How long after tilling in green manure till planting?

crookedgardenApril 14, 2013

Newbie question: This is the first time I'm trying green manure. I'm trying to amend my heavy clay soil which is low in organic matter and for most of the winter had a large tent sitting on top of the plot I'm planning to use as my vegetable patch.
I removed the tent in late winter and a glorious crop of purple flowered vetch took it over in the spring. I'm currently in the process of tilling it in to a depth of about 6-8 in.
If i understand correctly, decaying plant matter ties up available nitrogen in the soil, so my question is: after tilling in the vetch, how long does the soil have to sit before I can plant in it? Are there any tricks to speed up the decaying process so that I can plant in it sooner? Which would I need to wait longer before doing: sowing seeds directly, or transplanting into it?
Thank you in advance for your replies! My kids (6 and 9) are thrilled about growing their own food, and I'm a complete novice, but don't want to let them down!

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Raw_Nature(5 OH)

I never had any experience with vetch, but I heard it sets seed at different times, make sure your not adding seeds to your garden!

Man you didnt even have to buy seed did ya, came up right on it's own! Wish I didnt have to buy seed! I grow rye over the winter and I weedwack it down comes may-June, right after that I add a inch of compost and I plant in that.. My rye is never tilled in, so I don't have much concern about off balancing the soil.. It's not uncommon for me to cut the rye and plant in the
same day.. The rye is an outstanding mulch, and if you have a good,active soil foodweb, your much would be decomposed that same year..

"If i understand correctly, decaying plant matter ties up available nitrogen in the soil, so my question is: after tilling in the vetch, how long does the soil have to sit before I can plant in it? Are there any tricks to speed up the decaying process so that I can plant in it sooner? "

Decaying matter that is high in carbon ties up nitrogen, vice versa.. If you already have a good carbon/nitrogen balence, you really don't have to much to worry about along those lines... I am not experienced in tilling in cover crops,etc, but I can't see why you can't plant right after you till.. There are tons of tricks! The best trick is to kill your cover crop at the right time, before seed matures, but right when there is a nice balence in nitrogen/carbon in that crop.. It could be tricky because there's only so much you could do, it really the seeds that dictate when to cut it, but if you really observe it, you can catch it at the right time for the best of al worlds.. Note: every cover crop is different, that's why it's hard for me to till you exactly, my winter rye could be brown and not have mature seed, while your vetch could be green and already set seed.. But this is what i do: When I start to see my rye seeds drop pollen, swell and turn a little brown(looks half dead,halfs alive) that's when I cut I down... Also besides the timing, you could add nitrogen blood meal, composted poultry manure,etc, I always found compost to work great for my no till rye.. It's almost like the compost inoculated the rye with bacteria/fungi and it breaks it down allthe more faster! Maybe you should look into no till cover crops.. Maybe you don't want to till your vetch in.. Either way, your smart for planting a cover crop! Youre on your road to succes!!

Research about cover crops, there's plenty of information on the web...

Good luck,
Joe

    Bookmark   April 14, 2013 at 11:08AM
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crookedgarden

@Raw_Nature Thank you for your quick reply!
Yeah, I am lucky to have vetch growing everywhere every spring! I thought I was cursed at first and was planning to just weed it all out again but my kids asked me what the weed was with all the pretty flowers and exploding pods, so I googled it and in the process found out about green manure. I have my kids curiosity to thank for turning the accursed vetch into a boon. :)
I think I managed to just barely kill the vetch early enough. It had flowered, and there were a few seed pods beginning to form here and there, but not many.
So, let me see if I have this straight now, please correct me if not: Decaying browns tie up nitrogen, and decaying greens tie up carbon? Tied up carbon shouldn't be a problem for planting in fairly soon after tilling? Sorry to ask so many questions, but I just want to be sure. Thanks again!

    Bookmark   April 14, 2013 at 11:54AM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

Normally green manures are tilled in approximately 6-8 weeks prior to planting so they have some time to decompose. Is it possible to plant sooner than that, say a 2 weeks wait instead? Yes if certain adjustments are made.

The balance that needs to be maintained between greens and browns, carbons and nitrogens, for the ideal results is a bit complicated so most prefer to just let time take care of it. Let time resolve the nutrient binding process. But when you don't have that time you can compensate for that imbalance by adding additional nitrogen sources.

The ideal ratio is basically 3 parts carbons to 1 part nitrogen. Note "basically" as there are many other variables involved too. So by adding additional nitrogen - high N fertilizer in some form - you can offset that binding issue, give the plants the nitrogen they need, and give the soil the time it needs to balance itself out.

Then you need to take into consideration the nutrient needs of plants you will be planting in that early bed. They need to be nitrogen lovers like leafy greens and cole crops, not low-tolerance for nitrogen plants like legumes, peppers, or root crops. Wait on planting them until the vetch decomposition is well along and the soil balance has begun to stabilize. Normally not a problem as most of those plants have very different planting times anyway.

Following me?

In the future either till in much earlier or don't till, just mow and let it decompose on the top of the soil.

