Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/13/2007
Publication Date: 5/19/2007
Citation: Cabrera, A., Cox, L., Velarde, P., Koskinen, W.C., Cornejo, J. 2007. Fate of diuron and terbuthylazine in soils amended with two-phase olive oil mill waste. Journal of Agricultural and Food Chemistry. 54:4828-4834. Interpretive Summary: Addition of olive oil mill wastes can modify the binding capacity of soil for herbicides and subsequently their dissipation and leaching. Our results show that the source and the amount of organic amendments in soil can affect herbicide binding and that these effects can be different for different classes of herbicides. Our results also show that addition of these organic amendments to soil does not always ensure slower dissipation or decreased leaching of the herbicides; some herbicides can show slight increases in leaching. The possible slight increased leaching of the herbicide would be counterbalanced by the fact that the application of fresh or composted olive oil mill waste to the land would appear to be an extremely effective contribution to increasing crop yields and to maintaining or improving soil fertility if properly mixed and incorporated at acceptable loading rates. Producers will now benefit in having a practice that has been shown to be able to mitigate a large potential environmental problem associated with olive oil production wastes.
Technical Abstract: The addition of organic amendments to soil increases soil organic matter content and stimulates soil microbial activity. Thus, processes affecting herbicide fate in the soil should be affected. The objective of this work was to investigate the effect of olive oil production industry organic waste (alperujo) on soil sorption-desorption, degradation and leaching of diuron and terbuthylazine, two herbicides widely used in olive crops. The soils used in this study were a sandy soil and a silty-clay soil from two different olive groves. The sandy soil was amended in the laboratory with fresh (uncomposted) alperujo at the rate of 10% w/w, and the silty clay soil was amended in the field with fresh alperujo at the rate of 256 kg per tree during four years and in the laboratory with fresh or composted alperujo. Sorption of both herbicides increased in laboratory-amended soils as compared to unamended or field-amended soils, and this process was less reversible in laboratory-amended soils, except for diuron in amended-sandy soil. Addition of alperujo to soils increased half lives of the herbicides in most of the soils. Diuron and terbuthylazine leached through unamended sandy soil, but no herbicide was detected in laboratory-amended soil. Diuron did not leach through amended or unamended silty clay soil, whereas small amounts of terbuthylazine were detected in leachates from unamended soil. Despite their higher sorption capacity, greater amounts of terbuthylazine were found in the leachates from amended silty clay soils. The amounts of dissolved organic matter from alperujo and the degree of humification can affect sorption, degradation and leaching of these two classes of herbicides in soils. It appears that adding alperujo to soil would not have adverse impacts on the behavior of herbicides in olive production.