442 



NATURE 



[September 8, 1898 



years later by a hungry world ? What is to happen if the present 

 rate of population be maintained, and if arable areas of sufficient 

 extent cannot be adapted and made contributory to the subsist- 

 ence of so great a host ? 



Are we to go hungry and to know the trial of scarcity ? That 

 is the poignant question. Thirty years is but a day in the life of 

 a nation. Those present who may attend the meeting of the 

 British Association thirty years hence will judge how far my 

 forecasts are justified. 



If bread fails — not only us, but all the bread-eaters of the 

 world — what are we to do ? We are born wheat-eaters. Other 

 races, vastly superior to us in numbers, but differing widely 

 in material and intellectual progress, are eaters of Indian corn, 

 rice, millet, and other grains ; but none of these grains have the 

 food value, the concentrated health-sustaining power of wheat, 

 and it is on this account that the accumulated experience of 

 civilised mankind has set wheat apart as the fit and proper food 

 for the development of muscle and brains. 



It is said that when other wheat-exporting countries realise 

 that the States can no longer keep pace with the demand, these 

 countries will extend their area of cultivation, and struggle to 

 keep up the supply pari passu with the falling off in other 

 quarters. But will this comfortable and cherished doctrine bear 

 the test of examination ? 



Cheap production of wheat depends on a variety of causes, 

 varying greatly in different countries. Taking the cost of pro- 

 ducing a given quantity of wheat in the United Kingdom at 

 lOOj-., the cost for the same amount in the United States is67i-., 

 in India 66j., and in Russia 545-. We require cheap labour, 

 fertile soil, easy transportation to market, low taxation and rent, 

 and no export or import duties. Labour will rise in price, and 

 fertility diminish as the requisite manurial constituents in the 

 virgin soil become exhausted. Facility of transportation to 

 market will be aided by railways, but these are slow and costly 

 to construct, and it will not pay to carry wheat by rail beyond a 

 certain distance. These considerations show that the price of 

 wheat tends to increase. On the other hand, the artificial 

 impediments of taxation and customs duties tend to diminish as 

 ■demand increases and prices rise. 



I have said that starvation may be averted through the 

 laboratory. Before we are in the grip of actual dearth the 

 chemist will step in and postpone the day of famine to so distant 

 a period that we, and our sons and grandsons, may legitimately 

 live without undue solicitude for the future. 



It is now recognised that all crops require what is called a 

 ^' dominant " manure. Some need nitrogen, some potash, 

 others phosphates. Wheat pre-eminently demands nitrogen, 

 fixed in the form of ammonia or nitric acid. All other necessary 

 constituents exist in the soil ; but nitrogen is mainly of atmo- 

 spheric origin, and is rendered " fixed " by a slow and precarious 

 process which requires a combination of rare meteorological 

 and geographical conditions to enable it to advance at a suffi- 

 ciently rapid rate to become of commercial importance. 



There are several sources of available nitrogen. The distilla- 

 tion of coal in the process of gas-making yields a certain amount 

 of its nitrogen in the form of ammonia ; and this product, as 

 sulphate of ammonia, is a substance of considerable commercial 

 value to gas companies. But the quantity produced is compar- 

 atively small ; all Europe does not yield more than 400,000 annual 

 tons, and, in view of the unlimited nitrogen required to 

 substantially increase the world's wheat crop, this slight amount 

 of coal ammonia is not of much significance. For a long time 

 guano has been one of the most important sources of nitrogenous 

 manures, but guano deposits are so near exhaustion that they 

 may be dismissed from consideration. 



Much has been said of late years, and many hopes raised by 

 the discovery of Hellriegel and Wilfarth, that leguminous plants 

 bear on their roots nodosities abounding in bacteria endowed 

 with the property of fixing atmospheric nitrogen ; and it is 

 proposed that the necessary amount of nitrogen demanded by 

 grain crops should be supplied to the soil by cropping it with 

 clover and ploughing in the plant when its nitrogen assimilis- 

 ation is complete. But it is questionable whether such a mode 

 of procedure will lead to the lucrative stimulation of crops. 

