Carryover of Imazethapyr + Imazapic on Ryegrass and Non-tolerant Rice as Affected by Thickness of Soil Profile

Abstract

-Herbicides used in Clearfield ® rice system may persist in the environment, damaging non-tolerant crops sown in succession and/or rotation. These damages vary according to soil characteristics, climate and soil management. The thickness of the soil profile may affect carryover effect; deeper soils may allow these molecules to leach, reaching areas below the roots absorption zone. The aim of this study was to evaluate the effect of the thickness of soil profile in the carryover of imazethapyr + imazapic on ryegrass and nontolerant rice, sown in succession and rotation to rice, respectively. Lysimeters of different thicknesses (15, 20, 30, 40, 50 and 65 cm) were constructed, where 1 L ha -1 of the imazethapyr + imazapic formulated mixture was applied in tolerant rice. Firstly, imidazolinone-tolerant rice was planted, followed by ryegrass and non-tolerant rice in succession and rotation, respectively. Herbicide injury, height reduction and dry weight of non-tolerant species were assessed. There was no visual symptoms of herbicide injury on ryegrass sown 128 days after the herbicide application; however it causes dry weight mass reduction of plants. The herbicides persist in the soil and cause injury in non-tolerant rice, sown 280 days after application, and the deeper the soil profile, the lower the herbicides injury on irrigated rice.Keywords: degradation, imidazolinone, Lolium multiflorum, leaching, Oryza sativa. (15, 20, 30, 40, 50 RESUMO -Os herbicidas usados na cultura do arroz

Carryover of [imazapic + imazapyr] on differents crops systems in lowland areas with ALS tolerant rice

“…The subject discussed in the present experimentimpact of ALS inhibitor herbicides associated to Clearfield ® technology on succeeding crops, is studied by some researchers in slightly different edapho-climatic conditions. In a study similar to the present one, but installed under controlled environment (lysimeters), Bundt et al (2015) reported no visual symptoms of intoxication to ryegrass, but some reduction in dry mass when this species was planted 128 DAA of Kifix ® ; the same authors reported damages to rice planted on the succeeding summer (1 year after application) of about 70% in rice dry mass, compared to the control treatment with no application.…”

Phytotoxicity of imazapyr+imazapic on tolerant rice varieties Guri INTA CL and IRGA 424 RI

“…Although not causing severe damage to the two tolerant rice varieties studied, it is important to emphasize that imidazolinone herbicides have high persistence in the soil, being that their sorption is higher in soils with low pH and high organic matter (Kraemer et al, 2009a). In this way, the utilization of high rates may hamper the growing of crops in succession and rotation with Clearfield ® rice as ryegrass in the off-season and imidazolinones non-tolerant rice in the next growing season (Kraemer et al, 2009b;Bundt et al, 2015). Furthermore, this practice can lead to increased selection pressure, increasing the possibility of emergence of new resistant weeds.…”

Persistence of imazapyr+imazapic in irrigated rice area and effect on soybean due to soil moisture and phytoremediation in the off-season

“…Pinto et al (2009b) also emphasize that there is a linear reduction in the dry matter of this crop due to the increase of the residue of these herbicides, applied to the rice in the previous growing season. According to Bundt et al (2015), the seeding performed 128 days after application causes a reduction in the ryegrass dry matter. This finding corroborates with the present study, where the crop was planted 129 days after application.…”