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ABSTRACT: Native species seedling growth may be affected by allelopathic substances released by invasive forage species, mainly in natural regrowth areas. Thus, this research aimed to evaluate the growth characteristics of pequi trees influenced by concentrations of plant residues of different forage species (Urochloa decumbens, Melinis minutiflora and Paspalum notatum). A randomized block experimental design was arranged in a factorial 3 x 4 + 1, with four replications. Treatments consisted of incorporating plant shoot residues of three forage species to pequi seedling substrate (soil + fertilizer) at four concentrations (1%, 2%, 3%, and 4% mass/mass), plus pequi seedlings grown in a residue-free substrate (control). Pequi plant height, stem diameter, and leaf number were evaluated at fortnightly intervals. Leaf area, root/shoot ratio, leaf area ratio, specific leaf area, and leaf mass ratio were determined 100 days after transplanting. Forage residues added to substrate inhibited pequi growth, and with increasing residue concentration, this inhibition was intensified. Pequi leaf characteristics proved to be more sensitive to allelopathic effect, especially from U. decumbens residues.

ABSTRACT: This research aimed at investigating which sowing method is more suitable for the deployment of Urochloa ruziziensis to suppress the weed community in no-tillage. The design was a randomized block ones, with a 3 x 2 factorial design, in which the first factor was composed of three sowing methods (broadcast, broadcast with incorporation or line sowing) and factor B consisted in the application and non-application of the herbicide 2,4-D. On day 30 and 60 after sowing (DAS), the relative importance of the present plant species was determined. On day 120 and 180 DAS, the accumulation of biomass and the plant cover percentage on the soil provided by the cover crop and weed species were determined. Moreover, on day 180 DAS, the density of the existing weeds was determined. The weed with the highest occurrence in the area was Conyza canadenses, and the lowest percentage of soil covering by signalgrass and the greates occurrence of weeds occurred with broadcast seeding. It is possible to conclude that the broadcast seeding with the incorporation of signalgrass seeds and line sowing methods provide enough plant cover to suppress weed species, avoiding the application of the herbicide 2,4-D in order to suppress the infesting community.

The success of conservation systems such as no-till depends on adequate soil cover throughout the year, which is possible through the use of cover crops. For this purpose the species belonging to the genus Urochloa has stood out by virtue of its hardiness and tolerance to drought. Aiming ground cover for the no-till system, the objective was to evaluate the establishment of two species of the genus Urochloa, in three sowing methods, in the weed suppression and the sensitivity of these forages to glyphosate. The study design was a randomized block with a 2 x 3 x 3 factorial arrangement, in which factor A was composed of Urochloa ruziziensis and Urochloa hybrid CIAT 36087 cv. Mulato II, factor B was formed by sowing methods: sown without embedding, sown with light embedding and sown in rows, and factor C was composed of three doses of glyphosate (0.975, 1.625 and 2.275 kg ha-1 of acid equivalent). For determination of weed suppression, assessment of biomass yield and soil cover was performed, by brachiaria and weeds, at 30, 60, 90, 120 and 258 days after sowing. Visual assessment of the desiccation efficiency at 7 and 14 days after herbicide application was performed. It is concluded that embedding Urochloa seeds stands out in relation to sowing in the soil surface. Urochloa ruziziensis is more efficient in the dry weight yield, weed suppression, in addition to being more sensitive to glyphosate herbicide.