Escarificação mecânica com areia para superação de dormência em sementes de acácia-negra (Acacia mearnsii De Wild.)

Abstract

The black wattle (Acacia mearnsii De Wild.) is, the third forest specie of larger economical importance, more than 189 thousand ha are cultivated now, in Rio Grande do Sul, Brazil. According its socio-environmental importance it can be considerate the first in importancy in this state regarding the enormous benefits given to the black-wattle grower and to the environment, such as: regenerator of degraded soils specie; short life pioneering specie; quickly covering the soil; not presenting stump sprouting; it doesn't inhibit the local succession and the high deposition of their nitrogen rich leaves, cause the enriching of the soil. Black wattle has also the capacity of making symbiosis with microorganisms fixatives of atmospheric nitrogen. Producing quality wood for energy and cellulose; the tannin extracted from its peel is used for leather curing industry and in wines and beers clarification. More or less 60% of black wattle growers are of small producers, about 40 thousand families live from that activity. One of the limiting factors in the uniformity of the black-wattle's seedlings production is the low of quality of their seeds. The quality of the seedlings and the forest produced by them will depend on the dormancy and on the method used for its break. With the objective of accelerating and standardization of the germination in the process of seedlings production, we went after an alternative method that should be more practical and efficient, in the break of black-wattle s seed dormancy. To reach these objectives the mechanical scarification method was tested, using sand to polish as scarificant material and the model GDA-8 escarificator. This GDA-8 scarificator was developed as part of the research project during Post Graduation Program in Science and Technology of Seeds of FAEM (Faculdade de Agronomia Eliseu Maciel) / UFPEL, by comparing it to the conventional method that uses hot water. The black-wattle seeds used in this research are originated from trees that were three, four, five and six years old, in Joca Tavares district in Bagé / RS. Scarification was made using the following proportion: one part of seeds was used to three parts of sand with thin granularity average of 0,75 mm, for 1 1/2 minute. Mechanical damage, germination, first counting and weight of green and dry matter tests were developed, in the Laboratory of Analysis of Seeds of FAEM and Emergency and Emergency Velocity Index (IVG) in the vegetation home of Votorantim Cellulose and Paper s dependences, located in Capão do Leão/RS municipal district. The random experimental work was with three repetitions and the averages compared by the test of Tukey at the level of 5%.