What a crazy spring! We’ve had over 6” of rain after having none for almost a month. Hot then cold then hot again. Frost over Memorial Day weekend and now 4 days later it’s in the high 80’s in the shade. This morning I tried to beat the heat while cutting back an oat and field pea cover crop to prepare some beds for the big tomato and pepper transplanting. While I worked with Erin, friend and neighbor, I kept trying to think of a topic that was timely and relevant for this column. Voila! There it was on my mind and in my hands- -the importance of cover crops.
I used to think that they were just for large-scale farmers. However, through readings and workshops, I’ve come to understand their value even for small-scale homesteaders and gardeners. Now, I devote 1/3 or more of my growing beds to various cover crops and green manures. They prevent erosion; maintain & build soil fertility, organic matter & soil life; disrupt pest and pathogen habitats & life cycles; smother weeds; increase crop diversity; and offer habitat & food for beneficial insects, amphibians, reptiles and birds. Plus they’re beautiful.
The same crops can be grown either as a green manure or as a cover crop. The difference is in timing and how you use them. If you want to increase soil nitrogen quickly, you could turn the plants under when they are small. Then wait 2 weeks for the soil microbes to digest and stabilize the nutrients into the soil. If you want longer-term soil improvement then let them grow and cut just before seed is set. While the plants have been growing they have been creating a huge root mass (future organic matter) and have been feeding the soil microorganisms with the sugars from photosynthesis through root exudates. Leaving the stalks on the ground as mulch further improves soil texture and health as the decomposition of the ligneous material increases mycorrhizal fungal activity.
Some common cover crops & green manures: clovers, buckwheat, oats, field peas, Sudan grass, hairy vetch, (rye & other perennial grasses), field radish, and mustards. They all have attributes to recommend them,
I usually stick to the easier ones to grow and manage. Here’s how I use them in my garden.
Oat & pea mix- early plantings, as they don’t mind cold and wet, that I can leave grow out or do a cut and come again approach to use as mulch elsewhere (cut about 4-6” from soil so they’ll regrow). The peas are nitrogen fixers as well as biomass. I also plant them as beds empty out, like after the garlic is harvested, or do an under sowing in Sept/Oct. beneath tomatoes, peppers, asparagus brassicas and such. Both the oats and peas are winter killed, so they die back with no effort on my part and serve as mulch for the winter months.
Buckwheat-cold sensitive so wait to plant until after frost. I like buckwheat because if planted thickly smothers out weeds. It also has small clustered flowers, which the bees and beneficials love. It’s easily killed by frost or cutting. If seeds are allowed to mature it could become a weed- but I just love them whenever they pop up.
Sudan grass (sorghum)- grows kind of like corn with a stalk and wide leaves. It produces massive amounts of biomass if you want to cut for the compost or mulch. It also has a beneficial effect on carrots that follow it in rotation.
Clover- is a nitrogen fixer and beneficial attractant. I have a large area with white Dutch clover, which is low growing and somewhat of a perennial as it self-seeds and spreads by running. I plant right through the clover-mat by spading out a spot to put transplants. Tomatoes and brassicas love it. Usually I hand trim it several times a season, placing the cut clover around the stems of the vegetables.
Those are my faithful standbys. I hope to experiment with others, but things like vetch and rye need more attention than I can guarantee. If not cut back at the exact right time they become difficult to remove, especially for our hand tool operation. I have read (in that great NOFA publication- TNF) that mixing more types of seed into a planting increase the overall benefits, so I think I’ll start throwing some radishes into the mix. They go deep and bring up subsoil minerals which then become available to soil microbes when the roots winterkill. I also do succession cover cropping. Sometimes I’ll start with an early oat and pea planting then in June cut it very low to the ground, which prevents regrowth. After waiting until the stalks dry out I’ll then plant buckwheat right on top shuffling it with a rake and hope for rain. After the buckwheat has flowered, I cut it and do the same thing replanting the oats and peas.
Marc Fulford, who taught a NOFA Nutrient Density workshop with Dan Kittredge, shared how he prepared his future garlic bed by planting oats and field peas mixed with any needed soil amendments in late August or September. The garlic is planted through the cover crop, which has the opportunity to grow before it is winter killed. Their roots nurture the soil while holding it in place throughout the winter months. The tops die back making winter mulch for the garlic (you might need to add more) and as they decompose, they add nutrients back to the soil. My first year, the cover crop grew too tall to plant through it easily; so I cut it back first. Last year, it was about four inches tall and I was able to plant through it, while it continued to grow. I had a fantastic garlic year, without watering, even with the draught.
I hope I’ve sold you on the value of cover cropping in your home garden.
Experiment and see what works for you, I know you won’t be disappointed. Oh, this morning cutting back those peas, I snipped off the top couple inches and will have them for dinner tonight in a stir-fry; I don’t think my soil enhancement program will suffer and my taste buds will be thrilled. Yum, those fresh pea greens!
published June 2013 NOFA/Mass e-newsletter http://www.nofamass.org