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Wetted Bulb Dimensions From a Trickle Source1

Elsa S. Sepúlveda and Fedro S. Zazueta2

An estimation of the wetted bulb diameter dimensions is needed to determine the number of emitters per plant when using drip or trickle irrigation systems. It is generally recommended that a sufficiently large fraction of the root zone be wetted by irrigation to ensure adequate water and nutrient supply to the plant.

This software allows the calculation of the wetted bulb diameter from a point source in a sandy soil. Please note that the method has not been tested or calibrated for soils other than sands. In addition the method applies only to deep homogeneous, uniform soils.

Empirical Equation

There are several methods that allow estimations of wetted bulb diameters.This includes reports from field tests (Goldberg et. al, 1976), and the empirical equations presented by Schwartzmass and Zur (1985), and Zazueta (1992). Other approaches to present these results include tables, such as the ones published by Keller and Bliesner (1990).

This program implements the equation developed by Zazueta (1992):

Figure 2. 

where:

D = approximate wetted bulb diameter (m),

q = emitter discharge (l/hr),

r = root depth (m), and

I = basic infiltration rate (m/s).

Downloading and Installing the Software

This software can be downloaded from http://fsz.ifas.ufl.edu. The file is in compressed Zip format. Unzip the file and execute the included setup program. Follow the standard set of instructions on the screen to install into your Pocket PC.

Sample Run

Figure 1 shows the Pocket PC display when the program is running. Enter the information corresponding to each data field (emitter discharge, root depth and basic infiltration rate) and press the calculate button to obtain a result.

Figure 1. 

References

Goldberg, D., B. Gornat, and D. Rimon. Drip Irrigation. Drip Irrig. SCi. Pubs. Kfar Shmaryhu, Israel. 1976.

Keller, J. and R.D. Bliesner. Sprinkle and Trickle Irrigation. Van Nostrand Reinhold, New York. 1990. 652 p.

Scwartzmass, N., and B. Zur. 1985. Emitter Spacing and geometry of wetted soil volume. Journal of Irrigation and Drainage Engineering, ASCE. 112(3):242-253.

Zazueta, F.S. Microirrigación. ICFA International, Guadalajara, México, 1992. 212 p.

Footnotes

1.

This document is ABE351, one of a series of the Agricultural and Biological Engineering Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date March 22, 2004. Visit the EDIS Web Site at http://edis.ifas.ufl.edu.

2.

Visiting Scholar, Universidad de Concepción, Chile, in the Agricultural and Biological Engineering Department; Director and Professor, Office of Academic Technology, University of Florida, Gainesville, FL 32611

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other extension publications, contact your county Cooperative Extension service.

U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Millie Ferrer-Chancy, Interim Dean.