PREFACE ix 



land with the same manures. As the British farmer never 

 grows wheat continuously on the same land, and rarely uses any 

 kind of manure for it, the whole experiment is from one point 

 of view hopelessly unpractical ; indeed many men might con- 

 sider that to grow wheat at all nowadays is unpractical. But 

 the aim of the experiments is to find out how the wheat plant 

 grows, and the scheme of manuring and management adopted 

 is the most practical method of solving that problem. Experi- 

 ments which only aim at ascertaining how to derive the 

 greatest monetary return from a given crop, however necessary 

 they may be, are only of value for a short time and for the 

 particular soil and locality where they are carried out. During 

 the period the Rothamsted wheat field has been under experi- 

 ment the price of wheat has been as high as 75s. and as low as 

 23s. ; any conclusions reached as to the most paying system at 

 the former price would have to be altogether revised at the 

 lower rates. There is, of course, every probability that price 

 and other economic conditions may fluctuate just as much in 

 the future as they have done in the past, but the one thing 

 that will for ever remain unchanged is the manner in which the 

 crop draws its nutrition from the air, the water, and the soil. 

 Hence the farmer who best knows how this process takes 

 place will, other conditions being equal, be the one best fitted 

 to continue to derive a profit under the changing conditions. 



The great object, then, of the Rothamsted Experiments is 

 to obtain knowledge that is true everywhere, and to arrive 

 at principles of general application, leaving the farmer himself, 

 through his more immediate advisers, to adapt these principles 

 to his own practical conditions and translate them into pounds, 

 shillings, and pence. Thus the farmer who visits Rothamsted 

 must not expect to see demonstrations of the most profitable 

 means of growing this or that crop, but rather to obtain 

 information as to its habits and requirements which on 

 reflection he can make useful under his own conditions. 

 Some of the work also that is going on may seem to deal with 

 problems little connected with practice ; so remote, in fact, that 



