i6 



TROPICAL AGRICULTURE 



Sandy soils. 



Marls. 



Calcareous 

 soils. 



Vegetable 

 soils. 



to 20 per cent, of clay ; and like the other three classes, 

 lime may be present in or absent from them. 



Theji/th c/ass comprises the sandy soils, which contain 

 over 70 per cent, of sand, and they may also be with or 

 without lime. 



The sixth class or the marly soils, contain from 5 to 20 per 

 cent, of lime, and they may partake of the characters of the 

 first four classes, or of the eighth. Thus there are five sub- 

 divisions of the marly soils. 



The seventh class, or calcareous soils, contain more than 

 20 per cent, of lime, and they may partake of the characters 

 of the first, second, third, fourth, fifth and eighth classes. 

 Thus a loamy calcareous soil would contain from 30 to 50 

 per cent, of clay, and more than 20 per cent, of lime. And 

 a sandy calcareous soil would have over 70 per cent, of sand, 

 and more than 20 per cent, of lime. 



The eighth class contains the various vegetable soils, in 

 which humus or vegetable matter occurs in not less a quan- 

 tity than 5 per cent. The vegetable soils may in their turn 

 partake of the character of clayey, loamy or sandy soils, or 

 be composed almost entirely of vegetable matter as in the 

 case of bog and peat earth. 



In each of the sub-divisions of the first seven classes the 

 soil may be referred to three groups, namely poor, inter- 

 mediate and rich, according to the quantity of vegetable 

 matter contained in them. If we take, as an example, the 

 first class which includes the clay soils, the presence of 

 vegetable matter (or humus), if not more than a half per 

 cent, would cause it to be classed as 2, poor clay. If there 

 were above a half and not more than one and a half per 

 cent, of humus it would be an intermediate clay, and where 

 there is from one and a half to five per cent, of humus it 

 would be a rich clay. Above five per cent, of humus would 

 cause the soil to partake of the character of the eighth class 

 and it would become a vegetable soil. 



