Soil Building

digitS'

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I believe that John Jeavons, author of "How to Grow More Vegetables . . ," wrote that a gardener should devote 30% of the garden to the growing of compost crops. These were plants sown for the primary purpose of composting so as to increase soil fertility in the garden generally.

I was recently reading about a farmer who has been following a consistent crop rotation schedule for over 20 years. He grows crops on a field for 3 years and then takes it out of production for 3 years. During that time, he plants cover crops - 6 times!

Fall - Winter rye
Spring - Sudan grass

The ground is tilled both Spring & Fall and replanted. This continues until a final Fall plow down and the field is planted to a cash crop the following Spring.

Winter rye has a seeding rate of about 100 pounds per acre. Sudangrass can be sown at about 50 pounds per acre. Seed costs for both Sudan grass and Winter rye cost about the same - $25/acre. So, 6 sowings are costing the farmer about $150/acre not counting fuel costs.

The farmer could keep the field in production continuously but fertilizer costs alone would be about $150/acre. He would have some of the costs of cultivation either way but there would be income. He has found it better to take the field entirely out of production to gain the benefits of effective weed suppression, a soil organic content of better than 5%, and reduced fertilizer costs during production.

These 2 approaches, 30% of the ground used for compost crops and 3 years on/off production, make a lot of sense to me. How 'bout you??

Steve
 

Reinbeau

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It depends on what garden you're soil-building in. I'm a great believer in cow manure and mulch in the veggie patch. I mulch between rows with grass clippings, I layer on chopped leaves in the fall along with fresh manure, however, in the perennial borders I use the well-composted cow manure and a layer of leaf mulch. I can't take the iris bed or the peony border out of production for three years so I have to build the soil around the plants :D
 

digitS'

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Ann, for the organic gardener, composting and mulching will often be the best route but there never seems to be enuf!! I remember someone commenting on Ruth Stout's book "No-Work Garden" that she'd never WORKED SO HARD moving mulch into the garden.

Off-the-farm inputs for an organic farmer like manure, compost, etc. all require a source, handling, transport, and $$. Sometimes, mobility or other problems can make that unsustainable even for the gardener. Jeavons and this farmer aren't purchasing and transporting much other than seed.

I think it is somewhat interesting that the farmer didn't grow a legume for a cover crop. However, I've had some experience with Winter rye and oats for soil building. I can understand why he may be more interested in grasses. If he uses synthetic nitrogen fertilizer for these crops, it could all be a fairly easy process.

A limiting factor for gardeners may simply be square feet of garden space.

Steve
 

Reinbeau

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digitS' said:
A limiting factor for gardeners may simply be square feet of garden space.

Steve
I think that is very true for most on this forum! I live in a semi-rural area and there are still plenty of sources for manure, etc. I've tried cover crops but to me they were a pain in the butt, they cut into my schedule due to the time they need to be worked back in and rot. For large scale where you can allocate the space for renewal I'm sure they're wonderful, there are many seminars up at MOFGA (Maine Organic Farming and Garden Association) about cover cropping and rotation during the Common Ground Fair (I know they have ongoing sessions about it too). Since I'm not a large scale farmer I only know what I've read.
 

digitS'

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Ann, with Winter rye, I found it very helpful to plant it early in the season. In my garden, that was by August 1st.

By May 1st, the rye was waist-high and because of the the nature of my garden soil - it was very easy to simply pull out. The massive root structure could be a problem in other soil types but not in this gravel pile.

Planting the rye too late meant not being able to get ahold of the plants. So, I was essentially trying to kill a grass by tilling it in. That was difficult and it took a few weeks and repeat passes with a rototiller.

Using oats planted late was easy because Winter killed the plants. I didn't get nearly the amount of organic material, however.

I can see how Sudan grass would work much the same as oats since it can't survive the Winter. I've grown millet but not for soil building. My guess is that it would also be a fairly easy approach to increasing organic content or making compost. Some of the garden, I run the lawn mower over late in the season. And, talk about easily available and cheep (uh, cheap) seed . . .

A farmer not far from my large veggie garden did something that really surprised me one year. He had an old alfalfa field and pulled a chisel plow thru it. That didn't kill the alfalfa but it loosened the ground sufficiently that he was able to run his seed drill across the field. What did he plant? Corn!! I could hardly believe it! But, a couple months later he plowed down the alfalfa and corn (which was 3 or 4 feet high). For several years now, he has planted Spring wheat on that ground.

Right now, I'm planting every square foot of my gardens to flowers or vegetables but that's got to end. I get a pickup load (or 2!) of cow manure every year but it's no where near enuf. Buying synthetic fertilizer for the flowers and organic fertilizer for the veggies has been my only way out of the dilemma of depletion but I'm doing very little for soil.

I'm all for the easiest way out of this problem and buying some seed and growing my own soil amendments looks like it.

Steve
 

Reinbeau

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Ah, I see the difference between our zones, that accounts for the May 1st date in your post. I usually can get my peas in in March (in by St. Patrick's Day, peas and salmon for the Fourth of July). Lettuce, cole crops, etc. are all in by the end of March or the first week or so of April.

I think the cover crops will be a great experiment, post back here and let us know what you end up doing and how things progress!
tools.gif
 

digitS'

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Yep, for some time I could plant one-half of a small garden in Winter rye every Summer. Then, pull those plants on May 1st (or thereabouts) and have time to dig out the beds, bury the rye with a little fertilizer, and then plant warm-weather veggies like tomatoes about 3 weeks later.

Cool-weather veggies could go in during late April but those crops would be entirely out of the ground by late July. Nothing much can be planted here at that time because it is so hot and dry. (Altho', I have been surprised to find that I can start peas at that time.) Winter rye is tuff! It would come up just fine during August and make an excellent stand by the September frosts.

