Profundidade de semeadura e superação de dormência no crescimento inicial de sementes de Brachiaria dictyoneura (Fig. & De Not.) Stapf (1919) cv. Llanero

Abstract

O Brasil é o maior produtor, consumidor e exportador de sementes de espécies forrageiras de clima tropical. Objetivou-se, com este estudo, avaliar o desenvolvimento inicial de Brachiaria dictyoneura cv. Llanero, em função da profundidade de semeadura e dos métodos de superação de dormência. O trabalho foi realizado em casa de vegetação, em blocos casualizados, com quatro repetições e em esquema de parcela subdividida. Os tratamentos aplicados às parcelas foram cinco, com as profundidades de semeadura de 0,0; 2,0; 4,0; 6,0 e 8,0 cm e, nas subparcelas, os métodos de superação da dormência com e sem escarificação. Cada parcela experimental foi constituída de 25 sementes. A partir do 10º dia de semeadura iniciou-se a contagem de plantas emergidas, a fim de se determinar o índice de velocidade de emergência e, aos 35 dias posteriores à semeadura, avaliou-se a emergência das plântulas, a altura de plantas e a matéria seca da parte aérea. As sementes de B. dictioneura semeadas em torno de 4,0 cm de profundidade e submetidas à escarificação mecânica apresentaram melhor desenvolvimento em todos os parâmetros avaliados. A semeadura superficial e aquela em profundidades abaixo de 4,0 cm mostraram-se ineficientes para o desenvolvimento inicial de B. dictioneura.

Emergence of Razor Grass on the Basis of Origin and Seed Depth in the Soil Profile

“…Although the experiment has been conducted in a protected environment and incidence of solar radiation has not been evaluated, the reduction in seedling emergence percentage found in the present study is probably due to indirect incidence of solar radiation on seeds that were located at greater depths, which, according to Silva et al (2017), may not induce germination. Lack of seedling emergence at depths greater than or equal to 7.0 or 8.0 cm is due to the fact that the quantities of seed reserves (carbohydrates and proteins) are insufficient to break the physical barrier imposed by the soil (Pacheco et al, 2010;Zuffo et al, 2014;Santos et al, 2015).…”

“…An example is cultural control using equipment to prepare soil to incorporate seeds at unfavorable depths to depths that are ideal for seedling emergence (Voll et al, 2001;Maciel, 2014). Conversely, there are several studies in the literature pointing to the effect of sowing depth and initial development of pasture; it is indisputable that a sowing depth between 1.0 and 2.0 cm is the most appropriate for the whole of the forage grasses (Pacheco et al, 2010;Zuffo et al, 2014;Santos et al, 2015). Thus, by locating razor grass seeds at greater soil depths and seeds of forage grasses in the topsoil, it would be possible to facilitate germination, emergence and development of the forage species at the expense of weeds, and stimulate pasture establishment.…”

Seed quality response of Urochloa humidicola cv. Llanero to drying surfaces and environments1

“…Llanero is scarce. Research with this forage grass has evaluated the dormancy breaking and sowing depth (Almeida & Silva 2004, Zuffo et al 2014. Magalhães & Groth (1992) evaluated the drying of U. humidicola cv.…”

Physiological changes in hybrid Brachiaria cv. Mulato II after accelerated aging to overcome dormancy

“…For seeds of Brachiaria, chemical scarification with sulfuric acid has been recommended , but it presents operational risks to workers, pollutes the environment and, in addition, can promote qualitative damage to seeds (Usberti and Martins, 2007). Thus, mechanical scarification presents advantages by removing the external structures of the seeds, facilitating gas exchange by the seeds (Zuffo et al, 2014). In addition to the scarification methodologies, researches that evaluates the dormancy overcoming process of forage grass seeds, has considered the action of high temperatures and high humidity (Pereira et al, 2014;Lacerda et al, 2010).…”