Effect of sowing depth on seedling emergence of three species of Stylosanthes

Abstract

Interrelationships between sowing depths (2, 1, 0.5, 0.25 in. or soil surface) and emergence of fine-stem stylo (Stylosanthes sp. CPI 11493), S. guyanensis and Townsville lucerne were investigated on a basalt and a granite-derived soil at Brian Pastures Res. Stn. Soil moisture was maintained at field capacity to at least 3 in. depth by surface watering. On both soils, emergence of all 3 species was greatest from 0.25 and 0.5 in. sowing depths; on the granitic soil emergence of fine-stem stylo and Townsville lucerne from 0.25 in. was superior to that from 0.5 in. but differences were not significant. In the time taken to reach 50% emergence, there were no differences in response to sowing depths of 0.25 and 0.5 in. on basalt. On granite, emergence was slower from the 0.5 than from the 0.25 in. sowing depth. Optimum sowing depths were therefore 0.25 and 0.5 in. depending on soil type. It was concluded that depth of sowing was of great importance where soil moisture was adequate for the 3 species examined. Where it is impracticable to drill seed to a predetermined depth, it is recommended that seed be surface-sown following cultivation and that further mechanical treatment be restricted to rolling. -F.A.S.