Seed distribution
Depending on the area to be sown, broadcast sowing can be undertaken by hand by a chest-mounted spinning disk, a wheel-mounted spinning disk spreader or tractor-mounted equivalent. For really large-scale application, a tractor-mounted agricultural precision drill can be used. These are capable of giving very good results, however these are rarely available to urban projects. Their use in relation to seeding into existing meadow grassland and creating prairie vegetation on cultivated soils are discussed by Wells et al. (1987) and Morgan (1997), and see http://www. prairienursery. com/.
To obtain even distribution when broadcasting, it is necessary to calibrate your application technique. The principles involved in doing this are the same for all types of equipment. If hand broadcasting, a bulky carrier, such as sawdust, chick feeder crumbs or sand, is used to make sowing easier. Sand is the most readily available but the heaviest material to work with:
- from your seed mix calculations, establish the weight of seed that you wish to sow per
m2
- calculate the total weight required for the area to be sown, i. e. if the area is 200 m2 and
your mix is to be sown at 1.5g/m2, you need 300 g of seed mix
- for every m2 of the area to be sown add one handful of your seed-sowing carrier (e. g.
sand) to a clean wheelbarrow. If your area is 200 m2, add 200 handfuls. This is made much quicker by marking a plastic bucket to show the volume equivalent to 50 handfuls of sand
- add the seed for this area (300 g) to the sand in the wheelbarrow, mix thoroughly
- mark off the area to be sown with string lines into a series of 1 m wide corridors
- transfer some of the sand-seed mix to a bucket and walk along the corridor distributing a handful of sand-seed mix over each metre of travel. Work across the site to be sown in this manner.
The above technique gives accurate sowing and the string lines corridor approach provides feedback to inexperienced sowers that reduces the risk of running out of seed halfway across the area to be sown. Precision in seed sowing is most important for sowings close to buildings and with species and communities that will not readily fill-in large gaps by self-seeding. Less precision is required with native meadows sown with a grass component. With spinning disk seed-applicators, the seed is sown without a carrier. Calibration is still necessary and involves walking over a large sheet of black polythene at a standardised walking rate, with the disk spinning at a standardised speed for a set distance, for example 5 m. The time taken to travel the 5 m is also recorded. The width of the seed distribution swathe can be observed (for example, 2 m), and since the distance travelled is also known (5 m), so is the area sown, i. e. 10 m2. The seed on the polythene sheet is then carefully collected up and weighed on a balance. If the aim was to sow at 1.5g/m2, there should be 15 g of seed on the sheet. If there is 7.5 g, the sower needs to half their speed of travel; if there is 30 g., then the speed of travel needs to double, and so on.
