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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.
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By In the Garden
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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.