Wednesday, September 29, 2010

Sowing Oats

  "What's that grassy stuff in your gardens?" People ask me at this time of year.
  It's oats.
  While I very well could be growing the oats to make nutritious tea from the immature seed or oat straw, its purpose in the garden is to provide temporary cover for the soil -- a cover crop.
  Oats are my favorite cover crop. The seed is readily available at the local co-op or feed store, either as seed oats or as feed for horses. Oats germinate and grow quickly, so they can be planted throughout spring, summer and fall to follow almost any vegetable crop. Oats will be killed by temperatures lower than the mid-20s, but the brown plants still provide sufficient cover.
  If you want a small grain that provides green cover through winter, plant winter wheat or winter rye. They sprout more slowly than oats, so need to be planted sooner and will take more effort to “terminate” in the spring.
  Why does it matter whether the soil is bare? Why not just clear the garden and be done with it?
  Bare soil is prone to the erosive forces of wind and rain. Sunlight also oxidizes nutrients in the soil, which not only reduces the nutrients available to plants but might even contribute to greenhouse gases as oxidized carbon in the soil becomes carbon dioxide.
   Then why not just throw on a layer of hay or straw mulch? As the mulch decomposes it also adds valuable organic matter to the soil, which loosens it, helps improve both water retention and drainage, and adds a few  nutrients.
  The value of cover crops goes beyond adding organic matter to the soil. Their roots “trap” nutrients so they don’t leach from the soil in rain and snow melt. Then the nutrients remain available to your vegetables the following season. Mulch can't do that.
  Rotating small grains -- such as oats, wheat or rye -- with tomatoes helps reduce some diseases, such as verticillium wilt. Some, such as mustards, also help control damaging nematodes and other pests. Mulch can't do that, either. Using legumes as cover adds nitrogen to the soil. Mulch certainly can't do that.
  K-State has a great publication on using cover crops in vegetable growing ( I

  Usually a cover crop is cut down and “terminated” before it can flower. At this stage, the residue will break down quickly and you do not risk it setting seed and resowing. However, some cover crops, such as clovers and buckwheat, are lovely when in bloom. Others, such as cowpeas, provide their own crop for your use.
  Winter rye gets quite large when left to put on seed heads and can be quite difficult to pull out at that time,so cut it and use as hay mulch. Other tall cover crops also can be cut as “hay” mulch.
  Ideally, oats and other small grains are mixed with appropriate annual legumes in fall or spring. The quick growing oats protect the legumes until they get well established. For the best nitrogen-fixing, legume cover crops should be “inoculated” with a special bacteria that helps them transform the nitrogen in air and soil into a more plant-usable form.
  Mixing annual legumes with the oats takes additional planning because the seed is not as readily available. It often must be purchased by mail order or special ordered by the farmers cooperative or seed store. Some annual legumes are best suited for winter cover (crimson clover, Austrian winter pea), others as summer cover (berseem clover, annual white sweet clover, Canadian field pea). Many other annual legumes can be used as cover crops, but do not work well in mixes with grasses (grains). Whether you want a winter or summer cover also determines your choice of other covers.
  Buckwheat, neither a legume or grassy grain, is a great summer cover crop. I planted it this spring around some of my fruit trees and in garden areas that did not get planted to vegetables. According to the Extension publication, buckwheat is not drought tolerant, but another source said that it is at least moderately drought tolerant.
  In my experience this summer, the mature plant tolerated at least some drought, surviving three weeks of 100-plus degree temperatures and no rain in August.
Pretty buckwheat flowers attract bees.
  Buckwheat, and a few other cover crops, can grow so quickly and thickly that they out-compete and smother weeds -- when planted in the proper conditions.It also needs warm soil. The buckwheat I planted in April germinated only sparsely, while the buckwheat planted in a little warmer soil in early May did quite well.
  It can be sown throughout the summer, but does need some moisture to germinate.
  My method for planting the buckwheat and oats is to scatter the seed on loosened soil and rake in, then scatter on a light mulch of hay or straw to hold in moisture and keep the seed in place. You also can plant them in furrowed rows.
  Buckwheat blossoms are beautiful and highly attractive to bees. A friend told me that buckwheat is her favorite cover crop because is attracts so many beneficial insects. Buckwheat honey is an excellent cough suppressant, although most people will find its flavor too strong for use as a sweetener or topping for cornbread.
  The flowers are so attractive to bees that you might want to keep buckwheat from flowering while cucumbers, squash and melons and other pollinator-dependant vegetables are in bloom. Or the bees might ignore them in favor of the buckwheat blossoms. Young buckwheat greens also can be used as a green vegetable.
  Usually when you incorporate a cover crop into the soil you should give it a couple of weeks to decay before planting anything else. Buckwheat decomposes so rapidly that you can plant almost immediately after taking it down. Soon I will plant garlic in one area where buckwheat is growing. I will simply cut back the buckwheat, throw on the compost and plant the garlic right in the buckwheat stubble.
t focuses on the commercial vegetable grower, but the information is easily adapted to smaller scale gardening.

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