Seed Mix Sowing

Seed mix sowing means scattering a blend of several plants across the ground - broadcasting it, rather than setting each seed in a furrow - and letting them compete for what they find. The blend is used because it is sturdier than a single species. Several plants together hold weeds down better than one does, and if one fails the ground is still covered by the rest instead of left bare. That insurance is the reason for the mixture rather than a bonus from it, and a common floor is at least three species from two or three plant families.

The weakness is the method. A seed drill cuts a slot and presses each seed against moist soil; seed thrown on the surface may land on dry ground, be eaten by birds and mice, or lie shaded by crop residue, so germination is patchy and the rate has to be raised - around 67 to 78 kg per hectare (60 to 70 lb per acre) where a drill would use less. Within a blend, heavy seed flies further from a spinning spreader than light seed, so the mix separates as it is thrown, and a vigorous species is sown at a fraction of its solo rate - cereal rye at a quarter to a half - or it smothers its companions.

One broadcast method does have a mechanism behind it. Frost seeding is done in late winter onto ground that freezes at night and thaws by day: freezing water swells and lifts the surface, and the thaw drops soil back over the seed. It wants a loam or clay that holds water, since sand dries too fast, and it suits clovers well while alfalfa germinates too slowly to use it. Whatever the method, the usual failure is no catch at all, because rain did not follow or an established stand outgrew the seedlings. Two more things decide the result: a legume fixes nitrogen only if the right soil bacteria are there, which is why such seed is often coated with them, and a stand must be killed on time or it seeds itself into next season's weed problem.