The effect of seed treatment and depth of sowing on forage brassica crop establishment in no-tillage situations

Abstract

Unreliable establishment of brassica forage crops prompted an investigation into the effect of sowing depth and current commercial seed treatments on rates of emergence and total emerged seedling numbers. Three trials using Barkant forage turnip were sown by notillage in conditions managed to minimise invertebrate pressure. Rate of emergence was measured by seedling counts taken at multiple stages over the first 24 days after sowing. Trial A tested the effect of seed treatment (SuperStrike®, UltraStrike™, Gaucho® 600 FS 24 ml/ kg (14.4 g a.i imidacloprid/kg seed), Gaucho® 600FS 12 ml/kg (7.2 g a.i imidacloprid/kg seed) and untreated control) on seed sown at 10 mm depth, with no significant difference in the rate of emergence of any seed treatment and the untreated control (bare seed). Trial B tested the effect of seed treatment (SuperStrike® and untreated control) on seed sown on the soil surface (0 mm), with no difference in rate of emergence being found. Trial C tested the effect of sowing depth (surface (0 mm), 10, 25, 50 mm) on rate of emergence, and found that seed sown at 10 mm depth was initially faster to emerge (7 days after sowing). Subsequent counts established that 10 and 25 mm depths had equivalent rates of emergence and had reached the highest total number of seedlings emerged by 15 days after sowing. In contrast, seed sown on the surface (0 mm) or at 50 mm depth had a lower total emergence count. Trial C also found that subsurface sown seed (10, 25 and 50 mm depths) reached peak number of emerged seedlings faster (15 days after sowing) than seed sown on the soil surface (0 mm). Keywords: brassica, forage crop, seed treatment, sowing depth, emergence, agronomy