Cover crops are invaluable for controlling weeds, pre- venting soil erosion and preserving soil organic matter. Ideally, growers will vary cover crops from year to year to take advantage of different botanical characteristics such as rooting patterns, allelopathy and nitrogen fixation. Variety also helps thwart the establishment of certain weeds and pests. The hectic pace of the farming season, however, often means growers are scrambling to plant any crop at all by autumn. For the sake of easy establishment and reliability many will choose the old standby, fall rye.
By late August, cover crop choices are limited. Oats, brassicas (oilseed radish, rape/canola, mustard) and possibly buckwheat (very frost sensitive, little biomass) are a few options. Unlike fall rye, oats and brassicas win- terkill and leave little surface trash to contend with in the spring. Hairy vetch will not over-winter in many regions of Canada, but in some areas, late summer can be an ex- cellent time to establish this acid tolerant, leguminous crop for plough-down the following summer. It bears mentioning that in Atlantic Canada, at least, late summer is a good time to establish more long-term forage stands such as white clover, timothy and meadow fescue, partly because weed pressure is usually lower in the autumn than in spring.
For squeezing in a growing crop between fall and spring, however, fall rye is without equal. Rye can yield 2-6 tonnes dry matter per hectare depending on soil fertility and when it is ploughed under. The crop's expansive root system, autumn tillering, early spring growth and long straw provide excellent weed control.
Rye is also well known for its release of allelopathic chemicals - substances that retard the growth of certain weeds. These are found in a variety of crops and weeds and are being studied as possible alternatives to synthet- ic herbicides. The chemicals released by rye have inhibi- tory effects on weeds such as wild oats, red rooted pig- weed, ragweed and common purslane.
Fall Rye is a soil builder. This cereal grain grows quickly in the fall and survives winter weather even in zone 3. It bursts into growth in the spring so try to turn under or cut back before it reaches 30cm (12"). It is harder to turn under when it is 1m (3') tall. Extensive roots loosen top- soil and improve drainage. Plant in mid September for best results, but fall rye will germinate as late as early November. Seed no deeper than 5cm (2"). Use 30-60kg/ acre. 500g covers about 30sq m (300sq ft). (open polli- nated seeds)
Fall Rye can be left growing and vegetables can be seeded into the fall rye mulch as an organic no- till growing system.