THE LABORATORY AND POT CULTURE HOUSE. 



The fundamental problem before the Rothamsted workers is 

 to study the mutual relationships of the soil and the plant. For 

 convenience of working the problem is divided into two parts : the 

 investigation of the factors that make for greater and more vigorous 

 growth on the part of the plant, and the study of the factors that 

 bring about changes in the plant, particularly those associated with 

 "quality." 



At least six soil factors are now known to be concerned 

 in plant growth : a proper supply of plant food ; of water ; of air 

 for the roots ; sufficient temperature ; adequate root room ; and the 

 absence of harmful and injurious factors. In order to limit the 

 problem, the work is at present confined to one of these, which, 

 however, is often the most important in British agriculture; the 

 supply of nitrogenous plant food. Our researches are directed to the 

 elucidation of the chemical reactions involved in the production of 

 nitrates in the soil, the agents bringing about the changes, and the 

 influence on the whole process of soil and plant conditions. 



It has long been known that the complex nitrogen compounds 

 contained in farmyard manure, crop residues, etc., speedily change 

 to nitrates in the soil. The intermediate steps are unknown, but 

 a beginning has been made this year by Mr. Horton who is investi- 

 gating the nature of the organic substances present in the soil. 

 The work is necessarily slow and difficult, but until it is done a satis- 

 factory solution of the problem will not be possible. 



The complete system of crop and soil sampling adopted at 

 Rothamsted enables us to make up balance sheets showing what 

 becomes of the transformed nitrogen compounds. These prove that 

 the nitrification process is not complete ; a portion of the added 

 nitrogen compound does not appear as nitrate, and some of it indeed 

 cannot be traced at all. The last balance sheet was made up in 

 1894 ; but the plots are now being re-surveyed so as to bring it up 

 to date and to show the relative efficiency of the various manurial 

 schemes in use at Rothamsted. It is already evident, however, 

 that certain methods and especially those involving the use of much 

 farmyard manure, are wasteful of nitrogen, and on some of the plots 

 less than 50 per cent, of the added nitrogen is recovered in the crop; 

 but it is not known how the waste occurs or whether it is an inevit- 

 able accompanyment of high farming. 



The assumption has been made that in these cases an evolution 

 of gaseous nitrogen takes place, and this is of considerable scientific 

 interest because no biochemical process is known that would liberate 

 gaseous nitrogen under the conditions. But the economic interest 

 is much greater. Nitrogenous manures are by far the most expen- 

 sive, while stable or yard manure constantly tends to become dearer 

 to make and harder to buy. In modern agricultural conditions it is 

 essential to reduce waste and to get the greatest possible return 

 from the manures applied — indeed, the unsuccessful farmer often 

 differs from the successful man only in allowing to go unchecked 

 a series of wastages, each in itself small. A careful study has 

 therefore been begun to trace the missing nitrogen, to find out how 

 it gets lost and whether there is any means of saving it. Mr. 

 Appleyard is conducting experiments to see if gaseous nitrogen is 



