136 NATURE TEACHING 



sulphate of potash and \ oz. sulphate of ammonia.* 

 Scatter these substances evenly over the surface, stirring 

 each in before the next is added. Dig in the basic slag 

 somewhat deeply. 



Finally, spread an ounce of moist garden soil over 

 each, in order to ensure the presence of the nitrifying 

 organisms which would probably be absent from the 

 washed sand. 



If it is convenient to make plots, treat these in 

 exactly the same way, taking similar precautions with 

 regard to situation and drainage, as observed in the case 

 of the boxes. The amounts given above are for boxes 

 of the size mentioned, 2 feet long by 2 feet broad, that 

 is with a surface of 4 square feet. Larger or smaller 

 boxes would require correspondingly larger or smaller 

 quantities of manure. Similarly, a bed 8 feet long by 3 

 feet broad, or 24 square feet in surface, would require 

 six times the amounts given. The four boxes or plots 

 now stand as follows : 



A. No manure. 



B. Farmyard or stable manure, at the rate of about 



30 tons per acre. 



C. Nitrogen only, as sulphate of ammonia, about 



2 cwt. per acre. 



D. Nitrogen as sulphate of ammonia, about 2 cwt. 



per acre, together with potash and phosphate. 

 Raise in each box, or on each plot, a similar crop. 

 Barley, wheat, oats, turnips, beet or cabbage, are recom- 



* In accordance with what has been said before, it is advisable 

 to add the sulphate of ammonia about a week after the lime or 

 basic slag has been applied, to prevent the loss of the ammonia. 



