I'm curious if anyone has an information about the largest polyculture farms that have been able to be successful. Are planning and harvesting techniques good enough to make polyculture economically competitive at scale?
See Mark Shepperd's "Restoration Agriculture" for a good example.
Actual polyculture can be aggravating to run. Example:
Shepperd advocates rows of chestnuts, alternating with hazelnuts as the main trees, but also runs apples with grapes growing on the lower apple branches and raspberries in rows between the apple rows.
Elsewhere he advocates pigs for cleaning up the windfall apples.
Picking apples with the tree shoulder high in grape plants isn't asnwered. Neither is keeping the pigs from trampling the raspberries.
If you are using equipment then you have to deal with a lot of edges. This is why shelterbelts have lost popularity: It's difficult to cultivate next to the trees without damaging the roots.
Mixing grazing and tree crops also have issues. One of the ways to clear land here, is to graze it. In wet weather, the weight of the cow on that sharp edged hoof breaks poplar roots, and breaks off brush stems. If the grazing is light enough, the trees will recover, but it means running at about 1/4 of cows per acre compared to pasture. You can get away from this by using portable fencing and fencing the shelterbelts, or groves of trees when the soil is soft, and permit grazing only in late summer (hard soils) or in winter (frozen soils) But it becomes another management issue.
Multiple grazing systems can work well: E.g. Intensive grazing consists of putting too many animals on a patch, letting them eat everything, and moving them, giving the land lots of recovery time. This forces the grazers to eat the weeds as well as the stuff they like. You can extract more out of this by grazing with a succession of animals: E.g.
- Cows with calves. They get first pick of the best stuff to get growth/milk.
- Cows without calves. Second pick.
- Sheep. Will eat things cows wont.
- Turkeys or chickens. Will eat weed seeds, seeds in scat, bugs such as ticks.
The timing for this is critical, and you have to balance what each group eats. Doing this, and maintaining access for each group to water can also be a challenge. Poultry and sheep have to be protected from coyotes. Poultry have to be protected from foxes. Smaller poultry have to be protected from birds of prey.
OTOH Shelterbelts every 200 feet across the prevailing winter wind makes a big difference in marginally dry country for dryland grain farming. There is no reason this shelterbelt can't be a food crop. It may require close mowing under the trees if the crop is one that falls out of trees (chestnuts, hazelnuts) or require significant pruning (conventional fruit)
Some cover crop systems may work well. E.g. planting a small annual legume with a corn crop may decrease the amount of nitrogen you need for the following crop, and also reduce the weeding, but you aren't harvesting the legume crop as such. (Although if you process the corn stalks as cattle feed, having the legume mixed in would help.)
There are sequences of crops that can be used to deal with weedy land. E.g.
- Cultivate in spring, killing most of the spring crop of weeds.
- Plant buckwheat, which practically germinates as it falls into the dirt.
- Plough under the buckwheat as soon as it finishes blooming, and plant annual peas.
- Plough under hte peas when they finish blooming, and plant annual rye.
The rye doesn't have time to set seed before winter. In each case you are planting a cover crop that grows faster than the weeds, but not letting it go to seed.
In general the management issues grow with, I suspect, the factorial of the number of species you work with.
Running two crops -- an annual and a perennial works ok, particularly if one is finished before the other one needs attention. (E.g. You can get your grain off the field before the chestnuts fall.)
In general I think it works better to do your multicropping in time rather than in space. E.g. traditional mixed use agriculture, where you may have 2-3 different grain crops, a hay crop, a pasture, raising at least two different meat animals and doing intensive grazing. This is still a handful, but you find yourself not needing to clone yourself during the busy times.