39 



20,000 Ibs., would at this rate deplete the soil to the 

 extent of 12 \ Ibs. phosphoric acid, 50 Ibs. potash, 

 and 25 Ibs. nitrogen. In addition to this, allowance 

 must be made for a quantity of plant food necessary 

 to make good leaf, branch, and root growth, and for 

 the amount of these ingredients leached out of the 

 soil by rain or irrigation. Assuming the total 

 amount of plant food removed from the soil by 

 these agencies to be three times that taken out by 

 the fruit alone (Hume's estimate) then the quantity 

 of these substances lost to the land would be : 

 37 \ Ibs. phosphoric acid, 150 Ibs. potash, and 75 Ibs. 

 nitrogen. Allowing for an 18 percentage of phos- 

 phoric acid, a 50 percentage of potash, and a 20 per- 

 centage of nitrogen, this is equivalent to 2 cwt. of 

 superphosphate, almost 3 cwt. of sulphate of potash, 

 and 4 cwt. of sulphate of ammonia, or to a total of 

 about 9 cwt. of chemical fertilizers. 



Supposing such a crop of 400 cases of fruit were 

 removed from one acre of ground, 9 cwt. of chemical 

 manures would, therefore, be required to make good 

 the deficiency in the soil caused by the production 

 of this quantity of fruit. 



METHODS OF APPLICATION. 



Different classes of fertilizers may be applied at 

 various times of the year. Such slow -acting 

 manures as vegetable mould or bone dust, which 

 contain ingredients not easily leached out of the soil 

 by rain or irrigation, may be applied during winter 

 or early spring, as but little plant food would be lost 

 before the root activity commences. On the other 

 hand, fertilizers containing highly soluble ingredients, 

 such as most mineral superphosphates and the 

 various classes of nitrates, are best applied during 

 early spring or summer, when the roots of plants 

 are active^ Generally speaking, phosphates should 

 not be put into the ground later than October if the 

 current crop is to receive their full benefit, but 

 nitrates may often be advantageously applied, as in 



