I I7J DISEASES NOT DUE TO PARASITES OR OF UXKXOWX ORIGIN 



a verj^ different idea of the nature of the disease in each case. According 

 to the degree of disease, the following results were obtained : 



Oats very badh at tacked : U'.-hni-^dorl iiiaiuuc meal. 



Oat- badly attacked: Xitrateof soda, urea, titrate of inxa, 



ammonium bicarbonate. 

 Oat'=. clearly attacked : Double sulphale of ammonia and 



.-oda, cyanamicle. sulphate ot 



ammonia. 

 Oat'^ hardly attached at all : Ammonium chlor'de. 



On adding i gram of nitrogen to the pots it was found that the nitrate 

 of urea had given a better result than the nitrate of soda. According to 

 the degree of the disease there is obtained : 



Oats very badly attacked: Rehmsdcif manure meal, nitrate 



of soda. 



Oats badly attacked: Urea, ammonium bicarbonate. 



Oats clearly attacked : Nitrate of urea, cj^anamide. 



Oats weakly attacked : Sulphate of ammonia, double sul- 



phate of ammonia and soda. 



Completelj- healthy oats : Ammonium chloride. 



It will be seen from these facts that even the ver}^ best fertilisers may 

 often be the most injurious to the plants. 



The table of crops shows that the best jdeld was obtained through 

 ammonium chloride, because it checked the progress of the disease, while 

 the best nitrogenous manure, nitrate of soda, gave a less satisfactory result. 

 It should be noted that at the beginning of growth, before the onset of the 

 disease, the plants manured with ammonium chloride were not the best in 

 appearance, but later on there was a change in this. 



The writer has also studied the influence of various potassic and phos- 

 phatic manures and lime on the " Dorrfleckenkrankheit «, by manuring 

 pots with doses of these fertilisers. The experiments were continued for 

 5 consecutive years. They showed that a heavy lime manure had assisted 

 the onset of the disease. 



In another series of experiments the writer mixed the ordinary light soil 

 of a field successively with marsh soil, marl, clay and straw, and then stu- 

 died the relations between these additions and the outbreak of the disease. 



On the plot which had received marsh soil the oats were most clearly 

 attacked ; on those which had received marl and on the control plots the 

 disease was not so strong ; on the plots which had been given straw manure 

 the plants showed but few spots ; finally, on. the plots which had received 

 clay the plants were hardly attacked at all. These observations agree with 

 those obtained by Clausen, Tacke, Hudio and Zimmermaxn on ordinarv' 

 sandy, marshy and cla^-ey-silicious soil. It is difficult to give a precise ex- 

 planation of this phenomenon, but probably the temperature of the soil 

 plays a part, a high temperature being favourable to outbreak of the disease. 



As regards the relations between artificial fertilisers and the appearance 

 of the disease, the writer concludes that the disease is promoted by phj^sio- 



