Saturday, March 13, 2010

Turn under winter cover crops

If a winter cover crop of rye or Austrian winter pea was planted in the fall, turn it under a month before planting or seeding. I turned my winter rye under this past weekend adding “green manure” to the soil.

The large soil critters such as the earthworm pictured here (below right) and soil microorganisms will “chew” through the raw roots and tops over the next weeks for soil improvement. I left the soil “rough” and certainly didn’t step on and compact it. That’s an advantage of raised bed gardening – standing outside the bed to work your soil. It will not be tilled again when seeding or planting so the soil structure can be preserved as much as possible. More tilling would simply destroy it and there is no good reason for it.

First, why do you need to wait a month before planting? The living critters working over the plants consume soil oxygen and can create plant health problems if not tilled in ahead of time. Once the bulk of the “raw” plants have been consumed, the soil environment stabilizes and lack of oxygen for plant root growth is no longer a problem.

Second, it’s about more than the buried plants. If it was only the plants we could find a way to chop them into fine pieces and instantly improve the soil. The secret is what the soil critters add to the mix and the squeamish need read no further. Simply know that without them, you couldn’t realize the soil structure and fertility improvement benefits from planting and turning under cover crops.

Large and small critters feed on the buried plants adding substances such as slime, mucus and fungal mycelia. Analyzing these substances show things such as gums, waxes and resins which glue soil particles together. Clumped particles enhance the tilth, porosity, and water holding capabilities of soil – all good things for healthy plant growth.

Take care of your vegetable garden soil and it will take care of you.

Photo credit: Two soil spading photos - Carl Wilson

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