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There is a long list of the beneficial functions of green manure cover crops. The ones I have sought are:

• Suppressing weeds
• Adding organic matter
• Adding nutrients, especially nitrogen
• Bringing nutrients from deep down
• Encouraging micro-organisms
• Improving soil structure

In 2013 I planted:

• Buckwheat (as a Spring/Summer cover crop and green manure)
• Alfalfa and clover (Medic Mix) (as a Summer smother crop and green manure) which failed completely to germinate
• Cereal Rye (as a Winter cover crop and to add organic matter through its root system)

The challenge of planting cover crops where the area is to be used for growing the following season is timing:

• Can I move veggie crops out in time to allow the cover crop to germinate before cold weather comes? In 2013 it was a challenge to prepare the ground for planting of rye and vetch because the beans needed to dry out. We sowed the vetch too late for significant germination.
• Can I terminate the cover crop soon enough in the Spring/early Summer to plant an early crop like peas? In 2014 it was time to plant Spring peas before the rye had matured. This meant the rye wasn't ready to be terminated and required a second attempt later.

So significant factors in choosing a cover crop are how late in the Fall it can germinate and how long it occupies the area before it can be terminated effectively. These are in addition to serving a purpose of providing nutrients an organic matter.

We do leave about one-third of our garden in summer cover each year, which adds to the complexity of managing the remainder.

My choices for the 2014-2015 Winter season are:

• Crimson clover
• Medic mix (alfalfa and clover)
• Winter mix (Austrian winter peas, cereal rye, triticale, annual rye grass and crimson clover

I searched for a good cover crop for the heavy clay soil at one garden and wasn't pleased with the choices I had available. I settled on the Gardenway winter mix, the third in the list above. I'm hoping that a few of the varieties, probably winter peas and cereal rye, come close to surviving and thriving. The peas need a pole to climb on. I had no luck with vetch in the heavy soil last year and there's so little crimson clover that it won't have any effect if it services. So I did my best to plant early and then crossed my fingers. I found this at the local Grange Supply so I didn't need to wait for shipment from Oregon.