Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/28/2005
Publication Date: 10/1/2005
Citation: Price, A.J., Charron, C.S., Sams, C.E. 2005. ALLYL ISOTHIOCYANATE AND CARBON DIOXIDE PRODUCED DURING DEGRADATION OF BRASSICA JUNCEA TISSUE IN DIFFERENT SOIL CONDITIONS. HortScience. 40(6):1734-1739. Interpretive Summary: Methyl Bromide will be unavailable for grower use in 2005. An alternative fumigation strategy could include cover crops that contain biologically active compounds. Brassica species have been shown to suppress certain soil organisms as well as weeds. Little comprehensive research, combining multiple soil condition variables, has evaluated how different soil conditions affect compounds released from degrading Brassica tissues. Results show that sandy soils and warmer soils yield higher concentrations of biologically active compounds compared to clay soils and cooler soils. Sterilized soil also yielded higher concentrations of biologically active compounds and shows that some soil microbes may degrade the same compounds that are lethal to other soil microbes. Results also show that utilizing a solid-phase micro-extraction technique can be used to detect differences in volatile compounds released from degrading Brassica tissue.
Technical Abstract: An incubation study was conducted to quantify volatiles generated from Indian mustard (Brassica juncea L. Czerniak) residue under different soil conditions. Mustard residues were incorporated into non-covered and covered soil that varied by texture, temperature, moisture, pH, or sterility (autoclaved or non-autoclaved). Results show that sandy loam soil yielded 28% higher allyl isothiocyanate (AITC) concentration compared to clay loam texture soil. Also, relatively cooler 15ºC soil yielded 45% lower AITC concentration compared to 45ºC soil treatments. Autoclaved soils yielded 70% higher AITC concentration compared to non-autoclaved soil and covered soil treatments yielded 36% higher AITC concentration at all sampling times compared to non-covered treatments. There were no differences among soil moisture and soil pH treatments for AITC concentrations. Soil temperature also influenced CO2 evolution with the 15ºC soil treatment yielding at least 34% less CO2 concentration than either 30ºC or 45ºC soil treatments. The covered soil treatment yielded twice the CO2 concentration as non-covered soil treatment and the autoclaved soil treatment yielded 50% less CO2 than the non-autoclaved soil treatment. There were no main effect differences among soil moisture, soil pH, and soil texture treatments for CO2 concentrations. This information could be helpful in defining ideal soil conditions for field scale experiments as well as a sampling technique for testing fumigation potential of biofumigation and solarization systems that may have potential to replace methyl bromide.