Different Effects of a By‐product From Olive Oil Extraction on S‐Metolachlor and Bentazone Soil Fate

Abstract

Bentazone and S‐metolachlor are herbicides widely used for the control of broad leaf weeds in crops such as corn and soybean. The effect of the addition to soils with different texture and organic matter content of an organic waste (OW) from oil olive production (alperujo) on different processes affecting behaviour of both herbicides was evaluated. Sorption of S‐metolachlor increased upon amendment. A six‐fold increase could be observed for Kd values on the sandy soil amended at 10% rate and a five‐fold increase on the soil with higher content on clay (48%) and same rate of OW (10%). The results revealed that although an increase in soil total pore volume was found upon amendment (from 210 to 266 mm3 g−1 in sandy (S) soil, from 215 to 251 in clayey (19% silt) (T) soil, and from 240 to 289 in clayey (50% silt) (E) soil), leaching of the herbicide S‐metolachlor was greatly reduced (from 61 to 3.5% in the S‐soil and from 37 to <1% in the clayey T‐soil) since its behaviour in soils is strongly affected by sorption processes. Bentazone leaching was only slightly delayed upon amendment. Half‐life of both herbicides also increased upon amendment. The greatest increase was observed with the higher rate of OW (10%) in the soils with higher content of clay (48% in T‐soil and 31% in E‐soil). A 17‐fold increase was observed for S‐metolachlor half‐life in T‐soil and a four‐fold increase for bentazone in E‐soil. Thus, the use of the by‐product from olive oil extraction can be a good strategy to reduce the off‐site movement of S‐metolachlor by increasing its soil sorption, and therefore the risk of water pollution can be diminished. However, the higher persistence of both herbicides in organic amended soils should be taken into account.

Behaviour of bentazon as influenced by water and tillage management in rice‐growing conditions

“…for three different soils under conventional and reduced tillage, although the sorption values for those soils were on average 2.7 times greater than for the soils of the present study. However, much higher bentazon leaching losses were detected by Cañero et al . who described having recovered 100% of the herbicide initially applied from leachates of two soils with sorption values similar to those of the soils of the present study, although those two soils were very alkaline (pH ≥ 8.4).…”

“…for 16 different soils under aerobic conditions. However, they are much greater than those reported by Cañero et al . of 21 and 37 days for soils with similar (10.9 g kg −1 ) or much lower (2.5 g kg −1 ) TOC contents, respectively, although the moisture content was adjusted to 40% field capacity in that study instead of the 80% field capacity of the present study.…”

Tolerance of Brazilian Bean Cultivars to S-Metolachlor and Poaceae Weed Control in Two Agricultural Soils

“…The more intense damage caused by S-metolachlor in the Pérola and Talismã genotypes in Ultisol soil was probably due to the high sand content (84%) and low OM content (6.70 g dm −3 ) in this type of soil, since a large portion of the S-metolachlor herbicide is sorbed in soils with a higher clay content and especially OM [31,32]. The characteristics of the Ultisol soil probably provided greater bioavailability of the herbicide in the solution, increasing the risk of it being leached into the rooting zone.…”