Abstract
We aimed with this work to evaluate the efficiency of the herbicide [imazapic + imazapyr] in the weed control, especially of the jointvetch, and its reflex in rice plant establishment and grain yield. A field study was conducted, where treatments were: control without herbicide application; Kifix® 140g ha-1 (24.5 ga.i. ha-1 imazapic + 73.5 ga.i. ha-1 imazapyr) and Kifix® 280 g ha-1 (49 ga.i. ha-1 imazapic + 147 ga.i. ha-1 imazapyr). We evaluated crop emergence up to 25 days after sowing, crop plant height 12 days after emergence (DAE), jointvetch plant density 31 and 62 DAE, jointvetch dry mass 62 DAE and general weed infestation 62 DAE. At the end of the crop cycle we evaluated grains per panicle, panicle and 1000 grain weight, panicle density and crop grain yield. There is a risk of 15% reduction in the establishment of Clearfield® rice plants when the maximum dose of the herbicide [imazapic + imazapyr] is applied pre-emergence, but under appropriate conditions, the crop development tends to compensate for this reduction in establishment. The herbicide [imazapic + imazapyr] is effective on jointvetch, but under high infestation conditions, as in the present study, a complementary herbicide application is required to achieve adequate control of jointvetch and avoid rice grain yield reduction due to competition.
Highlights
Rice is one of the most important cereals produced in the world
The application was carried out one day after planting (DAP), via precision equipment propelled by CO2, connected to a bar with six 110.02 nozzles spaced in 0.5 m and subjected to the necessary pressure to apply the equivalent to 150 L ha-1 of herbicide solution
There was effect of the herbicide on rice plant establishment, and 20 DAP, about 200 plants m-2 were observed in the control plot, while about 170 plants m-2 were observed under application of 280 g ha-1 (Figure 1), which represents a potential reduction of approximately 15% in the establishment of Guri Inta CL plants when the maximum registered dose of Kifix® is applied pre-emergence to rice
Summary
Rice is one of the most important cereals produced in the world. It is cultivated mainly in paddy fields using a continuous flooding. Paddy rice cropping fields in southern Brazil are generally highly productive, yield averages are still lower than those achieved in areas that adopt recommended cropping practices such as experimental fields. The importance of weed infestation on rice grain yield has been increasing due to the adoption of minimum till and the low efficacy of non-selective herbicides against them
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