Question

What is the role of micro-organisms in increasing the soil fertility

Answer 1

Hint: In the natural environment, plants are part of a rich ecosystem that includes several and diverse microorganisms in the soil. It has been long recognized that some of these microbes play a vital role in improving the nutrient level of the plant. Rhizobium, nostoc, and pseudomonas are few organisms found in the soil.

Complete answer:
The majority of nutrients that are essential for the growth and development of plants becomes available to the roots due to weathering and the breakdown of rocks. These processes enrich the soil with dissolved ions and inorganic salts. Since they are derived from rock minerals, their role in plant nutrition is referred to as mineral nutrition. Soil consists of a wide variety of substances. It supplies minerals and nutrients from the microorganisms that fix the nutrients for the growth in plants.

A few of the minerals that are fixed in the soil are:
1. NITROGEN- Several types of symbiotic nitrogen fixing associations live in the soil. Nostoc, rhizobium are some of them that help in the reduction of nitrogen to ammonia, which is called biological nitrogen fixation. They live in association with the roots nodules of several leguminous plants. They fix up the nitrogen that is present in the free atmosphere and make it available for the plants as a nutrient for growth.

Rhizomes are associated with rhizospheres which is an important soil ecological environment for plant and microbes interaction. About 65% of the nitrogen is currently utilized in agriculture for sustained crops production.

2. PHOSPHOROUS- It is one of the major essential micronutrients for plant growth and development. It exists in two forms in the soil: organic and inorganic phosphates. The concentration of soluble P in soil is usually low. The precipitation of P in soil generally is dependent on pH and soil type. Pseudomonas, Bacillus and rhizobium are among the most powerful phosphate solubilizers while tricalcium phosphate etc. is degradable from the rock surface. It helps in providing phosphate to the soil.

Glomus, the fungi form symbiotic associations with plants. Many members of the genus Glomus form mycorrhiza. These fungi help in the absorption of phosphorus from the soil and pass it into the plant. Plants having such associations are resistant to root- borne- pathogens, tolerance to salinity and drought and an overall increase in plant growth and development.

Note: Soil is the major source of nutrients that are needed by plants for growth. If the plant is deprived of nutrients it can cause several symptoms just by looking at them. Some symptoms are dead leaves at the leaf tips, on the leaf edges, yellowing of the leaf, no growth and white or yellow streaks on the leaf veins.