PHOSPHORUS FOR SOILS. 177 



and phosphoric acid for the sake of the crop, lime for the sake 

 of the land. 



At the outset of cultivation size of crop will generally be de- 

 termined by the supply of the first three. After a term of years 

 the ability of the soil to respond to fresh applications of artifi- 

 cial manures will largely depend on its holding a sufficiency of 

 lime. 



The use of most of the ordinary artificial manures involves 

 the washing out of lime into the drains. Thus the application of 

 1 cwt sulphate of ammonia will, in ordinary circumstances, 

 cause an ultimate loss of more than its own weight of available 

 lime compounds in the drainage of waters. After a long period 

 of artificial manuring the use of ground lime as a soil corrective 

 has been rapidly gaining prominence in recent years. 



It is in view of this fact that among all artificial manures 

 basic slag possesses a special interest. While primarily em- 

 ployed as a phosphate, it contains ground lime as an accidental 

 constituent. Bones do not cause waste of available lime com- 

 pounds from the soil. Basic slag actually increases them. All 

 other artificial manures in common use, nitrogenous, phosphatic 

 and potassic, cause a gradual washing away of the lime com- 

 pounds from the land. 



Manures are applied not because the land is ever actually 

 deficient in nitrogen, potash or phosphoric acid at the time. They 

 are applied rather because the natural supplies of these are in a 

 form unsuitable for absorption by plants. 



The importance of lime in land is that it hastens the conver- 

 sion of the natural soil constituents into available forms. This 

 effect is exercised on the phosphates, on the potash, but above all 

 on the nitrogen. The general effect of liming on newly broken in 

 land, especially on peats, which are commonly deficient in lime, 

 is sufficient evidence of this. 



Leguminous crops, including clovers, vetches and beans, do 

 not require nitrogenous manures because they are able to utilize 

 atmospheric nitrogen. Lime greatly strengthens their power to 

 do this, thereby giving larger crops and enriching the land in 

 nitrogen at the same time. Basic slag has the same power part- 

 ly owing to the extra lime which it contains, the effect being 

 usually best seen in the stimulation of clovers in pasture leys. 



Basic slag is a by-product in the manufacture of steel by the 

 basic process. Pig iron frequently contains phosphorus, and steel 

 made from this is brittle unless the phosphorus is removed. In 

 the process of manufacture a blast of air is forced through the 

 molten pig iron, whereby the phosphorus in the pig is burned to 



