Use of vegetation cover in the control of different species of the genus Amaranthus

Soil cover has a physical, chemical, and biological effect on weed suppression. Although it depends on factors such as location and weed pressure, vegetation cover can even eliminate the need for herbicide application. Considering that the weeds popularly known as pigweed (Amaranthus sp.) have been expanding in agricultural areas and the use of only one form of management is not recommended for their control, this study aimed to evaluate the effect of using cover crop phytomass to control species of the genus Amaranthus. Soil vegetation cover at different percentage levels was evaluated in the control of the following weed species: Amaranthus hybridus, Amaranthus deflexus, and Amaranthus viridis, previously sown. The experimental design was completely randomized in a factorial scheme (9x4), with four replications. The treatments resulted from the combination of nine cover crops with Crotalaria species (Crotalaria juncea, Crotalaria breviflora, and Crotalaria spectabilis), black oats (Avena strigosa), sorghum (Sorghum bicolor), jack bean (Canavalia ensiformis), pigeonpea (Cajanus cajan), lablab bean (Dolichos lablab), and pencilflower (Stylosanthes macrocephala), and four percentage levels of phytomass (control – no phytomass; 50%, 100%, and 200% of the total mean production, identified as CONTROL, T50%, T100%, and T200%, respectively), with four replications. Black oats, pencilflower, and jack bean showed higher potential for controlling Amaranthus hybridus and Amaranthus deflexus, while sorghum and jack bean were more efficient in controlling Amaranthus viridis. Regarding the amount of green mass, the amounts T100% and T200% were the most promising in suppressing weeds.