I was actually researching green forages as alternative feed for
chickens when I noticed there is a large overlap between green forages and
green manures. Seeing that nothing is happening in the garden for most of winter I
decided to look into green manures a little bit more in detail to grow during the winter months as a cover crop. Here is what I found and thought that I should share
J
Green manures, also known as cover crops, are grown as part of a good
soil management and crop rotation scheme.
 |
Sunflower flied Green manure
Helianthus annuus
Flickr upload bot
Wikipedia |
Green manures fall into two main categories: Legumes (Nitrogen Fixers)
and Non-legumes. The legumes add nutrients to the soil by converting
atmospheric nitrogen (N2) to bio-available ammonia (NH3)
in the soil. This is performed by bacteria, Rhizobia
spp., that lives symbiotically with the plant contained in root nodules.
Non-legumes are not able to fix nitrogen, but accomplish all the other tasks of
green manures.
Green manures provide the following services:
ü Replace or hold soil nutrients
ü Improve soil structure (loosen hard soil, soil
conditioner)
ü Add organic material to soil
ü Suppress weed growth
ü Support the soil community (decomposers)
ü Insectaries (shelter and house beneficial
insects)
ü Mulch soil & prevent wind or soil erosion
ü Increase soil water retention
ü Keep soil temperatures warm
ü Flower to attract pollinating insects
ü Some have inhibitors that prevent soil disease
& pest build-up
Most vegetable gardens are dug over and the bare soil left as is for
the remainder of winter. This may lead to soil and nutrient loss due to
leaching and erosion. Green manures prevent this and it not like the plot is
used for anything else…
Although legumes add nutrients to the soil, they are generally slow
growing in autumn and provide less organic material (or biomass) than non-leguminous
plants. Therefore it is preferable to use a combination of both – to get the
best of both worlds J.
Some green manures have very deep reaching roots that grow into the
subsoil and harvest nutrients inaccessible to other plants – for this reason
they double dig.
Generally you can grow green manures in the warm or cool seasons. This
means that the tilling (cutting down and working into the soil) of the summer
manures occurs during autumn or winter frosts kills off the manure and winter
manures are tilled before spring planting. The plants are usually tilled before
flowering to prevent seed formation and the manures becoming weeds. Green
manures are tilled a month before sowing any new vegetable to ensure that they
have broken down and will not burn the following crop.
 |
Lacy Phacelia
Phacelia tanacetifolium
Curtis Clark
Wikidepia |
Here is a table with most of the well-known and widely used green
manures (those that aren’t in the table have been provided with links below).
An all-in-one resource J:
Name
|
Scientific Name
|
N2 Fixing
|
Winter Hardy
|
Season
|
Dig In
|
Chicken: Green Forage
|
Alfalfa
|
Medicago sativa
|
Y
|
Y
|
Winter
|
BF
|
Y
|
Buckwheat
|
Fagopyrum esculentum
|
N
|
N
|
Summer
|
BF
|
Y
|
Clover (White & Red)
|
Trifolium repens (W)
Trifolium pratens (R)
|
Y
|
Y
|
Summer (Mild winters)
|
AtF
|
Y
|
Fava Beans (Field, Broad beans)
|
Vicia faba
|
Y
|
Y
|
Winter
|
AT©
|
Y
|
Fenugreek
|
Trigonella foenum graecum
|
N
|
N
|
Summer
|
BF
|
|
Field Pea
|
Pisum sativum subsp. arvense
|
Y
|
Y
|
Winter
|
AT©
|
Y
|
Lupin (Bitter Blue)
|
Lupinus angustifolius
|
Y
|
Y
|
Summer
|
BF
|
|
Mustard
|
Sinapis alba
|
N
|
N
|
Winter
|
BF
|
Y
|
Oats
|
Avena sativa
|
N
|
N
|
Winter
|
BF
|
Y
|
Phacelia
|
Phacelia tanacetifolium
|
Y
|
Y
|
Winter
|
BF
|
|
Rye
|
Secale cereale
|
N
|
Y
|
Winter
|
BF
|
Y
|
Soybeans
|
Glycine max
|
Y
|
Y
|
Summer
|
AT©
|
Y
|
Sunflowers
|
Helianthus annuus
|
N
|
N
|
Summer
|
AF
|
|
Sunn Hemp
|
Crotalaria juncea
|
Y
|
N
|
Summer
|
BF
|
|
Trefoil (Bird’s foot)
|
Medicago lupulina
|
Y
|
Y
|
Winter
|
AT
|
|
Tyfon
|
Brassica napa
|
N
|
Y
|
W or S
|
AT
|
Y
|
Velvet Bean
|
Musuna puriens
|
Y
|
N
|
Summer
|
AT©
|
|
Vetch (Hairy, tares)
|
Vivia sativa
|
Y
|
Y
|
Winter
|
AtF
|
N
|
Abbreviations are as following:
BF = Before flowering
|
|
AT© = Any time, can let crop
|
|
AtF = At flowering
|
|
ArF = After flowering
|
|
On that note, some of the beans and peas can be left to crop as they
are easy to collect and will prevent them from going weedy. Some of the legumes are susceptible to soil borne pathogens and should not be followed by another legume crop, such a susceptible crop would be Vetch.
Sunflowers produce an allelopathic compound that suppresses weed and
other plants growing nearby (good to keep in mind not to plant among other
vegies!) Vetch needs to be cut at flowering for it to reach its full biomass
and N2-fixing capabilities.
Alfalfa and sunflowers are drought resistant and can grow in more arid
regions. Alfalfa and clover flowers attract a lot of bees! Rye and oats are
easily killed by cool conditions (can easily be frost-killed), therefore winter
rye and oats cultivars need to be grown in winter (those are featured in the
table).
I am specifically going to mention Alfalfa, because of its green forage
(alternative feed) potential for chickens. I will cover green forages for
chickens in another article (see
The C Files: Feed & Water). Alfalfa has a very deep rooting system and can
grow to 4-9 meters tall. After the formation of its crown, it can withstand continuous
grazing. It is a perennial that can live for up to 8 years and the flowers are
very attractive to bees (used in bee pasturages). Alfalfa is not readily
pollinated by western honey bees as the anther (structure with pollen) strikes
the bee on the head when it collects honey. Bees don’t like this and learn to
steal nectar from the side of the flower – thus the alfalfa leaf cutter bees
are provided to pollinate alfalfa. I do not know whether this applies to African
honey bees, but hopefully this will limit the seed-2-weed part. Also alfalfa
seeds fail to germinate in already existing stands due to auto-toxic compounds.
Since Alfalfa is drought tolerant, can grow in the winter and provides
green forage to chickens. So I decided that it should go well with my vegetable
garden.
 |
Alfalfa leafcutter bee
Megachile rotundata
Esculapio
Wikipedia |
Those not covered in the article you can get full details about here:
Ryegrass, arugula, buckwheat, field peas, forage radish, forage turnip/rape, hairy vetch, mustard, oats, red/white clover, sudan grass, teff ,reed canary grass, rye, wheat
Check out
Composting for more soil conditioning tips.
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