Period prior to interference of barnyardgrass is modified due to the spraying of cyhalofop-butyl alone or associated with penoxsulam in paddy rice crop

Abstract

Background

Weed competition is one of the main constraints to rice yield.

Objective

Determine the period prior to interference (PPI) of barnyardgrass ( Echinochloa spp.) on the irrigated rice crop as a function of the application of the herbicide cyhalofop-butyl alone and associated with penoxsulam.

Methods

A field experiment was carried out in a randomized block design, with four replications. The treatments were arranged in a 2×7 factorial scheme, with factor A consisting of the herbicides cyhalofop-butyl and the mixture penoxsulam + cyhalofop-butyl, while factor B consisted of seven coexistence periods: 0, 7, 14, 21, 28, 35, and 120 days after rice emergence (DAE). The herbicides were applied in each of these periods. The analyzed variables were crop height and shoot dry mass of the rice and barnyardgrass, number of grains per panicle, thousand-grain weight, and yield.

Results

The presence of barnyardgrass competing for environmental resources negatively affected the analyzed variables and rice yield for all periods with a coexistence longer than 28 DAE. Barnyardgrass competition during the entire rice cycle (120 DAE) reduced the shoot dry mass of the crop.

Conclusions

The PPI termination was determined at 14 DAE for the mixture cyhalofop-butyl + penoxsulam and 29 DAE for cyhalofop-butyl alone.

Oryza sativa; Echinochloa spp.; Chemical control; Mode of action of herbicides