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Cowpeas as a no-till summer cover crop

Cowpeas and buckwheat

Pulling up cowpeasYou may remember that I've been experimenting with mixing cowpeas in with my buckwheat cover crop this summer.  Although the cowpeas grew well, I'm not sure we'll plant them again next year for a few different reasons. 

The obvious strike against cowpeas is price.  Our local feed store doesn't stock cowpea seeds, and ordering cover crop seeds online is expensive.  Buckwheat seeds bought locally clock in at a bit over a dollar a pound, but once you factor in shipping, cowpea seeds cost me about $2.40 per pound even if you buy them in Cover crop decompositionbulk.  Now, to be fair, the one pound of seed I bought (for $4.25 plus shipping) seeded 23 beds in combination with buckwheat, which means that if I'd planted only cowpeas in those beds, I would have been spending about 37 cents per bed.  That price tag compares very favorably to the roughly $1.33 per bed I would have spent on straw to mulch the beds down for the six weeks between crops.

The next problem is ease of killing.  Cowpeas aren't nearly as hard to kill as the overwintering grains I fought with this spring, but they do tend to resprout if mow-cut.  Even when I pulled up individual plants (a method that turned out to be faster than mow-cutting), perhaps 10% of the cowpeas survived to reroot.  On the small scale I've been experimenting with, this regrowth barely had an impact on my gardening time, but I wouldn't want to have a large area planted in cowpeas.

Nitrogen-fixing nodules on cowpeasFinally, I was disappointed by how long the cowpeas took to decompose.  I'd read that cowpeas have a very good C:N ratio of 21, compared to the not-so-shabby C:N of 34 for buckwheat.  Those numbers mean that cowpeas should break down even faster than buckwheat and be ready to plant into quickly.  However, when I pulled up beds of cowpeas and buckwheat a week before planting and laid the plants on the soil surface to die, the buckwheat leaves were completely gone and the stems were halfway decomposed by planting time.  In contrast, the cowpea leaves were still somewhat visible and the stems were thick and green.  Again, since I was experimenting on a small scale, it was no big deal to layer the cowpea stems as a mulch around the edges of the garden beds, but on a larger scale, I'd probably instead have to kill the cowpeas an extra two or three weeks before planting into them.  I guess cowpeas aren't such a quick summer cover crop after all.

Buckwheat cover cropThe good news is that I'm learning to love buckwheat.  My gut feeling last year was that buckwheat didn't do much for the garden beds, but now that I've tried the cover crop in non-waterlogged, more loamy portions of the garden, I'm more impressed by this little producer.  Filling garden gaps with buckwheat certainly doesn't hurt the organic matter content of the soil, and the bees definitely love them.  Next summer, it's going to be buckwheat all the way!

Our chicken waterer keeps the flock hydrated during hot summer days.


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I look at it from a different angle. Judging from the pic, the cowpeas are way more valuable for building humus than lightweight buckwheat because of all the cellulose and lignins and such in those tough stems, plus those gorgeous N-fixing nodules. I would pile them into a compost heap at one end of the bed, interspersed with a bit of dirt, and either use the heap in the spring as a grow heap, or spread it over the bed. I would probably try scything it to leave the roots in the ground and deal with the regrowth by hand, but that might be above and beyond the call of duty! Speaking of which, I'd better get going with my winter cover. I appreciate your blog; it can be quite motivating.

Comment by Jackie Sat Aug 27 19:09:29 2011
Oh. After reading the posts referenced in this post, I see why you choose buckwheat. Cheers.
Comment by Jackie Sat Aug 27 19:20:47 2011

Jackie --- I totally agree with your points if we were using the summer cover crops the way we use winter cover crops. We don't tend to have windows long enough for that to make sense in the summer garden, though, so we add the organic matter with the winter cover crops (oats and oilseed radish.) If we were going to leave beds fallow all summer, though, for serious rehabilitation, cowpeas would probably be a good choice.

I've actually found that pulling the plants kills more of them than when Mark cut them right at the ground surface with the weed eater. It doesn't seem to take any longer either, but then, I'm a fast plant-puller. :-)

Good luck with the winter cover!

Comment by anna Sat Aug 27 19:56:21 2011

One very unique homestead, $1,500 per acre, the opportunity of a lifetime