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United States Department of Agriculture

Agricultural Research Service

Telone (1,3-D)
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1 - Aniline
2 - Reaction with Composted Manure
3 - References
Reaction with Composted Manure
 
Effect of Amendment Rates on the Degree of Acceleration
The potential use of soil organic matter amendments for reducing 1,3-D emissions on a management scale must consider amendment rates that are practical for field applications. To determine the dependence of enhanced degradation on amendment rates, 1,3-D degradation was measured in soils amended with different proportions of CM. Degradation of both 1,3-D isomers in nonsterilized amendment-soil mixes was essentially unaffected when the mixing ratio was reduced from 1:2 to 1:8. It then decreased, but not proportionally, as the ratio further decreased from 1:8 to 1:40 (Table 2).
 
The non-proportionality of the response of degradation to the mixing ratio was reflected in that, at 1:40, the degradation of the (E) or (Z) isomer was still about 3 times as fast as that in the unamended soil (Table 2). The rapid degradation of 1,3-D at such a low amendment-to-soil ratio implies that significantly enhanced degradation can be achieved with typical field application rates of amendments (10-50 t ha-1). Disappearance of 1,3-D at various mixing ratios generally followed first-order kinetics, with better fits in the 1:2 to 1:8 range than at the lower ratios, and in the sterilized mixes as compared to the nonsterilized mixes (Table 2). When the disappearance of 1,3-D in the nonsterilized mixes was depicted on a logarithmic scale, it becomes apparent that two phases began to develop as the mixing ratio was decreased from 1:8 to 1:40; and the degradation during the second phase was consistently more rapid than during the first phase (Fig. 4). The initialization of the second phase was prolonged as the ratio decreased, and the biphasic phenomenon was more evident for (E) 1,3-D than that for (Z) 1,3-D (Fig. 4). It is likely that at high CM rates, stimulated biodegradation occurred immediately after the treatment, and the first phase was too short to be visible. Microbial activity measured as CO2 evolution showed a similar response to the mixing ratio as did the 1,3-D degradation (Table 1). For instance, the total amount of CO2 evolved from 50 g of the 1:40 mix during the 6-d incubation was 5.8 mg, which was almost 70% of that from the 1:2 mix, or 12 times that from the unamended soil. The contribution of biodegradation to the overall 1,3-D degradation as induced by amendment addition was calculated for various mixing ratios from the difference of degradation rate constant k (d-1) between the sterilized and nonsterilized treatments (Table 2). For (Z) 1,3-D, biodegradation contributed about 60-70% of the induced degradation for mixing ratios ranging from 1:2 to 1:8, but this figure increased to about 80% when the mixing ratio was decreased to 1:20 or 1:40 (Table 2). Similar trends were also found among the different mixes for (E) 1,3-D (Table 2). Therefore, it can be concluded that while chemical degradation was significant (30-40% of the enhanced degradation) for soils amended with CM at high rates, its role gradually decreased and microbial degradation gained more dominance as the amendment-to-soil ratio was further reduced.
 
Reduction of 1,3-D Emissions by Surface Amendment
Volatilization losses of 1,3-D from unamended and CM-amended soil columns were followed for 432 h (or 18 d) after Telone-II was injected at the 30 cm depth. The averaged volatilization fluxes in μg h-1 and the cumulative losses in % of applied fumigant are given for both isomers in Fig. 5. The volatilization fluxes of (Z) or (E) 1,3-D during the first 200 h were much greater from the unamended columns than columns containing 1:20 CM-amended soil in the top 5 cm, though the difference gradually diminished thereafter (Fig. 5a). For instance, the maximum flux for (Z) 1,3-D from the unamended treatment was >2.5 times that from the amended treatment. Cumulatively, about 34% and 25% of the applied (Z) and (E) 1,3-D were lost, respectively, from the unamended columns at the end of the experiment. In comparison, the total loss of (Z)- and (E) 1,3-D from the CM-amended columns was only 18% and 14% of the applied amount, a reduction of >40% of that from the unamended soil (Fig. 5b). As column packing, fumigant treatment, sampling and sample analysis were kept under the same conditions for all four columns, the difference in 1,3-D emissions between the two treatments can be mainly attributed to the incorporation of 5% CM into the top 5-cm soil layer. The results from this experiment are therefore indicative of the potential usefulness of surface amendment as a management practice for minimizing 1,3-D emissions. More studies, such as emission monitoring and efficacy tests under field conditions, however, should be conducted to validate these laboratory observations. Longevity of soil organic matter amendments for causing enhanced degradation, and interactions of amendments and fumigant leaching should be also investigated.
 
Summary
This research demonstrates that integrating organic amendments with 1,3-D fumigation may significantly reduce 1,3-D atmospheric emissions by causing enhanced rates of fumigant degradation. Rapid degradation occurred at amendment rates low enough to allow realistic applications under field conditions, where the amended surface layer may act as a "cap" to reduce the emission, but the concentration below is not lowered to compromise the efficacy. This approach can be especially beneficial for sandy textured soils, where gas-phase diffusion is very rapid and degradation is relatively slow. As the negative environmental and toxicological effects of chemical fumigants are being realized, but applicable non-chemical methods are yet to be developed, environment-benign and yet effective strategies that integrate multiple approaches are urgently needed for soilborne pest control. The findings from this study indicate a promising integration of 1,3-D fumigation and organic amendment application that warrant further research on larger scales and under different conditions.
 
Volatilization of 1,3-dichloropropene isomers
 
Volatilization of 1,3-dichloropropene isomers from columns packed with the Arlington sandy loam with and without composted manure amendment after Telone-II was injected at the 30 cm depth. Voaltilization fluxes in μg/h

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Cumulative volatilization losses
Cumulative volatilization losses in % of applied 1,3-D

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Last Modified: 11/4/2009
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