KOTHAMSTED EXPERIMENTS 37 



phosphates and alkali salts are also applied. When 

 nothing but ammonia salts is applied (plot ioa), barely 

 2 bushels of wheat per cwt. of sulphate of ammonia are 

 obtained. When superphosphate is also employed, as on plot 

 n, the yield becomes nearly 3 bushels per cwt. of sulphate. 

 To reach the full return of 5 bushels per cwt., it is needful to 

 apply the salts of potash, soda and magnesia as well as super- 

 phosphate. Other experiments in the same field, which \ve 

 need not quote in detail, show that of these salts those of 

 potash are by far the most important. 



It must always be borne in mind that the profit to be 

 obtained from the use of sulphate of ammonia entirely depends 

 on the presence of a sufficient supply of phosphates and potash 

 in the soil. In the case of most farms the return yielded by 

 sulphate of ammonia will be greatly improved by the addition 

 to it of superphosphate, and of kainite supplying potash, soda, 

 and magnesia. The need for a supply of ash constituents to 

 the soil will, however, generally be less than would appear 

 from the results shown in the Rothamsted wheat field. 

 When wheat is grown in a rotation in which a liberal 

 manuring of farmyard manure and superphosphate is applied 

 to the root crop ; when cake is purchased and consumed on 

 the farm, and only a part of the straw is sold; it will never be 

 necessary to supply the large amount of phosphates and 

 potash which has been used at Rothamsted. Whether these 

 additional manures are required or not, and if required what 

 dressings of them are necessary, must be ascertained by the 

 experience acquired on each farm. Every farmer should 

 make himself acquainted with the particular deficiencies of his 

 own soil, without this knowledge it will be impossible for him 

 to employ artificial manures with the greatest profit. It is 

 easy to ascertain by trials in his own fields whether it pays to 

 add superphosphate along with a dressing of sulphate of 

 ammonia, and if kainite is also needed. These manures are 

 cheap, but a farmer who aims at profit will be careful not to 

 apply any more than is required to produce the desired effect. 



Influence of Climate. In the table already given we 

 have seen the average effect produced by ammonia salts 



