
Soil Microbial Diversity Test to Evaluate Toxicity Level of Bio-based Fertilizers (BBFs)
The increasing world population growth poses a major challenge in meeting food needs. Currently, the use of bio-based fertilizers (BBFs) or can also be called organic fertilizers/biological fertilizers is being developed to increase production in the agricultural sector.
BBFs are made from organic materials such as plant, animal, and microbial waste so that their use is considered more environmentally friendly. However, BBFs need to go through a series of safety tests to ensure that the product does not contain any unnoticed hazardous substances.
Hazardous materials such as pollutants, heavy metals, and other chemical compounds may accumulate in BBFs due to the manufacturing process. Contaminants in these fertilizers can affect the diversity of soil microbes which are very important for the decomposition process and nutrient cycle, which has an impact on plant growth.
Soil microbial diversity testing is important to understand the effects of organic fertilizers on the diversity of microbes that are useful for increasing nutrient content in the soil which ultimately affects plant growth and health.
The test results obtained play an important role in choosing the right raw materials and production methods, so that they can produce safe, quality fertilizers that support sustainable agriculture.
What is Bio-based Fertilizers (BBFs)?
The types of fertilizers used in the agricultural sector to increase production vary widely. One that is often used is mineral fertilizers.
Mineral fertilizers are usually produced through the process of mining raw materials such as phosphate and nitrogen. This process not only drains limited natural resources, but can also cause environmental damage, such as soil and water pollution. Therefore, many researchers have developed more environmentally friendly fertilizers.
Bio-based Fertilizers (BBF) or organic fertilizers/biological fertilizers are considered more environmentally friendly because they come from materials that are part of the existing natural cycle, for example the remains of living things, both plants and animals, which are used to increase soil fertility.

Organic fertilizers can be in the form of compost, green manure, manure, and agricultural waste. These fertilizers act as additional components in soil and plant management practices, such as crop rotation, organic adjustment, soil processing maintenance, recycling of crop residues, restoring soil fertility, and biological control of pathogens and insect pests.
The use of organic fertilizers has advantages, including reducing dependence on limited resources, helping to maintain ecosystem balance, and being able to increase the activity of soil microbes that contribute to the breakdown of organic matter and the release of nutrients into the soil.
Although organic fertilizers have many benefits, there are also risks that need to be considered. Improperly processed fertilizers can contain pathogens, heavy metals, or other toxic materials, which can affect soil and plant health. Therefore, it is important to conduct toxicity tests to ensure that the organic fertilizers used are safe for the environment.
The Importance of Testing Soil Microbial Diversity Before Applying Fertilizer
Soil microbial diversity testing is a process used to evaluate the types and numbers of microorganisms present in the soil. Soil microbes consist of various groups, including bacteria, fungi, archaea, and protozoa.
This diversity is very important because microbes play a key role in biogeochemical processes, decomposition, and nutrient cycling that support plant growth and thus increase agricultural productivity. Improper use of organic fertilizers, such as unfermented manure, can increase pathogens that are detrimental to plants. High microbial diversity plays a role in maintaining the balance of the soil ecosystem, while decreased diversity can indicate soil health problems.
Soil microbial diversity testing needs to be done to detect toxicity in organic fertilizers. This test can also be used as a guide for farmers in choosing effective and safe organic fertilizers. By understanding the impact of organic fertilizers on microbes, sustainable soil management practices can be implemented.
Soil microbial diversity testing has been conducted on tomato plants to assess the effects of organic fertilizers on mycorrhizal fungal communities (such as Glomus spp.), which play a role in nutrient uptake. In addition, tests have been conducted on guava plants to assess the impact of organic fertilizers on soil microbial diversity, focusing on phosphate solubilizing bacteria (Pseudomonas spp.). The study found that the use of organic fertilizers increased microbial diversity, which contributed to the availability of phosphorus for guava plants.
Soil microbial diversity tests can be carried out using various methods, both traditional and modern. Here are some commonly used methods, both traditional methods (colony counting and gram staining) and modern methods (PCR and DNA sequencing).
Colony Forming Units (CFU)
This method involves taking a soil sample and diluting it in a suitable growth medium. After incubation, the number of microbial colonies that emerge is counted. CFU can provide information about the number of microbes that can grow on a particular medium, such as bacteria or fungi
Gram Staining
This method is used to distinguish between Gram-positive and Gram-negative bacteria. After taking a soil sample, the bacteria are stained with Gram stain and then observed under a microscope. This method can provide basic information about the composition of bacteria.
Polymerase Chain Reaction (PCR)
PCR is a molecular technique used to amplify a specific microbial species based on its DNA. By using specific primers, we can identify microbes present in the soil, even if they do not grow in culture.
DNA Sequencing
After performing PCR, sequencing can be used to analyze the DNA sequence of microbes. This method can provide more detailed information about microbial diversity and can identify microbes that are difficult to culture.
Soil microbial diversity testing needs to be conducted in a comprehensive laboratory like IML Testing and Research. Improve the quality of your fertilizer products by understanding the microbial diversity within them. Test your soil microbial diversity now at IML Testing and Research and obtain accurate data for more effective soil management strategies.
References
Albert, S., & Bloem, E. (2023). Ecotoxicological methods to evaluate the toxicity of bio-based fertilizer application to agricultural soils – A review. Science of the Total Environment, 879: 1-15. http://dx.doi.org/10.1016/j.scitotenv.2023.163076.
Tariq, M., Jameel, F., Usman, I., Muhammad, A., & Kamran, R. (2022). Biofertilizer microorganisms accompanying pathogenic attributes: a potential threat. Physiol Mol Biol Plants, 28(1): 77-90. https://doi.org/10.1007/s12298-022-01138-y.