MISCELLANEOUS EXPERIMENTS 119 



Ibs. of rape cake. If we take the whole of the nitrogen as of 

 equal manurial value, the return of the nitrogen in i cwt. of 

 sulphate of ammonia is 28 cwts. of swede roots, and nearly 

 3 cwts. of leaves. 



2. Miscellaneous Experiments on Farms. It is 

 probable that a greater number of field experiments have been 

 made on the turnip crop than on any other crop grown by the 

 farmer. The returns obtained from the manures applied are 

 very various in different farms and seasons, which is perhaps 

 the reason why these experiments are so often repeated. Little 

 or no effort is generally made to trace out the cause of the 

 peculiar results which frequently appear. The action, or want 

 of action, of the manures is not studied in relation to the phy- 

 sical or chemical condition of the soil, and in some cases no 

 reference is made to the character of the weather during the 

 growing period. It is extremely difficult to deal with this mass 

 of heterogeneous results, and little can be done in sorting and 

 classifying them, because so little is stated as to the special 

 conditions of each experiment. 



The addition of sulphate of ammonia to the other turnip 

 manures used in these experiments has sometimes given the 

 farmer a considerable increase of crop ; more usually the in- 

 crease is small ; sometimes the sulphate of ammonia has pro- 

 duced no increase in the weight of roots, and the weight of leaf 

 is seldom recorded ; finally in not a few cases the weight of 

 roots is diminished by the use of the salt. Similar results are 

 obtained when the experiments are made with nitrate of soda. 



The common reason of the failure of sulphate of ammonia 

 is clearly that the crop had all the nitrogen it could make use 

 of without this additional manure. This reason is sometimes 

 plainly indicated by the weight of the crop obtained without 

 ammonia. Thus in the experiments on nine farms made by 

 the University College of North Wales in 1897, ^ appeared in 

 every case that the addition of one cwt. of sulphate of ammonia 

 to a dressing of 6 tons of dung, 4 cwts. of superphosphate, 

 and 2 cwts. of kainite, produced no increase of crop ; but in 

 these experiments the average produce without ammonia was 

 25 tons of swedes per acre ! We can readily understand 



