Nitrogen budget relating with food production and consumption in 1885 was calculated from the agricultural statistics. The amount of protein supply per capita was estimated to be about 70% of that in today. In 1885, one hectare of arable land fed 5 people. This number is grater than that of the current world average. This intensive agriculture required much nitrogen, and nitrogen supply was the limiting factor of food production. They had used green manure and human excrement. This let the society circulatory and prevents water pollution in rivers and lakes.
