Lactic acid bacteria (LAB) are beneficial microorganisms known for their significant role in various fermentation processes, commonly associated with foods like yogurt and sauerkraut. In agriculture and horticulture, these bacteria are increasingly recognized as powerful microbial inoculants for improving plant health and soil ecology. When introduced into the garden or farm system, LAB species like Lactobacillus contribute to a more balanced and productive environment for plants. Utilizing a homemade serum containing these organisms offers a cost-effective and environmentally sound method for promoting vigorous plant growth and overall resilience.
Preparing Your Own Lactic Acid Bacteria Serum
The process of creating a Lactic Acid Bacteria Serum (LABS) begins with a simple rice wash to collect the initial culture. Rinsing uncooked rice with chlorine-free water creates a starchy liquid rich in carbohydrates. This liquid acts as a nutrient medium to attract and cultivate indigenous microbes, including the desired Lactobacillus species, from the air. Place the rice wash in a container with a loose cover, such as cheesecloth, and let it sit in a shaded area for three to four days. A thin film forms on the surface, and a mildly sour smell indicates a successful collection of microorganisms.
To isolate and multiply the LAB, mix the collected rice wash with fresh milk, typically using a 1:10 ratio. The lactose in the milk provides a specific food source, allowing the acid-tolerant Lactobacillus to rapidly outcompete most other microbes. Leave this mixture to ferment in a loosely covered container for approximately three to seven days, depending on the ambient temperature. Warmer environments accelerate the separation process.
Fermentation is complete when the mixture separates into three distinct layers: a curd layer floating on top, a bottom layer of sediment, and the middle layer of clear, yellowish whey (the serum). This middle layer is the concentrated LABS and must be carefully siphoned or strained through cheesecloth to separate it from the solids. To ensure long-term viability, stabilize the serum by mixing it with an equal volume of a carbohydrate source, such as molasses or brown sugar. This stabilized concentrate can be stored at room temperature for up to a year.
Application Techniques and Dilution Rates
The concentrated LAB serum must always be diluted with water before application to prevent damage from its acidity and concentration. The specific dilution rate depends on the application method and intended purpose. For general use as a microbial boost or a gentle foliar spray on established plants, a dilution ratio of 1:500 to 1:1,000 is recommended. This translates to about 1 to 2 milliliters of LABS concentrate per liter of water.
When applying the serum directly to the soil via drenching or irrigation, the goal is to introduce the beneficial bacteria into the root zone (rhizosphere). A common maintenance rate for soil application is a 1:500 dilution, used every two to four weeks throughout the growing season. For seedlings or young plants, a more conservative dilution of 1:1,000 is advisable to avoid overwhelming their systems. Apply the diluted serum during cooler parts of the day, such as early morning or late afternoon, to prevent damage to the microbes from intense sunlight.
Foliar application involves spraying the diluted serum directly onto the leaves, allowing the LAB to colonize the leaf surface (phyllosphere). Keep the dilution light, around 1:800 to 1:1,000, to ensure even coverage without leaving residues that could attract pests. To manage surface molds or mildews, a slightly stronger ratio (1:200 to 1:500) may be used, but this requires close monitoring of the plant’s reaction. Regular application, such as weekly or bi-weekly, is more effective than infrequent, heavy doses, as it ensures a consistent presence of the beneficial bacteria.
The Role of LAB in Promoting Plant Vigor
Once introduced to the growing environment, Lactic Acid Bacteria exert their beneficial influence primarily within the soil’s root zone. These bacteria produce organic acids, chiefly lactic acid, which acidifies the immediate environment around the roots. This slight acidity is instrumental in solubilizing minerals. This process makes essential nutrients like phosphorus and potassium more accessible for plant uptake, as they are often locked in insoluble forms in the soil.
LAB also contributes significantly to the breakdown of complex organic matter, accelerating decomposition and releasing nutrients back into the soil faster. Some strains are capable of nitrogen fixation, transforming atmospheric nitrogen into forms the plant can readily absorb. This enhanced nutrient cycling and availability directly support robust plant development and improved yields.
LAB actively secretes various plant growth-promoting substances, including phytohormones such as auxins and gibberellins. These compounds stimulate root hair development and overall root surface area. This dramatically improves the plant’s ability to absorb water and nutrients. This enhanced root system also contributes to greater resilience against abiotic stresses, such as drought and extreme temperatures.
Lactic acid bacteria play a significant role in fostering a balanced microbial community, acting as a protective shield for the plant. They produce antimicrobial compounds, including bacteriocins and organic acids, which inhibit the growth of common fungal and bacterial phytopathogens. By outcompeting harmful organisms and modulating the plant’s defense mechanisms, LAB helps to create a healthier ecosystem with reduced incidence of disease.