Soil microbial biomass – Definition & Detailed Explanation – Soil & Fertilizers Glossary

I. What is Soil Microbial Biomass?

Soil microbial biomass refers to the total amount of living microorganisms present in the soil. These microorganisms include bacteria, fungi, protozoa, and other microbes that play a crucial role in the soil ecosystem. Soil microbial biomass is essential for nutrient cycling, decomposition of organic matter, and maintaining soil structure. These microorganisms are responsible for breaking down organic matter into nutrients that are available for plants to absorb, making them vital for plant growth and overall soil health.

II. Why is Soil Microbial Biomass Important?

Soil microbial biomass is important for several reasons. Firstly, these microorganisms play a key role in nutrient cycling within the soil. They break down organic matter, releasing nutrients such as nitrogen, phosphorus, and potassium that are essential for plant growth. Without soil microbial biomass, these nutrients would remain locked up in organic matter and unavailable to plants.

Additionally, soil microbial biomass helps to maintain soil structure by producing substances that bind soil particles together. This improves soil aggregation, water infiltration, and aeration, all of which are important for plant root growth and overall soil health.

Furthermore, soil microbial biomass also plays a crucial role in suppressing plant diseases and pests. Some microorganisms produce antibiotics and other compounds that inhibit the growth of harmful pathogens, protecting plants from disease.

III. How is Soil Microbial Biomass Measured?

There are several methods used to measure soil microbial biomass. One common method is the chloroform fumigation-extraction technique, which involves fumigating a soil sample with chloroform to kill the microorganisms, extracting the microbial biomass with a solvent, and then measuring the amount of carbon or nitrogen released.

Another method is the substrate-induced respiration technique, which involves adding a substrate such as glucose to a soil sample and measuring the amount of carbon dioxide released as the microorganisms break down the substrate.

DNA-based techniques such as polymerase chain reaction (PCR) and next-generation sequencing are also used to quantify soil microbial biomass by analyzing the genetic material of the microorganisms present in the soil.

IV. Factors Affecting Soil Microbial Biomass

Several factors can affect soil microbial biomass. Soil moisture is a critical factor, as microorganisms require water to survive and thrive. Soil pH also plays a role, as most microorganisms prefer a neutral to slightly acidic pH range.

Temperature is another important factor, as microorganisms are more active and reproduce faster in warmer temperatures. Soil texture can also influence microbial biomass, with sandy soils generally having lower microbial biomass compared to clay soils.

The type and amount of organic matter present in the soil can also affect microbial biomass, as microorganisms require organic matter as a food source. Additionally, land management practices such as tillage, fertilization, and pesticide use can impact soil microbial biomass.

V. Role of Soil Microbial Biomass in Soil Health

Soil microbial biomass plays a crucial role in maintaining soil health. These microorganisms are responsible for breaking down organic matter, releasing nutrients, and improving soil structure. They also help to suppress plant diseases and pests, making them essential for plant growth and overall ecosystem functioning.

Healthy soil microbial biomass can improve soil fertility, increase crop yields, and reduce the need for chemical fertilizers and pesticides. By enhancing soil microbial biomass, farmers can improve soil health, increase crop resilience, and promote sustainable agriculture practices.

VI. Management Practices to Enhance Soil Microbial Biomass

There are several management practices that farmers can implement to enhance soil microbial biomass. One key practice is to reduce tillage, as excessive tillage can disrupt soil structure and decrease microbial biomass. No-till or reduced tillage systems can help to preserve soil microbial communities and improve soil health.

Adding organic matter to the soil through cover cropping, crop residues, and compost can also enhance soil microbial biomass. Organic matter serves as a food source for microorganisms and provides essential nutrients for plant growth.

Rotating crops and practicing crop diversification can also benefit soil microbial biomass by promoting a diverse microbial community. Different crops have different root exudates and residues, which can support a variety of microorganisms in the soil.

Reducing the use of chemical fertilizers and pesticides can also help to enhance soil microbial biomass. These chemicals can harm beneficial microorganisms in the soil and disrupt the soil ecosystem. Using organic and natural fertilizers and pest control methods can help to maintain a healthy soil microbial community.

In conclusion, soil microbial biomass is a critical component of soil health and ecosystem functioning. By understanding the importance of soil microbial biomass, measuring it accurately, and implementing management practices to enhance it, farmers can improve soil fertility, increase crop yields, and promote sustainable agriculture practices. Investing in soil microbial biomass is investing in the future of agriculture and the health of our planet.