop. Important nutrients are therefore removed from the soil. Often the soil is not able
to replenish all the nutrients by itself, that is where fertilizers are crucial in supplying the nutrients that are lacking.
 A biofertilizer is a substance which contains living micro-organisms which when applied to seeds, plant surfaces, or soil, colonize the
rhizosphere or the interior of the plant and promotes growth by increasing the supply or availability of primary nutrients to the host plant.
 They improve soil structure, enhance nutrient absorption and soil productivity by nitrogen fixation, phosphorous and potassium
solubilization, and synthesis of growth-promoting substances.
WHY BIOFERTILIZERS?
 The need for biofertilizers arose due to the tremendous harm caused by the continuous use of chemical fertilizers which causes harm to
soil microbes thereby decreasing soil fertility.
 Although chemical fertilizers like urea, calcium nitrate, and ammonium sulphate increase crop production, their overuse has led to
hardening of the soil due to accumulation of phosphorus, increase in soil alkalinity due to the accumulation of insoluble salts like
(calcium, sodium, and magnesium), and contamination of groundwater due to water eutrophication caused by overabundance of
phosphorus and nitrogen.
 Biofertilizers help to correct the ill-effects of chemical fertilizers since they do not contain traces of hazardous and poisonous materials.
They are also cost effective, eco-friendly (as it will not pollute the environment) and convenient to use safely.
 They enable slow release of nutrients which allows time for microbial activity to breakdown the organic materials in the fertilizers.
Microbial activity refers to the natural microbes which include beneficial insects, fungus, and bacteria found in the soil.
 They also increase the quality and physical properties, such as water-holding capacity of the soil. Farmers can save money in the long run
by using biofertilizers.

2.  The main sources of biofertilizers are bacteria (rhizobium, azospirillum, and azotobacter), fungi, and cyanobacteria (blue-green
algae).
 They are generally produced as solid or liquid-based formulations and applied to seedlings, seeds, and soil.
 Historically, fertilization came from natural or organic sources such as compost, animal manure, ground bone, harvested
minerals, crop rotations and by-products of human-nature industries.
 The commercial history of biofertilizers dates back to 1895 using “Nitragin” by Nobbe and Hiltner with a laboratory culture
of Rhizobium sp. Before that, compost was used by Romans in the Akkadian Empire in the Mesopotamian valley.
 For centuries, the red water fern Azolla filiculoides has been utilized as a green manure for lowland rice in Vietnam and China.
Applications
When used as a seed treatment, biofertilizers colonize the roots of the plant and promote growth.
They can also be used as a foliar spray, which are absorbed by the leaves of the plant and transported to the roots, and can be
drenched in soil, where they help to bring live microorganisms back into the soil, improving soil structure and overall soil health,
as well as bringing symbiotic benefits to the plants in it.

3.  Agricultural waste, such as crop residues and organic matter, contains valuable nutrients. By converting this
waste into biofertilizer, these nutrients can be recycled and reintroduced into the soil, enhancing its fertility.
 Combining animal manure such as poultry litter, cow dung, and goat manure with crop residues can enhance
the nutrient content and microbial activity in the biofertilizer.
 The various types of biofertilizers which help the plant to grow at different levels of its growth are:
 Nitrogen Fixing Biofertilizers: Plants often contain 1-5% nitrogen contain micro organisms such as
Azotobacter (free-living bacteria), Rhizobium (root nodule bacteria) and cyanobacteria which convert
atmospheric nitrogen into a plant-usable form (ammonia), thereby enriching the soil with essential nitrogen
compounds.
 Phosphate Biofertilizers: Phosphorus (P) makes up about 0.1 to 0.5% of a plant and is involved in energy
storage and transfer, root growth, early maturation, quality, and disease resistance.
 Phosphorous Solubilizing Biofertilizers: By breaking down insoluble phosphates, making them accessible to roots,
these microorganisms (Bacillus, aspergillus and pseudomonas) help plants develop stronger root systems and absorb
essential nutrients more efficiently.
 Phosphorus Mobilizing Biofertilizers: Mycorrhizal fungi forms symbiotic relationships with plant roots, thereby
facilitating phosphorus uptake.
 Potassium Solubilizing Biofertilizers: e.g Pseudomonas and azospirillum break down complex potassium
compounds in simpler ones hence making them available to plants. Potassium (K) concentration in vegetative
tissue usually ranges from 1 to 4% of dry matter and influences enzyme activity, water and energy relations,
transpiration and translocation, and nitrogen uptake and protein synthesis.