This publication is part of a series developed to assist Florida homeowners with managing their landscapes to reduce environmental impacts. This is a joint publication of multiple departments and programs in UF/IFAS, including the Florida-Friendly Landscaping™ program, the Department of Soil and Water Science, the Environmental Horticulture Department, and the Center for Landscape Conservation and Ecology. This fact sheet was produced with support from the Florida Turfgrass Association through a Florida Department of Agriculture and Consumer Services Specialty Crops Block Grant.
For the rest of this series, visit https://edis.ifas.ufl.edu/topic_series_environmental_landscape_management.
Proper irrigation management is critical to proper nutrient management in the home landscape. How lawns and landscapes are fertilized and irrigated can directly impact the natural environment through nutrient runoff and leaching. Landscape maintenance professionals and homeowners should adopt environmentally-friendly approaches to irrigation and nutrient management. After selecting the right plant for the right place in the landscape, water is the next critical factor in maintaining a healthy landscape. If plants receive too much irrigation, water and nutrients pass below the root system and are unavailable to the plant. These practices of over-irrigating and fertilizing can lead to leaching soluble nutrients into groundwater.
This publication discusses the "blue dye" test, which is one way that Extension professionals can show homeowners how water and nutrients move through the soil following irrigation. The information should be useful for county agents to demonstrate basic irrigation and nitrogen management practices and their effects on nitrate-nitrogen (N) leaching.
Blue Dye Test
Extension professionals are often looking for new tools to teach nutrient and water management principles to homeowners. One new tool is a water-soluble marking dye that can demonstrate how water and nitrogen fertilizer move through the soil profile following irrigation. This blue-dye test has been used to demonstrate irrigation management in field-grown vegetables (Simonne et al. 2011; Simonne et al. 2012). The same approach can be used in home landscapes to demonstrate water and nitrogen movement in the soil beneath lawns and landscapes.
Careful planning is required for a successful dye demonstration. The following table summarizes the main components of setting up and completing the demonstration in a turfgrass landscape area.
If you plan an education program to accompany a blue dye test, you should do the following:
Discuss the importance of irrigation and nitrogen fertilizer in the landscape.
Present the UF/IFAS recommendations for irrigation and nitrogen management using the Florida-Friendly Landscaping™ principles (http://fyn.ifas.ufl.edu/homeowners/nine_principles.htm).
Discuss the role of soil type in water management (for example, water easily moves in sandy soils).
Discuss the concept of the root zone and how irrigation is managed to keep the water and nutrients in the root zone.
Key Points and Questions
Are there any differences in the depth of the dye relating to the amount of irrigation applied?
Can you see the root system and the depth of the root system relative to the dye movement?
Explain the potential environmental challenges presented when the dye moves below the root system.
Describe the soil texture at the site and how texture relates to water movement. Use the EDIS publication MG451/SL268 Soils and Fertilizers for Master Gardeners: Soil Physical Properties to discuss soil texture (Shober 2012; https://edis.ifas.ufl.edu/mg451).
An Example Dye Demonstration
The following photos illustrate the main steps in conducting a dye test (Figure 2–Figure 5). These photos are from a dye demonstration conducted in Gainesville, Florida.
When water moves through the soil, nitrogen and other nutrients move with it. The sandy soils of Florida are especially prone to nitrate-N leaching. Extension agents can teach this concept using a blue dye demonstration. During the dye demonstration, you can apply varying amounts of irrigation to show how excessive irrigation causes the water and dye to move below the root zone. This test illustrates how water and nitrogen move in the soil. Excessive irrigation leads to fertilizer loss, resulting in economic loss and leaching that pollutes water bodies.
Shober, A. L. 2012. Soils and Fertilizers for Master Gardeners: Soil Physical Properties. SL268. Gainesville: University of Florida Institute of Food and Agricultural Sciences. https://edis.ifas.ufl.edu/mg451.
Simonne, E. H., D. W. Studstill, M. D. Dukes, J. Duval, R. C. Hochmuth, G. McAvoy, T. Olczyk, and S. M. Olson. 2011. How to Conduct an On-Farm Dye Test and Use the Results to Improve Drip Irrigation Management in Vegetable Production. HS980. Gainesville: University of Florida Institute of Food and Agricultural Sciences. https://edis.ifas.ufl.edu/hs222.
Simonne, E. H., D. W. Studstill, R. C. Hochmuth, J. T. Jones and C. W. Starling. 2012. On-Farm Demonstration of Soil Water Movement in Vegetables Grown with Plasticulture. HS1008. Gainesville: University of Florida Institute of Food and Agricultural Sciences. https://edis.ifas.ufl.edu/hs251.
How to develop and complete a successful blue dye test1