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I 



But though the above letter proves the great want 

 and the importance of manures in this country, it 

 would be useless to discuss in a book specially 

 written for India the advantages of manures that are 

 not available to the Indian agriculturist, and I will 

 therefore confine my observations to such materials 

 only as are easily accessible to him. 



It must be remembered that the fertility of a soil 

 depends upon the quantity of fertilizing elements 

 which it contains in physical combination, and that it 

 should be the chief object of agriculture to maintain a 

 balance of these substances in sufficiently large quan- 

 tities to enable the soil to yield remunerative crops. 

 The average yield of wheat-lands in India is 660 Ibs. 

 of grain and about 1,650 Ibs. of straw per acre ; 

 and the loss sustained by the soil will amount to 

 about 8 Ibs. of phosphoric acid, 15 Ibs. of potash, 

 and 50 Ibs. of silica, besides the other minor 

 mineral constituents. If we now assume that the 

 soil contains within reach of the plant a thousand 

 times this quantity of mineral plant-food, the roots 

 of the plant will find, in the following year in every 

 part of the soil, a thousandth part less of nourish- 

 ment; and supposing climatic influences to be exactly 

 the same, the soil will naturally yield a smaller crop 

 in the next year, the proportion to the previous 

 year's outturn being 999 : 1,000. That is to say, 

 250 years hence the outturn would be reduced by 



one-fourth. But it having been assumed that all 



