12 AGRICULTURAL RESEARCH AND THE FARMER : 



necessarily hold in the case of plants growing in the field. Before 

 we can say precisely what happens however, we must have exact 

 information regarding the chem.ical substances which are formed 

 in the soil during the change from the original nitrogen coni- 

 pounds to the soluble nitrates absorbed by the plant roots. The 

 problem is a chemical one, and its solution depends largely upon 

 the elaboration of methods of chemical analysis. Such methods 

 are now being worked out at Rothamsted. The devising of 

 new methods of analysis is not, however, an easy matter ; for 

 example, the methods of estimating the amounts of soil ammonia 

 and nitrates now in use at Rothamsted were devised by a former 

 worker after an investigation covering about two years. On 

 the other hand, even a slight advance on existing methods of 

 analysis is of great importance in speeding up chemical research, 

 and also in making easier the large amount of routine work 

 which is a feature of all chemical laboratories. The importance 

 of discovering quicker methods of routine analysis will be realised 

 from the fact that at Rothamsted, between 1,500 and 2,000 

 analyses for nitrogen, phosphoric acid, and potash are made each 

 year, and a larger number of determinations of total dry matter. 

 The soils, manures, and crops of all the experimental plots are 

 analysed, to ascertain the relation existing between the manuring 

 and the composition and food value of the manured crop. 



Farmyard Manure and the Clover 'Crop. 



While research into the problems of the soil must lead to 

 results which will be applicable to many aspects of cultivation 

 or manurial treatment, the direction in which its value will be 

 most appreciated is — as we have already said — that of the supply 

 of organic matter to the soil. It has long been recognised that 

 the presence of humus in the soil is an essential for the proper 

 growth of crops, but it is only recently that the peculiar value of 

 farmyard manure, as compared with artificials, has been demon- 

 strated. In the gro\\ing of clover, for instance, farmyard manure 

 appears to occupy a unique position as a fertiliser, and in this 

 connection we have a problem which may have a two-fold bearing. 

 On the one hand, we want to know how the falling-off of clover 

 known as " sickness," which prevents a more extensive use of 

 this valuable crop, can be prevented ; on the other hand, we 

 want to know why it is that farmyard manure exerts such a 

 useful influence on the clover crop, for in answering this question 

 we should doubtless throw light on the wider one of the value cf 

 dung in general. The work now in progress deals particularly 

 with the latter aspect of the problem, and arose from a considera- 

 tion of the results of experiments conducted in one of the Rotham- 



