After successful completion of this Lesson, you have learned to: List the 3 indicators of soil health. List the physical indicators that help to know a healthy soil. Explain how different physical indicators reveal the soil health status. List chemical conditions in soils that influence soil health. Virtual Academy for the Semi Arid Tropics Lesson 2: How to know that a soil is healthy? Course on Soil and Soil Health Module II: Soil Health

After successful completion of this Lesson, you have learned to: Describe different soil chemical conditions which can provide information on soil health. List the biological indicators that control soil health. Understand various biological activities which can improve or affect soil health. Virtual Academy for the Semi Arid Tropics Lesson 2: How to know that a soil is healthy? Course on Soil and Soil Health Module II: Soil Health

Soil health is evaluated in terms of indicators that measure specific physical, chemical and biological properties. Although this separation is useful, it is important to note that many of these properties are interrelated. Some physical properties are shaped by biological activity, biological activity can be enhanced or limited by physical and chemical conditions, and chemical properties are altered by microorganisms. Virtual Academy for the Semi Arid Tropics Lesson 2: How to know that a soil is healthy? Course on Soil and Soil Health Module II: Soil Health

In this Lesson there are 3 Units: Unit 1: Physical Indicators Unit 2: Chemical Indicators Unit 3: Biological Indicators Virtual Academy for the Semi Arid Tropics Lesson 2: How to know that a soil is healthy? Course on Soil and Soil Health Module II: Soil Health

Virtual Academy for the Semi Arid Tropics Course on Soil and Soil Health Module II: Soil Health Unit 3: Biological Indicators Lesson 2: How to know that a soil is healthy? After successful completion of this Unit, you will be able to answer 1.List out various microorganisms present in a soil? 2.What soil conditions influence the microbial population in a soil? 3.How soil microorganisms are beneficial? 4.What is humus? 5.How can you know the organic matter content in a soil?

Virtual Academy for the Semi Arid Tropics Course on Soil and Soil Health Module II: Soil Health Unit 3: Biological Indicators Lesson 2: How to know that a soil is healthy? After successful completion of this Unit, you will be able to answer 6.What is nitrogen mineralization? 7.How do you assess increased nitrogen mineralization? 8.What soil respiration indicates? 9.How soil respiration is measured? 10.How soil respiration is related to soil health?

Virtual Academy for the Semi Arid Tropics Course on Soil and Soil Health Module II: Soil Health Unit 3: Biological Indicators Lesson 2: How to know that a soil is healthy? Biological Indicators Microbial population Organic matter content Nitrogen mineralization Soil respiration

Virtual Academy for the Semi Arid Tropics Course on Soil and Soil Health Module II: Soil Health Unit 3: Biological Indicators Lesson 2: How to know that a soil is healthy? Microbial population Many soil microorganisms live in the soil. These microorganisms include  bacteria,  Fungi,  algae,  actinomycetes, etc.

Virtual Academy for the Semi Arid Tropics Course on Soil and Soil Health Module II: Soil Health Unit 3: Biological Indicators Lesson 2: How to know that a soil is healthy? Microbial population A single gram of soil (about 1/5 tea spoon) contain 100 million (10 crores) bacteria, 10 million (one crore) actinomycetes, 100,000 (1 lakh) fungi etc. The exact proportions of each of these organisms will depend on soil conditions such as available moisture, aeration, organic matter levels and the type of plants present. Chemical conditions such as acidity and alkalinity will greatly affect microorganism populations.

Virtual Academy for the Semi Arid Tropics Course on Soil and Soil Health Module II: Soil Health Unit 3: Biological Indicators Lesson 2: How to know that a soil is healthy? Microbial population Many soil organisms are beneficial but some others are devastating to crops, humans and animals. Beneficial organisms take part in many physical and chemical reactions that improve soil structure, break down organic matter and recycle nutrients.

Virtual Academy for the Semi Arid Tropics Course on Soil and Soil Health Module II: Soil Health Unit 3: Biological Indicators Lesson 2: How to know that a soil is healthy? Microbial population Others, however such as the tiny nematode, a worm, less than 0.1 mm long, and disease causing fungi and bacteria can cost farmers enormous money, every year, in loss of crop production. So, soil should contain more population of beneficial microorganisms for it to be in good health.

