Microbes: Every farmer’s not so secret superstar
Our soil is one of the most prominent reasons that life is possible on this planet.
By definition, soil is particulate surface material made up of various minerals as well as organic matter. Soil supports and nourishes plant and animal life by providing it with nutrients. The ancients changed their fates and ours when they evolved from hunter-gatherers to cultivators of the land. Over time, our chemistry with soil has evolved and helped form the foundation of our thriving civilization on this planet.
From tiny unicellular algae to complex vascular plants, almost all flora need soil for their development. All soils present on earth are a mix of three components: clay, silt and sand. These components directly reflect soil properties such as water holding capacity and nutrient levels and play a crucial role in agricultural practices. It is necessary for any farmer to take into account soil composition to ensure successful yields.
Understanding soil also helps a farmer choose the right irrigation system for his crops. For example, loam, the most fertile soil type, contains approximately equal proportions of clay, silt and sand. It has better water holding capacity with an optimum aeration rate as well as high nutrient composition, all essential to healthy plant growth. On the other hand, sandy soil has high aeration and water drains through very easily. Clay is made of fine particles and has a greater surface area. Soil with a higher percentage of clay has higher water holding capacity and excessive water supply leads to accumulation of water at the roots.
All soils in the world contain two types of mineral content. Primary minerals directly reflect the parent material from which the soil is formed, like calcium, iron, magnesium, silica, etc. On the other hand, secondary minerals are the result of weathering of primary minerals. They are responsible for the release of several ions as well as stabilising the mineral form. The mineral content of the soil varies by geography. For instance, red soils from the Western Ghats contain high quantities of iron oxides, whereas, soils in the Ganga basin are rich in silicates.
Along with minerals, organic content is another crucial component of healthy plant growth. Dead animals and plants, as well as animal faecal matter, are the highest contributors of organic content in soil. Soil rich in organic content is best for agriculture as it supplies crops with essential elements such as nitrogen, sulphur and carbon. Organic content also holds moisture and keeps roots hydrated.
Soil nurtures our agriculture and agriculture sustains and defines our lives by providing food. However, agriculture is often disruptive to natural ecosystems as not all soils are suitable for farming. This need to alter and enhance the soil and increase yield led to the invention and use of synthetic fertilisers. Their rampant, injudicious and improper use has led to a global crisis of soil infertility as well as disturbed and damaged ecosystems all over the world.
Microorganisms like bacteria, protozoa and fungi are the microflora of the soil. They reside in the soil and use organic matter and minerals present in the soil as their food. These microorganisms are fully equipped biochemical factories that carry out various actions to nourish crops.
Let’s take the example of nitrogen fixation. Our atmosphere is made up of 78 percent Nitrogen. Nitrogen is also present in all living forms, starting from our genetic makeup to amino acids. Despite being composed of nitrogen, no animal or plant can consume atmospheric nitrogen directly. Atmospheric nitrogen first needs to be fixed in the soil from where it starts its journey through our ecosystems and into our food. Microorganisms fix the nitrogen in soil by converting it into nitrates and then nitrites, consumed by plants. Nitrogen-fixing bacteria or fungi are present in the soil in two forms, free-living and in symbiotic association with plant roots. Free-living bacteria like Azotobacter do not require a host to fix nitrogen. On the other hand, symbiotic bacteria shelter in plant roots, forming a nitrogen-fixing structure. Symbiotic bacteria like Rhizobia are mainly present on the leguminous plants. Rotational crop systems involved cultivating leguminous plants as they restored nitrogen used up by the previous crop, maintaining the nutrient balance in the soil.
Along with nitrogen, phosphorus is the second key element essential for plant development. In the early stages of plant growth, an adequate supply of phosphorus is crucial for the development of reproductive parts of plants. Phosphorus strengthens plants by providing vitality and disease resistance as it is responsible for root ramification. It also regulates seed formation and maturation in cereals and legumes. Deficiency of Phosphorus stunts plant growth.
Though present in abundance in soil, in organic and inorganic forms, its availability is limited due to its insoluble nature. Several bacterial, actinomycetes and fungal species can solubilise phosphorus present in the soil. Solubilised phosphorus is a bioavailable form that facilitates uptake by plant roots. The temperature, as well as the presence of other nutrients such as nitrogen and oxygen greatly influence the phosphate solubilising ability of these microorganisms.
Along with nutrients and water, crops require plant hormones including auxins, gibberellins, cytokinins, abscisic acids and ethylene. Though plants can synthesize hormones to promote their growth, the amount is often insufficient. Bacteria, as well as fungi residing in the rhizosphere, also produce plant hormones as their secondary metabolites. The proximity of these microbes helps plants to absorb the hormones and meet requirements.
Across the globe, numerous studies and research have been conducted on microbes to use their ability to boost agricultural production. This research has led to the development of bio-fertilisers and bio-pesticides used in sustainable farming practices. Judicious use of these eco-friendly products has the potential to take our planet farther along on the path to food safety. Bio-fertilisers are formulations made of live bacteria or fungi. These organisms are plant-specific, and their targeted actions on specific plants supply them with required nutrients as well as hormones.
Unlike synthetic nitrogen and phosphate fertilisers, bio-fertilisers do not cause any harm to the soil. After four decades of Green Revolution, chemical fertilisers and their salts have accumulated in the soil, resulting in increased alkalinity and acidity. Bio-fertilisers can not only boost the plant growth but also restore land quality.
They contain denitrifying bacteria, which reverses the effects of nitrogen leaching. Urea, one of most prominently used chemical fertilisers, resulted in excessive nitrogen in the soil. Denitrifying bacteria use ammonia and its salts and convert it into gaseous nitrogen that is released into the air. By reducing the load of nitrogen from the soil, they reverse chemical pollution and leave plants with healthy soil to grow in and flourish.
Bio-fertilisers come in various forms; farmers can use these fertilisers by either coating them on seeds or directly applying them to the soil. They form a healthy ecosystem with plant roots that help them to absorb more nutrients from the earth. Fungal bio-fertilisers establish mycorrhizal associations with plant roots that maintain moisture and prevent roots from dehydration. Bio-fertilisers also synthesize products that act as antibiotics against root invading pathogens, i.e., they provide plants disease resistance.
Along with nutrition, microbes can be used to protect plants from notorious pests, a primary threat to growing crops. There are incidences in the history where pests have led to famines in various areas of the world. There are many reports of pesticide accumulation in rivers and lakes that have damaged local flora and fauna. DDT, the infamous pesticides used in India, has been responsible for wiping out entire populations of birds and fish. Some chemical pesticides are mutagens – chemicals inducing tumour formation.
Bio-pesticides have many advantages over chemical pesticides. They are plant-specific products that contain invasive genes to attack pests. They are harmless to humans or ecosystems and their targeted actions bring down pests leaving the plant to thrive. Bio-herbicides possess invasive genes that attack weeds that compete with crops for water and nutrients and eventually kill them.
Microbes from bio-fertilisers, bio-pesticides and bio-herbicides are self-replicating. If we compare the cost of synthetic products used every season to that of bio-products, there is no contest. Bio-products win hands down.
We often hear our grandparents talk about how vegetables used to be tastier when they were children. They aren’t wrong. Synthetic fertilisers and pesticides are robbing our crops and vegetables of taste! Imagine a world where everything tastes bland. Don’t we and generations to come deserve to know the real taste of nourishing food like our grandparents did? If this is the future we want, then microbial technology is our answer. Plus, using microbial technology to sustain agricultural production is by far the most befitting response to nature’s abundant generosity and one to which she is truly entitled.
This post first appeared on LinkedIn