The objective of this research was to study the periods of weed interference in soybean crop, variety IAC-11, in northeastern Mato Grosso do Sul. The experiment treatments consisted of control with and without weeds, and different times of weed control, so that the soybean culture was maintained in the presence or the absence of the weeds up to the 10, 20, 30, 40 and 50 days after its emergence. Soil covering evaluations according to weed species were accomplished as well as culture growth and productivity evaluations. Soybean culture was found to coexist well with the weeds until 49 days after its emergence and the weeds they germinated after 20 days of its emergence did not affect its productivity. The occurrence of the initial period of possible coexistence (PAI= 49 DAE), larger than the final period (PTPI= 20 DAE), confers the coexistence periods a different characteristic without the occurrence of the critical Interference Prevention Period. Thus the recommended weed control is the momentary method, with post-emergent herbicide or mechanically applied, only once within the period ranging. From PTPI end to PAI end, or pre-emergent herbicide with residual effect surpassing PTPI.
Glycine max; Cenchrus echinatus; weed interference
