90 



the market price is often such that a better 

 return will be obtained by expenditure on 

 other phosphatic and nitrogenous manures. 



Fish Guanos also supply both nitrogen and 

 phosphates, and are very valuable for all 

 forms of intensive culture, but, here, again, the 

 unit price may be so high that the mineral 

 manures give the best return for money. 



Potash is essential for potatoes, fruit and 

 leguminous crops, but our supply is likely to 

 be below requirements until export from 

 Alsace it increased. In the meantime much 

 may be done by utilising wood ashei, as 

 stated above, and by the application of lime, 

 which liberates the potash reserves in the soil. 

 Blast furnace flue dust, containing some 

 5-7 per cent, potash, has given satisfactory 

 results, and may be employed. Most market 

 gardeners, however, will probably return to the 

 use of sulphate of potash or kainit as soon as 

 these are obtainable, the former containing 

 48 per cent, potash, and the kainit rather 

 over 12 per cent. 



The relative values of diflferent fertilisers 

 can easily be compared by means of the unit 

 system of valuation. The unit adopted is 

 1 per cent, of a ton, that is, j^^ of 2,2401b. 

 or 22 •41b. 



The Fertilisers and Feeding stuflFs Act pro- 

 vides that a seller must state on his invoice 

 the actual percentages of Nitrogen, Phosphate 

 and Potash contained in the manure. 



The unit price of an ingredient is found by 

 dividing the price per ton by the percentage 

 present of that ingredient. An example will 

 make the method clear : — 



Sulphate of Ammonia contains 20 per cent, 

 of Nitrogen and is sold at £17 10s. per ton, 

 that is, one ton contains 20 units of Nitrogen, 



hence the cost per unit is '- = 17s 6d. 



^ 20 



The value of a compound manure may be 



obtained in the same way : — 



Invoice. 



Nitrogen 4% 



Soluble Phosphates 15/^ 

 Insoluble Phosphates 5% 

 Potash 47 



Price 



per Unit. 



17s. 6d. 

 4s. 3d. 

 Is. 6i. 

 8s. Od. 



Value per ton = £8 13 3 



The cheapest manure to suit one's purpose 

 can thus be readily ascertained from the 

 market prices and a few simple calculations, 

 and thus a substantial saving made on the 

 year's fertiliser bill. 



