CHAPTER III 



THE FUNCTION AND COMPARATIVE VALUE OF 

 NITROGENOUS MANURES 



Nitrogen promotes the Vegetative Activity of the Plant — Growth 

 proportional to Nitrogen Supply — With Excess of Nitrogen 

 Maturity is deferred and the Proportion of Straw to Grain is 

 increased — Variation of Composition of Crop with Nitrogen 

 Supply — Susceptibility of Plants to Disease when supplied 

 with Excess of Nitrogen — Crops requiring Large Quantities 

 of Nitrogen — Relative Availability of Nitrogenous Manures — 

 Nitrate of Soda v. Sulphate of Ammonia — Question to be 

 decided by the Nature of the Soil — Residues left by the 

 Different Nitrogenous Manures — Greater Value attached by 

 Farmers to Manures containing Nitrogen in Organic Com- 

 bination. 



Before passing on to a comparison of the values ot 

 the different nitrogenous manures, it is necessary to 

 consider how far nitrogen exerts on the plant a specific 

 effect that shows itself whenever there is either an excess 

 or defect of the constituent in the soil. To answer 

 this question properly, we should require to know what 

 is the physiological function of nitrogen in the nutrition 

 of the plant, and though we are still far from any full- 

 ness of knowledge, certain general conclusions may be 

 drawn both from field experiments and from the experi- 

 ence of the farm. In the first place, nitrogen is mainly 

 concerned with the vegetative growth of the plant, with 

 the formation of leaf and stem that are the necessary 



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