The Manuring of Vineyards. 67 



Dining' the war the price soared up to an enormous figure, but at 

 present it is gradually coming down again. Towards the end of 1919 

 the lowest quotation received was about £15 per ton for superphos- 

 phate containing 19 per cent, water-soluble phosphoric oxide, i.e. 

 about 15s. 9d. per unit. This price is still much higher than that 

 of other forms of phosphate available to the farmer. There is every 

 likelihood that superphosphate will be manufactured locally in con- 

 siderable quantities in the near future, and the price will then 

 probably be much lower. Superphosphate is a strongly acid 

 fertilizer, and should be used on soils which either contain sufficient 

 lime or which have previously received a dressing of lime. 



Double Super phosphate is a concentrated form of superphosphate, 

 containing about twice as much phosphoric oxide as ordinary super- 

 phosphate, and usually costing twice as much. Its only advantage 

 over superphosphate is its smaller bulk and the consequent saving 

 of freight. 



Bone-dust is one of the best and safest of phosphatic fertilizers. 

 It consists of finely ground sterilized animal bones. The fineness is 

 a most important factor. Under the Fertilizer Act at least 50 per 

 cent, must pass through a sieve of 1/25-inch mesh. It contains 3| to 

 4| per cent, nitrogen and 23 to 25 per cent, phosphoric oxide in a 

 fairly available form. During the war period there was a very great 

 demand for local bone fertilizers, and, as was the case with all fertili- 

 zers, its price rose considerably. Recent quotations for bone-dust 

 range from £11 to £13 per ton, whereas the pre-war price was about 

 £7 per ton. We assume that the nitrogen in bone-dust is slower 

 acting than the other common forms, and give it an arbitrary value 

 of 20s. per unit. This means that phosphoric oxide in bone-dust 

 to-day costs about 7s. per unit. In general the finer the bone the 

 quicker it acts. Bone-meal is very coarse and, therefore, slow in its 

 action. Bone-flour is even finer than bone-dust, thus more rapid in 

 its action. 



" Dissolved Bones " is a form of superphosphate prepared from 

 bones. It contains from 2 to 3 per cent, nitrogen and 15 to 16 per 

 cent, phosphoric oxide, most of which is water-soluble. Its market 

 value will be regulated according to the market value of superphos- 

 phate and nitrogen. 



Basic Slag {Thomas Phosjjhate) is a phosphatic fertilizer obtained 

 as a by-product in the manufacture of steel. Before the war large 

 quantities were imported into this country, and the trade will 

 probably be re-established in the near future. It is an extremely 

 fine grey-black powder, containing, if of good quality, 15 to 20 per 

 cent, phosphoric oxide and about 40 per cent, of free lime. It is 

 slow in its action and therefore applied early. It is especially 

 suitable for acid soils and for heavy, wet soils. Prior to the war its 

 price was about £4 per ton ; to-day, of course, the price is greatly 

 inflated. In order to decide what price he should pay for slag to-day, 

 the farmer is advised to give the phosphoric oxide a value at most 

 equal to that of bone-dust phosphoric oxide, i.e. 7s. per unit, and 

 to allow about 10s. to 15s. per ton for the lime present. Thus 20 per 

 cent, slag to-day is worth not more than £7. 15s. per ton, and 15 per 

 cent, slag £6 per ton. 



