Last edited Tue Feb 23, 2016, 10:24 PM - Edit history (1)
and would require a return to the use of Oxen and Horses whose urine will return those elements to the soil.
http://www.grit.com/farm-and-garden/farming-with-oxen-zm0z13mazgou.aspx
http://www.nytimes.com/2011/05/04/dining/04oxen.html?_r=0
http://www.midwestoxdrovers.com/blog/files/8c4a2da16ff2e692165fa37eab2425e4-8.html
http://www.theagitator.com/2005/01/20/ox-vs-tractor/
http://www.dailymail.co.uk/news/article-1385193/Take-bull-horns-Farmers-America-trade-tractors-oxen-beat-soaring-fuel-prices.html
http://www.homesteadingtoday.com/general-homesteading-forums/homesteading-questions/365681-save-world-raise-oxen-sell-your-tractor.html
Horses vs Tractors:
http://www.motherearthnews.com/homesteading-and-livestock/farming-with-horses-zmaz87jazgoe.aspx
https://www.ruralheritage.com/back_forty/economics_career.htm
1935 report on why you had 1 Million Tractors in the US in 1935, but only 15,000 tractors in Germany:
http://www.jstor.org/stable/1807806
Horse outnumbered Tractors in US Farms till 1946 (The paper states Horses only outproduce tractors if you work a horse to death, but the report the paper is based on only states if the horse is used throughout the year it is more productive than a tractor, but if most of the year the horse is idle, the tractor is cheaper for the tractor only uses oil when it is being used, a horse eats every day:
http://www.theatlantic.com/business/archive/2012/03/how-the-tractor-yes-the-tractor-explains-the-middle-class-crisis/254270/
Paper on tractors vs Horses in Ireland from 2009, the paper says on small farms horses are more economical:
http://www.horsepowerinireland.com/uploads/4/0/2/9/4029783/dissertation_on_horse_traction_in_ireland.pdf
Another paper says on farms less then 200 acres, Horses are superior to Tractors, but on larger farms, Tractors win hands down:
http://modernfarmer.com/2015/12/horsepower-vs-horse-power/