Green Manure In the Garden WDEV Vermont Radio Talk

Using Green Manure in Your Garden (In the Garden 2018 Episode 7)

Green Manure and Cover Crops

Often in the garden you have a bed that is empty after harvest.  If you don’t have anything that you plan to plant in that bed consider using a green manure crop, sometimes called a cover crop.  A cover crop was initially used to prevent erosion of open land after a harvest but in now used as a ‘green manure’ to both hold the soil to prevent soil erosion but also to enrich the soil, adding nitrogen, organic matter (sometimes referred to as biomass I used to call it humus), as well as improving soil structure.

An added benefit can be the suppression of weeds, help prevent nematode infestation and helps condition the soil with deep tap roots.  As the name green manure indicates the comparison that legumes are used to add nitrogen to the soil much like an animal manure add nitrogen to the soil. With all that organic matter in the soil it definitely encourages earth worms and they are on of the best soil conditioners, both aerating the soil but adding their worm castings as well.

What to Use as Green Manure Crops

The most common green manures are legumes to add nitrogen as mentioned. Field Peas, Clovers, Vetch all add nitrogen to the soil. Grains like Winter Rye or Oats are used to add organic matter, suppress weeds. Mustard is used to suppress nematodes, add biomass and help suppress weeds. One unusual green manure crop is Daikon Radish.  I can grow10” deep into the soil and 2” around, It is useful in breaking up clay soil and hardpan as well as adding a huge about of organic matter to the soil.

Another thing to consider with green manures is that they can be used in a crop rotation plan. Crop rotation is important in organic gardening to help prevent soil borne diseases cause by planting the same crop in the same place year after year. 

Learning to use green manures is well worth the effort for the gardener on many levels.  It adds fertility, conditions the soil, adds organic matter to the soil.  They also help with weed and nematode suppression.  What more could you want?

Listener Questions

Garlic Harvest

Q:  Mora in North Ferrisburg wanted to let us know that her husband enjoyed the show but she worked on Saturdays except today so she had a question about garlic.  Mora bought four types of from a nursery in Oregon and planted them last fall.  She wanted to know how to tell when to harvest the bulbs. 

A: Garlic is ready to harvest when one third of the leaves turn brown.  Also it is a good idea to check clove formation by actually pulling on of the bulbs to check that the individual wrappers are forming around the individual clove. If the cloves are not formed it is too soon to harvest.  On the other hand if you see that the bulb is opened up and you can see individual clove the it is ‘over ripe’ in a sense.  Although this doesn’t spell disaster it usually considered to effect the long term storage life of the bulb.

Nitrogen and Tomatoes

Q: Fred in Monkton Ridge said he put too much nitrogen on his ‘Mexican Tomatoes’ because he misinterpreted the application rate. 

A: It is hard to unring that bell, but you can use a few tricks.  One is to use a wood chip or sawdust mulch, both are notorious for leaching nitrogen from garden soil. Two is you can water very thoroughly twice a week to leach away some of the nitrogen.  You can try to plant squash plants close to the tomato plants, they are heavy feeders and will grow in a manure pile.

Kale Worries

Q: Brenda in Huntington planted Kale sets and they seem to be wilting not growing.

A: It sound like the Cabbage Root Maggot.  Pull one of the affected plants and inspect the roots.  The maggot will wiggle and are about 1/ 4” long.  At this point it might be too late to do anything about it but I have been able to save some of my plant by mixing in some wood ashes in the soil around the roots and water.  It is worth a try.  The best treatment strategy is prevention like crop rotation and barriers like a hoop house and woven fiberglass cloth like Reemay or Argibon row cover cloth. But for immediate releif try the wood ashes. Then use a foliar spray fertilizer like fish emulsion or liquid sea kelp to give the plants a boost.

Blueberry Bugs

Q: Forbes in Corinth is battling Voles in his blueberry patch, he was wondering about using Spearmint oil to ward off the Voles.  He also wondered if I had heard any preventative measures for the Spotted Wing Drosphila, a fruit fly sized insect that lays egg inside fruits like blueberries and raspberries. 

A; The best approach with Voles as with Mice or Chipmunks is to trap them and eliminate them to cut down the population of the colony. The colony will come back so it is a periodic effort that you should expect to do every few years.  Eliot Coleman’s book Four Season Farm describes the trap he used in his greenhouse and I haven’t seen a better one!

Mole Confusion

Q: Evan in Montpelier called to correct me, again, for disparaging the poor mole that only eats earthworms.  It is only the VOLE that that eats plants and roots.

A: I stand gratefully corrected!

Racoons in Morrisville

Q: Joe and Angela both of Morrisville called separately to say that it seemed that the Pro Gro from Northern Organics had changed it formula because it was attracting More racoons that usual. The racoons were actually eating the pelleted fertilize!

A: The only answer I could offer was to call them and ask them about it.

Soil Nutrients

Q: Rich in Starksboro wanted to know how to add the Kelp meal, Azomite and fertilizer after plants are planted.

A: All of the amendments can be side dressed at any time in the season.  None of them risk burning the plants.  Once spead just water them in with a spray nozzle on the hose or watering can.

Refreshing Your Beds

Q: Norm in Bristol was wondering what to add to the raised beds next spring for soil amendments.

A: I recommend for a 4×4 bed, a cup of fertilizer at least.  Check your pH and if it is not 7 then add a cup of lime.  Rock powders, Azomite, Greensand are slow acting and one application when the bed is made will be effective for several years.

Thanks, that it for this show. See you In The Garden next week Saturday at 12:30.