I mixed some various random amendments with compost to see which worked best for starting squash and cucumber seeds.

Tried: leaves, wood chips, wood chunks, wood wafers, corn cob slices, brown cubic rot, and as a control also used jiffy seed starting mix.

The best result by far was the corn cob mix.

2nd best was compost and wood chunks or a wood wafer.

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Here is a link that might be useful: Seedling mix trials