ON THE NITROGEN INDUSTRY AND OUR FOOD SUPPLY. 437 



only 20 per cent. Though in this case a growth of grass in the winter after the experi- 

 ment had been completed showed that the fertiliser had not been used during the 

 summer. 



Food Production. 



The food of a man in this country is approximately — 



Meat, Fish .... 15'5 per cent. 

 Cereals ..... 18-5 

 Milk, cheese, &c. . . . 24-5 



Potatoes and roots . . .25-8 



Sugar, Fruit, &c. . . . 15-5 



and the nitrogen efficiency in growing these foods from fertilisers is probably about 

 17 per cent. 



The amount of protein consumed per head is 86-5 grams per day ('Our Food 

 Supply Before and After the War,' by A. W. Flux. Presidential Address to the 

 Royal Statistical Society, June 1930). This contains 14 grams of nitrogen, so that 

 if this food were grown by using fertilisers at an efficiency of 17 per cent, we should 

 require to use 82 grams of nitrogen in fertilisers to produce the food for one person 

 for one day. Or the fertiliser required to feed one person for a year must contain 

 365 X 80 grams or 29 kilos of nitrogen. One ton of nitrogen in the form of sulphate 

 of ammonia or nitrate of soda will therefore produce enough food for thirty-four 

 people for one year. 



Since the total amount of nitrogen consumed in fertilisers during 1928 was 

 1,658,000 tons, the amount of extra food produced from this fertiliser would contain 

 enough nitrogen in the form of proteins to support 56,000,000 people. And there 

 would be sufficient carbohydrates and fat associated with this protein to form a 

 complete diet. 



Sir Daniel Hall in his presidential address to the Agricultural Section at Oxford 

 showed that 2 to 2^ acres of land were required under cultivation to feed one person. 

 Let us compare this with 1/34 tons of fixed nitrogen. If we assume that the total 

 capital required to build a nitrogen factory is £70 to £100 per ton year of nitrogen, 

 this is inclusive of everything, then for a maximum of £3 invested we can support one 

 person. If would be impossible to bring 2 to 2^ acres of land under cultivation at 

 so low a capital cost. 



I do not think that land can usually be settled and cultivated at a less capital 

 cost than £10 per acre, including roads and railways, houses and agricultural machinery, 

 so that to bring 2J acres under cultivation would need £25 capital as compared with 

 £3 necessary to produce the fertiliser to produce the same amount of food. I would 

 particularly like to draw attention to this calculation in some countries where govern- 

 ments are always ready to consider and finance schemes to build railways and roads 

 to open up new country or to build irrigation schemes, although the capital to be 

 invested for a given amount of food-producing capacity is often enormous. Let these 

 countries rather devote attention to making fuU use of the land already cultivated 

 near their consuming centres or on roads and railways, and when these are producing 

 at their full capacity it will be time to open up new districts. 



The Stability of the Nitrogen Fixation Industry. 



When we obtained increased yields of crops with artificial nitrogen fertilisers we 

 are usually making use of the stored-up energy of the sun in past ages. We will 

 therefore consider whether we are using our store of energy extravagantly in this 

 way — in other words, is the game worth the candle ? 



In fixing 1 ton of nitrogen and making it into fertilisers we use for all purposes 

 about 5J tons of coal, so that to provide the fertiliser to feed one person for a yeai 

 we require 3 J cwts. of coal. 



The population of the world (excluding China and Turkey) is now about 

 1,940 millions, and we have seen that 56 millions, or 2-8 per cent., are now being fed 

 with food grown by nitrogen fertilisers. 



Of the nitrogen fertilisers consumed in the year 1928 about 1,000,000 tons of 

 nitrogen was produced by synthesis, needing 515,000,000 tons of coal. This quantity 

 of coal is almost negligible when compared with 1,500,000,000 tons mined every year. 

 The rest of the nitrogen was produced by bye- product coke-ovens or as nitrate of 

 soda from ChUi. 