Dave

    Bookmark   April 14, 2013 at 12:18PM
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Raw_Nature(5 OH)

Man, if I waited 6-8 weeks for the cover crop to decompose, I would lose half my growing season! Winter rye has to be cut after the pollen drops, or it will most likely come back to finish it's lifecycle, I'm sure winter rye isn't the only cover crop like this... Its a different ballgame tilling it and just mowing it, but inhear lots of stories about people tilling their rye several times and it's still coming back, that's because they didn't let the plant do it's job! I don't know of to man cover crops that would grow over th winter here.. Farmers don't even plant a cover crop to begin with, the soil stays bare all winter...

Crookedgarden:

If I was you I would weedwack the vetch, rake up the cut biomass, add an inch or two of compost ontop of the cut stems, plant in that, then mulch with the biomass from the vetch...

    Bookmark   April 14, 2013 at 11:37PM
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donnabaskets(Zone 8a, Central MS)

I live in a mild winter climate. I sowed crimson clover seed into my garden last fall. It came up and grew through the winter under row covers, which were placed over them to keep deer out.

About a month ago, I went out with my spade and just turned the soil over. There is no trace of the plant left in the ground now. But the soil is the most beautiful condition it's ever been in. This will definitely become a yearly process.

    Bookmark   April 15, 2013 at 3:34PM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

Man, if I waited 6-8 weeks for the cover crop to decompose, I would lose half my growing season!

Not at all assuming it is planted and tilled in at the proper time. Proper tilling time for winter rye is 10-12" tall and prior to bloom which is normally mid-January to early Feb. depending on zone. Plenty of time for decomp prior to planting. Well-tilled at that time results in no grow-back.

If weather prevents tilling at the proper time and you have to resort to mowing instead then yes, to kill rye by mowing, it should be done at flowering when the anthers are extended, and pollen falls from the seed heads. If mowing is done earlier, the rye simply grows back.

Important timing distinction between tilling it and mowing it.

Dave

    Bookmark   April 15, 2013 at 5:44PM
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Raw_Nature(5 OH)

Proper tilling time for winter rye is 10-12" tall and prior to bloom which is normally mid-January to early Feb. depending on zone"

Dave, you ever grow winter rye? I grow it every year and it is no where a foot tall iin Jan-feb.. Maybe 3-6 inches.. You must be talking the tropics! My winter rye ain't that tall until may-June.. Even if I wait to till it at planting(mid may for warm crops) it will only be, maybe a foot, can only imagine trying to squeeze in a cold crop! At that height you would lose ALOT of biamass, and do much more work to get it to die back.. My rye grow 2-4 feet roughly at pollen drop, thats the best time for carbon/nitrogen balence, easy dieback, as well as the mos biomass.. It is known that winter rye delays cash crop production, perhaps that is why no farmers around here plant it, they don't even plant oats or anything...

    Bookmark   April 15, 2013 at 8:01PM
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crookedgarden

Thanks for the replies! I'm going to wait at least 3-4 weeks after I finish tilling in the vetch before planting anything. I need the time for my indoor seedlings to grow before transplanting anyway. Especially those tomatoes which are taking their sweet time to germinate. :(

    Bookmark   April 17, 2013 at 1:05AM
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Raw_Nature(5 OH)

Glad you found solutions my friend! A lot of climates have different growing conditions,etc.. The secret is knowing what to look for and when to cut down.. After a year or two you will be a old pro! There is good info on the web! Keep growing cover crops, especially if you grow them free, it is very good for your soil! Experiment with different ones.. What zone you in?

Man my tomatoes germinated in two days, sprouted in 3-4 days.. Just threw them ontop soil and kept moist..

Don't hesitate to ask any questions, we are more than happy to help you, or try to that is!

Happy growing,
Joe

    Bookmark   April 17, 2013 at 1:19AM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

Dave, you ever grow winter rye? I grow it every year and it is no where a foot tall iin Jan-feb.. Maybe 3-6 inches.. You must be talking the tropics! My winter rye ain't that tall until may-June.

Yep. Just about every year. Sounds like you need to be planting it a lot earlier. And nothing says you have to wait until it is 10-12" to till it in. Sure you lose some biomass but you still get most all the benefits and that is the purpose for growing it.

Seasonal gardening that involves cover crops is supposed to be a balanced route, optimization not maximization, of all the factors involved.

Sounds like crookedgarden has a pretty well optimized solution.

Dave

    Bookmark   April 17, 2013 at 10:03AM
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Raw_Nature(5 OH)

Very interesting, Dave.

I plant my winter rye as soon as my tomatoes as other warm crops come out, I don't plant to many fall crops, just to devote that time to the rye.. The rye germinates overnight at 60-80 degrees, takes a week 40-50 degrees.. I try to give it as much time to establish a nice thick carpet on my beds.. Perhaps your warmer weather/microclimate really does do that much more for the rye, lucky! When do you plant yours Dave?

Thanks,
Joe

Ps- don't optimization and maximization go hand to hand?

    Bookmark   April 17, 2013 at 10:19AM
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