672 



SCIENCE. 



[N. S. Vol. VIII. No. 200. 



on which to grow the aditional amount re- 

 quired. By increasing the present yield 

 per acre from 12.7 to 20 bushels we should, 

 with our present acreage, secure a crop of 

 the requisite amount. Now from 12.7 to 

 20 bushels per acre is a moderate increase 

 of productiveness, and there is no doubt 

 that a dressing with nitrate of soda will 

 give this increase and more. 



The action of nitrate of soda in improv- 

 ing the yield of wheat has be.en studied 

 practically by Sir John Lawes and Sir 

 Henry Gilbert on their experimental field 

 at Rothamstead. This field was sown with 

 wheat for thirteen consecutive years with- 

 out manure, and yielded an average of 11.9 

 bushels to the acre. For the next thirteen 

 years it was sown with wheat, and dressed 

 with 5 cwt. of nitrate of soda per acre, 

 other mineral constituents also being pres- 

 ent. The average yield for these years was 

 86.4 bushels per acre — an increase of 24.5 

 bushels. In other words, 22.86 pounds of 

 nitrate of soda produce an increase of one 

 bushel of wheat. 



At this rate, to increase the world's crop 

 of wheat by 7.3 bushels, about 1^ cwt. of 

 nitrate of soda must annually be applied 

 to each acre. The amount required to 

 raise the world's crop on 163,000,000 acres 

 from the present supply of 2,070,000,000 

 bushels to the required 3,260,000,000 bush- 

 els will be 12,000,000 tons, distributed in 

 varying amounts over the wheat-growing 

 countries of the world. The countries 

 which produce more than the average of 12.7 

 bushels will require less, and those below 

 the average will require more ; but, broadly 

 speaking, about 12,000,000 tons annually 

 of nitrate of soda will be required, in addi- 

 tion to the 1,250,000 tons already absorbed 

 by the world. 



It is difBcult to get trustworthy estimates 

 of the amount of nitrate surviving in the 

 nitre beds. Common rumor declares the 

 supply to be inexhaustible, but cautious 



local authorities state that at the present 

 rate of export, of over 1,000,000 tons per 

 annum, the raw material ' caliche,' contain- 

 ing from 25 to 50 per cent, nitrate, will be 

 exhausted in from twenty to thirty years. 



Dr. Newton, who has spent years on the 

 nitrate fields, tells me there is a lower class 

 material, containing a small proportion of 

 nitrate, which cannot at present be used, 

 but which may ultimately be manufactured 

 at a profit. Apart from a few of the more 

 scientific manufacturers, no one is sanguine 

 enough to think this debatable material 

 will ever be worth working. If we assume 

 a liberal estimate for nitrate obtained from 

 the lower grade deposit, and say that it 

 will equal in quantity that from the richer 

 quality, the supply may last, possibly, fifty 

 years, at the rate of a million tons a year y 

 but at the rate required to augment the 

 world's supply of wheat to the point de- 

 manded thirty years hence it will not last- 

 more than four j'ears. 



I have passed in review all the wheat- 

 growing countries of the world, with the 

 exception of those whose united supplies 

 are so small as to make little appreciable 

 difference to the argument. The situation 

 may be summed up briefly thus : The 

 world's demand for wheat — the leading 

 bread-stuff — increases in a crescendo ratio 

 year by year. Gradually all the wheat- 

 bearing land on the globe is appropriated 

 to wheat-growing, until we are within 

 measurable distance of using the last avail- 

 able acre. We must then rely on nitroge- 

 nous manures to increase the fertility of 

 the land under wheat, so as to raise the 

 yield from the world's low average— 12.7 

 bushels per acre — to a higher average. To 

 do this efficiently and feed the bread- eaters 

 for a few years will exhaust all the avail- 

 able store of nitrate of soda. For years 

 past we have been spending fixed nitrogen 

 at a culpably extravagant rate, heedless of 

 the fact that it is fixed with extreme slow- 



