16 



It is hoped as a result of this work that they may become 

 calculable and therefore insurable, just as is the risk of death. 

 We want to be able to say to farmers, "If your soil and weather 

 conditions are of a certain kind, the chances are so many to one 

 that a specified fertiliser mixture will give an increased crop of so 

 many tons or bushels per acre." The difficulties of the work are 

 very great, but they are being steadily overcome. 



Meanwhile, however, the farmer urgently needs precise in- 

 formation about fertilisers, and it becomes necessary to adopt a 

 third method which, though not as accurate as the single factor or 

 the statistical methods already described, nevertheless gives some 

 of the information desired. This consists in repeating a field 

 experiment as exactly as possible at a number of centres carefully 

 chosen to represent important soil and climatic conditions. For 

 example, a Wold farmer sees our experiments, and asks if he 

 could get the same results on his own farm. At present we 

 cannot say, because we do not know the effect of differences in 

 soil type and climatic conditions ; but this can be ascertained by 

 repeating one of our typical experiments on a typical Wold farm 

 and then comparing the results with our own. This is being done 

 on some 20 carefully selected farms in different parts of the 

 country. 



FERTILISER INVESTIGATIONS. 



In addition to field and pot tests these necessitate a consider- 

 able amount of chemical work, which is carried out in the Chemical 

 Department under Mr. Page. 



thp: new nitrogenous manures.— urea. 



Our experiments indicate that this substance has a value 

 between that of nitrate of soda and sulphate of ammonia. In 

 addition it has two attractive features — it is highly concentrated 

 and it exerts no harmful influence on the soil (p. 93, p. 101). 



AMMONIUM CHLORIDE. 



Experiments made in the past two seasons at Rothamsted and 

 the outside centres show that the yields from ammonium chloride, 

 when those from ammonium sulphate containing an equal amount 

 of nitrogen are put at 100, are : — 



Cereals . 



Potatoes . 

 Mangolds 



1921 



Rothamsted 



104 



112 

 95 



Average of all 

 outside centres 



117 

 91 



112 

 85 



95 



1922 



Rothamsted 



103 



not 



Average of all 

 outside centres 



99 



98 

 98 



Two groups of results in each case. 



t With dung. The value without dung was ?9. 



