How can I make manure without cows?
Background
There is a world with flora and fauna based on the life forms that evolved on Gondwana (see here for previous questions). Humans colonized this continent from a distant one some thousands of years ago, before the advent of agriculture (similar to human colonization of Australia) and caused the extinction of most of the large mammals. The remaining megafauna has a few species such as elephants and giant sloths, but is heavily weighted towards birds and reptiles.
Now humans have developed agriculture in primarily tropical areas. I am using as a basis for development the actual human development of agriculture in sub-Saharan Africa. One of the biggest things that held back African agriculture was the lack of traction animals, to provide both plowing and manure. My people have a similar problem; there are no animals that they can domesticate to plow. However, the important part isn't the plowing itself (enough people with hoes can replicate that work) but the manure those animals create. Without the ability to fertilize monsoonal tropical soils, they become leached of nutrients. In Indian and SE Asia, water buffalo were around to chew up local vegetation and poop it onto fields; in Africa water buffalo were excluded by tsetse fly, fields lost fertility, and agriculture had to slash and burn rotating fields in the forest...a much less efficient proposition.
Problem
I want to replicate the manure creating effect of large domesticated animals like cows and water buffalo for a tropical region where there are no domesticated large animals.
The obvious answer might be composting; but composting has its own problems. First, compost takes at least a year, while cow's stomach takes a few days. Second, composting means lots of human labor to move things into a pile, then spread them out onto the fields. Cows move food into their stomachs then carry it into their stalls to deposit in piles; they also are used to drag the piles of manure out into the fields to spread them out.
What is the least human labor intensive way to generate tons of manure/compost to continually fertilize a tropical farm?
Considerations
- Technology level is Bronze Age.
- You may assume any non-mammal, non-megafauna life form from Gondwana (South America, Africa, and Australia) is present.
This post was sourced from https://worldbuilding.stackexchange.com/q/102502. It is licensed under CC BY-SA 3.0.
1 answer
Use chicken manure.
Other animals, besides livestock, also produce good manure, with different qualities. Now, not all manures are created equal; they differ in composition, volume, and production rate. If we define one "animal unit" as 1,000 pounds of animal, then one dairy cow unit produces 15 tons of manure per year, while one chicken unit produces only a little bit less than that. So in terms of animal mass alone, chickens are as good as cows.
There are also some compositional differences. Cows can, under good conditions, produce up to 17 lbs of nitrogen per ton, and 11 lbs of phosphorous per ton. Poultry can beat that by a lot - 32 lbs per ton and 56 lbs per ton, respectively. Not all of the nitrogen and phosphorus in the dung is usable, but that's fine - chickens still beat out cows by a lot.
Per animal, yes, chickens come nowhere near cows. But that's fine; chickens don't eat as much as cows. And besides, that's pretty much your only option for non-human-based manure.
Also, chickens have other uses - and when selecting an animal for manure, that's something you want to take into account. With chickens, you get . . .
- Eggs.
- Meat - in this case white meat - which is good if you want some protein but obviously don't have beef available.
- A form of pest control, in some cases.
- An animal that might be loud, but at the least won't trample crops in the same way that a cow could.
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