THE CAUSES OF THE FERTILITY, ETC, 
39 
These are deductions which most farmers know to be 
correct from their own experience. Still, they do not ex- 
plain anything : they only state the facts. 
Let us first examine the figures dealing with the prin- 
cipal materials which a crop contains. 
A crop of 15 bushels and weighing 2,500 lb. or about 
2 tons of grain and straw has removed from the 
soil during the period of growth- 
24 lb. Nitrogen ; 
io£ lb. Phosphoric Acid ; and 
14J lb. Potash. 
If we compare these figures with the amount of nitrogen, 
phosphoric acid and potash which a great number of analyses 
of wheat soils made by myself and others reveal, it would 
seem as if it was quite unnecessary to manure at all, because : 
24 lb. nitrogen, compared with the average weight 
of a 6-inch layer of soil on 1 acre surface= 
about 0.0015% ; 
10 J lb. phosphoric acid, compared with the average 
weight of a 6-inch layer of soil on 1 acre surface 
=about 0.006% ; and 
14J lb. potash, compared with the average weight 
of a 6-inch layer of soil on 1 acre surface= 
about 0.001%. 
While the wheat soils show an average content of — 
Nitrogen =0.085% (maximum 0.1) ; 
Phosphoric acid=o.oo68% (maximum 0.01) ; 
Potash=o.oi6% (maximum 0.02). 
The trouble, however, is that wheat-plants (as other 
green plants) can only absorb raw material from the earth 
in solution, and that, unfortunately, the above quantities 
are not all found in water or citric acid soluble form. 
Therefore, they are not all available to the plants, and 
the plant must look elsewhere for part of its supplies. 
As you see, wheat is above all a nitrogen-feeder. Now, 
I found (and others found the same) that the addition of 
nitrogenous and potassic manures in Western Australian 
wheat lands does not pay. Some experiments made in these 
regions gave the following results : — 
Field. 
Manure. 
1908. 
1909. 
I9IO. 
19m 
I 
No manure 
Bushels 
6 
Kushels 
Bushels 
7 i 
Bushels 
F ailure 
2 
90 lb. Superphosphate . . . 
14 
1 i 
3 
90 lb. Superphosphate, 28 
lb. Sulphate of Ammonia, 
and 28 lb. Sulph.of Potash 
I2f 
i 4 i 
m 
ft 
