Bat guano, the excrement of bats, is a natural, highly concentrated organic fertilizer prized by gardeners. It is packed with macro and micronutrients that support robust plant development across all growth stages. Unlike synthetic fertilizers, guano introduces beneficial microorganisms to the soil, improving its structure and promoting overall health. This guide details how to properly apply bat guano to boost vegetative growth and enhance flowering and fruiting.
Understanding Guano Composition and Forms
The nutrient composition of bat guano is not uniform; it varies based on the bat’s diet and the age of the deposit. Guano from insectivorous bats is high in nitrogen, ideal for supporting vigorous leaf and stem growth during the vegetative phase. Conversely, guano from fruit or nectar-eating bats tends to be higher in phosphorus, which drives strong root development and prolific flowering.
Consumers typically encounter guano as fine powder, granules, or pelletized material. Aged guano, which has undergone more decomposition, often has a higher phosphorus content, while fresher deposits are frequently higher in nitrogen. Always check the NPK ratio (Nitrogen-Phosphorus-Potassium) on the packaging to ensure the guano suits your plant’s current needs.
Methods for Direct Soil Application
Applying guano as a dry amendment is the most traditional method. It provides a slow-release source of nutrients as it breaks down in the soil over time.
Pre-Planting Amendment
Pre-planting amendment establishes a nutrient-rich foundation for new plants. When preparing a garden bed or mixing potting soil, incorporate the powdered or granular guano directly into the medium. Mix one to two tablespoons of guano per cubic foot of soil or potting mix, ensuring it is evenly distributed. The guano must be thoroughly blended into the soil before seeds or seedlings are introduced to prevent direct contact with tender roots. This method allows nutrients to become available gradually throughout the initial growth phase.
Top Dressing Established Plants
For established plants, top dressing delivers a nutrient boost during the growing season. Sprinkle a small amount of powdered or pelletized guano around the base of the plant, keeping it a few inches away from the main stem. Lightly work the guano into the top layer of soil to help activate the nutrients. Always water the area thoroughly immediately after top dressing to dissolve the nutrients and carry them into the root zone.
Creating and Using Liquid Guano Teas
Brewing a liquid guano tea allows for rapid nutrient uptake and maximum utilization of the guano’s beneficial microorganisms. Use non-chlorinated water, as chlorine can eliminate the microbes; tap water can be left uncovered for 24 hours to dissipate chlorine. A common recipe involves mixing one to two tablespoons of guano per gallon of water.
The most effective teas are aerated, which promotes the growth of beneficial aerobic bacteria. This is achieved by placing an air stone connected to an aquarium pump into the mixture, bubbling it vigorously for a period of 24 to 48 hours. Some gardeners also include a simple food source for the microbes, such as a quarter cup of unsulfured molasses, to accelerate microbial reproduction. Once brewed, the resulting liquid is highly concentrated and should be used immediately.
Root Drench
The most common application is a root drench, where the liquid is used to water the soil around the base of the plant. This delivers soluble nutrients and the active microbial population directly to the root zone for quick absorption and enhanced soil life.
Foliar Spray
Alternatively, the tea can be strained and used as a foliar spray, applied directly to the leaves. Foliar feeding provides immediate, targeted delivery of micronutrients and can help protect the leaves from certain fungal diseases. Ensure the tea is finely filtered to avoid clogging the sprayer nozzle and apply it during cooler times of the day to prevent leaf burn.
Timing, Ratios, and Safety Considerations
Applying guano at the correct time ensures the plant receives the right nutrients during its specific growth stage. High-nitrogen guano (higher first NPK number) is best applied during the vegetative stage to support foliage and stem growth. High-phosphorus guano should be reserved for the transition into flowering and fruiting, supporting bloom development and fruit set.
When determining ratios, start conservatively, as guano is highly concentrated and can cause nutrient burn if over-applied. For dry applications, use one to two tablespoons per square foot of garden space or per gallon of soil. For liquid tea, the standard ratio is typically one to two tablespoons of powdered guano per gallon of water.
Safety precautions are necessary when handling dry, powdered guano. The fine dust can contain spores of the fungus Histoplasma capsulatum, which causes the respiratory illness histoplasmosis if inhaled. Always wear a dust mask or respirator when mixing or applying dry guano. Wear gloves and wash your hands thoroughly after handling the product.