i6 



Yield of Wheat. 



Phosphoric Acid. — Unlike barley and turnips, wheat does not 

 respond to large quantities of phosphoric acid, but is well able 

 to satisfy its requirements from the soil. Phosphoric acid, of 

 course, is necessary, but its most marked effects are secondary. 

 It hastens maturity, and is therefore effective in a backward 

 season or in late districts, since it enables a crop to be harvested 

 in time which otherwise might be damaged or lost. Extra- 

 ordinary returns are obtained for small quantities of super- 

 phosphate in Australia. 



Potash.— Wheat is usually able to satisfy its potash require- 

 ments from the soil, but at Rothamsted, on the plots which have 

 become depleted of potash, the deficiency is shown by a reduced 

 yield, especially in dry seasons, and by increased tendency to 

 disease, rust, &c. 



Organic Matter. — Autumn-sown wheat is less dependent than 

 most farm crops on good texture of the soil, and grows freely 

 even when the amount of humus in the soil is a low one. On the 

 Rothamsted plots, where wheat has been grown for so long with 

 manures containing no organic matter, no difficulty is experienced 

 in obtaining a plant ; the seed germinates and grows away freely. 

 Similarly, Prout at Sawbridgeworth has grown wheat and other 

 cereals on the same land since 1864, using no farmyard manure 

 and growing clover (the roots and stubble of which would supply 

 some humus) only about once every seven years. In England it 

 is not customary to use much manure for wheat ; in the Eastern 

 Counties farmyard manure is very generally put on the temporary 

 hay or clover before it is ploughed for wheat, but this is to some 

 extent a matter of convenience in handling the manure. Beyond 

 this, specific manures are rarely employed, except perhaps soot or 

 a top dressing of nitrate of soda in the spring if the plant is 

 backward. Wheat is usually grown after clover or a well-manured 

 mangold crop, and therefore on land recently enriched with 

 nitrogen ; an excess of phosphoric acid is also generally applied 

 to the turnip crop in the rotation, and its influence persists until 

 the wheat crop comes round. 



(2) Rainfall. — Wheat being a deep-rooting plant and sown in 

 England in autumn, is less dependent on spring and summer 

 rainfall than most other crops. Thus the very dry years — 1854, 

 1864, 1898 — were all good wheat years; indeed, an old English 

 proverb runs: "Drought never bred dearth in England." The 

 lowest rainfall was in 1864 (i8'5 inches), and the crop was above 

 the average, especially on the plot receiving dung. Further, the 

 great wheat growing districts of England are also those of lowest 

 rainfall. Wheat is, therefore, one of the crops best adapted to 

 dry regions, probably not because it requires relatively little 

 water, but because it flourishes best in a dry atmosphere, and 



