January 20, 19 16] 



NATURE 



579 



of his researches on the various species of cochineal 

 insects. 



3000 francs to Fran(7ois de Zeltner, to contribute to 

 the cost of a proposed expedition to the Sudanese 

 Sahara, more particularly in the Air massif. 



2500 francs to Leonard Bordas, to assist him in 

 pursuinij his investigations relating to insects attack- 

 ing trees and forests, and more especially species which 

 at the present time are devastating the woods of the 

 central plateau and west of France. 



3000 francs to Joseph Bouget, botanist at the Pic du 

 Midi Observatory, for realising his cultural experi- 

 ments on a larger scale, with special reference to the 

 improvement of the pastures of the Pyrenees. 



3000 francs to Henry Devaux, professor of plant 

 physiology at Bordeaux, for the continuation of his 

 researches on the cultivation of plants in arid or semi- 

 desert regions. 



2000 francs to Victor Piraud, for the continuation of 

 his studies on the fauna of Alpine lakes and torrents, 

 particularly at high altitudes. 



2000 francs to Niarc TifTeneau, for the continuation 

 1 his studies on the phenomena of molecular trans- 

 position in organic chemistry. 



THE PRINCIPLES OF CROP PRODUCTION J 



IN any discussion of the principles of crop production 

 it is necessary to begin with the year 1840. By 

 that time it was definitely known that plants consist 

 mainly of organic matter along with a little mineral 

 matter — phosphorus, calcium, potassium, sodium, etc. 

 to which, however, very little importance was 

 .titached. The practical man knew that farmyard 

 manure was the great fertiliser; he also knew that 

 other substances, bones, salt, etc., had, in certain cir- 

 cumstances, considerable fertilising value. The most 

 obvious facts were the large amount of organic matter 

 in the plant and the large amount of organic matter 

 in the best manures ; and it is only natural that 

 chemists and physiologists should have connected these, 

 and argued that the object of the manure was to 

 furnish organic matter for the plant. 



By a brilliant stroke Liebig, in 1840, brushed aside 

 this obvious connection and declared that the true 

 function of the manure was to provide, not organic 

 matter, but the mineral constituents which the chemists 

 liad ignored. The first step, he said, was to find out 

 what mineral constituents the plant contains, and then 

 '<) supply those substances in a suitable form. If any 

 lit- of them is lacking the soil is rendered infertile, 

 iid matters will not be put right until that one is 

 ulded. Thus the whole art of manuring was reduced 

 til an exact science. 



Unfortunately Liebig's prescriptions failed in prac- 

 tice. The Rothamsted experiments showed that his 

 ash constituents gave little better crops than no manure 

 at all. Liebig had left something out ; it was necessary 

 to add nitrogen as well before complete growth could 

 be obtained. 



The critics urged that the effects would only be tem- 

 porary; that in time the land supplied with "arti- 

 ficials " would give out. Experience has shown that 

 this is not so; similar good results have been ob- 

 tained at Rothamsted over the long period of more 

 than sixty years (Fig. i). 



Part, therefore, of Liebig's principle is perfectly 



Kirrect : the mineral constituents are indispensable and 



!ust be supplied to the plant. The mistake was to 



ppose that they were sufficient. We mav take it as 



-lablished that crops can be grown satisfactorily and 



indefinitely by supplying proper quantities of suitable 



' Lecture delivered he'ore t'-e Chemical Societv on November i3, 1015, 

 'v Dr. E. ). Ku's II. Abridged from the Journal of the Society for 

 ' '^cemler, 1015. 



NO. 2412, VOL. 9(5] 



compounds of nitrogen, phosphorus, and potassium. 

 This we can call our first principle. Difficulties arise, 

 however, directly one tries to develop it in practice. 

 Trouble began with the attempts to find out what are 

 suitable quantities to use. Liebig had supposed that 

 the requirements of a crop could be gauged by the 

 composition of the ash. Lawes and Gilbert showed 

 that this was not the case. Thus the ash of the turnip 

 crop contains a considerable amount of potash but 

 only little phosphate ; according to Liebig, it should 

 have required mainly a potassic fertiliser. Lawes and 

 Gilbert showed, however, that it i-equired phosphates 

 and not potash, and they concluded that the special 

 requirements of a crop could only be discovered by 

 actual trial. 



Bpoadbalk Wheat. 



Fk;. I.— Yield rf wheat on the Bro.idbalk plots, average of sixty-one 

 years' lesu't-i (The; figires in the diamond-shaped spaces denote 

 bushels ol g'.iin and cwis. of straw respectively ) 

 When nitrogen compounds a-e withhtid the jield is little bet'er than oni 

 the unmanured plot. Coniplete anihcial feriilis^rs give a full crop which is 

 fully maintainerl to the present lime, and in this case is better than that 

 given by farmyard manure. 



This view was developed in the 'si.xties in a series of 

 brilliant lectures by Ville. After numerous experi- 

 ments (he says " many thousands "), he drew up the 

 following list, showing the special need, or, as he 

 called it, " the dominant," for each crop : — 

 Ville's List of Dominants. 



for Cereals. 



,, Beetroot. 



,, Potatoes. 



,, Vines. 



,, Cane-sugar. 



„ Flax. 



In order to ascertain the special needs of the crop 

 on a particular soil, he grew the plants on a series of 

 plots, one of which was given the complete manure. 



Nitrogen 



Potash 



Calcium phosphate 

 No dominant 



