A FORTNIGHTLY REVIEW 



OF THE 



IMPERIAL DEPARTMENT OF AGRICULTURE FOR THE WEST INDIES. 



Vol. XV. No. 361. 



BARBADOS, FEBRUAKA' 26, 191C. 



Price Id. 



The Principles of Crop Production. 



7^ TfJlii^HE lecture delivered last November before 

 r^ ^Athe Chemical Society of London by Dr. E. J. 

 ^$fe§o^ Russell, Director of the Rothamsted E.xperi- 

 nieiital Station, comprises a very clear and interesting 

 statement of current ideas in relation to the chemistry 

 of the soil. Dr. Russell proceeded to show that, since 

 the year 1S40, when Liebig, by a brilliant stroke 

 brushed aside the popular conception that the 

 plant took up its organic in:itier from the soil, 

 W(^ have been steadily bringing fresh light to bear 

 upon the mysteries of plant nutrition, and that 



at the present time it is possible to enunciate 

 certain fundamental principles. The first one, which 

 is now recognized by everyone, is that the plant 

 must have a sufficient supply of all necessary 

 nutrients, especially of nitrogen, potassium and phos- 

 phorus. The second is less fully appreciated, and has 

 reference to soil bacteria. As has often happened in 

 the history of agricultural chemistry, the originating 

 idea of this principle was obtained from an out- 

 side technical problem, in the present case from 

 the investigation of Schloesing and Miintz into the 

 better purification of sewage. They found thaft 

 satisfactory purification involved bhe conversion of 

 ammonia into nitrate, which later they found 

 out was effected through the agency of bacteria, 

 and that in experiments these could be supplied 

 in a little extract of soil. It was at once seen 

 that the soil was not an inert mass, but that ib 

 was teeming with life and pulsating with change. 

 The decomposition of organic matter was more fully 

 investigated, and the conditions under which the 

 end-products like gaseous nitrogen, nitrates and carbon 

 dioxide are formed, were established. This led to the 

 enunciation of the second principle, that the biological 

 decompositions in the .soil must proceed smoothly and 

 quickly with a minimum loss of nitrogen. 



Thirdly, there is the principle of the limiting factor. 

 Plant growth increases with increasing supply of any 

 one of its favourable factors, but this only happens 

 so long as the supply of every other factor is adequate. 

 When anything is lacking, the increase in growth is 

 not kept up, and additional supplies give no extra 

 crop. Finally, a stage is reached when the extra 

 supplies may harm, either by direct injury, or by cutting 



