Depth of sowing-seed incorporation

Incorporating seed into the soil post-sowing by raking or harrowing on a large scale increases seed contact with moist soil and improves germination and establishment. The germination of small seed is sometimes (but not always) inhibited by darkness, and this may negate some of the benefits of incorporation post-broadcasting. Since most seed mixes will contain large, medium and small seed, there are several options:

– sow and rake into the top 5-10 mm of the soil

– mix the seed as two batches based on approximate seed size—medium-large and small.

The former is sown first and is raked in. The small seed is then oversown onto the

Depth of sowing-seed incorporation

6.11

The effect of controlling aggressive grass weeds on density and diversity of sown forbs: (a) a plot in an experiment with no grass control in year one; and (b) the same experiment but with grass control in year one

surface. Given that incorporation by raking or harrowing is a very crude process, with some seed always remaining on the surface, in our experience splitting the seed into two batches is rarely justified.

Where possible, sown sites should be rolled with a heavy roller post-sowing, especially if small seed has been surface sown. Rolling improves seed-soil contact and is most important on dry sites or with species that are particularly sensitive to moisture stress at germination.