368 Journal of the Department of Agriculture. 



COMPOSITION AND VALUATION OF FERTILIZERS 

 AND FEEDING STUFFS. 



By C. 0. Williams, B.Sc, A.R.C.S., Chemist, Scliool oi Agriculture, 



Cedara. Natal. 



This article originally appeared in the various newspapers and 

 journals circulating- more particularly in Natal, but has been re- 

 written and adapted for insertion in the Journal of Agriculture so as 

 to be applicable to the whole Union. The object of the article more 

 especially is to enable farmers and ag-riculturists generally to ascertain 

 for themselves the comparative values of the various fertilizers and 

 feeding- stuffs on the market at the present time. 



Fertilizers. 



It may be mentioned at the outset that the present condition of 

 the fertilizer market is far from normal, and it is liable to so many 

 sudden fluctuations that any fig-ures given in this article are to be 

 accepted as very approximate, and may have ^o be appreciably 

 modified before the end oif the season. 



Distinction between the Market Value and Agricultural Value of </■ 



Fertilizer. 



It should be pointed out that the commercial or market values 

 dealt with in this article are different to the agricultural or real values 

 of the corresponding fertilizing ingredients to the farmer. - The 

 market value of a manure is determined by the cost of the materials 

 which enter into its composition and depends upon commercial condi- 

 tions, i.e. on supply and demand; if the demand is great while the 

 supply is small the price will be high, and conversely. The agricul- 

 tural value, on the other hand, is the real value of a manure to the 

 farmer in bringing about an increase in his crops and in building up 

 " condition " in the soil. This agricultural value would be greater 

 for some crops than for others, and would also depend largely upon 

 the soil, locality, climate, etc. To further explain this distinction 

 let us take an example: — Nitrate of soda during ihe war reached an 

 exceptionally high price owing to its use in the manufacture of 

 explosives, and even now it is over double the price asked for it a few 

 years ago. Most soils in South Africa respond very poorly to nitro- 

 genous fertilizing, so that nitrate of soda at the present high price is 

 liardly an economical proposition to the ordinary farmer; that is, its 

 market value is out of proportion to its agricultural value. 



Th^ Constituents on which the Valuation of Fertilizers is Based. 



The three elements usually found deficient in soils for the healthy 

 growth of plants are nitrogen, phosphorus, and potassium, so that 

 compounds containing any of these three elements have often to be 

 supplied in the form of manures or fertilizers. 



The nitrogen must usually be combined with certain other 

 elements, in the form of a nitrate, before it can be absorbed by the 



