This is an interesting issue and I not a simple one. The numbers Elderoo is quoting are based on some particular piece of land (or an average) and may not be particularly correct for
yours (though it will still probably that general order of magnitude). And anyone reading Andy Lee's chicken tractor book should be aware that he was, um, a very optimistic guy
Here is another way of looking at it. I apologize in advance for the length.
There are basically 3 things chickens "do" to land: devegetate it by eating and scratching; poo til the nutrient ratios and pH are so out of whack that no plants can grow there; and compact the soil. These things depend on the number of chicken-density-hours the run experiences (# chickens per sq feet times how much they're in there), but they depend on other factors TOO, and the three processes proceed at different rates so it depends on what exactly you're trying to save your soil FROM.
Devegetation is fastest. At first, most of the plants gone but the roots of perennials such as grass are still in ok shape so they'll regenerate once the chickens are gone. Beyond that, the plants get eaten down so badly for so long that the roots' reserves are gone and when you remove chickens not much comes back besides a few thistles etc. (Poor-to-no regrowth can also result from soil damage, but here I'm just talking about the plants getting et to death).
If you have healthy long-established grass roots in decent soil, grass can still come back after getting eaten VERY bare. (Depends on your type of grass). But
if you do this too often (allowing things to be eaten down to dirt) or too frequently, the grass' roots will start to run out of steam and you're in a downward spiral towards nuthin' but thistles (followed by nuthin' at all).
Reseeding or laying turf are possible as long as the soil is basically ok (see below), but they will NOT produce anything like the durable grass you had before, unless you can give them a YEAR unmolested (and regularly mowed) before you put stock onto them. If you don't give them that time, you will be halfway along the spiral-down-to-oblivion already because they do not have healthy well established roots, so they will not be able to bear near the chicken-traffic that your original lawn did.
Nutrient poisoning and soil compaction are the slower of the two processes. Depending on your stocking density (which for the following discussion I will assume is REASONABLE, i.e. I am
not talking about meat chickens at all nor about layers given only 2-4 sq ft per hen total space) and all that, it can take weeks to months til significant signs appear. It would take a lower stocking density than most people here have in their runs to defer it more than a year, absolute max.
On clayey soil it these are much more of a problem than on very free-draining sandy soil. Clay will compact hard and then tend to stay that way, whereas sand pretty much doesn't compact at all. On clay, most of the nutrients in the chicken poo will just sit there forever (especially once the soil is compacted and the vegetation killed), whereas on sand or any other very free-draining soil the rain, assuming you live in a climate that gets some <g>, will gradually leach them through and out, to a significant degree.
You can go a fair ways towards
preventing nutrient poisoning and compaction (on any soil) by letting plants do the work for you i.e. never letting the place become devegetated and giving it a good long rest in between. This requires that either that your chickens are not *in* a run (e.g. they're in an electromesh paddock in a larger fenced field) or that you have 2 or more runs to rotate between, or that you use a tractor (see below). If rotating 2+ runs, you will also need a sacrifice run that the animals can be kept in when no good pasture is available. For chickens, this would be a run filled with sand or gravel or roadbase. They are allowed into one of two-or-more grassy runs when the grass and the land can gracefully bear it; when that grass and/or land needs a rest, they go into the other grassy run; when that one needs resting, if the other hasn't regenerated enough yet, you confine the chickens to the sand run til a gracefully-healed grassy run is available.
It is not possible to give a time schedule for pasture or run rotation. It will vary throughout the year and between regions and between soil types, as well as depending what kind of shape your grass and soil are in right now. With horses and cows, the general scheme is to remove them when grass gets mowed down to 2-4" and put them into a new paddock where grass is 6-10" tall (depending). With chickens you have to look at the extent of the scratched-bare areas as well. You pretty much have to experiment, because there is such a high diversity of soil types and grass types and grass health out there in chicken runs. I would propose that if you do not see grass regrowing most-everywhere within 4-6 days of removing the chickens (assuming decent soil moisture) then they may have been in there too long and the grass roots may be poopin' out.
Note that the above, rotational-grazing methods require a LOT of extra fencing, and/or a tolerance to the possibility of losses to harder to exclude predators (weasels, hawks, etc).
A tractor lets you do all this quickly and cheaply. Andy Lee and all the many other proponents of tractors and arks are happy to tell you so.
However what they
don't tell you is things like: a tractor cannot give your chickens very much space per chicken, and cannot house large numbers at once unless they are quite packed in there or you have a lotta tractors (to have to manage). If it's not inside an electric fence, a tractor is also more vulnerable to predators than a run. Furthermore the tractor COMMITS you to moving the chickens, so it is no good going away or getting distracted or a week later you will discover you've really trashed a rectangle of ground. I find that tractoring the lawn actually promotes weeds (!), unless I fertilize appropriately afterwards, which you would hope to not have to do after the darn chickens have just been there
. And finally, a tractor is at best only marginally usable (many tractors, "unusable") as winter quarters in a very Northern climate.
As for this "the chickens will prepare a garden bed, no tilling needed", it depends. On sandy soil, or a really nice loam, I expect it works as advertised. On
clayey soil, however, not so much. Ask me how I know
If you leave the chickens in one place long enough to put a permanent dent in the grass, they compact the soil significantly, and you end up with a layer of not yet composted chicken-poopy organic material lying on top of mashed-down clay. When it rains, voila, stinky soup in a bowl. It is NOT even remotely planting-ready, unless you have very low expectations for the plot. I had to go turn the darn stuff in with a shovel after all (to break up the compacted clay), and it wasn't any easier than if the chickens had never been there.
Mind, I am not anti-tractor (I have 2 hens in a tractor in the front yard right now); but I think the advantages are often MASSIVELY oversold and the drawbacks left for people to discover on their own.
So really, a traditional, single, fixed run may not actually be
such a terrible or unreasonable thing. If you floor it with sand or gravel or roadbase (a mix of sand, gravel and dirt) it's essentially a permanent sacrifice paddock. You would want to throw in plenty of green stuff to entertain and, uh, 'nutrify'
the chickens, but if you weed garden beds you're generating plenty of that anyhow. Or you can cut stuff specifically for them. If the sand gets too poo-filled and you give up on raking it clean, put it in your compost pile and the compost piles of your neighbors (it will be great!) and get new sand.
Alternatively, if you start a run as grass and let it wind down into dirt, you can
repair the soil whenever you need to by liming and tilling. The chickens can go right back on it (assuming you've used the right kind of lime), as it is now a 'refreshed' dirt run; or if you no longer want to run chickens there, you can rest and then reseed it. It's not like the soil is destroyed for all time.
Again, I am
not in any way against pasture rotation or tractors. I do the former with my horses (and eventually will with the chickens once I get more runs built), and the latter with my original chickens. But
I think there are a whole big lot of people who would NOT benefit from these things, and for whom (if the chickens aren't free-ranging, which has its own good and bad points)
a traditional fixed run, be it sand or dirt-floored, can be a perfectly reasonable choice.
JMHO,
Pat
