ON THE NITROGEN INDUSTRY AND OUR FOOD SUPPLY. -iSO 



humus ? Wliat happens to the dissolved nitrogen going down the rivers into the 

 Hca ? And how much comes back to land in the form of fish ? Again how much 

 nitrogen is liberated again from combination ? 



Is there a dj-namic equilibrium in this nitrogen cycle, or are we drifting in one 

 direction ? Are we gaining nitrogen in the air or are we losing it '! 



We cannot get answers to these questions. There is no doubt that in the past 

 nitrogen was stored up in coal, and in Chili nitrate and this is being liberated now^ — 

 it is a mere drop in the ocean of nitrogen, but we do not know whether nitrogen is 

 being stored up anywhere at the present time. 



The vegetable foodstuffs consumed by man in the U.K. are estimated to contain 

 50,000 tons of nitrogen. If these are grown with a nitrogen efficiency of 20 per cent., 

 then 250,000 tons of nitrogen is requii'ed in the soil. Of this nitrogen it is assumed 

 that 50,000 tons go into vegetable foods 8,000 tons into straw which forms farmyard 

 manure, and the rest 192,000 tons are washed out of the ground by rain water and 

 lost to the rivers and seas. 



It will be noticed that I have assumed that the wastage of nitrogen derived from 

 humus is the same as the wastage of nitrogen from artificial fertilisers. I have no 

 direct evidence for this. I have no evidence at all, but I cannot think of a more 

 reasonable assumption than the one I have made. 



I have taken no account of the animal and vegetable life on the moors and mountains 

 except so far as it provides human food. Probabl,v I have neglected some other 

 important factors, but I make no apology for offering you the first attempt at a 

 nitrogen flow sheet for the country. 



We are now getting much better statistics of agricultural production than formerly, 

 and I believe that consideration of these statistics with other statistics now available 

 has opened up new fields of study in agricultural economics. 



I have calculated the average amount of nitrogen obtained from an acre of crops 

 in different countries. 



The figures in the next table are for the year 1928. They were obtained by 

 calculating the weight of nitrogen in each crop for each country and then adding up 

 the total amounts of nitrogen for each country. This weigh'; of nitrogen is then 

 (iivided by the area on which the crops grew, and we get the weight of nitrogen in the 

 crop in lbs. per acre average over the whole country. By crop we mean the portion 

 of the crop taken away for consumption by man or animals, for instance of wheat 

 the grain, of potatoes the tubers, &c. The rest of the crop usually goes back to the 

 land and is considered as part of the agricultural system of the country. 



Table IV. 



Since some crops give a larger yield of nitrogen in the useful part of the crop than 

 others, the figures in the table are to some extent affected by the different crops and 