So, it was fairly simple to have Winter rye follow early crops of lettuce and such. Then tomatoes, peppers, and eggplant could follow the rye . . . I suppose quite a few gardeners do something like this.

One pleasant surprise was that if I dug down to the buried rye the following Spring, it was still there - or, at least, the decomposing roots and a little of the stems were still there. This was 10 months later! I don't know if the same would be true where the soil tends to be warmer - doubt it. But, I felt really good about this rotation.

Then, I got really, really serious about succession plantings of veggies. Now, I've got essentially NO open ground at anytime during the growing season. I think I've lost something good.

digitS'
 

patandchickens

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I'm going to play Devil's advocate here - not that I don't think that green manuring is a good thing in some circumstances, just that I think it often translates poorly from farm to many gardens.

First, it needs plentiful garden space and/or season length. Unfortunately some people, like me at present, have very limited area available for vegetables (too little to fallow any for a year) and a winter that comes in hard and early. Winter rye would be my best shot, but I'd have to rip out the tomatoes early (gee, mine don't start getting going til August!) and not plant again til early summer, which would leave me with not much besides beans to grow! Phoo.

Secondly, if you have easier 'free' ways to add organic matter to the soil and don't have problems keeping temporarily-bare soil covered, why bother with green manure crops. I have chicken cleanings and lots of weeds and whatever shavings or hay gets soaked when the barn has its annual spring flood. Other people have things like neighbors' (un-chemical-treated) lawn clippings and leaves, and weeds, and kitchen scraps, and whatever else you can skim from neighbors or local businesses. These things take a lot less money, time, attention and work than digging in cover crops.

Third, using green manure crops takes attention and punctuality, in my experience... things that farmers tend to be much better at than most recreational gardeners :p Let your cover crop grow too tall and gnarly, or worse procrastinate til you discover it's set seed, and all of a sudden it is really hard work to cut down, chop up and dig in; takes much longer to break down; and may become a horrible weed (do not even talk to me about buckwheat please ;)).

Fourth, it adds carbon and the physical benefits of humus to the soil (legumes may also add a little nitrogen, IF dug in thoroughly and promptly), but it does NOT add any other nutrients - not even the ones contained in that humus. All of the other elements that plants need -- potassium, copper, iron, molybdenum, etc etc -- are just taken out of the soil by the growing cover crop and eventually returned to it once the cover crop finished decomposing. No net gain. Until that decomposition is complete, these nutrients are actually depleted from the soil, which may sometimes matter.

Finally, it requires a lot a lot of hacking and digging or tilling, which can be physically difficult for some home gardeners and which is often not good for the soil. I try to disturb my soil as little as possible, partly for the sake of soil structure (and to avoid creating a hardpan layer, which I fear would be quite easy on this clay!) but also because we have so many weed seeds in the soil and I hate bringing any more of them than necessary to the top where they will sprout. (I enjoy weeding, actually, but have very limited time for it these days). 'Regular ole' organic matter can either be composted then just put on top of the soil for worms etc to mix it in, or put uncomposted on the garden in fall then just roughly spaded under in spring, which I don't feel is giving me as many weeds as if I did more extensive digging/mixing/tilling.

There certainly are home gardeners who may get good use out of green manure crops, especially if you have a very large veg (or I suppose bedding-plants) garden and are going to be very assiduous and punctual about managing the process.

But there are also LOTS of people out there like me who are really better off without it.

JMO,


Pat
 

Reinbeau

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I agree, Patandchickens, I just said it in fewer words. I garden, as opposed to running a hobby farm on my puny .6 acre. However, there are those here who have the land and want to experiment - I wish them well! :dance
 

digitS'

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Pat, I'm a great believer in pine needles for mulch but my gardens have grown over the year to the point that I would need 18-wheelers for transport.

I was looking at a Mother Earth News article on mulching using the Ruth Stout method. They are recommending a minimum of 25 50-pound bales of hay for mulching a 50 feet by 50 feet garden. That's a fairly good-sized home garden but I'd consider those 25 bales as a REAL minimum. Regardless of what one sees as the drawbacks of using hay, nearly one ton of mulch is a lot of material to move.

You've moved wet manure out of a corral? At the end of a stick that some folks call a shovel? Then shovel it out of a pickup and move it around with a wheelbarrow? Oh Gosh!! Not only is it difficult to find and transport but it's difficult to move.

I'm just remembering an easier time and circumstance of building the organic content of my garden soil. Granted the gardens were smaller but I'm not going to give "ground" both ways. I had smaller gardens and grew more green manure . . . huh?

Despite conscientious accumulation of kitchen scraps, collecting manure & bedding from a tiny flock of birds, and raking the leaves of 2 large trees in my yard there's no way that I could make any real contribution to a large garden. The lawn is mowed as often as possible just to keep the clippings right where they fall but I could compost them and that would help for the garden. Far more material could be grown specifically for composting if that ground wasn't growing dwarf grass. (And, in no way am I trusting my neighbors NOT to use Weed 'n' Feed with all its herbicide, not to mention all the dandelion killer they are spraying!)

There are no pine trees in my yard so that requires that I haul the needles from elsewhere and I'm often the guy doing the raking to get that done. A lot of my time could be spent collecting compostables - honestly, I'd prefer to spend time and fuel hauling the cow manure instead but I simply cannot physically do that much material handling. Just can't.

Composting often requires the addition of a high N fertilizer and that is especially true if one is collecting truck-loads of dry leaves. Live green material would cut down on the amount of nitrogen required but harvesting a crop is removing soil nutrients one way or another. And, one way or another, they need to be replaced.

Oh, and dont be pulling your tomatoes at the end of July to plant a cover crop pull your gone-to-seed lettuce.

Steve's digits
 

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