38 



HOOS FIELD 



J^ffect of Mineral Manures. 



The diagram, Fig. 12, shows in a graphic form the effects of the 

 various mineral manures, the nitrogen supply being the same in all cases. 



The great importance of phosphoric acid to the barley crop is seen on 

 comparing Plots 3 and 4, which only differ from one another in the 

 omission of phosphoric acid on Plot 3. In the field the most striking 



Total Produce 

 per Acre. 



6000 Ib.- 



Plot 10 



Unmanured 



40. 



Minerals 

 only. 



4 A. 



Minerals 



+43 Ib.N. 



as Ammonia. 



^ 



Grain per Acre, lb. 



4C. 7-2 



Minerals Farmyard 



+49lb. N. Manure 

 as Raoe Cake. 



Straw per Acre, lb 



Fig. 11. — Yield in Barley (Grain and StrawJ with different sources of Nitrogen. 

 Averages for 51 years (1852-1902). 



The figures in the labels indicate bushels of Grain and cwt. of Straw. 



effect is seen in the hastened maturity brought about by the phosphoric 

 acid. By comparing Plot 2 with Plot 4 we can see the effect of omitting 

 potash from the manure. Where nitrate of soda is used as the source of 

 nitrogen the soda liberates sufficient potash from the soil to supply the 

 needs of the crop, but with ammonium-salts the omission of potash has 

 latterly begun to tell upon the yield, though it did not do so in the 

 earlier years of the experiment. 



