84 THE farmers' handbook. 



The wheat crop depends practically entirely upon the soil for its nitrogen, 

 so that for the whole of the above quantities of food the wheat is dependent 

 upon the supplies existing in the soil. Now, 48 lb. nitrogen is equivalent 

 roughly to about -003 per cent., as indicated by analysis in a soil of average 

 weight 6 inches deep. This quantity is very much less than the average 

 percentage of nitrogen in our soils, which is quite "1 per cent. In the same 

 way 21 lb. phosphoric acid represents about "001 per cent, phosphoric acid in 

 a soil of average weight and depth. This quantity is present ten times 

 over, even in poor soils, as is also "002 per cent, potash, the quantity 

 represented by 29 lb. potash, required by the 30-bushel crop. If, then, it were 

 possible to convert the plant-food in the soil into an available form at the 

 times that the plant could make use of them, the necessity for manuring of any 

 sort would be done away with and the poorest soil would contain abundance 

 of plant-food for a succession of several crops. But wheat does not appear 

 to be capable of utilising the soil-ingredients to their full extent, consequently 

 the application of soluble manures is particularly beneficial to it and the 

 other cereals. 



The Use of Superphosphate in Manuring Wheat. 



In the great majority of cases the manuring of wheat lands resolves itself 

 into the application of a small quantity of superphosphate, either applied 

 broadcast on the land or drilled in with the seed when sown. In this respect 

 the practice is opposed to that which prevails in the older wheat-growing 

 countries of the European Continent and in England and America, where the 

 application of nitrate of soda is almost universal. With us the application 

 of nitrate of soda (or of ammonium salts) by itself is found to be of little or 

 no benefit, whereas in most cases the addition of a small proportion of super- 

 phosphate in the early stages of the plant's growth insures an increased 

 harvest. The soundness of this view has been confirmed by exact experiments 

 carried out in all the Australian States, including our own. The reason of 

 this want of response to nitrogen in the wheat crop is, I think, to be found in 

 the different conditions as to rainfall under which the crop is grown, and the 

 effect thereby produced in the natural formation of nitrates within the soil. 



In Europe the grain sown in autumn remains dormant after germination 

 for four to five months during the late autumn and winter, its period of active 

 growth being practically confined to the months of April, May, and June, 

 and being particularly active in May and June. It is during this dormant 

 period that the greatest fall of rain takes place. The ground is covered 

 with snow during the winter months, so that during the thaws, when 

 the frost breaks up in February and March, the soil is subjected to a very 

 heavy leaching. This applies more particularly to Northern Europe and 

 America, where there is little thawing during the actual winter, and the 

 whole of the accumulated snow melts in a comparatively short time, flooding 

 the land, and leaching out the nitrates which have been produced during the 

 previous summer and autumn. The leaching process is continued by the 

 spring rains — which are usually fairly heavy — of March and April, so that 

 when the plant enters upon the period of its most active growth in May, the 

 soil's store of nitrates is removed beyond the reach of the roots, and the 

 addition of readily available nitrogenous manures such as nitrate of soda or 

 sulphate of ammonia is essential for a satisfactory harvest. 



The Rothamsted experiments show that nitrification is most active during 

 summer and autumn, the formation of nitrates increasing from July to 

 October. When wheat was grown at Rothamsted after fallow the increased 

 yield was found to be almost wholly due to the retention in the soil of the 



