Abstract
Mechanical sugarcane harvest without burning and continuous straw on the soil surface may affect the Rottboellia exaltata infestation dynamics in sugarcane fields. Three greenhouse experiments were conducted with the aim of studying the effects of sowing depth (0, 2.5, 5, 7.5, and 10 cm), amount of sugarcane straw on the soil surface (0, 5, 10, and 15 ton ha -1 ), and residual herbicide (clomazone, flumioxazin, imazapyr, isoxaflutole, and s-metolachlor) on the emergence of Rottboellia exaltata. For each experiment, a completely randomized design with four replicates was applied. The combination of mulch on soil surface (especially with larger amounts of straw) with deeper sowing depths provides less emergence and mass accumulation of R. exaltata. In bare soil, the sowing depth did not affect the weed dynamics. Clomazone and imazapyr were effective herbicides controlling R. exaltata regardless of the amount of straw on the soil surface. Flumioxazin was also effective in controlling R. exaltata but only under bare soil conditions. Even with 60 mm of accumulated rainfall over the 4 day period after application, the amount of flumioxazin leached to the soil was not enough to ensure the same control observed when applying the herbicide on bare soil.
Highlights
Rottboellia exaltata L.f. (synonym R. cochinchinensis (Lour.) Clayton) is an annual or perennial species depending on environmental conditions, and it is reproduced by seeds produced from stem fragments with budding nodes (KISSMANN, 1997)
Emergence of Rottboellia exaltata influenced by sowing depth and presence of sugarcane straw on the soil
For the control treatment and the clomazone, isoxaflutole and imazapyr herbicides, weed density and dry matter did not vary with increasing amounts of straw on the soil surface (Figure 3). These results indicated that weeds did not germinate and/or emergence was inhibited by the presence of sugarcane straw and that herbicides were not affected by mulch on the soil
Summary
Rottboellia exaltata L.f. (synonym R. cochinchinensis (Lour.) Clayton) is an annual or perennial species depending on environmental conditions, and it is reproduced by seeds produced from stem fragments with budding nodes (KISSMANN, 1997). (synonym R. cochinchinensis (Lour.) Clayton) is an annual or perennial species depending on environmental conditions, and it is reproduced by seeds produced from stem fragments with budding nodes (KISSMANN, 1997). Agronomy in the soil that may inhibit germination and/or growth of adjacent species, including weeds and cultivated crops (KOBAYASHI et al, 2008; MEKSAWAT; PORNPROM, 2010). R. exaltata is the main weed for at least 18 crops in Africa, Central America, South America, Unites States, Australia, and Papua New Guinea (ANNING; GYANYEBOAH, 2007; HOLM et al, 1991; KISSMANN, 1997). This weed frequently occurs in Brazilian sugarcane crops in Rio de Janeiro There are reports of its occurrence in northern and central-western regions of Brazil (KISSMANN, 1997)
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