With the objective of evaluating the effect of different timings of weed control performed by hand weeding or herbicide application, on the corn yield and agronomic characteristics, an experiment was set up on the "Capão da Onça" School Farm (UEPG) in Ponta Grossa - PR, under the no-tillage cropping system. The experimental arrangement employed was a randomized block design in a 2 x 5 factorial with six replications. The hybrid utilized was the XL 212, planted on 11/11/97. The herbicides used and their respective applications timings were: atrazine (1400 + 1400 g/ha) at 2 and 19 days after the emergence (DAE); atrazine + nicosulfuron (1400 + 12 g/ha) at 8 DAE; atrazine + nicosulfuron (1600 + 20 g/ha) at 19 DAE; atrazine + nicosulfuron (1000 + 40 g/ha) at 26 DAE; and nicosulfuron (60 g/ha) at 31 DAE. The hand weeding procedures being performed at the same timings. The predominant weeds were Brachiaria plantaginea, Triticum aestivum, Raphanus raphanistrum, Galinsoga parviflora and Richardia brasiliensis. It was observed that the delay in weed control timing from ten DAE onward negatively affected the characteristics of the plants evaluated, more markedly so for the control through herbicides. Except for the weight of 100 kernels, the other components of yield and grain yield declined with the delay in control timing from ten DAE onward.
Zea mays L.; weed Competition