 ~ It must be admitted that practfce has long been ahead of 

 science, and for ages farmers have valued and cultivated legu- 

 minous crops. The four-course rotation is turnips, barley, 

 clover, wheat — a sequence popular more than two thousand 

 years ago. On the continent, in certain localities, there has 

 been some extension of microbe cultivation ; at home we have 



NO. 1506, VOL. 58] 



not reached even the experimental stage. Our present know- 

 ledge leads to the conclusion that the much more frequent 

 growth of clover on the same land, even with successful microbe- 

 seeding and proper mineral supplies, would be attended with 

 uncertainty and difficulties. The land soon becomes what is 

 called " clover sick " and turns barren. 



There is still another and invaluable source of fixed nitrogen. 

 I mean the treasure locked up in the sewage and drainage of our 

 towns. Individually the amount so lost is trifling, but multiply 

 the loss by the number of inhabitants, and we have the startling 

 fact that, in the United Kingdom, we are content to hurry down 

 our drains and water-courses, into the sea, fixed nitrogen to the 

 value of no less than 16,000,000/. per annum. This unspeakable 

 waste continues, and no effective and universal method is yet 

 contrived of converting sewage into corn. Of this barbaric 

 waste of manurial constituents Liebig, nearly half a century 

 ago, wrote in these prophetic words : ' ' Nothing will more 

 certainly consummate the ruin of England than a scarcity of 

 fertilisers — it means a scarcity of food. It is impossible that 

 such a sinful violation of the divine laws of nature should for 

 ever remain unpunished ; and the time will probably come for 

 England sooner than for any other country, when, with all her 

 wealth in gold, iron, and coal, she will be unable to buy one- 

 thousandth part of the food which she has, during hundreds of 

 years, thrown recklessly away." 



The more widely this wasteful system is extended, recklessly 

 returning to the sea what we have taken from the land, the more 

 surely and quickly will the finite stocks of nitrogen locked up 

 in the soils of the world become exhausted. Let us remember 

 that the plant creates nothing ; there is nothing in bread which 

 is not absorbed from the soil, and unless the abstracted nitrogen 

 is returned to the soil, its fertility must ultimately be exhausted. 

 When we apply to the land nitrate of soda, sulphate of ammonia, 

 or guano, we are drawing on the earth's capital, and our drafts 

 will not perpetually be honoured. Already we see that a virgin 

 soil cropped for several years loses its productive powers, and 

 without artificial aid becomes infertile. Thus the strain to meet 

 demands is increasingly great. Witness the yield of forty 

 bushels of wheat per acre under favourable conditions, dwindling 

 through exhaustion of soil to less than seven bushels of poor 

 grain, and the urgency of husbanding the limited store of fixed 

 nitrogen becomes apparent. The store of nitrogen in the 

 atmosphere is practically unlimited, but it is fixed and rendered 

 assimilable by plants only by cosmic processes of extreme 

 slowness. The nitrogen which with a light heart we liberate in 

 a battleship broadside, has taken millions of minute organisms 

 patiently working for centuries to win from the atmosphere. 



The only available compound containing sufficient fixed 

 nitrogen to be used on a world-wide scale as a nitrogenous 

 manure is nitrate of soda, or Chili saltpetre. This substance 

 occurs native over a narrow band of the plain of Tamarugal, in 

 the northern provinces of Chili between the Andes and the 

 coast hills. In this rainless district for countless ages the C(jn- 

 tinuous fixation of atmospheric nitrogen by the soil, its con- 

 version into nitrate by the slow transformation of billions of 

 nitrifying organisms, its combination with soda, and the crystal- 

 lisation of the nitrate have been steadily proceeding, until the 

 nitrate fields of Chili have become of vast commercial importance, 

 and promise to be of inestimably greater value in the future. 

 The growing exports of nitrate from Chili at present amount to 

 about 1,200,000 tons. 



The present acreage devoted to the world's growth of wheat 

 is about 163,000,000 acres. At the average of 127 bushels per 

 acre this gives 2,070,000,000 bushels. But thirty years hence 

 the demand will be 3,260,000,000 bushels, and there will be 

 difficulty in finding the necessary acreage on which to grow the 

 additional amount required. By increasing the present yield 

 per acre from 127 to 20 bushels we should with our present 

 acreage secure a crop of the requisite amount. Now from 127 

 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 improving the yield of wheat 

 has been studied practically by Sir John Lawes and Sir Henry 

 Gilbert on their experimental field at Rothamsted. This field 

 was sown with wheat for thirteen consecutive years without 

 manure, and yielded an average of 1 1 "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 present. The average yield for these years was 36*4 



