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ARS Home » Southeast Area » Miami, Florida » Subtropical Horticulture Research » Research » Publications at this Location » Publication #241192
Title: Endosulfan has no adverse effect on soil respiration

Author
item JOSEPH, RICARDO - Former ARS Employee
item Reed, Stewart
item JAYACHANDRAN, KRISH - Florida International University
item CLARK-CUADRADO, CHRISTINA - Natural Resources Conservation Service (NRCS, USDA)
item Dunn, Christopher - Chris

Submitted to: Agriculture, Ecosystems and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/19/2010
Publication Date: 6/16/2010
Citation: Reed, S.T., Joseph, R., Jayachandran, K., Clark-Cuadrado, C., Dunn, C.B. 2010. The effects of Endosulfan on Microbial Respiration. Agriculture, Ecosystems and Environment. 138:181-188.

Interpretive Summary: Endosulfan is an organochlorine (carbon based compound containing several chlorine atoms) broad spectrum contact insecticide. The continuous agricultural production of tomatoes, green beans, and squash make Miami-Dade County, Florida one of the heaviest users of this pesticide in the country. Few studies have investigated the effects of endosulfan on soil microorganisms in a field situation. Microorganisms are responsible for a variety of essential soil processes. Soil microorganisms decompose organic compounds (including some pesticides), making nutrients available to plants, sequester carbon, suppress plant diseases, and play an integral role in water dynamics by creating soil aggregates. Respiration is a measure of microbial activity. A field study was initiated at the USDA, Subtropical Horticulture Research Station in Miami, FL to examine the effects of endosulfan on soil respiration. Snap bean and adjacent bare soil fields were treated either with or without endosulfan. Soil respiration was measured weekly as the difference between carbon dioxide in the air and that generated in the soil. Treatments were repeated four times and the study continued over three growing seasons. Respiration from bare soil was similar to that from fields planted to snap bean implying soil microbes were the dominant source of CO2 compared to root respiration. Endosulfan applications resulted in inconsistent increases in soil respiration. Increases were short-lived. By the end of the study soil respiration was higher in endosulfan treated than untreated plots. The soil water content most likely influenced soil respiration rate more than the amount of endosulfan applied. Endosulfan had a short-lived inhibitory effect on soil fungi but bacteria increased in number in response to endosulfan applications. Individual bacteria were not identified and it is possible that one or two bacterial species decomposed the endosulfan and rapidly multiplied causing the increase bacterial colony count. In general there were no adverse effects of endosulfan on soil respiration found.

Technical Abstract: Endosulfan (6,7,8,9,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,4,3-benzodioxathiepin-3-oxide) is a chlorinated hydrocarbon used as a broad spectrum contact insect/acaricide. The continuous agricultural production of tomatoes, green beans, and squash make Miami-Dade County, Florida one of the heaviest users of this pesticide in the country. A field study was initiated at the USDA, Subtropical Horticulture Research Station in Miami, FL to examine the effects of endosulfan on soil respiration. Snap bean (Phaseolus vulgaris) and adjacent bare soil plots were treated either with or without endosulfan. Soil respiration was measured weekly as the difference between CO2 in the ambient air and that generated within a 10-cm diameter, 1178-cm3 chamber secured at the soil surface. Treatments were replicated four times and the study continued over three growing seasons. Respiration from bare soil was similar to that from plots planted to snap bean implying soil microbes were the dominant source of CO2 compared to root respiration. Endosulfan applications resulted in inconsistent increases in soil respiration. Increases were short-lived. By the end of the study more CO2 was evolved from endosulfan treated than untreated plots. Soil moisture likely influenced soil respiration rate. Endosulfan had a short-lived inhibitory effect on soil fungi but bacteria increased in number in response to endosulfan application. Individual microbial colonies were not identified and it is possible that one or two bacterial species decomposed the endosulfan and rapidly multiplied causing the increase bacterial colony count. There were no adverse effects of endosulfan on soil respiration found.