Lettuce Seed Test: A Sensitive Test to Detect Phytoxic Levels of Fumigants in Soil
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Lettuce Seed Test: A Sensitive Test to Detect Phytoxic Levels of Fumigants in Soil

   

Lettuce Seed Test: A Sensitive Test to Detect Phytoxic Levels of Fumigants in Soil 1

Robert A. Dunn2

Most soil fumigants are toxic to plants as well as to the pests we use them to control. They usually are applied long before planting, to avoid injuring new seeds or transplants. However, soil moisture, temperature, organic matter and clay content, and application methods can all influence the wait between fumigant application and safe planting. The test described here provides a simple way to determine if fumigant vapors are sufficiently gone from treated soil to be able to plant safely.

Materials

Procedure

  1. Fill 2 or more jars 3/4 full with fumigated soil, and cap tightly. Take soil from the depth at which the chemical was applied, at or very near an application point. In an uneven field, sample the lowest spots in the fumigated area. If soil is dry when sampled, moisten it in the jar and recap immediately.

  2. Fill 2 jars 3/4 full with soil from untreated areas; moisten if necessary, as for soil from fumigated areas. Cap the jars. These are the untreated "controls."

  3. Soak seed 1/2 hr in water at room temperature.

  4. For each jar of soil to be tested, dip an absorbent cotton square in water and drain off the excess water. Do not squeeze the cotton, because that will remove too much water.

  5. Place 10 to 15 pre-soaked seeds on top of each wet cotton square or roll moist cotton in a generous supply of the seed, so many stick to the cotton.

  6. Remove the cap from each jar, quickly place a wet cotton square on top of the soil with the seeds on top of the cotton, not touching the soil, and re-cap each immediately, so it is open as little as possible.

  7. Leave jars at room temperature in an area with indirect daylight, not in the dark, but also not in direct sunlight that can over-heat their contents.

  8. Examine the jars after two (2) days. If seeds in the jars of untreated soil ("controls") are germinating but seeds with treated soil are not, there is still too much fumigant in the soil. Light cultivation can accelerate escape of fumes. If germination in all jars is good and equal, it should be safe to plant. If there was no germination in samples of either soil, the seeds probably were not viable, and the test is useless.

Footnotes

1. This document is Fact Sheet ENY-036 (formerly RF-NG036), one of a series from the Department of Entomology and Nematology, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. March 1997. Reviewed: April 2002. Please visit the EDIS Web site at http://edis.ifas.ufl.edu.

2. Robert A. Dunn, retired professor, Department of Entomology and Nematology, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 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. Larry Arrington, Dean.


Copyright Information

This document is copyrighted by the University of Florida, Institute of Food and Agricultural Sciences (UF/IFAS) for the people of the State of Florida. UF/IFAS retains all rights under all conventions, but permits free reproduction by all agents and offices of the Cooperative Extension Service and the people of the State of Florida. Permission is granted to others to use these materials in part or in full for educational purposes, provided that full credit is given to the UF/IFAS, citing the publication, its source, and date of publication.