Virtual Academy for the Semi Arid Tropics Course on Soil and Soil Health Module II: Soil Health Unit 3: Biological Indicators Lesson 2: How to know that a soil is healthy? Organic Matter You have already learnt from the previous lessons about the importance of organic matter in soils. The organic matter content in soils ranges from almost nil (in sandy soils) to 15 to 20% (in forest areas). Most of the cultivated soils contain 0.5% to 5% of organic matter.

Virtual Academy for the Semi Arid Tropics Course on Soil and Soil Health Module II: Soil Health Unit 3: Biological Indicators Lesson 2: How to know that a soil is healthy? Organic Matter The organic matter content in a soil indicate the health of a soil. More the amount of organic matter better will be its health. It should be remembered that the organic matter in the soil is not stable and decomposed by many microorganisms over time and converted into humus. So, ultimately it is humus content that keeps going many activities in a soil.

Virtual Academy for the Semi Arid Tropics Course on Soil and Soil Health Module II: Soil Health Unit 3: Biological Indicators Lesson 2: How to know that a soil is healthy? A soil analysis will provide the information on the organic matter content in a soil. One can assess the organic matter content in a soil by observing, and feeling with fingers a sample of top soil. Soil rich in organic matter will be dark in color (compare right side soil sample with the left side one), mellow, and a good amount of decomposing roots and plant residues.

Virtual Academy for the Semi Arid Tropics Course on Soil and Soil Health Module II: Soil Health Unit 3: Biological Indicators Lesson 2: How to know that a soil is healthy? Observing a soil profile also gives you an idea about organic matter content in a soil. Look at the dark top layer in the left side soil profile and compare with the right side one.

Virtual Academy for the Semi Arid Tropics Course on Soil and Soil Health Module II: Soil Health Unit 3: Biological Indicators Lesson 2: How to know that a soil is healthy? Nitrogen Mineralization Nitrogen mineralization refers to the conversion of organic (unavailable) nitrogen in the soil to a form of nitrogen the plants can utilize for their growth and development. Organic Nitrogen Mineralization Inorganic Nitrogen

Virtual Academy for the Semi Arid Tropics Course on Soil and Soil Health Module II: Soil Health Unit 3: Biological Indicators Lesson 2: How to know that a soil is healthy? Nitrogen Mineralization This mineralization is carried out by certain microorganisms (bacteria etc.). Organic Nitrogen Mineralization Inorganic Nitrogen Microorganisms

Virtual Academy for the Semi Arid Tropics Course on Soil and Soil Health Module II: Soil Health Unit 3: Biological Indicators Lesson 2: How to know that a soil is healthy? Nitrogen Mineralization So, higher nitrogen mineralization, due to increased activity microorganisms, results in more availability of nitrogen in soils for crop use. Thus, better crop growth with the increased available nitrogen content in soil indicates a healthy soil. A soil test will reveal the amount of available nitrogen content in soils.

Virtual Academy for the Semi Arid Tropics Course on Soil and Soil Health Module II: Soil Health Unit 3: Biological Indicators Lesson 2: How to know that a soil is healthy? Soil Respiration Soil respiration is one of the most frequently used indicator for measuring microbial activity in the soil. You have already learnt that microorganisms are the driving force in many biochemical processes (decomposition, mineralization etc.) taking place in soil.

Virtual Academy for the Semi Arid Tropics Course on Soil and Soil Health Module II: Soil Health Unit 3: Biological Indicators Lesson 2: How to know that a soil is healthy? Soil Respiration Soil respiration is measured by the production of net carbon-di-oxide and consumption of oxygen in a soil due to the microbial activities. A higher rate of soil respiration is indicative of intense microbial activities in a soil and consequent benefits for better crop growth.

With this the Unit 3 on biological indicators in the Lesson 2 and also this Module II concludes. Next, Module III is about managing and improving soil health. Select Module III from the list of Course contents Virtual Academy for the Semi Arid Tropics Lesson 2: How to know that a soil is healthy? Course on Soil and Soil Health Module II: Soil Health