Ground speed : its influence on the direct seeding of jack pine (Pinus banksiana Lamb.) with the Bracke scarifier

Abstract

The effects that ground speed and obstacle height have upon microsite creation by the Bracke scarifier and upon the seeding characteristics of the integral seeder were studied. The study was conducted in a former gravel pit with homologous soil conditions and uniform obstacle sizes to minimize sources of variation. Jack pine {Pinus banksiana Lamb.) seed was treated with ^Scandium, a gamma-emitting labelling agent. The trial involved running the scarification unit at four speeds, over three obstacle sizes. Data were collected on microsite dimensions, seeder performance and seed placement. A field trial was also conducted to follow trends seen in the gravel pit portion. Results indicated that the height of an obstacle had more effect on microsite attributes, seeder performance and seed placement than did the ground speed at which the scarifier was drawn. Microsite length and longitudinal seed placement decreased as obstacle height increased, while lateral seed placement increased with increasing obstacle height. It was recommended that the Bracke scarifier/seeder be operated at 40 m/min in order to reduce the influence of obstacles. The seeder must be properly calibrated to account for the influence of obstacles: a modified technique was discussed. Trends observed in the gravel pit trial were not apparent in the smaller field trial.