Effect of tillage practices on the fate of hard seeds of subterranean clover in a ley farming system

Abstract

In a rotation of 1 year pasture/l year crop, a subterranean clover (Trifolium subterraneum cv. Daliak) pasture was either left untilled or subjected to minimum or conventional tillage. One set of tillage treatments was imposed in each ofthree crop years while another set of treatments was imposed in only the first crop year. Regenerating clover plants were prevented from setting seed. In the first crop, 44% of the clover seeds were buried below 2 cm of soil by minimum tillage; this proportion was 65% in the conventional tillage treatment. In the first pasture regeneration year, seedling densities were highest in the no-tillage treatment. Conversely, there were more residual seeds in the tilled treatments and, in the second and third pasture regeneration years, this led to higher seedling densities than in the no-tillage treatment. The effects of tillage were more marked in the conventional than in the minimum-tillage treatment. Clover establishment was improved by repeat tillage operations which returned some of the buried seeds closer to the soil surface. Although more seedlings overall were obtained from the no-tillage treatment, the disadvantage of fewer seedlings in the tilled treatments was offset by the spread of seedling establishment over a number of pasture years. This spread, which would be more marked with harder-seeded cultivars, could be desirable in environments in which clover seed production is unreliable.