EFFECTS OF DEPTH OF SEED BURIAL AND SOIL AGGREGATE SIZE ON SEEDLING EMERGENCE OF ALOPECURUS-MYOSUROIDES, GALIUM-APARINE, STELLARIA-MEDIA AND WHEAT

Seedling emergence of Alopecurus myosuroides Huds., Stellaria media L. (Vill.), Galium aparine L. and wheat (Triticum aestivum L.) was compa red at a range of depths of soil cover from 2 to 11 cm, The covering s oil was a fertile agricultural soil with 60% clay content which had be en sieved into four aggregate sizes. The aggregate sizes used were 26- 50 mm, 14-25 mm, 6-13 mm and below 6 mm. Total emergence of all specie s was reduced with increased depth of soil cover. With A. myosuroides and S. media, total emergence was lowest in fine soil conditions. Alop ecurus myosuroides showed a marked interaction whereby response to dep th of sowing was least with fine tilth. The time to 50% emergence show ed a similar response. With all four species, seedling emergence was s lowest at greater depths of sowing and with the finest tilth, the diff erences tending to increase with increasing depth of sowing. A very hi gh proportion of the time to 50% emergence was accounted for by the la g time between sowing and the first recorded emergence.