1921.] ROTHAMSTED EXPERIMENTAL STATION. 763 



Experiment shows that the clover crop may be benefited by 

 four means : — 



(1) Improvement in the method of sowing, to give the seed- 



ling a good chance of establishing itself; 



(2) Dressing of ground limestone or chalk; 



(3) Application of phosphates, and, where necessary, potash 



before sowing; 



(4) The use of farmyard manure. 



In some of the Rothamsted experiments the weights of the 

 young plants at the time of cutting the barley were: — 



Young 







clover plant*. 

 (cijjrt. per acre). 



Barley,. 

 (cwt. per. acre). 



No manure ... 





'4-8 



21-2 



Slag and lime 





... 6-7 



317 



Superphosphate 

 potash ... 



and sulphate 



of 



11-2 



28-1 



Farmyard mairnr 





10-3 



282 



Superphosphate 

 manure ... 



and farmya 



rd 



15-0 





The effect of farmyard manure is so important that it is 

 being studied in detail in the bacteriological laboratory: so 

 far the results indicate that some of the constituents of farm- 

 yard manure have a special action on the organisms in the 

 nodules of the clover roots. For other results see Fig. 2. 



Sufficiency of Lime. — Farmers throughout the country 

 realise the necessity for applying lime to their soil, and fre- 

 quent inquiries are made at Rothamsted as to the proper 

 amounts to use, the relative advantages of lime and limestone, 

 etc. Laboratory methods have been devised to enable agricul- 

 tural chemists to deal with inquiries of this kind, and attempts 

 are constantly being made to improve upon them. At present 

 chemists can advise farmers only in a general way as to the 

 need for lime, and it rarely happens that a reliable, straight- 

 forward recommendation can be made on the basis of analysis 

 alone. 



The Proper Use of Artificial Fertilisers. — When cultivation 

 has been properly done, sufficient farmyard manure or proper 

 substitute applied, and adequate care exercised in the selection 

 of suitable varieties of crops, then the farmer can hope to 

 derive the greatest possible benefit from artificial manures. 

 It is, however, necessary for him to know three things : — 

 (a) the proper mixture to use, (b) the proper amount to apply 

 per acre, nnd (c) the best time for application. Nothing short 

 of direct field experiments gives the necessary information, 



