Abstract
This study aimed to evaluate the selectivity of the acetolactate synthase (ALS) inhibitor recommended herbicides for upland rice cultivars on different developmental stages. The experiment was conducted in the field, in Nova Xavantina-MT, Mato Grosso, Brazil, from season 2009/2010. The experimental design was the one of randomized blocks in factorial scheme, composed by the herbicide treatments penoxsulam (36 g ha -1 ); bispyribac-sodium (50 g ha -1 ); pyrazosulfuron-ethyl (20 g ha -1 ) and weeded control. Herbicides were applied at three times: 15, 30 and 45 days after emergence (DAE) with four replications in two upland rice cultivars: BRS Pepita and BRS Monarca. At 7, 14 and 28 days after application (DAA) the following assessments were performed: phytotoxicity to the crop, plant height, dry weight, number of panicles m -2 , grains per panicle -1 and productivity. The highest levels of phytotoxicity were observed in plants treated with bispyribac-sodium applied at 15 and 30 DAE. The rice plants were able to recover as for height influenced by herbicides from 14 DAA. The dry weight of plants was not affected by herbicide application. Since they have not reduced the grain productivity, the herbicides tested, when applied at 30 DAE, have showed their potential to be used only in BRS Monarca cultivar.
Highlights
The Brazilian rice production is spread across the country with two main types of basic production systems, upland rice and irrigated one
This study aimed to evaluate the selectivity of the acetolactate synthase (ALS) inhibitor recommended herbicides for upland rice cultivars on different developmental stages
The development of rice cultivars with higher yield potential, combined with high fertility in soils earlier cultivated with soybean has provided high yields of upland rice and profitability for the farmer
Summary
The Brazilian rice production is spread across the country with two main types of basic production systems, upland rice and irrigated one. In the Cerrado region there is predominantly upland rice, known to have a lower production. The culture of upland rice, undemanding in inputs and with good tolerance to acid soils, had played a significant role as an opening cultivar to new areas during the agricultural occupation of the Cerrado region, started in the 60s (Pinheiro, 2006). In the Cerrado region, the rice farmers are returning to old areas and gradually generating the new status of rice as main crop (Beling, 2007). The development of rice cultivars with higher yield potential, combined with high fertility in soils earlier cultivated with soybean has provided high yields of upland rice and profitability for the farmer. The inclusion of this cultivar in general in the area of soybean seeding has presented some problems, such as the difficulty for weed control, since most of the areas cultivated with soybeans are highly infested by many species (Pacheco et al, 2009), the upland rice presents few herbicide options, what increases the risk of such activity
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