A new idea in green manure

[Pulsegleaner]

Hi guys,

I wanted to bounce an idea I had a couple of nights ago off of you, to see if it actually makes sense.

It concerns the idea of green manure, plants (usually legumes) planted in advance of the intended crop to be tilled under to make the soil better.

It suddenly occurred to me that there might actually be an ADVANTAGE to selecting green manure species that are too day length sensitive for ones area. That way you don't have to worry about any plants you miss seeding themselves and interfering with the intended crop, or becoming weeds themselves (a real possibility for some of the more vigorous ones.) Or if you are growing to eat, having to pick them out (I have come to realize that something like 80-85% of the off seeds I have found in my searches are either from other crops or from plants that might have been put in as green manure or fodder.)

Granted, you lose the ability to save seed of your green manure for the future and so have to buy fresh seed every year. But as far as I know, most modern farmers do that anyway.

I'm planning to test this out this upcoming year, using a cocktail of tropical green manure species (like Macroptilium atropurpureum,Calopogonium caeruleum, Centrosema macrocarpum and Alysicarpus rugosus).

 

[flowerbug]

for me the optimal use was a separate area where i could harvest what was needed. in most vegetable gardens you can plant a mix of species so that you are not putting a huge demand for nutrients in the entire plantings. so via select amending with worm castings and green manure in only certain spaces you should be able to get by when you inlcude crop rotations. at least that is what i've been doing for quite a long time and it works.

not that green manure and cover crops aren't important and useful, i wish i could do a lot more with them here, but the management doesn't like the looks of some things in the off season that i would not mind at all. a cover crop of field peas from the fall protecting the garden through the winter would be just fine with me, and the same with winter-wheat and winter-rye. both very useful cover crops and soil conditioning plants, but she doesn't like the results.

 

[digitS']

It makes some sense to little olde me (in the dark re the species mentioned). Here's why:

I have read that gardeners generally overestimate the N value to the soil of legume crops. One reason is that they require months to do much gathering of atmospheric nitrogen and don't usually have sufficient time.

What that makes me wonder, besides improving soil tilth, if the most important value is from the seeds planted. Dense planting of a green manure crop is recommended partly because the plants are intended to be turned into the soil in a short amount of time. However, sowing something like 5 pounds on 1,000 square feet wouldn't bring much outside nutrients to the garden. Twenty pounds of seed would. Full growth would be hampered but for 6 weeks or so, that would amount to little. It may be considerably more expensive but, for a home gardener, it should be very comparable to applying many commercial fertilizers or even cheaper.

Steve

 

[flowerbug]

It makes some sense to little olde me (in the dark re the species mentioned). Here's why:

I have read that gardeners generally overestimate the N value to the soil of legume crops. One reason is that they require months to do much gathering of atmospheric nitrogen and don't usually have sufficient time.

What that makes me wonder, besides improving soil tilth, if the most important value is from the seeds planted. Dense planting of a green manure crop is recommended partly because the plants are intended to be turned into the soil in a short amount of time. However, sowing something like 5 pounds on 1,000 square feet wouldn't bring much outside nutrients to the garden. Twenty pounds of seed would. Full growth would be hampered but for 6 weeks or so, that would amount to little. It may be considerably more expensive but, for a home gardener, it should be very comparable to applying many commercial fertilizers or even cheaper.

Steve

yes, most green manure crops are used in the fall as nutrient trap absorbers and then they can be turned under in the spring. if you are only spring sowing seeds then you've missed that functional difference and are doing them for weed suppression and soil conditioning and some trace organic matter which is always useful.

for the trace amount of nutrients and organic matter that probably fits pretty closely with many composts. composts are long term soil nutrition IMO. same with cover crops sown early spring. useful, yes, not a huge nutrient gain, but it's ok.

 

[Zeedman]

What that makes me wonder, besides improving soil tilth, if the most important value is from the seeds planted.

A good point, if the seeds are planted at a high density.

An interesting experiment. The use of short-day crops as green manures in the higher latitudes only makes partial sense IMO. Based upon my observations, tropical plants often react to longer days by producing rampant vegetative growth; so a lot of green material. But because green manures are normally turned under while immature, the lack of seed production is irrelevant. For legumes, the concentration of nitrogen is generally highest when flowering.
link

Then too, since tropical seed must be imported (and would likely enter the country as food, not seed) the risk of introducing disease may be a contra-indication, and should be weighed in terms of benefit/risk.

Perennial legumes make the best green manures, because they they have deep tap roots & also function as Winter catch crops. A Winter-hardy grass (such as winter wheat) is a good Winter catch crop if it follows legumes, and will add a lot of organic matter when turned under. Beans, sad to say, are one of the least effective green manures.

 

[Pulsegleaner]

A good point, if the seeds are planted at a high density.

An interesting experiment. The use of short-day crops as green manures in the higher latitudes only makes partial sense IMO. Based upon my observations, tropical plants often react to longer days by producing rampant vegetative growth; so a lot of green material. But because green manures are normally turned under while immature, the lack of seed production is irrelevant. For legumes, the concentration of nitrogen is generally highest when flowering.
link

Perennial legumes make the best green manures, because they they have deep tap roots & also function as Winter catch crops. A Winter-hardy grass (such as winter wheat) is a good Winter catch crop if it follows legumes, and will add a lot of organic matter when turned under. Beans, sad to say, are one of the least effective green manures.

It's irrelevant if you manage to get ALL the plants turned under. But people tend to be sloppy, and a few plants usually make it through. And that CAN be a problem if the seeds of you cover crop are toxic (like say vetch) and you are using your crop for food.

From what I have seen in my searches, farmers in India and China will use almost ANYTHING for their green cover. For example Back in the early days the rice beans were simply LOADED with Mimosa (both a little pudica and a LOT of invisia sensitive plant's bigger spinier more aggressive cousin* There was Puerrina phraseoloides the tropical form of kudzu. There was Indigofera viciosa , an indigo, but not one you can use for dye.

And then there are the head scratchers, like the fact that some Indian farmers appear to be using field peas as a green manure for......field peas.(at least, that is the best explanation I have for the occasional showing up of an older, colored skinned pea in a crop that is otherwise pure modern white.)

* And I mean LOTS. I filled one and a half pint bottles with Mimosa invisia seeds I found, and the seeds are only about as big as sesame seeds.

 

[flowerbug]

it may just be that a few odd ball crosses or mutations showed up and didn't get sorted out. with modern sorting technologies being used, as you noted in another thread/post a bit ago, not much unusual stuff is being found in the sorted bags any longer.

here, it's fairly chaotic and i don't mind at all if i find some off types when i'm sorting. i have so many i can't possibly do anything with them but i also have a very hard time getting rid of them (via the worm farm or cooking and eating them).